duration of posttraumatic amnesia and the glasgow coma scale as
TRANSCRIPT
DURATION OF POSTTRAUMATIC AMNESIA AND THE GLASGOW
COMA SCALE AS MEASURES OF SEVERITY AND
THEIR RELATIONSHIP TO COGNITIVE OUTCOME
FOLLOWING CLOSED HEAD INJURY
by
MICHAEL T. ROPACKI, B.A., M.A.
A DISSERTATION
IN
PSYCHOLOGY
Submitted to the Graduate Faculty of Texas Tech University in
Partial Fulfillment of the Requirements for
the Degree of
DOCTOR OF PHILOSOPHY
Approved
Acc/^pted
August, 2000
ACKNOWLEDGEMENTS
This dissertation would not have been possible without the never ending
assistance, commitment, and dedication of Jeff Elias, Ph.D.. Jeff went above and beyond
in all aspects of my training-I owe a great deal of who and where I am today to this
extraordinary man. His dedication to teaching and loyalty to his students is unyielding.
His knowledge base is amazing, and devotion to research and great science unparalleled.
Jeff has been a wonderful advisor, instructor, mentor and fiiend. He was my first official
introduction to neuropsychological research and theory, and a major reason I have chosen
this area of specialization for my career path. Jeff is unselfish, giving of his time, and
always willing to let his students, including me, pursue their own research endeavors. I
am Jeffs last doctoral student at Texas Tech University. After his official departure fi-om
the Texas Tech University Department of Psychology, Jeff remained steadfast in his
commitment to seeing my training to completion. For all these reasons, I wish to thank
Jeff, and dedicate this dissertation to him.
I would also like to express my eternal gratitude and thanks to Julie Treland,
Ph.D. for her role in my training and professional development. Julie was my first
clinical supervisor of and introduction to neuropsychological assessment. She helped
plant the seed that has blossomed into my career. Julie (Jeffs wife) never complained
when Jeff and I put in long hours working on my research, and was always willing to
help out in any way possible. She has been extremely supportive throughout my
professional development. Julie always provided excellent advice regarding my clinical
n
training in particular, and life in general. Her guidance and inspiration is extremely
appreciated. Jeff and Julie have consistently been there for me throughout my training,
even attending national meetings when I have presented our research. They have gone
the extra mile not only in their dedication to training, loyalty, and support, but also in
their hospitality and fiiendship. I look forward to continuing personal and professional
contacts with Jeff and JuUe throughout my lifetime. Jeff and Julie, I truly appreciate all
you have both done for me personally and professionally.
I would also like to express my appreciation to Stephanie Harter, Ph.D.. Dr.
Harter always put in extra time and effort to help assist with my training, even though I
was not a student in her laboratory. She was the second reader for my master's paper,
and put extra care and time in editing both my master's paper and Doctoral dissertation.
Dr. Harter's attention to detail and commitment to helping students put out top quality
work is unrivaled. She was an excellent instructor, supervisor, and resource throughout
my training at Texas Tech University. Dr. Harter has been an extraordinary advisor
regarding psychology in general, but also clinical neuropsychology in particular. She
advised me on many aspects of the internship application, interview, and selection
process. Dr. Harter was the primary reason I applied to and completed my internship
training at the University of Oklahoma Health Sciences Center-the best career move I
could have ever made in clinical neuropsychology. I would also like to express my
gratitude to Drs. Epkins and Fireman for all their support, guidance, and contributions to
my training. Their willingness to participate on my dissertation committee will always be
appreciated, thank you.
HI
This dissertation would not have been possible without the assistance of
Elizabeth Linder, Ed.D., and Roger Wolcott, M.D.. Through an external practicum
placement with Dr. Linder, I was able to collect the clinical data required for this
dissertation. Dr. Wolcott's support and assistance through this process was appreciated.
I would also like to thank Drs. Linder and Wolcott, as well as the other individuals in our
office who assisted with my dissertation.
I also wish to express my continued appreciation and many thanks to my family
for their support through this long process, but especially my wonderful, supportive, and
loving parents. They always helped make my dreams possible and have been unwavering
in their dedication to seeing me through my doctoral training. Finally, I would like to
thank Ann Ewing, Ph.D. who was my first advisor, instructor, and mentor in psychology.
Ann is the reason I became a psychology major, someone I have attempted to emulate
throughout my training and development as a professional, and a great fiiend.
IV
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ii
ABSTRACT vii
LIST OF TABLES ix
LIST OF FIGURES xi
CHAPTER
L INTRODUCTION 1
Statement of the Problem 8
n. METHODOLOGY 11
Participants 11
Procedure 13
Measures 13
Wechsler Adult Intelligence Scale-Revised 13
Wechsler Memory Scale/Wechsler Memory Scale-Revised 14
Controlled Oral Word Association Test 15
Stroop 15
Clock Face Drawing Test 16
Trail Making Test 16
IIL RESULTS 18
Demographics 18
Glasgow Coma Scale and Posttraumatic Amnesia Analyses 23
Patterns of correlations between GCS/PTA and
cognitive outcome variables 24
Correlational patterns across domains 38
Comparison by group on cognitive outcome variables 39
Comparison by group: Pre/Post Intellectual Functioning 39
IV. DISCUSSION AND CONCLUSIONS 49
Summary and suggestions for future research 55
REFERENCES 59
APPENDICES
A. EXTENDED LITERATURE REVIEW 67
B. SEVERITY CLASSIFICATION SYSTEMS 107
VI
ABSTRACT
The Glasgow Coma Scale (GCS) and duration of posttraumatic amnesia (PTA) are
the most commonly used clinical instruments for determining severity and predicting
outcome in closed head injury (CHI). Many investigations have attempted to determine
the relationship between head injury severity and cognitive outcome, as measured by
neuropsychological assessment performance, but found mixed results with respect to
utility of prediction. The present study proposed that a major reason for these mixed
results was other investigations' inclusion of individuals with conditions known to
detrimentally affect neuropsychological test performance (i.e., history of alcoholism,
drug abuse, psychiatric history, or previous neurologic insult) into their closed head
injury sample. This investigation directly examined this hypothesis by adding an
additional comparison group, a closed head injury-clean group (CHI-C), and comparing
this groups' performance against a closed head injury not-clean group (CHI-NC). The
effects of combining the CHI-C and CHI-NC groups into one closed head injury
combined (CHI-Comb) group, as previous studies have done, was also examined.
Fifty-one consecutive patients (N = 51) underwent neuropsychological assessment
following brain injury. Participants were included if they had exited PTA, demonstrated
uncompromised upper extremity use, displayed adequate verbal communication, and
were judged capable of completing full Wechsler Adult Intelligence Scale-Revised
(WAIS-R), Wechsler Memory Scale, Controlled Oral Word Association Test, Stroop, and
Trail Making Tests.
vn
Separating the CHI individuals into the CHI-C and CHI-NC groups, and use of a
logarithmic transformation, resulted in better prediction fi-om severity measures to post-
injury cognitive performance than observed in previous investigations. Moreover,
despite the increased power of adding the CHI-C and CHI-NC groups into one CHI-
Comb group, this combination obscured findings as predicted. Duration of PTA was a
more reliable injury severity predictor than the GCS. Combining both measures in a
prediction equation did not improve prediction. This investigation did not find the unique
effects of closed head injury above that of other brain insults. Although the CHI-C and
CHI-NC groups did not significantly differ on PTA duration and GCS severity level, the
use of a pre-morbid PIQ estimate showed the CHI-NC group to have a greater post-injury
PIQ loss than the CHI-C group. Furthermore, the mean VIQ/PIQ discrepancy was
significantly larger for the CHI-NC group as compared to the CHI-C group. In
conclusion, these findings as well as others fi-om this investigation were discussed in
terms of cognitive reserve theory.
vni
LIST OF TABLES
3.1 Demographic Characteristics of Sample by Percentage 19
3.2 Correlations between GCS/PTA and demographic variables by group ... 20
3.3 Correlations between GCS/PTA and pre-morbid history variables 22
3.4 Significant correlations by group between GCS/PTA and cognitive outcome variables (CHI-C) 27
3.5 Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (CHI-C) 29
3.6 Significant correlations by group between GCS/PTA and cognitive outcome variables (CHI-NC) 30
3.7 Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (CHI-NC) 31
3.8 Significant correlations by group between GCS/PTA and cognitive outcome variables (CHI-Combined) 32
3.9 Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (CHI-Combined) 33
3.10 Significant correlations by group between GCS/PTA and cognitive outcome variables (MN) 35
3.11 Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (MN) 36
3.12 Means and Standard Deviations by group across WAIS-R subtests and indices 40
3.13 Means and Standard Deviations by group across WMS/WMS-R subtests and indices, as well as the Stroop and Trail Making Test 41
3.14 Means and Standard Deviations by group for the Clock Face Drawing Test and COWA 42
IX
3.15 ANOVA comparison of OPIE formulas by group 44
3.16 Mean Difference Between Obtained and Predicted IQ's Using the OPIE Best Formula Presented by Diagnostic Category and the Total Sample ... 45
3.17 Means and Standard Deviations by group for Predicted versus Obtained FSIQ, VIQ, and PIQ 48
LIST OF FIGURES
3.1 The relationship between PTA duration and FSIQ scores
for the CHI-C group 25
3.2 The relationship between the GCS and FSIQ for the CHI-C group 26
3.3 Mean WAIS-R subtest scores for the CHI-C and CHI-NC groups 46
XI
CHAPTER I
INTRODUCTION
The incidence of head injury in the United States has been estimated to be
between 500,000 to more than 1.9 million per year with 400,000 to 500,000 individuals
requiring hospitalization or dying fi-om their injuries (Lezak, 1995). Initial severity
classification of a closed head injury (CHI) became measurable and quantifiable by the
emergence of the Glasgow Coma Scale (GCS) (Diller, 1994). According to Teasdale and
Jennette (1974), the GCS is a short assessment that was designed to assess severity,
describe the posttraumatic states of altered consciousness, and predict outcome following
head injuries (see Appendix B). A patient's GCS total score is the sum of their scores for
eye-opening, verbal performance, and motor responsiveness. Although the GCS is
widely used and accepted, there is considerable disagreement on how well the GCS can
determine severity and predict outcome (Coppens, 1995; Garcia, Garrette, Stetz,
Emanuel, & Brandt 1990; Gupta & Ghai, 1996; Haut & Shutty, 1992; Katz, 1992;
McMillan, Jongen, and Greenwood 1996; Nelson & Adams, 1997; Reid & Kelly, 1993;
Richardson, 1990; Stambrook, Moore, Lubusko, Peters, & Blumenschein 1993; Vilkki et
al., 1994).
McMillan et al. (1996) reported that the duration of posttraumatic amnesia (PTA)
is the "best yardstick" for predicting outcome that exists. Duration of PTA has been
defined as the period from the time of injury until the individual can form new memories
and continuously recall day-to-day events (Oder et al., 1992). Posttraumatic amnesia
duration varies considerably by case, but once determined it is compared to severity
classification criteria (see Appendix B). Many investigators concur that duration of PTA
has greater utility for determination of head injury severity and prediction of outcome
(Katz, 1992; Gupta & Ghai, 1996; McClelland, 1988) but other investigators have
reported its limitations (Alfano, Neilson, & Fink, 1993; Bohnen & Jolles, 1992; Coppens,
1995; Gass &Apple, 1997; Levin et al., 1987; Lezak, 1995; Vilkki et al., 1994).
Haslam, Batchelor, Feamside, Haslam, Hawkins, and Kenway (1994) stated that
there is considerable variation in the literature regarding the ability of severity indices'
such as the GCS and PTA duration to predict cognitive outcome. Levin et al. (1990)
listed many impediments that have hindered progress in CHI research. Specifically,
some of these problems included inadequate analysis of cognitive performance in relation
to neurologic severity indices (e.g., the GCS and duration of PTA), non-uniform methods
of characterizing type of head injury and severity, failure to exclude pre-existing
neurological or psychiatric disorders, and wide variation in the measures employed to
assess outcome.
Bennett-Levy (1984), Brooks, Aughton, Bond, Jones, and Rizvi (1980), Haslam et
al. (1994), Haslam, Batchelor, Feamside, Haslam, and Hawkins (1995), Levin et al.
(1990), Stuss et al. (1999), and Vilkki, Poropudas, and Servo (1988) all commented on
the failure of the CHI research literature to consistently demonstrate the relationship
between measures of severity (e.g., the GCS and PTA duration) and cognitive outcome.
Early investigations using the Wechsler AduU Intelligence Scale (WAIS) (Mandleberg,
1976; Mandleberg & Brooks, 1975) found that the duration of PTA was not related to
VIQ performance after three months and PIQ performance after six months. Levin,
Grossman, Rose, and Teasdale (1979) used the WAIS and other measures and found that
the relationship between severity level, as measured by the GCS, and cognitive outcome
was "not invariable." Furthermore, they found that cognitive deficits on the WAIS were
evident for up to three years following CHI, contrary to the results of Mandleberg (1976),
and Mandleberg and Brooks (1975).
Brooks et al. (1980) employed the Raven's Progressive Matrices, Mill Hill
Vocabulary Scale, Logical Memory subtest. Story 1 of Form 1 from the Wechsler
Memory Scale (WMS), Inglis Paired Associate Learning test, Rey Picture, "three
measures of word fluency," Part 5 of De-Renzi and Vignolo Token Test, a copy condition
of the Rey Picture, and the WAIS Block Design subtest and found that severity level, as
measured by the GCS, was not related to performance on these measures. However,
Brooks et al. (1980) did find that severity level, determined by PTA duration, was related
to Associate learning (delayed condition) and Logical Memory Story 1 Form 1 of the
WMS, Rey Picture (immediate and delay conditions), and one word fluency condition out
of three.
Alexandre, Colombo, Nertempi, and Benedetti (1983) also employed a large
number of cognitive measures including the Wechsler-Bellevue Form 1, Benton's test of
visual memory, Rey Auditory Verbal Learning Test (RAVLT), Corsi's test for spatial
memory, Kimura's test for recognition memory, and the Token test and did not find any
significance between severity of injury, determined by length of PTA, and cognitive
outcome. Moreover, Alexandre et al. (1983) found that severity level, as measured by the
GCS, was not consistently reliable for predicting outcome, except when the outcome
measure was mortality.
Vilkki et al. (1988) looked at the relationship between Digit Span, Similarities,
and Block Design of the WAIS and coma duration, but found no relationship. Paniak,
Silver, Finlayson, and Tuff (1992) investigated the relationship of cognitive outcome, as
measured by the Wechsler Aduh Intelligence Scale-Revised (WAIS-R), to injury
severity as determined by PTA duration. They found that only one subtest. Digit Span,
was related to severity of injury. Moreover, Haut and Shutty (1992) investigated the
relationship between cognitive outcome, as measured by the WAIS-R, to severity level,
as measured by the GCS, but failed to find any significant relationships.
The relationship between cognitive outcome, as measured by memory and
attention/concentration measures, and head injury severity measures has also produced
varying results. Brooks (1974) looked at the relationship between recognition memory
and severity of injury, as determined by PTA duration. He found that duration of PTA
was related to total amount correct and number of false positives produced, but not the
number of false negatives produced. To extend his earlier work. Brooks (1976)
investigated the relationship between memory performance on the WMS and injury
severity, as determined by PTA duration. Of all the subtests and conditions. Brooks
(1976) found that PTA duration was only related to Logical Memory and Associate
Learning performance.
Gronwall and Wrightson (1981) completed a two-study investigation to determine
the relationship between attention/concentration, memory, and injury severity as
determined by the duration of PTA. In the first study, attention/concentration abilities
were measured by the Paced Auditory Serial Addition Task (PASAT), while the WMS
was used to assess memory performance. Overall, these investigators found moderate
correlations between severity level and performance on the PASAT, and the Mental
Control and Associate Learning subtests of the WMS. In the second study, they again
used the PASAT, but to assess memory they used the Selective Reminding Task and the
Visual Sequential Memory subtest of the Illinois Test of Psycholinguistic Abilities.
Severity level was related to PASAT performance and total amount correct on the
Selective Reminding Task, but not to the Visual Sequential Memory test.
In Bennett-Levy's (1984) investigation, a large number of memory assessment
devices were compared to severity level, as determined by PTA duration. Overall, the
only significant finding for assessment performance by severity level was on the Logical
Memory subtest of the WMS (delayed recall & percent forgetting conditions), the
Keeping Track Test, and the Rey-Osterrieth (recall condition).
Vilkki et al. (1988) looked at the relationship between memory performance on
free and cued recall conditions of the WAIS Similarities subtest and the Benton Visual
Recognition Test (BVRT) with homogeneous interference, and coma duration as
determined by the GCS. They only found significant difference by severity level on the
free and cued recall conditions of the BVRT and percentage forgetting of the BVRT.
Crosson, Novak, Trenerry, and Craig (1988) investigated performance on the
California Verbal Learning Test (CVLT) in relation to severity level, as determined by
coma duration and length of PTA, but found no relationship between any of the CVLT
trials and severity indices. Haut and Shutty (1992) also examined CVLT performance to
severity of injury, as determined by the GCS, but also failed to find any significant
relationships. Geffen, Butterworth, Forrester, and Geffen (1994) examined memory
functioning, as measured by the RAVLT, and severity of injury determined by PTA
duration. Overall, the RAVLT includes seven trials and severity of injury was related
only to performance on the seventh trial, remote verbal memory.
Reid and Kelly (1993) investigated the relationship between severity of injury, as
measured by both PTA duration and the GCS, to memory performance on the Wechsler
Memory Scale-Revised (WMS-R). They failed to find a relationship between severity of
injury and memory performance across any of the subtests. Gupta and Ghai (1996)
examined memory performance with three WMS subtests (Digit Span, Associate
Learning, and Visual Reproduction) and attention/concentration with the PASAT.
Specifically, these investigators compared the relationship between performance on these
measures to injury severity, as measured by PTA duration. Overall, these authors failed
to find significant differences by group except on the Visual Reproduction subtest.
Haslam et al. (1994) and Haslam et al. (1995) investigated memory performance
with the RAVLT and attention/concentration with the PASAT and Symbol Digit
Modalities Test (SDMT), and examined their relationship to injury severity. Their
measures of severity were numerous, but the ones important here were the GCS and PTA
duration. These authors performed a principal component factor analysis on the
cognitive measures and a square root transformation on PTA duration in both
investigations. Haslam et al. (1994) found that PTA duration, and transformed PTA
duration were significant predictors of recent memory performance, while transformed
PTA duration was a significant predictor of information processing speed up to twelve
months post-injury. Haslam et al. (1995) determined that PTA duration, transformed
PTA, and coma duration were significantly related to recent memory performance, while
speed of information processing was significantly related to transformed PTA duration,
PTA duration, and coma duration up to two-years post-injury.
Loken, Thorton, Otto, and Long (1995) assessed severe CHI patients' abihty to
sustain attention on a visual continuous performance task "of sufficient ease and duration
to assess stability of performance over time," (p. 593) and compared these performances
to severity of injury as measured by duration of PTA. According to Loken et al. (1995),
correlational analyses failed to reveal a significant relationship between performance on
this task and injury severity.
The most striking finding of this body of literature was the lack of consistency
between investigations (Bennett-Levy, 1984; Brooks et al., 1980; Haslam et al, 1994;
Haslam et al., 1995; Levin et al, 1990; Loken et al., 1995; Vilkki et al., 1988). Duration
of PTA and the GCS have both been related to measures of cognitive outcome in some
investigations, but not in others. Most of the positive findings in these reviewed
investigations were minute considering they often gave numerous measures (e.g., only
WMS Logical Memory Story 1, not Story 2), and the positive findings varied by
investigation.
The second most striking finding from this body of literature was the lack of
refinement in participant selection. Only one study (Haslam et al, 1995) excluded
participants with a history of previous head trauma, alcoholism, drug abuse, neurological
condition, and psychiatric problems. Interestingly these investigators found a significant
relationship between severity level and cognitive outcome on measures of memory and
attention/concentration up to two-years after injury.
Third, Levin et al (1990) make an excellent point that CHI research on severity
and outcome is also hindered by the wide variation of measures employed to assess
outcome from one study to the next. However, with the exception of Haslam et al. (1994,
1995), many of the more recent investigations using newer, well-known, commonly used,
and accepted assessment measures (e.g., Crosson et al, 1988; Geffen et al, 1994; Haut &
Shutty, 1992; Paniak et al, 1992; Reid & Kelly, 1993) have failed to demonstrate
consistent and significant findings.
Statement of the Problem
Considering the issues that were raised in the review of the CHI literature, it
would seem that some of the inconsistency in predicting outcome from severity indices
could be due to the inclusion of individuals in study groups without regard to their
previous history of head trauma, neurologic problem, alcohol or drug abuse, or
psychiatric involvement. Therefore, the primary purpose of the present study was to use
CHI groups that were both "clean" and "not clean" with respect to prior history. Both
PTA duration and the GCS were used to determine initial injury severity level so that a
comparison could be made as to which is the better index of severity and predictor of
cognitive outcome. Furthermore, they were examined in combination to determine if
8
both could contribute significant individual variance to the prediction of cognitive
outcome. As a general hypothesis it was expected that the refinement of closed head
injury groups into "clean" and "not clean" groups would provide better prediction of
cognitive outcome from PTA duration and the GCS severity indices than would
combining them into one group, which is the typical procedure in most closed head injury
research. Data from neurologically impaired populations frequently presents
distributional problems for analyses involving linear relationships. Therefore in addition
to refining the study groups, the distributional aspects of data were closely observed for
their effect on linear analyses.
A "mixed neurologic" comparison group was also included in this investigation,
based upon the advice of Satz et al. (1999), who proposed that simply contrasting groups
of healthy normals to closed head injury groups adds nothing to our understanding of the
unique effects of the head injury, to help determine what persistent cognitive deficits
were unique to the closed head injury and not other factors such as pre-morbid history
(e.g., alcoholism) or general brain insuh (e.g., cerebral vascular accident, aneurysm,
neoplasm, and so on). Specifically, a range of tests (these measures are discussed in
detail in the procedures) were used to examine the degree to which refining the study
groups would illustrate differences across measures. The WAIS-R subtests, indices (i.e..
Freedom from Distractibility, Perceptual Organizational, and Verbal Comprehension),
and summary scores (i.e.. Verbal IQ, Performance IQ, and Full Scale IQ) were compared
to assess general intellectual/cognitive functioning by group. The Wechsler Memory
Scale/Wechsler Memory Scale-Revised subtests and indices (i.e.. Verbal Memory,
Visual Memory, General Memory, Attention-Concentration, and Delayed Memory) were
examined for group differences on attention and memory functioning. The Stroop test.
Trail Making Test, and Clock Face Drawing Test were included for their role in
measuring attention/concentration/executive functioning differences across groups.
Finally, the Controlled Oral Word Association Test was used to examine how verbal
fluency may differ by group.
10
CHAPTER n
METHODOLOGY
Participants
Fifty-one consecutive patients (N = 51), twenty-six males and twenty-five
females, were referred for a neuropsychological assessment from various hospitals (i.e.,
Methodist Hospital, St. Mary's Hospital, and University Medical Center) in the Lubbock,
Texas area following brain insult. Participants were included if they had uncompromised
use of their upper extremities as determined during clinical interview (i.e., a brief motor
screen was completed), were able to verbally communicate, and judged capable of
completing a fiill length WAIS-R, WMS-R, Controlled Oral Word Association Test
(COWA), Stroop, and Trail Making Tests (TMT-A; TMT-B). All participants were
tested after their transition to inpatient rehabilitation or as soon as possible after their
discharge from the hospital.
Participants in the CHI-clean group (CHI-C; n = 17) were excluded for a history
of alcoholism, drug abuse, head trauma, psychiatric problems, or neurologic disorder.
Moreover, participants' charts were examined (e.g., history and physical, lab results,
physician notes) to ensure that there was no confounding of assessment findings due to
complications resuhing from alcohol or drug use at the time of the participants' head
injury. The CHI-C group had a mean age of 42.94 years (SD = 23.57) range 18-86 with
an average of 12.06 years of education (SD = 3.01) range 5-16. Participants in the CHI-
not clean group (CHI-NC; n = 9) were not excluded for these criteria. The CHI-NC
11
group's mean age was 62.11 (SD = 25.03) range 19-90 with 12.56 years of education
(SD = 3.47) range 7-16. The Mixed Neurologic group (MN; n = 25) included individuals
referred following cerebral vascular accident, subdural hematoma, aneurysm, anoxia, and
neoplasm. Participants in the MN group were not excluded for a history of alcoholism,
drug abuse, neurologic condition, or psychiatric history. The mean age of the MN group
was 63.48 years (SD = 15.89) range 25-84, and education level 12.14 years (SD = 3.43)
range 6-18.
All participants were judged to have cleared PTA before assessment.
Furthermore, a check to ensure that the patients PTA had remitted and that the
participants were suitable for and able to withstand a neuropsychological evaluation was
completed by the author. Specifically, participants' GCS score was obtained from
hospital records when available and compared to their PTA duration severity
classification as determined by the author. Duration of PTA was determined through the
course of clinical interview questioning (i.e., last memory prior to incident, first memory
following the incident, and assessment for retum of continuous day-to-day memory
return), an accepted, reliable, and valid method for assessing PTA (McMillan et al,
1996). Participants were judged to have exited PTA from the results of their mental
status examination, memory surrounding the incident, combined with assessment to
ensure continuous memory for day-to-day events had returned.
12
Procedure
Participants' severity level, according to GCS was retrieved from hospital records
for all but three MN patients who, because of the nature of their injuries, did not have a
GCS score recorded in their hospital records. Severity level was also determined
according to duration of PTA using the guidelines proposed by McMillan and colleagues
(1996). As with the GCS scores, two MN patients' duration of PTA was not
determinable because of medical conditions that confounded an accurate estimate of PTA
duration. All participants' assessment data was retrieved from archived records.
Following data extraction, premorbid intelligence was estimated using the standardized
procedures for obtaining the Best Full Scale IQ estimate with the Oklahoma Premorbid
Intelligence Estimation (OPIE), a standardized, validated, reliable linear prediction
algorithm developed from the WAIS-R standardization sample (Spreen & Strauss, 1998;
Tremont, Hoffinan, Scott, Adams, & Naldone, 1997). The OPIE takes into account
demographic variables of age, education, occupation, and race, in addition to
performance on the WAIS-R Picture Completion and Vocabulary subtests (Krull, Scott,
& Sherer, 1995; Spreen & Strauss, 1998).
Measures
Wechsler Adult Intelligence Scale-Revised. The WAIS-R is considered the "gold
standard" in intelligence testing and one of the most frequently used measures in
neuropsychological batteries (Lees-Haley, Smith, Williams, & Dunn 1996; Scott, Sherer,
& Adams, 1995). The WAIS-R is comprised of eleven subtests that yield a Full Scale IQ
13
(FSIQ) score. Of these eleven subtests, six are verbal subtests while five are performance
subtests. The verbal subtests combine to form a Verbal IQ (VIQ) score and the
performance subtests combine to form a Performance IQ (PIQ) score. With the
exceptions of the WAIS-R Object Assembly (r = .68) and Picture Arrangement (r = .74),
it has extremely high overall split-half reliability (ranging from r = .81 to .97). Finally,
test-retest reliability ranged from r = .69 to .95 for 25-34 year-olds and from r = .67 to .97
for 45-54 year olds depending upon the subtest (Wechsler, 1981).
Wechsler Memory Scale/Wechsler Memorv Scale-Revised. The WMS-R is a
widely used and accepted individually administered memory assessment device. The
WMS-R contains nine subtests and was designed as a diagnostic instrument for use
during general neuropsychological examinations or other clinical examinations where
memory performance is at question (Wechsler, 1987). Assessment of immediate and
delayed verbal and visual memory, as well as assessment of auditory memory for
numerical information, cognitive speed and flexibility, and orientation information is
accomplished with the WMS-R. Average intemal consistency ranges from r = .41
(Verbal Paired Associates II) to r = .88 (Digit Span) across the subtests. Interrater
reliability for Logical Memory and Visual Reproduction subtests were r = .99 and r = .97
respectively (Wechsler, 1987). Some subjects in this investigation received the WMS
(Wechsler, 1945) instead of the WMS-R. The WMS has also been a widely used an
accepted memory measurement device with a large body of literature supporting its use
across a variety of clinical populations (Wechsler, 1987). Differences between the two
versions include the addition of the Figural Memory, Visual Paired Associates, and
14
Visual Memory Span subtests in the newer WMS-R. Moreover, in comparison, minor
changes (e.g., easier items added to Visual Reproduction, Information and Orientation
subtests lengthened, et cetera) were made across some subtests from the WMS to the
WMS-R. It should be noted that Memory Quotients were not used in this investigation.
Finally, this study standardized the two versions by converting all scores to standard z-
scores so that the different versions could be compared on the same metric.
Controlled Oral Word Association Test. The COWA (a.k.a. FAS) is a measure of
phonemic fluency that measures an individual's ability to spontaneously produce word
beginning with a specific letter (i.e., F, A, and S) under time constraints. Specifically,
individuals are given one-minute to produce as many words as possible that begin with
the letters F, A, and S. Testing rules include that individuals may not provide words
which are proper names (e.g., Phyllis, Phoenix, et cetera) or words that have the same
beginning but different endings (e.g., eat and eating). Provided words are examined to
help provide insight into a search strategy and for errors (e.g., perseverations, intrusions,
and paraphasias) to elucidate evidence towards the diagnosis of certain types of disorders.
Inter-rater reliability estimates range from r = .70 to .88 (Spreen & Strauss, 1998) for this
measure.
Stroop. The Stroop is a measure of selective attention and cognitive flexibility
that also taps into executive fiinctioning (Spreen & Strauss, 1998). The Stroop has three
parts that require the individual to name the color of X's (Stroop Color), name the color
of non-color words (e.g., "when," "hard," and "over" printed in blue, red, yellow, or
green; Stroop Word), and name the color of color words (e.g., the words "blue," "red,"
15
"yellow," or "green" printed in a color other then the one the word describes; Stroop
Color-Word). Time to completion and number of errors are recorded for each of these
parts. The Stroop is based on the pretense that it will take longer to name the color of
color words, due to interference, than it takes to name the color of X's. Spreen and
Strauss (1998) reported test-retest reHability estimates of r = .90, .83, and .91 for Stroop
Color, Stroop Word, and Stroop Color-Word, respectively.
Clock Face Drawing Test. Clock face drawing tests require visuospatial,
graphomotor, and executive functioning abilities for successful completion. However,
Royal, Cordes, and Polk (1998) have devised an executive clock drawing task, the
CLOX, with a scoring system that reflects the specific contribution of executive
functioning over visuospatial praxis abilities. The CLOX scoring system has two parts, a
free-drawing condition (CLOXl), and a copy condition where the examiner provides a
model (CL0X2). CLOXl inherently requires more executive functioning abilities, and
the subtraction of CLOXl from CL0X2 reflects the specific contribution of executive
control (Royall et al , 1998). The CLOX scoring system has high intemal consistency
(Cronbach alpha = .82). Interrater reliability on the two conditions CLOXl and CL0X2
are r = .94 and r = .93 respectively (Royall et al, 1998).
Trail Making Test TTMT-A; TMT-B). The Trail Making Test taps into
information processing speed, knowledge of numerical and alphabetical sequencing,
visual search/scan abilities, motor functioning, and mental flexibility. Part A (TMT-A)
requires the participant to connect by pencil, in order, twenty-five encircled numbers that
are randomly distributed on a page. Part B (TMT-B) requires the participant to correctly
16
connect by pencil, in correct sequence, twenty-five encircled numbers and letters in
alternating order. Time to completion and number of errors committed is determined.
Comparison of a participants' TMT-A versus TMT-B competed protocols yields
information regarding their mental flexibility. Therefore, this comparison is considered
to provide insight into an individual's executive functioning abilities because TMT-A and
B tap into the same domains minus the ability to alternate between numbers and letters.
Interrater reliability varies by study, but Spreen and Strauss (1998) reported it as .94 for
TMT-A and .90 for TMT-B.
17
CHAPTER III
RESULTS
Demographics
Demographic characteristics by sample are presented in Table 3.1. A one-way
three-group analysis of variance (ANOVA) revealed no group differences for education
[F (2, 48) = .078, E = .925], or time since injury [F (2, 45)= 2.03 e = -143], but a
significant age effect [F (2, 48) = 5.56, p = .007] was observed between the CHI-C, CHI-
NC, and MN groups. Additional one-way ANOVAs revealed that age approached
significance between the CHI-C and CHI-NC groups [F (1,24) = 3.73, p = .065], was
significantly different between the CHI-C and MN groups [F (1, 40) = 11.42, p = .002],
and was not statistically different between the CHI-NC and MN groups [F (1, 32) = .04, p
= .851]. Mean time since injury until assessment was 167 days (SD = 308) for the CHI-C
group, 76 days (SD = 109) for the CHI-NC group, and 44 days (SD = 46) for the MN
group. The relations between GCS/PTA and the demographic variables of age,
education, and occupation were examined and no significant correlations were observed
for the CHI-C and CHI-NC groups (see Table 3.2). However, age was significantly
related to the GCS for the MN group while education and occupation were not.
Correlations between PTA and age, education, and occupation were not statistically
significant for the MN group. However, sample size may have reduced the ability to
identify relationships.
18
Table 3.1: Demographic Characteristics of Sample by Percentage.
Gender Males Females
Race Caucasian African-American Latin-American Other
Marital Status Married Single Divorced Widow/er
Occupation Professional/Technical Managers/Administrator/
ClericaVSales Craftsman/Foreman Operators/Service/
Domestic/Farmers Laborers Unemployed
Retired Yes No
CHI-C
17.6(52.9) 15.7(47.1)
15.7(47.0) 3.9(11.8) 9.8 (29.4) 3.9(11.8)
17.6(52.9) 11.8(35.3) 0.0 (00.0) 3.9(11.8)
5.9(17.6)
3.9(11.8) 2.0 (05.9)
11.8(35.3) 7.8 (25.3) 2.0 (05.9)
5.9(17.6) 27.5 (82.4)
CHI-NC
9.8 (56.6) 7.8 (44.4)
13.7(77.8) 0.0 (00.0) 3.9 (22.2) 0.0 (00.0)
11.8(66.7) 2.0(11.1) 0.0 (00.0) 3.9 (22.2)
5.9(33.3)
3.9 (22.2) 0.0 (00.0)
2.0(11.1) 5.9 (33.3) 0.0 (00.0)
11.8(66.7) 5.9(33.3)
MN
23.5 (48.0) 25.5 (52.0)
37.3 (76.0) 0.0 (00.0)
11.8(24.0) 0.0 (00.0)
29.4 (60.0) 2.0 (04.0) 2.0 (04.0)
15.7(32.0)
7.8(16.0)
9.8 (20.0) 2.0 (04.0)
19.6(40.0) 9.8 (20.0) 0.0 (00.0)
27.5 (56.0) 21.6(44.0)
Note: CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic. Scores in parentheses represent percentages within group.
19
Table 3.2: Correlations between GCS/PTA and demographic variables by group.
CHI-C (n=17)
Age Education Occupation Time since injury
CHI-NC (n = 9)
Age Education Occupation Time since injury
MN (n = 25)
Age Education Occupation Time since injury
GCS
.398
.127 -.264 -.024
.538 -.165 -.280 .099
.496 -.107 .043
-.094
p-value
.114
.628
.307
.928
.135
.671
.466
.801
.019*
.636
.848
.677
PTA
-.334 -.371 .433 .381
-.446 -.382 .612
-.049
-.119 -.403 -.079 .095
p-value
.190
.142
.083
.131
.228
.311
.080
.901
.589
.057
.721
.684
Note.- CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic. •Denotes statistically significant correlations.
20
No correlations were calculated between GCS/PTA and history of alcoholism,
drug abuse, neurologic condition, and/or psychiatric history for the CHI-C group because,
by definition, this group was excluded for these conditions. However, as can be seen in
Table 3.3, within the CHI-NC group GCS performance was significantly correlated with
a history of drug abuse (r = -.881, p = .001) and neurologic condition (r = .621, p = .037),
but not alcoholism (r = -.438, p = .094) or psychiatric condition (r = .027, p = .473).
Duration of PTA for the CHI-NC group was significantly correlated with history of drug
abuse (r = .807, p = .004), but was not significantly correlated with alcoholism (r = .395,
P = .114), neurologic condition (r = -.485, p = .093), or psychiatric history (r = -.381, p =
.156). However, small sample size in the CHI-NC group may have obscured the
relationships between the GCS/PTA and alcoholism, neurologic condition, and
psychiatric history for this group.
As seen in Table 3.3, history of alcoholism, drug abuse, neurologic condition, and
psychiatric problems were not significantly related to GCS or PTA for the MN group
despite the greater power available with the increased sample size of the MN group. It
should be noted that if the MN group (n = 25) was broken down into "clean" and "not
clean" subgroups it would have 12 "clean" and 13 "not clean" participants. Removal of
the MN "clean" participants and re-computation of the correlations between pre-morbid
history variables (e.g., history of alcoholism) and GCS/PTA also did not yield any
significant relationships. Overall, the significant correlations between drug abuse and
GCS/PTA plus the magnitude of correlations between alcoholism, neurologic condition
and psychiatric condition and GCS/PTA for the CHI-NC group suggest that the
21
Table 3.3: Correlations between GCS/PTA and pre-morbid history variables.
GCS
CHI-NC (n = 9)
History of: Alcoholism -.438 Drug Abuse -.881 Neurologic Condition .621 Psychiatric Condition .027
MN (n = 25)
History of: Alcoholism -.305 Drug Abuse* Neurologic Condition .139 Psychiatric Condition .237
p-value
.094
.001
.037
.473
.084
.269
.144
PTA
.395
.807 -.485 -.381
-.288
-.092 -.195
p-value
.114
.004
.093
.156
.091
.338
.187
Note: CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic •There was no reported drug abuse for any of the mixed neurologic participants.
22
segregation of the closed head injury group for history of drug abuse, alcoholism,
neurologic problem, and psychiatric condition was a valid procedure.
Glasgow Coma Scale and Posttraumatic Amnesia Analyses
A one-way analysis of covariance (ANCOVA) for all three groups, witii age as
the covariate, found no statistically significant differences between groups for the GCS [F
(2, 43) = 1.21, p = .305] or PTA [F (2,44) = .668, p = .518] variables. Three MN
participants were excluded from the GCS comparisons between group because of missing
GCS scores, whereas two MN participants were excluded from the PTA comparisons
because their PTA duration was indeterminable. The CHI-C group had a mean GCS
score of 9.41 (SD = 5.34) and mean PTA duration of 365.82 hours (SD = 506.22). The
CHI-NC group mean GCS score was 13.56 (SD = 2.79) and 105.67 hours (SD = 185.09)
mean PTA duration. The MN group had a mean GCS score of 12.91 (SD = 3.29) and
mean PTA duration of 302.35 hours (SD = 426.88). According to the GCS and PTA
severity classification systems from Lezak (1995; Appendix B), the GCS severity level
by group was as follows: the CHI-C group had 7 mild, 2 moderate, and 8 severe
participants; the CHI-NC group had 7 mild, 1 moderate, and 1 severe participant; and the
MN group had 17 mild, 1 moderate, and 4 severe participants. The severity levels by
group according to the PTA severity classification system (Lezak, 1995; Appendix B)
were as follows: the CHI-C group had 5 mild, 2 moderate, and 10 severe participants; the
CHI-NC group had 3 mild, 3 moderate, and 3 severe participants; and the MN had 8
mild, 2 moderate, and 13 severe participants. Thus, the CHI-C group had more severely
23
impaired individuals according to the GCS and duration of PTA severity classification
systems, although this was not reflected as a significant difference between mean scores.
Patterns of correlations between GCS/PTA and cognitive outcome variables
Inspection of the pattern of correlations between the GCS/PTA severity measures
and the cognitive outcome variables is instructive with respect to the following issues.
First, the magnitude of correlations can be compared between the log transformed and
non-log transformed GCS and duration of PTA and cognitive outcome variables.
Second, the magnitude and significance of correlations can be compared between the
CHI-C, CHI-NC, and Closed Head Injury-Combined (CHI-Comb) groups.
Inspection of the distributions of the GCS and the PTA variables found that both
scales had a skewed distribution of scores due to the number of individuals with a score
of zero for PTA duration and GCS score of fifteen. Furthermore, as a group, individuals
with very mild head injury scores showed a wide range of performance on the cognitive
measures compared to a more circumscribed performance observed when scores were
above zero on the PTA and below fifteen on the GCS (see Figures 3.1 & 3.2).
Consequently, the PTA and GCS variables were transformed to logarithms (Log x lo + 1
for PTA and Log x lo for GCS) for purpose of computing linear correlation (Howell,
1992).
Table 3.4 illustrates that, prior to logarithmic transformations, the CHI-C group
had a total of 14 significant correlations between GCS as well as 14 significant
correlations between PTA and the 48 cognitive outcome variables examined. Following
24
CO
Cm-C: RELATIONSHIP BETWEEN
PTA DURATION AND FSIQ
0 200 400 600 800 1000 1200 1400 1600
Time since injury in hours.
Figure 3.1 The relationship between PTA duration and FSIQ scores for the CHI-C group.
25
c/ I—I CO
CHI-C: RELATIONSHIP BETWEEN
THE GCS AND FSIQ
5 6 8 9 10 11 12 13 14 15 16
GLASGOW COMA SCALE SCORE
Figure 3.2 The relationship between the GCS and FSIQ for the CHI-C group.
26
Table 3.4: Significant correlations by group between GCS/PTA and cognitive outcome variables (CHI-C).
GCS p-value PTA p-value
CHI-C (n= 17)
WAIS-R Arithmetic Scaled Block Design Comprehension Comprehension Scaled Digit Symbol Scaled Similarities Scaled Vocabulary Vocabulary Scaled
FDI VCI PIQ VIQRAW VIQ FSIQ
COWA S
Stroop Color in seconds
.424
.458
.497
.577
.424
.456
.569
.606
.397
.557
.387
.422
.525
.481
.415
-.567
.045
.037
.021
.008
.045
.033
.005
.005
.057*
.010
.069*
.046
.015
.030
.049
.014
,475 ,468 ,489 ,532 ,545 ,451 ,564 579
540 ,528 ,471 444 ,516 540
.027
.027
.023
.014
.012
.035
.018
.007
.015
.015
.033
.037
.017
.015
.277 .14r
.140 .309^
NUMBER OF SIGNIFICANT CORRELATIONS FOR CHI-C GROUP BY: GCS = 14/48 (29%) PTA = 14/48 (29%) GRAND TOTAL = 28/96 (29%)
Note: CHI-C = Closed Head Injury-Clean. The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. •These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA).
27
the logarithmic transformation, the number of significant correlations changed to a total
of 7 significant correlations between the GCS and the 48 cognitive variables and 23
significant correlations for PTA with these same cognitive outcome variables (see Table
3.5). The average magnitude of the significant correlations, post-transformation, between
the GCS and PTA were r = .35 and r = .54 respectively for the CHI-C group. Before
logarithmic transformation, the CHI-NC group had a total of 6 significant correlations
between GCS and 2 significant correlations between PTA and the 48 cognitive outcome
variables (see Table 3.6). Logarithmic transformation resulted in 9 significant
correlations between GCS and the 48 cognitive outcome variables, and 1 for PTA and
these same variables (see Table 3.7). The average magnitude of the significant
correlations, post-transformation, between the GCS and PTA were r = .65 and r = .36
respectively for the CHI-NC group.
When the CHI-C and CHI-NC groups were combined to form the CHI-Comb
group this resulted in only 2 significant correlations between the GCS and the 48
cognitive outcome variables and 8 for PTA and these same variables pre-logarithmic
transformation (see Table 3.8). Following logarithmic transformation, 2 significant
correlations were found between GCS and the 48 cognitive outcome variables, and 16
between PTA and these same variables (see Table 3.9). Furthermore, despite the
increased sample size, the magnitude of the correlations for the CHI-Comb group were
equal to or smaller than those for the equivalent variables in the CHI-C group. Overall,
the average magnitude of the significant correlations, post-transformation, between the
GCS and PTA were r = .29 and r = .44 respectively for the CHI-Combined group.
28
Table 3.5: Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (CHI-C).
GCSLOG
CHI-C (n= 17)
WAIS-R Arithmetic .253 Arithmetic Scaled .362 Block Design .098 Comprehension .416 Comprehension Scaled .493 Digit Symbol Scaled .378 Information .197 Information Scaled .255 Picture Arrangement Scaled .328 Similarities Scaled .399 Vocabulary .511 Vocabulary Scaled .541
FDI .329 POI .273 VCI .469 PIQRAW .031 PIQ .328 VIQRAW .340 VIQ .436 FSIQRAW .178 FSIQ .394
Stroop Color in seconds -.548 Color-Word in seconds -.313
p-value
.163*
.076*
.359*
.048
.022
.067*
.225*
.162*
.107*
.056*
.018
.012
.099*
.153*
.029
.455*
.107*
.091*
.040
.254*
.066*
.017
.138*
PTALOG p-value
-.485 -.604 -.549 -.605 -.633 -.591 -.496 .501 .508 .516 .610 .638
.495
.416
.634
.279
.542
.561
.612
.454
.615
540 509
.025
.005
.014
.005
.003
.006
.022
.020
.023
.017
.005
.003
.022
.054
.003
.148
.015
.010
.005
.039
.006
.019
.032
NUMBER OF SIGNIFICANT CORRELATIONS FOR CHI-C GROUP AFTER TRANSFORMATION BY: GCS = 7/48 (15%) PTA = 23/48 (48%) GRAND TOTAL = 30/96 (31%)
Note: CHI-C = Closed Head Injury-Clean. The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA).
29
Table 3.6: Significant correlations by group between GCS/PTA and cognitive outcome variables (CHI-NC).
GCS p-value PTA p-value
CHI-NC (n = 9)
WAIS-R Digit Symbol Scaled Similarities Scaled
WMS-R Logical Memory I Logical Memory II
COWA F A S Total Score
-.670 -.595
-.642 -.665
-.592 -.713 -.684 -.737
.035
.046
.060*
.051*
.047
.049
.021
.012
082 167
748 855
248 208 178 235
.423*
.333*
.026
.007
.260*
.141*
.323*
.271*
NUMBER OF SIGNIFICANT CORRELATIONS FOR CHI-NC GROUP BY: GCS = 6/48 (15%) PTA = 2/48 (4%) GRAND TOTAL = 8/96 (8%)
Note: CHI-NC = Closed Head Injury-Not Clean. The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA).
30
Table 3.7: Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (CHI-NC).
GCSLOG p-value PTALOG p-value
CHI-NC (n = 9)
WAIS-R Digit Symbol Scaled Similarities Scaled
WMS-R Logical Memory I Logical Memory II Mental Control
-.641 -.604
-.677 -.715 -.632
.043
.042
.048
.035
.047
059 .267
508 606 ,275
.445*
.243*
.123*
.075*
.255*
Verbal Memory Index -.797 .053* .410 .247'
-.750 .043 Stroop
Color in
COWA F A S
seconds
Total Score
.425
-.596 -.713 -.666 -.730
.20 r
.045
.016
.025
.013
283 001 090 156
.230*
.999*
.410*
.345*
NUMBER OF SIGNIFICANT CORRELATIONS FOR CHI-NC GROUP AFTER TRANSFORMATION BY: GCS = 9/48 (19%) PTA = 1 /48 (2%) GRAND TOTAL = 10/96 (10%)
Note: CHI-NC = Closed Head Injury-Not Clean. The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA).
31
Table 3.8: Significant correlations by group between GCS/PTA and cognitive outcome variables (CHI-Combined).
GCS p-value PTA p-value
CHI-Combined (n = 26)
WAIS-R Arithmetic Scaled Comprehension Scaled Vocabulary Vocabulary Scaled
FDI VCI VIQ FSIQ
.312
.317
.322
.329
.274
.295
.331
.235
.061*
.057*
.054*
.050
.088*
.071*
.049
.141*
,383 ,334 417 407
331 ,373 401 394
.027
.048
.017
.020
.049
.030
.021
.031
NUMBER OF SIGNIFICANT CORRELATIONS FOR THE CHI-COMBINED GROUP BY: GCS = 2/48 (4%) PTA = 8/48 (17%) GRAND TOTAL = 10/96 (10%)
Note: The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA).
32
Table 3.9: Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (CHI-Combined).
GCSLOG p-value PTALOG p-value
CHI-Combined (n = 26)
WAIS-R Arithmetic Scaled Comprehension Comprehension Scaled Digit Symbol Scaled Information Information Scaled Picture Arrangement Scaled Similarities Scaled Vocabulary Vocabulary Scaled
FDI VCI PIQ VIQRAW VIQ FSIQ
WMS-R Information Visual Paired Associates II
Stroop Word in seconds
.278
.196
.291
.094
.139
.208
.131
.136
.310
.320
.238
.271
.068
.210
.296
.202
.181 -.420
-.347
.084*
.168*
.075*
.327*
.250*
.154*
.272*
.254*
.061*
.056*
.120*
.090*
.379*
.152*
.071*
.178*
.194*
.041
.049
,450 .386 .420 .353 .522 .516 .365 .389 .548 .545
.383
.523
.374
.447
.522
.509
.330 322
.011
.026
.017
.042
.003
.004
.040
.023
.002
.002
.027
.003
.039
.011
.003
.066*
.054*
.097*
.459 .024
NUMBER OF SIGNIFICANT CORRELATIONS FOR THE CHI-COMBINED GROUP AFTER TRANSFORMATION BY: GCS = 2/48 (4%) PTA = 16/48 (33%) GRAND TOTAL = 18/96 (19%)
Note: The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA).
33
Before logarithmic transformation, the MN group had 13 significant correlations
between the GCS and the 48 cognitive outcome variables and 15 between PTA and these
same variables (see Table 3.10). Following logarithmic transformation tiie number of
significant correlations was 13 between the GCS and the 48 cognitive outcome variables,
and 28 for PTA these same variables (see Table 3.11). The average magnitude of
significant correlations, post-transformation, between the GCS and PTA for the MN
group were r = .36 and r = .47, respectively.
Based upon the number of significant correlations, following logarithmic
transformation, across groups the GCS had a total of 31 significant correlations with
cognitive outcome variables as compared to 68 between PTA duration and these same
variables. Therefore, in response to the issue concerning the reliability of PTA duration
versus the GCS in predicting cognitive outcome, it appeared that PTA duration was
generally the more reliable predictor. Furthermore, greater predictability resulted when
PTA duration was log transformed to overcome the skewness in the distribution of PTA
scores across groups. This skewness was due to the wide range of performance on
cognitive outcome variables when there was no PTA (PTA = 0). To assess whether
including both the GCS and or PTA in a prediction equation would improve
predictability above the GCS or PTA duration alone, stepwise multiple linear regressions
were computed with each cognitive outcome variable. The results of these analyses
indicated that adding both of these severity indicators into a regression equation did not
improve predictability above that of either one of them alone.
34
Table 3.10: Significant correlations by group between GCS/PTA and cognitive outcome variables (MN).
GCSLOG p-value PTALOG p-value
MN (n = 25)
WAIS-R Comprehension Comprehension Scaled Digit Span Digit Span Scaled Information Information Scaled Picture Arrange. Scaled Vocabulary Vocabulary Scaled
FDI VCI VIQRAW VIQ FSIQ
WMS-R Information Logical Memory II Attention/Concentration
Index
Stroop Word in seconds Word # of errors Color-Word # of errors
.370
.397
.288
.336
.478
.523
.498
.352
.383
.335
.423
.423
.417
.363
.147 .041
.298
-.627 -.642 -.483
.050
.037
.097*
.063*
.014
.007
.013
.059*
.043
.069*
.028
.028
.030
.058*
.257*
.431*
293 298 360 356 371 354 261 482 ,513
,387 401 302 ,444 ,370
,458 ,367
.093*
.089*
.046
.048
.045
.053*
.126*
.011
.007
.037
.032
.086*
.019
.050
.014
.046
.174* -.497 .035
.001
.001
.034
Trail Making Test (TMT-A; TMT-B) TMT-A # of errors -.170 .243* TMT-B # of errors -.526 .039
NUMBER OF SIGNIFICANT CORRELATIONS FOR THE MN GROUP BY: GCS = 13/48 (27%) PTA = 15/48 (31%) GRAND TOTAL = 28/96 (29%)
.314
.485
.569
.522 -.085
.077*
.011
.011
.009
.391*
Note: MN = Mixed Neurologic. The total number of cognitive outcome variables examined from the WAIS-R, WMSAVMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for companson to the other severity indicator (i.e., GCS or PTA).
35
Table 3.11: Significant correlations by group between transformed GCS/PTA and cognitive outcome variables (MN).
GCSLOG p-value PTALOG p-value
MN (n = 25)
WAIS-R Arithmetic Arithmetic Scaled Comprehension Comprehension Scaled Digit Span Digit Span Scaled Information Information Scaled Picture Arrangement Picture Arrange. Scaled Picture Completion Picture Completion Scaled Vocabulary Vocabulary Scaled
FDI VCI PIQ VIQRAW VIQ FSIQRAW FSIQ
WMS-R Information Attention/Concen. Index Visual Reproduction I
Stroop Word in seconds Word # of errors Color-Word # of errors
.178
.235
.395
.413
.300
.346
.474
.512
.279
.497
.128
.330
.353
.389
.336
.427
.272
.423
.419
.237
.358
.187
.323
.149
-.662 -.651 -.491
Trail Making Test (TMT-A; TMT-B) TMT-A # of errors .340 TMT-B # of errors -.502
.220*
.152*
.038
.031
.088*
.058*
.015
.009
.117*
.013
.291*
.072*
.058*
.041
.068*
.027
.123*
.028
.029
.157*
.061*
.203*
.153*
.284*
.001
.001
.032
.077*
.048
.363
.385
.387
.430
.480
.507
.502
.502
.369
.367
.537
.562
.494
.502
.534
.495
.445
.582
.582
.542
.582
•.427 -.573 .484
.369
.376
.630
.472
.269
.049
.039
.038
.023
.010
.007
.009
.009
.050
.051*
.005
.004
.010
.009
.005
.010
.022
.002
.002
.006
.003
.021
.016
.021
.046
.043
.005
.018
.188*
36
Table 3.11: Continued.
GCSLOG p-value PTALOG p-value
COWA S -.343 .059* -.462 .013
NUMBER OF SIGNIFICANT CORRELATIONS FOR THE MN GROUP AFTER TRANSFORMATION BY: GCS = 13/48 (27%) PTA = 28/48 (58%) GRAND TOTAL = 41/96 (43%)
Note: MN = Mixed Neurologic The total number of cognitive outcome variables examined from the WAIS-R, WMS/WMS-R, Stroop, Trail Making Test, and COWA was 48. *These correlations did not reach statistical significance, but were included for comparison to the other severity indicator (i.e., GCS or PTA)
37
Correlational patterns across domains
Significant first-order Pearson correlations between the cognitive outcome
variables and the transformed severity indicators can be seen in Tables 3.5, 3.7, 3.9, and
3.11. Examination of these various groups' tables revealed some trends. The GCS
consistently had significant positive relations with the WAIS-R subtests (cf, Paniak et
al., 1992) thought to be more resistant to the effects of a head injury (e.g.. Vocabulary)
for the CHI-C and MN groups (Farr, Greene, Fischer-White, 1986). Consequently,
significant positive relations between the GCS and the VCI and VIQ for the CHI-C and
MN groups resulted. For the CHI-NC group, the GCS was significantly and inversely
related to the WAIS-R Digit Symbol and Similarities subtests, but no other significant
relationships with any indices or summary scores resulted. When the CHI-C and CHI-
NC groups were combined into the CHI-Comb group, all significant relations between
the WAIS-R variables and the GCS disappeared as shown in Table 3.9. Finally, with the
exception of the CHI-NC group, duration of PTA was consistently and inversely related
across a variety of WAIS-R variables, indices, and summary scores at a statistically
significant level.
No consistently significant relationships were observed between the GCS or PTA
duration and the WMS-R memory variables across groups (see Tables 3.5, 3.7, 3.9, and
3.11). Likewise, the GCS and duration of PTA were not consistently and significantly
related across the CHI-C, CHI-NC, and MN groups for the Stroop, Trail Making Test,
CLOX, or COWA variables.
38
Comparison bv group on cognitive outcome variables
Although the groups did not differ significantly on the severity indices, all
cognitive variables were submitted to one-way ANCOVAs with age as a covariate and
CHI-C, CHI-NC, and MN as the groups. Despite the multiple analyses, no significant
group differences were observed. Means and standard deviations for the cognitive
measures by group can be seen in Tables 3.12-3.14. It should be noted that the
ANCOVA for a VIQ/PIQ discrepancy by group just failed to obtain statistical
significance [F (2, 42) = 3.01, p = .059]. The VIQ/PIQ mean discrepancies by group
were CHI-C = 6.13 (SD = 10.22), CHI-NC = 18.14 (SD = 15.54), and MN = 4.52 (SD =
14.52). However, the low sample size (n = 9) in the CHI-NC group may have resulted in
lowered power to detect group differences.
Comparison bv group: Pre/Post Intellectual Functioning
The calculation of OPIE pre-morbid IQ scores permitted a unique analysis for the
IQ measures. Although the CHI-C and CHI-NC groups did not significantly differ in
level of initial severity, it would be expected that the CHI-NC would be more vulnerable
to the effects of a closed head injury than the CHI-C group (Satz, 1993). A CHI-C by
CHI-NC Group by Pre-Post analysis was conducted with the OPIE scores as pre-morbid
IQ scores and the FSIQ, VIQ, and PIQ scores as the post-measures. In this analysis the
group by pre-post interaction is the same as the main effect for a change score analysis
given that the correlation between pre- and post scores is about r = .90 or greater, which it
39
Table 3.12: Means and Standard Deviations by group across WAIS-R subtests and indices.
VERBAL SUBTESTS Arithmetic Comprehension Digit Span Information Similarities Vocabulary
CHI-C (n=17)
9.35 (4.46) 8.59 (3.04) 8.88 (4.34) 7.76 (2.88) 8.41 (2.83) 8.65 (3.35)
PERFORMANCE SUBTESTS Block Design Digit Symbol Object Assembly Picture Arrangement Picture Completion
INDICES FDI POI VCI VIQ PIQ FSIQ VIQ/PIQ discrepancy
7.88 (2.66) 6.82 (2.60) 7.19(2.64) 7.75 (2.24) 7.82 (3.09)
90.93 (19.24) 87.38(14.15) 90.78 (15.46) 89.77 (16.02) 84.63 (13.76) 87.38 (14.85) 6.13(10.22)
CHI-NC (n = 9)
8.33 (2.40) 8.78 (3.63) 8.89(2.14) 8.67 (2.69) 7.78 (3.38) 9.33 (4.47)
4.71 (2.93) 5.25(2.31) 5.00 (3.79) 7.25 (3.77) 7.67 (3.57)
90.91 ( 9.54) 74.71 (20.51) 92.38(17.81) 91.89(14.23) 75.57 (17.37) 85.00(15.58) 18.14(15.54)
MN (n = 25)
7.42 (2.43) 8.21 (3.09) 7.04 (3.25) 8.21 (3.05) 7.88 (2.36) 8.25 (3.03)
6.95 (2.77) 6.48(2.91) 6.78 (3.61) 7.35 (2.60) 7.42 (2.65)
83.37(14.30) 83.61 (15.72) 89.56(14.05) 87.21 (14.01) 83.04(12.67) 85.13(11.67) 7.70(15.63)
Note: CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic. Means with standard deviations in parentheses.
40
Table 3.13: Means and Standard Deviations by group across WMS/WMS-R subtests and indices, Stroop, and Trail Making Test.
CHI-C (n=17)
CHI-NC (n = 9)
MN (n = 25)
WMS-R* Figural Memory Logical Memory I Logical Memory II Mental Control Verbal Paired Assoc. I** Verbal Paired Assoc, n Visual Memory Scan Visual Paired Assoc. I Visual Paired Assoc. II Visual Reproduction I Visual Reproduction n
WMS-R INDICES Attention/Concentration Delayed Recall General Memory Verbal Memory Visual Memory
STROOP Color time in sees. Color errors Word time in sees. Word errors Color-Word time in sees. Color-Word errors
-.07 ( .93) -.14 ( .74) -.06 ( .90) .33 ( .96) .18(1.01) .11(1.10)
-.15 ( .89) -.08 ( .95) .03 ( .96) .48 ( .98) .34(1.07)
92.23 (25.63) 76.77 (19.58) 71.31 (16.08) 74.54(15.95) 80.54(17.98)
21.93 ( 8.84) .47 ( .92)
23.06(12.82) 1.38 ( 2.33)
50.14(22.69) 3.93 ( 5.74)
TRAIL MAKING TEST (TMT-A; TMT-B) TMT-A time in sees. 51.47 (16.24) TMT-A errors .06 ( .24) TMT-B time in sees. 167.18 (92.37) TMT-B errors 1.71 ( 3.05)
.21 (1.26) -.10(1.13) .29(1.35)
-.04 ( .71) -.13 ( .95) -.08(1.00) .38(1.27) .20(1.23)
-.08(1.21) -.26(1.48) .03(1.40)
89.00 (19.56) 87.25 (24.58) 77.75 (32.48) 78.80 (20.96) 86.50 (35.59)
23.17(12.47) 1.83 ( 3.25)
18.88 ( 7.59) .13 ( .35)
24.60 ( 8.85) .40 ( .89)
128.67 (97.80) .22 ( .44)
241.23(92.38) .67 ( .58)
-.15(1.10) .12(1.12)
-.05 ( .96) -.22(1.07) -.09(1.01) -.06 ( .94) -.08 ( .91) -.05 ( .81) .04 ( .99)
-.31 ( .67) -.35 ( .63)
84.64(16.35) 76.67(15.01) 80.25 (17.90) 83.36 (20.50) 82.00(11.98)
32.09 (16.25) 2.00 ( 3.26)
32.17(33.29) 1.00 ( 1.87)
51.83(23.26) 7.61 ( 8.35)
78.19(66.69) 100.27 (78.44) 250.89 (97.48)
1.53 ( 2.79)
Note: CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head hijury-Not Clean; MN = Mixed Neurologic. *A11 Wechsler Memory Scale subtest data is presented as a z-score, which has a mean of 0 and a standard deviation of 1. **Assoc. = Associates. Means with standard deviations in parentheses.
41
Table 3.14: Means and Standard Deviations by group for the Clock Face Drawing Test and COWA.
CHI-C (n=17)
CLOCK FACE DRAWING TEST CLOXl CLOX2 Fraction Score
COWA F A S FAS Total
11.36( 2.73) 13.50 ( .94)
.55 ( . 27)
8.47 ( 5.59) 7.47 ( 5.14) 8.59 ( 4.54)
24.94 (14.91)
CHI-NC (n = 9)
9.40 (3.97) 11.20(4.09)
.54 ( .23)
7.56 (3.47) 4.33(2.18) 7.00 (4.06)
18.89(8.67)
MN (n = 25)
9.74 ( 2.86) 11.90( 2.38)
.55 ( .68)
6.32 ( 4.21) 6.39 ( 4.56) 6.04 ( 4.13)
16.88(11.07)
Note: CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic. Means with standard deviations in parentheses.
42
is in this study Huck & McLean (1975). The correlations between pre- and post-FSIQ,
VIQ and PIQ were r = .91, r = .90, and r = .78, respectively.
One-way ANOVA comparisons of the various OPIE pre-morbid indices (i.e.,
OPIE-Best, OPIE-FSIQ, OPIE-VIQ, and OPIE-PIQ) by group (i.e., CHI-C, CHI-NC, and
MN) were not statistically different by group as expected (refer to Table 3.15 for means
and standard deviations by group). This lack of difference in the pre-injury OPIE scores
is why the main effect for group, which is a combination of pre- and post-injury scores, is
underestimated in this design and not interpretable (Huck & McLean, 1975). Also, as
expected, significant differences were found within each group between their obtained
and predicted mean FSIQ scores, using the OPIE Best as the estimate of pre-morbid
abilities (see Table 3.16), indicating that head injury had a negative influence on
cognitive performance.
When the CHI-C and CHI-NC groups were compared for the age-standardized
post-injury IQ scores only, there were no significant differences between CHI-C and
CHI-NC for the FSIQ [F (1, 21) = .121, p = .731], VIQ [F (1, 21) = 1.802, p = .742], or
PIQ [F (1, 24) = 111, p = .194] summary scores. However, the VIQ/PIQ discrepancy was
significantly different [F (1, 22) = 4.90, p = .038] between the CHI-C and CHI-NC
groups with the CHI-C group demonstrating less discrepancy. The average VIQ/PIQ
discrepancy for the CHI-C group was 6.13 (SD = 10.22), while the CHI-NC was 18.14
(SD = 15.54), see Figure 3.3.
43
Table 3.15: ANOVA comparison of OPIE formulas by group.
CHI-C (n=17)
CHI-NC (n = 9)
MN (n = 25)
p-value
OPIE BEST OPIE VIQ OPIE PIQ
97.11 (14.88) 93.31(15.86) 92.51(13.54)
99.58(16.66) 95.80(18.55) 94.17(15.74)
97.51 (12.30) 92.90(14.51) 93.21 (12.48)
.9067
.8920
.9556
MN = Mixed Neurologic. OPIE BEST = FSIQ estimate calculated with the best of either the participant's Vocabulary or Picture Completion raw score.
OPIE VIQ = VIQ estimate calculated with the Vocabulary raw score. OPIE PIQ = PIQ estimate calculated with the Picture Completion raw score.
44
Table 3.16: Mean Difference Between Obtained and Predicted IQ's Using the OPIE Best Formula Presented by Diagnostic Category and the Total Sample.
Group N FSIQ Obtained M(SD)
FSIQ Best M(SD) Difference p-value
CHI-C CHI-NC MN TOTAL
17 9
25 51
87.38 (14.85) 85.00(15.58) 86.65 (14.76) 85.89(13.18)
97.11(14.88) 99.58 (16.66) 97.51 (12.30) 97.75 (13.76)
9.73 14.58 10.86 11.86
19.45 20.52 61.15 95.26
.001
.004
.000
.000
Note: CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic.
Means with standard deviations in parentheses.
45
WMS-R SuMlAi: CHI-C Vt. CHI-NC
1
^ / / / / / / / / / /
/
WAI8-R SuUwts
Figure 3.3. Mean WAIS-R subtest scores for the CHI-C and CHI-NC groups.
46
Table 3.17 shows the means and standard deviations for the pre-morbid OPIE
scores and the post-morbid FSIQ, VIQ, and PIQ scores. The group by pre-post
interaction for the FSIQ scores was non-significant [F (1,21) = 1.01, p = .32]. The group
by pre-post interaction for the VIQ scores was also non-significant [F (1,24) = .01, p =
.90]. The group by pre-post interaction for the PIQ scores was significant [F (1,21) =
4.56, p = .04] indicating that the estimated 18.60 point reduction fi-om pre- to post-injury
in the CHI-NC group was significantly greater than the estimated 8.68 point loss in the
CHI-C group. An analysis of covariance with the pre-morbid scores as the covariate,
showed the same significant outcome.
47
Table 3.17: Means and Standard Deviations by group for Predicted versus Obtained FSIQ, VIQ, and PIQ.
CHI-C CHI-NC MN (n=17) (n = 9) (n = 25)
Predicted / Obtained Predicted / Obtained Predicted / Obtained
FSIQ 97.11 (14.88)/87.38 (14.85) 99.58 (16.66)/85.00 (15.58) 97.51 (12.30)/85.13 (11.67) VIQ 93.31 (15.86)/89.77 (16.02) 95.80 (18.55)/91.89 (14.23) 92.90 (14.51)/87.21 (14.01) PIQ 92.51 (13.54)/84.63 (13.76) 94.17 (15.74)/75.57 (17.37) 93.21 (12.48)/83.04 (12.67)
Note: CHI-C = Closed Head Injury-Clean; CHI-NC = Closed Head Injury-Not Clean; MN = Mixed Neurologic.
Means with standard deviations in parentheses.
48
CHAPTER W
DISCUSSION AND CONCLUSIONS
The primary hypothesis of this investigation was that refining the CHI group by
breaking the group into CHI-C and CHI-NC groups would improve the prediction of
cognitive outcomes fi-om the PTA and GCS severity indices. Both before and after
adjusting the PTA and GCS indices for the skewed distribution caused by the number of
zero and fifteen scores respectively, the majority of evidence supports this hypothesis.
The first evidence that separating head injury patients into CHI-C and CHI-NC
groups would lead to better prediction between severity indices and cognitive outcomes
was the presence of significant correlations between history of alcoholism, drug abuse,
neurologic condition, and psychiatric condition and the severity indicators. As seen in
Table 3.3, for the CHI-NC group the correlation between a history positive for drug abuse
and both severity indicators was extremely robust. Moreover, for the CHI-NC group,
there was a significant correlation between a history of previous neurologic insult and
GCS scores. This same relationship approached significance for duration of PTA.
Finally, for the CHI-NC group, a history positive for alcoholism approached significance
with the GCS.
Further examination of correlation Table 3.4 revealed that pre-log transformation
the CHI-C group had a total of 28 significant correlations between the GCS and PTA
duration and cognitive outcome variables. In comparison, looking at Table 3.6, the CHI-
NC group only had a total of 8 significant correlations between the GCS and PTA
49
duration and cognitive outcome variables pre-log transformation. Log transformation of
the GCS and PTA duration scores reduced the skew of the distributions and the ensuing
correlations fiirther illustrated the point that separating the groups is necessary to yield
improved prediction between severity indicators and cognitive outcome. Overall, 30
significant correlations were found between both GCS and PTA duration and cognitive
outcome variables for the CHI-C group (see Table 3.5), as compared to only 10 for the
CHI-NC group (see Table 3.7). It is acknowledged that a Bonferroni may have been
appropriate given the large number of correlations computed. However, a Bonferoni
correction was not completed because doing this across groups would have uniformly
lowered the number of significant correlations, and because a main goal of this
investigation was to find out if separating a CHI group into subgroups was a usefiil
procedure or not.
A number of the reviewed investigations had larger closed head injury samples
than this investigation (cf Alexandre et al., 1983; Brooks et al., 1980; Paniak et al.,
1992). Nevertheless, larger samples still did not translate into consistent and positive
findings across these investigations and they did not break their groups down into
subgroups. For illustrative purposes in this study, the CHI-C and CHI-NC groups were
combined into a CHI-Comb group with increased sample size (n = 26). Thus, the
probability of finding a greater number of significant correlations between severity
indicators and cognitive outcome variables could have been increased. However, as
predicted, the summation of the CHI-C and CHI-NC into a CHI-Comb group only
obscured findings as illustrated by the decreased number of significant correlations
50
between the severity indicators and cognitive outcome variables. In addition to
decreasing the number of significant correlations, the magnitude of the resuhing
correlations was also generally lower for the CHI-Comb group as compared to the CHI-C
group.
In general, it appeared that duration of PTA was a better choice as a predictor of
cognitive outcome. The magnitude of the correlations between duration of PTA and pre
morbid history variables was consistently less than that between these same variables and
the GCS indicating that the PTA may be less influenced by a history of previous head
injury, neurologic problems, mental illness, alcoholism or drug abuse. Furthermore, log
transformed PTA duration appeared to be consistently and significantly related to general
intellectual fimctioning (i.e., WAIS-R subtests, indices, and IQ summary scores) for the
CHI-C and MN group whereas the GCS was not as consistently related to these same
variables. Duration of PTA was also significantly related to a larger number of cognitive
outcome variables across groups compared to the transformed GCS. The combination of
PTA duration and the GCS were examined to determine if using them in combination
would contribute significant individual variance and improve prediction of cognitive
outcome. However, the use of both PTA and the GCS in a multiple regression equation
did not add to the predictability above that of PTA duration alone. This was likely due to
the shared variance between the GCS and PTA, and the fact that the PTA scores were
more meaningfiil for post-injury predictions. The predictability of cognitive outcomes
fi-om PTA duration was not as consistent in the other cognitive domains including
memory fimctioning, attention/concentration, executive fimctioning, or verbal fluency.
51
Overall, a primary purpose of this investigation was to examine whether separating a
closed head injury group into "clean" and "not clean" groups would improve prediction
of cognitive outcome fi-om PTA duration and/or the GCS, and it was.
Comparing the CHI-C, CHI-NC, and MN groups across the various cognitive
outcome measures with one-way ANCOVAs, covarying for the age effect, did not result
in any significant group mean differences. Significant correlations between PTA
duration and the WAIS-R variables were uniformly found for both the CHI-C and MN
group. Therefore, in this investigation, the inclusion of a MN group to illustrate what
persistent cognitive deficits were unique to the closed head injury versus a generalized
brain insult were not supported by mean differences across groups or correlational
analyses.
Few studies have attempted to adjust for the non-linear distribution of PTA and
GCS scores. This lack of linearity is due principally to the wide variability in cognitive
performance for those whose PTA duration was zero and/or had a GCS score of fifteen.
This results in a skewed distribution of scores at one end of the PTA and GCS measures.
The literature shows that approximately 90% of mild CHI patients demonstrate little or
no deficits three-months post-injury (King, 1996; Satz et al., 1999). However, between
5-15% (Alexander, 1995) report deficits (e.g., memory problems, decreased attention,
mood lability, headache, dizziness, fatigue, and diplopia) that are equal to or worse than
that of severe CHI patients several months-to-years post-injury. Therefore, inclusion of
these mild head injury patients in any investigation examining severity indices and
cognitive outcome variables can result in distributional problems. However, only a few
52
authors have attempted to correct for this difficulty (Haslam et al., 1994; Haslam et al.,
1995) by transforming their severity indices with a square-root transformation. In the
case of Haslam et al. (1994 & 1995), the square root transformation only pulled in the
outliers and did not affect the bunching of scores for the most mildly head injured
participants. Therefore, despite the transformation, the skewed score issue still remained
in these investigations. A log transformation is more appropriate when skewness is due
to a bunching of scores at one end of a distribution as well as a range of scores at the
other end of the distribution (Howell, 1992).
The use of the OPIE scores as pre-estimates of IQ fimctioning added an extra
dimension to this investigation. The OPIE was chosen as an estimate of pre-morbid
intellectual fimctioning because previous research had demonstrated that it was a reliable
estimate of pre-injury intellectual fimctioning for normals (Krull et al., 1995), and clinical
populations (Ropacki & Elias, 1999; Scott, Krull, Williamson, Adams, & Iverson, 1997).
Furthermore, the OPIE Best, OPIE VIQ, and OPIE PIQ formulas were chosen because
these prediction equations were found superior to the original OPIE FSIQ formula, which
uses both Vocabulary and Picture Completion raw scores (Scott et al., 1997), and because
these formulas most closely approximate an expected mean of 100 and standard deviation
of 15 (Ropacki & EUas, 1999; Scott et al.,1997) The use of the OPIE as a pre-morbid
indicator for comparison to post-injury performance in a pre-post design had not been
previously validated. Finally, the use of the pre-post design was possible because of the
extremely high and comparable correlations between predicted OPIE IQ scores and
obtained WAIS-R IQ scores (Huck & McLean, 1975).
53
As expected, no significant differences were found between the CHI-C, CHI-NC,
and MN groups on their predicted pre-morbid abilities, and all groups showed a
significant reduction fi-om pre-morbid estimated to post-morbid assessment. It has been
proposed that VIQ is a more stable following brain insult whereas PIQ is more sensitive
to the effects of neurologic insuh (Crosson, Greene, Roth, Farr, & Adams, 1990; Farr et
al., 1986). Therefore, it is not surprising that any difference between the mean
performance of the CHI-C and CHI-NC groups would be more likely to occur for the PIQ
comparison and the VIQ-PIQ discrepancy. This finding fits with what is referred to as
the "brain reserve capacity and threshold theory" (Satz, 1993).
Satz (1993) completed a comprehensive literature review on cognitive reserve
theory (a.k.a. brain reserve capacity or threshold theory) that is helpfiil to understanding
the CHI-C and CHI-NC group differences. Basically, according to this theory, previous
neurologic insult increases vulnerability to the fixture effects of neurologic problems such
as dementing illnesses, whereas higher education and larger head circumference serve as
buffers to the development of fiiture neurologic problems. Review of all the support for
this theory is beyond the scope of this investigation, but is well reviewed in Satz, 1993.
Since 1993, fiirther support has been found for the cognitive reserve theory in the areas of
Parkinson's disease (e.g., Glatt et al., 1996; Schmand, Smit, Geeriing, & Lindeboom,
1997), Alzheimer's disease (e.g., Alexander, Gurey et al., 1997; Graves et al., 1996),
Schizophrenia (e.g., Dwork et al., 1998), HIV (e.g., Pereda et al., 2000; Stem, Silva,
Chaisson, & Evans, 1996), but no investigations were found that examined the effects of
closed head injury on cognitive reserve. In the current investigation, there were less
54
severe head injuries in the CHI-NC group, but greater pre-post differences for PIQ and a
significantly larger VIQ/PIQ discrepancy for the CHI-NC group as compared to the CHI-
C group. Furthermore, the significant PIQ difference and VIQ/PIQ discrepancy was
found despite nearly equivalent pre-injury education levels between CHI-C and CHI-NC
groups. Examination of Figure 3.3 reveals that these significant discrepancies are largely
resultant fi-om the divergence of group performance across the performance subtests, but
especially two WAIS-R subtests that comprise the POI (i.e.. Block Design and Object
Assembly). Moreover, the subtests that make up the POI and PIQ are thought to measure
"fluid" intelligence, which is believed to be more sensitive to the effects of brain insult.
In comparison, the subtests that comprise the VIQ and reportedly reflect "crystallized"
intelligence, which is thought to be relatively stable following brain injury (Kaufinan,
1990). Overall, it appeared that the CHI-NC group was more sensitive to the effects of
the head injury than those in the CHI-C group supporting the cognitive reserve theory
with closed head injury. Moreover, these findings provide fiirther support for the need to
clean data for CHI investigations and suggest a direction for fiiture research.
Summarv and suggestions for fiiture research
In summary, this investigation contributed to the closed head injury literature in a
number of ways. First, it demonstrated that separating those with a positive pre-morbid
history of drug and alcohol abuse, neurologic condition, and psychiatric problems from
those without such a history results in increased predictability between severity indicators
and cognitive outcome variables. Duration of PTA was found to be better predictor of
55
cognitive outcome following a closed head injury in this investigation. Furthermore, this
study showed that fiiture closed head injury research should be alert to the effects of
including those with mild CHI into their samples because of potential issues of non-
linearity of data. This investigation did not find the unique effects of closed head injury
above that of other brain insuhs. That is, no mean differences were observed between the
CHI groups and the MN group. Nevertheless, it was shown that the CHI-NC was more
sensitive to the effects of head injury than the CHI-C group when pre-morbid estimates of
fimction were estimated. This latter finding is in support of the cognitive reserve theory
(Satz, 1993). Finally, this investigation has important implications not only for fiiture
research, but also for clinical practice because of the fiirther vaUdation of the OPIE with
CHI patients, and the demonstrated importance of obtaining a thorough history and
background in regards to pre-morbid history for a more accurate assessment and
diagnosis.
Future research can focus on some of this investigation's shortcomings.
Specifically, generalizability was limited in this study by the inclusion of only individuals
referred to rehabilitation following insuh. A great number of individuals are not referred
to rehabilitation following injury because they either do not seek initial medical attention,
or because lack of resources. Such individuals are often seen throughout the acute phase
of their injury and then discharged because of lack of resources (i.e., insurance). Also,
many individuals with continuing problems have a higher probability to be referred for
rehabilitation. Future investigations could somewhat ameliorate this problem by pre-
screening all emergency room admissions following closed head injury, with follow-up
56
neuropsychological assessments regardless of whether they are admitted and treated
and/or transferred to rehabilitation.
Another problem, that appears to be unavoidable, is the time since injury versus
severity of injury issue. Specifically, in this investigation the time since injury was
greater in the CHI-C group than the CHI-NC or MN groups, but not at a statistically
significant level. The CHI-C group also had a larger number of severe head injuries as
compared to the CHI-NC group, but not at a statistically significant level. It seems
logical that the more severe the injury, the longer time from injury until assessment and
that these two issues will be hard to separate in research studies. Although group
differences in times since injury and severity of injury were not significant problems for
this investigation, fiiture studies could match groups to include a more equivalent number
of patients of each severity level.
Future studies can also improve upon this investigation's findings, support the
significant findings of this study, and help fiirther delineate the effects of head injury
versus other variables. For instance, a fiiture large-scale investigation could include
multiple comparison groups including a CHI-C litigating, CHI-C non-litigating, CHI-NC
litigating, CHI-NC non-litigating, other injury group (01) excluded for pre-morbid
history variables, psychiatric group, and non-impaired group excluded for pre-morbid
history variables (e.g., those referred for neuropsychological evaluation prior to job entry
such as police officer, pilots, et cetera). Through multiple comparisons, this investigation
could help delineate what deficits are attributable to the head injury versus other factors
even if the CHI groups sustained bodily injury. Only three investigations similar to this
57
proposed investigation have been completed (Asamow et al., 1995; Bijur, Haslum, &
Goldfing, 1990; Dikmen, Machamer, Winn, & Temkin, 1995), and two of these focused
on children (Arsanow et al., 1995; Bijur et al., 1990), while none examined the effects of
litigation.
58
REFERENCES
Alexander, G. E., Furey, M. L., Grady, C. L., Pietrini, P., Brady, D. R., Mentis, M. J., & Schapiro, M. B. (1997). Association of premorid intellectual fimction with cerebral metabolism in Alzheimer's disease: implications for the cognitive reserve hypothesis. American Journal of Psvchiatrv. 154. 165-172.
Alexander, M. P. (1995). Mild traumatic brain injury: Pathophysiology, natural history, and clinical management. Neurology. 46.1253-1260.
Alexandre, A., Colombo, F., Nertempi, P., & Benedetti, A. (1983). Cognitive outcome and early indices of severity of head injury. Journal of Neurosurgerv. 59. 751-761.
Alfano, D. P., Neilson, P. M., & Fink, M. P. (1993). Long-term psychosocial adjustment following head or spinal cord injury. Neuropsvchiatrv. Neuropsvchologv. and Behavioral Neurology. 6. 117-125.
Arsanow, R. F., Satz, P., Light, R., Zaucha, K., Lewis, R., & McCleary, C. (1995). The UCLA study of mild closed-head injury in children and adolescents. In S. Broman & M. E. Michel (Eds.), Traumatic brain injury in children (pp. 117-146). New York: Oxford University Press.
Bachman, D. L. (1992). The diagnosis and management of common neurologic sequelae of closed head injury. Journal of Head Trauma Rehabilitation. 7. 50-59.
Barth, J. T., Macciochi, S. N., Giordani, B., Rimel, R., Jane, J. A., & Boll, T. J. (1983). Neuropsychological sequelae of minor head injury. Neurosurgerv 13. 529-533.
Bennett-Levy, J. M. (1984). Long-term effects of severe closed head injury on memory: evidence from a consecutive series of young adults. Acta Neurologica Scandinavica. 70. 258-298.
Bijur, P., Haslum, M., & Golding, J. (1990). Cognitive and behavioral sequelae of mild head injury in children. Pediatrics. 86. 336-344.
Bohnen, N., & Jolles, J. (1992). Neurobehavioral aspects of postconcussive symptoms after mild head injury. Journal of Nervous and Mental Disease. 180. 683-692.
Brooks, D. N. (1974). Recognition memory, and head injury. Journal of Neurology. Neurosurgerv. and Psychiatry. 37. 794-801.
59
Brooks, D. N. (1976). Wechsler Memory Scale performance and its relationship to brain damage after severe closed head injury. Journal of Neurology. Neurosurgery, and Psychiatry. 39. 593-601.
Brooks, D. N., Aughton, M. E., Bond, M. R., Jones, P., & Rizvi, S. (1980). Cognitive sequelae in relationship to early indices of severity of brain damage after severe blunt head injury. Journal of Neurology. Neurosurgery, and Psychiatry. 43. 529-534.
BuUard, J. A., & Cutshaw, R. (1991). Vocational evaluation of the closed head injury population: a challenge of the 1990's. Vocational Evaluation and Work Adjustment Bulletin. 24. 15-19.
Coppens, P. (1995). Subpopulations in closed-head injury: preliminary results. Brain Injury. 9. 195-208.
Crosson, B., Greene, R. L., Roth, D. L., Farr, S. P., & Adams, R. L. (1990). WAIS-R pattern clusters after blunt-head injury. The Clinical Neuropsychologist. 4. 253-262.
Crosson, B., Novack, T. A., Trenerry, M. R., & Craig, P. L. (1988). California Verbal Learning Test (CVLT) performance in severely head-injured and neurologically normal adult males. Journal of Clinical and Experimental Neuropsychology. 10. 754-768.
Dikmen, S. S., Machamer, J. E., Winn, H. R., & Temkin, N. R. (1995). Neuropsychological outcome at 1-year post head injury. Neuropsychology. 9. 80-90.
Diller, L. (1994). Finding the right treatment combinations: changes in rehabihtation over the past five years. In A. Christensen & B. Uzzell (Eds.), Brain injury and neuropsychological rehabilitation: International perspectives (pp. 1-16). Hillsdale, NJ: Erlbaum.
Dwork, A. J., Susser, E. S., Keilp, J., Waniek, C, Liu, D., Kaufinan, M., Zemishlany, Z., & Prohovnik, I. (1998). Senile degeneration and cognitive impairment in chronic schizophrenia. American Journal of Psychiatry. 155. 1536-1543.
Esselman, P. C, & Uomoto, J. M. (1995). Classification of the spectrum of mild traumatic brain injury. Brain Injury. 9. 417-424.
60
Farr, S. P., Greene, R. L., & Fisher-White, S. P. (1986). Disease process, onset, and course and their relationship to neuropsychological performance. In S. Filskov & T. Boll (Eds.), Handbook of Clinical Neuropsychology. Volume 2 (pp. 213-253). New York: John Wiley and Sons.
Garcia, J. M., Garrett, K., Stetz, M., Emanuel, L., & Brandt, J. (1990). Early behavioral responses in severe head injury. Cognitive Rehabilitation. 8. 30-33.
Gass, C. S., & Apple, C. (1997). Cognitive complaints in closed-head injury: relationship to memory test performance and emotional disturbance. Journal of Clinical and Experimental Neuropsychology. 19. 290-299.
Geffen, G. M., Butterworth, P., Forrester, G. M., & Geffen, L. B. (1994). Auditory Verbal Learning Test components as measures of the severity of closed-head injury. Brain Injury. 8. 405-411.
Glatt, S. L., Hubble, J. P., Lyons, K., Paolo, A., Troster, A. I., Hassanein, R. E., & Koller, W. C. (1996). Risk factors for dementia in Parkinson's disease: effect of education. Neuroepidemiology. 15. 20-25.
Graves, A. B., Mortimer, J. A., Larson, E. B., Wenzlow, A., Bowen, J. D., & McCormick, W. C. (1996). Head circumference as a measure of cognitive reserve. Association with severity of impairment in Alzheimer's disease. British Journal of Psychiatry. 169. 86-92.
Gronwall, D., & Wrightson, D. G. (1981). Memory and information processing capacity after closed head injury. Journal of Neurology. Neurosurgery, and Psychiatry. 44. 889-895.
Gupta, A., & Ghai, D. (1996). Memory and information processing capacity after closed head injury. Indian Journal of Clinical Psychology. 23. 170-177.
Haslam, C, Batchelor, J., Feamside, M. R., Haslam, S. A., Hawkins, S., & Kenway, E. (1994). Post-coma disturbance and post-traumatic amnesia as nonlinear predictors of cognitive outcome following severe closed head injury: findings from the Westmead Head Injury Project. Brain Injury. 8. 519-528.
Haslam, C, Batchelor, J., Feamside, M. R., Haslam, S. A., & Hawkins, S. (1995). Further examination of post-traumatic amnesia and post-coma disturbance as nonlinear predictors of outcome after head injury. Neuropsychology. 9, 599-605.
Haut, M. W., & Shutty, M. S. (1992). Pattems of verbal learning after closed head injury. Neuropsychology. 6, 51-58.
61
Howell, D.C. (1992). Statistical methods for Psychology (3"^ edX Boston: PWS-Kent Publishing.
Huck, S. & McLean, R. (1975). Using a repeated measures ANOVA to analyze the data from a pretest-posttest design: A potentially confiising task. Psychological Bulletin. 82(41311-318.
King, N. S. (1996). Emotional, neuropsychological, and organic factors: their use in the prediction of persisting postconcussion symptoms after moderate and mild head injuries. Joumal of Neurology. Neurosurgery, and Psychiatry. 61. 75-81.
Kaufinan, A. S. (1990). Assessing adolescent and aduh intelligence. Boston, MA: Allyn and Bacon, Inc.
Katz, D. I. (1992). Neuropathology and neurobehavioral recovery from closed head injury. Joumal of Head Trauma Rehabilitation. 7. 1-15.
Kmll, K., Scott, J., & Sherer, M. (1995). Estimation of premorbid intelligence from combined performance and demographic variables. The Clinical Neuropsychologist. 9. 83-87.
Lees-Haley, P. R., Smith, H. H., Williams, C. W., & Dunn, J. T. (1996). Forensic neuropsychological test usage: an empirical survey. Archives of Clinical Neuropsychology. 11.45-51.
Levine, M. J., Van Hom, K. R., & Curtis, A. B. (1993). Developmental models of social cognition in assessing psychosocial adjustments in head injury. Brain Injury. 7. 153-167-
Levin, H. S., Gary, H. E. Jr., Eisenberg, H. M., Ruff, R. M., Barth, J. T., Kreutzer, J., High, W. M., Portman, S., Foulkes, M. A., Jane, J. A., Marmarou, A., & Marshall, L. F. (1990). Neurobehavioral outcome 1 year after severe head injury. Joumal of Neurosurgery. 73. 699-709.
Levin, H. S., Grossman, R. G., Rose, J. E., & Teasdale, G. (1979). Long-term neuropsychological outcome of closed head injury. Joumal of Neurosurgerv. 50. 412-422.
Levin, H. S., High, W. M., Goethe, K. E., Sisson, R. A., Overall, J. E., Rhoades, H. M., Eisenberg, H. M., Kalisky, Z., & Gary, H. E. (1987). The neurobehavioural rating scale: assessment of the behavioural sequelae of head injury by the clinician. Joumal of Neurology. Neurosurgery, and Psychiatry. 50. 183-193.
62
Levin, H. S., WilUams, D. H., Eisenberg, H. M., High, W. M. Jr., & Guinto, F. C. Jr. (1992). Serial MRI and neurobehavioural findings after mild to moderate closed head injury. Joumal of Neurology. Neurosurgery, and Psychiatry. 55. 255-262.
Lezak, M.D. (1995). Neuropsychological Assessment. (3'^ edX New York: Oxford University Press.
Loken, W. J., Thorton, A. E., Otto, R. L., & Long, C. J. (1995). Sustained attention after severe closed head injury. Neuropsychology. 9 (4). 592-598.
Mandleberg, I. A. (1976). Cognitive recovery after severe injury: 3. WAIS Verbal and Performance IQs as a fimction of post-traumatic amnesia duration and time from injury. Joumal of Neurology. Neurosurgerv. and Psychiatry. 39. 1001-1007.
Mandleberg, I. A., & Brooks, D. N. (1975). Cognitive recovery after severe head injury: 1. Serial testing on the Wechsler AduU Intelligence Scale. Joumal of Neurology. Neurosurgery, and Psychiatry. 38. 1121-1126.
Man, D. W. K. (1996). Remediation of cognitive deficits following closed head injury through occupational therapy procedures: a multiple baseline across behaviours design. In E. Bonke, E. Benno, & J. G. Bovill (Eds.), Memory and awareness in anesthesia III (pp. 151-163). Assen, Netherlands: Van Gorcum & Co.
McClelland, R. J. (1988). Psychosocial sequelae of head injury: anatomy of a relationship. British Joumal of Psychiatry. 153. 141-146.
McMillan, T. M., Jongen, E. L. M., Greenwood, R. J. (1996). Assessment of posttraumatic amnesia after severe closed head injury: retrospective or prospective? Joumal of Neurology. Neurosurgery, and Psychiatry. 60. 422-427.
Nelson, L. D., Adams, K. M. (1997). Challenges for neuropsychology in the treatment and rehabilitation of brain-injured patients. Psychological Assessment. 9. 368-373.
Oder, W., Goldenberg, G., Spatt, J., Podreka, I., Binder, H., & Deecke, L. (1992). Behavioural and psychosocial sequelae of severe closed head injury and regional cerebral blood flow: a SPECT study. Joumal of Neurology. Neurosurgery and Psychiatry. 55. 475-480.
Paniak, C. E., Silver, K., Finlayson, M., A, & Tuff, L. P. (1992). How usefiil is the WAIS-R in closed head injury assessment? Joumal of Clinical Psychology. 48, 219-225.
63
Pereda, M., Ayuso-Mateos, J. L., Gomez Del Barrio, A., Echevarria, S., Farina, M. C, Garcia Palomo, D., Gonzalez Macias, J., & Vazquez-Barquero, J. L. (2000). Factors associated with neuropsychological performance in HFV-seropositive subjects without AIDS. Psychological Medicine. 30. 205-217.
Ponsford, J., & Kinsella, G. (1992). Attentional deficits following closed-head injury. Joumal of Clinical and Experimental Neuropsychology. 14. 822-838.
Reid, D. B., & Kelly, M. P. (1993). Wechsler Memory Scale-Revised in closed head injury. Joumal of Clinical Psychology. 49. 245-254.
Richardson, J. (1990). Clinical and neuropsychological aspects of closed head injury. London: Taylor.
Ropacki, M. T., Elias, J. W. (1999). Further validation of the Oklahoma Premorbid Intelligence Estimate with closed head injury and mixed neurologic patients. Archives of Clinical Neuropsychology. 14 (8). 788.
Royall, D. R., Cordes, J. A., & Polk, M. (1998). CLOX: an executive clock drawing task. Joumal of Neurology. Neurosurgery and Psychiatry. 64. 588-594.
Satz, P. (1993). Brain reserve capacity on symptom onset after brain injury: A formulation and review of evidence for threshold theory. Neuropsychology. 7 (3). 273-295.
Satz, P., Alfano, M. S., Light, R., Morgenstem, H., Zaucha, K., Asamow, R. F., & Newton, S. (1999). Persistent post-concussive syndrome: A proposed methodology and literature review to determine the effects, if any, of mild head and other bodily injury. Joumal of Clinical and Experimental Neuropsychology. 2L 620-628.
Schmand, B., Smit, J. H., Geerlings, M. I., & Lindeboom, J. (1997). The effects of intelligence and education on the development of dementia. A test of the brain reserve hypothesis. Psychological Medicine. 27. 1337-1344.
Scott, J. G., Kmll, K. R., WiUiamson, D. J. G., Adams, R. L., & Iverson, G. L. (1997). Oklahoma Premorbid Intelligence Estimation (OPIE): Utilization in clinical samples. The Clinical Neuropsychologist. 11 (2). 146-154.
Scott, J. G., Sherer, M., & Adams, R. L. (1995). Clinical utihty of WAIS-R factor-derived standard scores in assessing brain injury. The Clinical Neurologist, 9(1), 93-97.
64
Smith-Seemiller, L., Lovell, M. R., Franzen, M. D., Smith, S. S., & Townsend, R. N. (1997). Neuropsychological fimctioning in restrained versus unrestrained motor vehicle occupants who suffer closed head injury. Brain Injury. 11. 735-742.
Spreen, O., & Strauss, E. (1998). A compendium of neuropsychological tests (3""̂ ed.). New York: Oxford.
Stambrook, M., Moore, A. D., Lubusko, A. A., Peters, L. C , & Blumenschein, S. (1993). Altematives to the Glasgow Coma Scale as a quality of life predictor following traumatic brain injury. Archives of Clinical Neuropsychology. 8. 95-103.
Stem, R. A., Silva, S. G., Chaisson, N., & Evans, D. L. (1996). Influence of cognitive reserve on neuropsychological fimctioning in asymptomatic human immunodeficiency vims-1 infection. Archives of Neurology. 53. 148-153.
Stuss, D. T., Binns, M. A., Carmth, F. G., Levine, B., Brandys, C. E., Moulton, R. J., Snow, W. G., & Schwartz, M. L. (1999). The acute period of recovery from traumatic brain injury: posttraumatic amnesia or posttraumatic confiisional state? Joumal of Neurosurgery. 90. 635-643.
Teasdale, G., & Jennett, B. (1974). Assessment of coma and impaired consciousness: a practical scale. Lancet. 2. 81-84.
Tremont, G., Hoffinan, R. G., Scott, J. G., Adams, R. L., & Nadolne, M. J. (1997). Clinical Utility of Wechsler Memory Scale-Revised and predicted IQ discrepancies in closed head injury. Archives of Clinical Neuropsychology. 12. 757-762.
Vilkki, J., Ahola, K., Hoist, P., Ohman, J., Servo, A., & Heiskanen, O. (1994). Prediction of psychosocial recovery after head injury with cognitive tests and neurobehavioral ratings. Joumal of Clinical and Experimental Neuropsychology. 16,325-338.
Vilkki, J., Poropudas, K., & Servo, A. (1988). Memory disorder related to coma duration after head injury. Joumal of Neurology. Neurosurgery, and Psychiatry, 51. 1452-1454.
Wechsler, D. (1945). A standardized memory scale for clinical use. Joumal of Psychology. 19. 67-70.
Wechsler, D. (1955). Manual for the Wechsler Adult Intelligence Scale. New York: Psychological Corporation.
65
Wechsler, D. (1981). Manual for the Wechsler Aduh Intelligence Scale-Revised. San Antonio, TX: Psychological Corporation.
Wechsler, D. (1987). Manual for the Wechsler Memory Scale-Revised. San Antonio, TX: Psychological Corporation.
Wilson, J. T., Hadley, D. M., Wiedmann, K. D., & Teasdale, G. M. (1992). Intercorrelation of lesions detected by magnetic resonance imaging after closed head injury. Brain Injury. 6. 391-399.
66
APPENDIX A
EXTENDED LITERATURE REVIEW
67
Introduction
Closed head injury (CHI) has been called the "silent epidemic" of our time
(Bullard & Cutshaw, 1991; Man, 1996; McClelland, 1988). Closed head injuries are
those head injuries where the skull remains intact and the brain is not exposed (Lezak,
1995). This excludes head injury from missiles or other penetrating objects. Lezak
(1995) indicated that the incidence of head injuries in the Untied States ranges from
500,000 to more than 1.9 million per year with 400,000 to 500,000 necessitating
hospitahzation or resulting in death. Esselman and Uomoto (1995), citing a citing a
National Health Interview Survey, reported that only 89% of those sustaining a head
injury consuU a physician, and 16% were admitted to a hospital. McClelland (1988)
proposed that head injury is "the" major cause of death for those 35 years-old and
younger. In summary, it is clear that CHI has become an increasingly prevalent malady
in the United States making it a major, important, and costly sociohealth problem facing
westem society today (Alfano et al., 1993; Bullard & Cutshaw, 1991).
Assessment of Closed Head Injury Severity
Glasgow Coma Scale. The GCS (Teasdale & Jennette, 1974) is a brief
assessment technique designed to assess severity, describe the posttraumatic states of
altered consciousness, and predict outcome in head injuries (see Appendix B). A
patient's total GCS score is based on standardized cumulative scores for eye-opening,
verbal performance, and motor responsiveness. For example, for eye opening, if a patient
68
opens their eyes on their own this is scored as a four, a three is assigned if the patient
opens their eyes to a loud voice, a two is assigned if the patient opens their eyes to
painfiil stimulus administration, and if the patient does not open their eyes to painftil
stimulus administration they receive a one. Overall, scores are summed across tiiree
domains: (1) eye opening, (2) verbal response, and (3) motor responsiveness to yield a
total GCS score. The GCS total score can range from three to fifteen, and once
determined the GCS total score is compared to established severity classifications (see
Appendix B). Traditionally, patients with a GCS greater than 13 are considered to have a
mild CHI, between 9-12 a moderate CHI, and less than 8 is indicative of a severe CHI.
The GCS was designed for use by emergency medical technicians, nurses, and doctors.
Lezak (1995) stated that the GCS's "greatest virtue" was its ability to predict outcome,
and that it has been generally accepted as the standard measure for determining severity
of injury in patients with compromised consciousness. However, not everyone agrees
that the GCS is the standard measure for determining injury severity or predicting
prognosis (cf, McMillan et al., 1996; Stambrook, et al., 1993; Vilkki et al., 1994).
Although many clinicians and investigators accept and use the GCS in their work
(e.g., Esselman & Uomoto, 1995; Levin et al., 1992; McMillan et al., 1996; Smith-
Seemiller et al., 1997; Wilson, Hadley, Wiedmann, & Teasdale, 1992), there is
considerable disagreement on how well the GCS can determine severity and predict
outcome. For instance, Garcia, Garrrett, Stetz, Emanuel, and Brandt (1990) explained
that the GCS presents a range of patient behaviors grossly categorized within a restricted
number of descriptive ratings. Furthermore, the GCS has a restricted range (3-15)
69
additionally compromising its predictive utility. The utihty of the GCS in predicting
outcome of moderate and mild CHI has been questioned because it was not designed to
make sharp distinctions of lesser severity (Stambrook et al., 1993). Richardson (1990)
stated that when the GCS is used as it was designed to be used, that is in the first hours to
days post-insuh, it often fails to correctly classify unusual cases. For example, when the
patient is admitted intoxicated or under the influence of a controlled substance, their
admission GCS score is not valid. Unreliable GCS scores are often produced by
intoxicated individuals, or individuals under the influence of a controlled substance.
Some of these individuals may have overdosed on either or a combination of both. Under
these conditions, GCS scores may be incorrectly attributed to head trauma severity, or
head trauma may be erroneously attributed to substance abuse (Stambrook et al., 1993).
Furthermore, some trauma patients are lucid for a short period following CHI, but then
deteriorate (Lezak, 1995). Hence, these individuals' GCS scores would be inaccurate.
Moreover, some CHI patients are intubated or anesthetized prior to emergency room
assessment with the GCS rendering their GCS assessment results suspect. Another
problem involves individuals who experience multiple trauma as often is found in CHI
patients involved in vehicular accidents. Specifically, one or more examination
modalities (e.g., their ability to speak, open their eyes due to facial trauma, or paralysis
and fractures compromising their motor abilities) may not be assessable due to injury
thereby limiting the utility of the GCS (Reid & Kelly, 1993; Stambrook et al., 1993).
Coppens (1995) reported that the GCS severity ratings are often unreliable as evidenced
by the variability in patients' outcome despite initial ratings of severe CHI. Although the
70
GCS has demonstrated reliability in predicting mortality, its ability to predict cognitive
and psychosocial outcome has been criticized (Coppens, 1995; Garcia et al., 1990; Haut
& Shutty, 1992; Levin et al., 1987; Reid & Kelly, 1993).
Duration of Posttraumatic Amnesia. According to McMillan et al. (1996), since
Russell's proposition in 1932, tiiat the sum of the comatose and confiisional periods was
the most usefiil predictor of outcome, "many studies" have demonstrated that the duration
of PTA provides the "best yardstick" for predicting outcome that exists. Duration of
PTA has been defined as the interval from the time of injury until the patient can form
new memories and continuously recalls day-to-day events (Oder et al., 1992).
Traditionally, PTA has been retrospectively assessed during clinical interview by
questioning the patient. Specifically, retrospective assessment typically involves the
clinician (i.e., physician, psychologist, or nurse) asking the patient questions regarding
their accident, their memory surrounding the accident, and other questions to determine if
the patient has formed memories for routine daily events. Posttraumatic amnesia
duration can range from minutes to days, and once determined it is compared to an
established severity classification system (see Appendix B). For example, PTA duration
of five minutes to one hour is considered a mild CHI whereas PTA duration of one-to-
seven days is indicative of a severe CHI. Many investigators agree that PTA duration has
superior utility in assessing severity and predicting outcome (Gupta & Ghai, 1996; Katz,
1992; McClelland, 1988). For instance, Katz (1992) reported that PTA's relationship to
outcome was more reliable than that of the GCS. McMillan and colleagues (1996)
asserted that the duration of PTA is a better indicator than depth or duration of coma and
71
MRI changes. Nonetheless, not all researchers are as steadfast in their convictions
regarding the reHability of PTA duration to classify severity and predict outcome (cf,
Coppens, 1995; Vilkki et al., 1994).
Although the duration of PTA is commonly used to determine severity and predict
CHI outcome, investigators have pointed out the duration of PTA's limitations (Alfano et
al., 1993; Barth et al., 1983; Bohnen & Jolles, 1992; Coppens, 1995; Gass & Apple,
1997; Levin et al., 1987; Lezak, 1995; Vilkki et al., 1994). For instance, Coppens (1995)
stated that PTA's relationship to recovery of language and "cognitive functioning" is less
than adequate. Coppens (1995) blamed the heterogeneous nature of CHI for the lack of
correlation between initial severity ratings and recovery. Moreover, difficulties
determining the duration of PTA make its usefuhiess questionable. Specifically, by
definition, the endpoint of PTA occurs when the patient can continuously register
memories of daily events. However, many of these authors believe that, in practice, this
determination is a highly subjective decision for the clinician because determining the
point at which continuous memory retums is often difficult to specify. Lezak (1995)
pointed out that the clinician's decision is even more clouded by the fact that many CHI
patients experience transient periods of confusion while others are aphasic.
Another limitation of PTA duration is its usage with milder cases of CHI.
According to Bohnen and Jolles (1992), the reliability of PTA to assess severity and
predict outcome decreases if PTA duration is less than one hour. Moreover, many CHI
individuals have a lack of insight into their deficits rendering their reports questionable,
and family members' memories are often unreliable due to the stressfulness of the
72
situation (Alfano et al., 1993; Gass & Apple, 1997; Levin et al., 1987; Lezak, 1995;
McMillan et al., 1996). Dmg use and alcohol consumption also limits the usefiihiess of
PTA duration to assess severity and predict outcome. Alcohol consumption and/or dmg
usage often makes the estimation of PTA inaccurate and severity classification
complicated (Bohnen & Jolles, 1992). Finally, adding to duration of PTA's reliability
problems are the fact that many CHI individuals sustain mild injuries and are eitiier not
admitted or discharged before their PTA has ended.
McMillan and colleagues (1996) attempted to address the limitations of using
PTA duration to determine severity and predict outcome. Furthermore, these
investigators wanted to determine if assessing PTA duration prospectively with the
Galveston Orientation and Amnesia Test (GOAT) was statistically more accurate than
determining PTA duration retrospectively through questioning and patient interview.
The prospective assessment of PTA duration involves asking the patient questions daily
such as their name, the day, date, month, and what they recall occurring before and
following the injury. Their performance is compared to objective data (e.g., the family's
reports and the actual date), then scored. Once the patient obtains a score in the "normal"
range on the GOAT, defined as three consecutive performances of 75% correct or better,
they are considered to have cleared from their PTA. Therefore, the duration of the
patient's PTA is considered the interval between the accident and the time when three
consecutive scores of 75% or higher are obtained on the GOAT.
McMillan et al. (1996) attempted to re-contact (N = 126) consecutive patients that
sustained a severe closed head injury. Of the original patients, 79 were traceable (73%).
73
Specifically, 3.5 to 5.0 years post-discharge, an interviewer blind to their original hospital
records recontacted these CHI patients. By interviewing and retrospective questioning
this interviewer attempted to determine the duration of PTA for each former patient.
Following this interview, the interviewer then attempted to determine each patient's
severity classification (see Appendix B). McMillan and colleagues determined tiiat both
prospective and retrospective approaches for determining PTA duration were reliable and
vahd techniques for assessing injury severity and predicting outcome. Specifically, their
results did not support the notion that retrospective assessment of PTA was unreliable or
that prospective assessment was more accurate. These authors also reported "highly
significant correlations" between the GCS, days of lost consciousness, and both methods
for assessing PTA duration. Finally, McMillan and colleagues reported that both
methods for determining duration of PTA (i.e., retrospective questioning and prospective
questioning with the GOAT) were superior to the other outcome measures (i.e., GCS) as
evidenced by these patients' psychosocial outcome, making PTA duration the "gold
standard" in severity and outcome assessment.
Severity assessment and outcome prediction with the GCS and PTA duration have
some of the same limitations. For instance, a patient's waxing and waning cognitive
status is problematic for both as are dmg and/or alcohol usage. However, when
determining PTA duration if the patient is under the influence of a substance, more time
can pass before a severity determination and outcome prediction has to be made. On the
other hand, the GCS does not require patient or family reports, which are often biased
due to lack of insight into deficits or the stress of the situation. Nevertheless, the GCS is
74
typically completed at emergency room admission, hence, one or more assessment
modalities may be compromised due to injury. The GCS and PTA duration have some
overiapping limitations, but mostly their problems are unique. Hence, the GCS and
duration of PTA could be used to complement one another, but research comparing their
cumulative abilities for assessing severity and predicting outcome is needed.
Studies examining the relationship between CHI severity and cognitive outcome
Mandleberg and Brooks (1975) investigated the "natural course of recovery" of
cognitive functions as measured by the WAIS (Wechsler, 1955). These investigators
conducted serial testing with (n = 48) head-injured patients and compared their results to
"comparison individuals" (n = 40) serial testing results. Mandleberg and Brooks' CHI
participants were unrepresentative of the CHI population because they were admitted to
the Institute of Neurological Sciences, Southem General Hospital, Glasgow after being
preselected for possible neurosurgical intervention. Specifically, forty out of forty-eight
CHI participants were positive for skull fracture, twenty-nine had a motor abnormality,
and seventeen hematoma. This limits the generalizability of the findings to only severe
CHI individuals with similar medical complications. In addition, Mandleberg and
Brooks' "comparison individuals" included (n = 13) individuals referred for vocational
guidance and (n = 27) "neurotics" referred for treatment. Mandleberg and Brooks
reported that these "comparison individuals" had histories of alcoholism, dmg abuse,
and/or psychiatric problems. However, the authors did not state whether the head-injured
participants were screened for these problems or history of head trauma and/or
75
neurological problems. This lack of control of the participants used in both groups
potentially adds error variance, obscures findings, and renders any found results
questionable because these conditions are known to affect performance on
neuropsychological assessment.
Mandleberg and Brooks reported that practice effects did not affect the three-year
WAIS scores from their head-injured group. These authors also found that Performance
subtests were more deteriorated during the earlier stages of recovery and take longer to
recover as compared to the Verbal subtests. However, they added that "the cognitive
abilities of the head-injured patients as a group eventually retumed to normal levels,
despite the severity of their injuries as measured by duration of PTA" (p. 1125). Overall,
these authors concluded that the duration of PTA does not predict long-term cognitive
outcome.
In a two-study investigation, Mandleberg (1976) looked at the relationship
between PTA duration and cognitive functioning with the time of injury treated as "an
important independent variable." In the beginning of the article, Mandleberg admitted
that his subjects were unrepresentative of the CHI population because they were admitted
to the Institute of Neurological Sciences, Southem General Hospital, Glasgow after being
preselected for neurosurgical intervention. His participants were more severely impaired
and they had a "disproportionate number with intracranial hematoma." This limits the
generalizability of the findings to only severe CHI individuals with similar medical
complications. Moreover, inclusion/exclusion criteria regarding a history of previous
head trauma, alcoholism, dmg abuse, psychiatric problems, and/or neurological problems
76
was lacking for both study one and two. This lack of control over the participants used in
both studies potentially adds error variance, obscures findings, and renders any found
results questionable. Nevertheless, study one included (n = 51) CHI participants,
subdivided by their PTA duration into subgroups that completed serial testing on the
WAIS. Study two included (n = 98) "non-systematic retumees" whose earliest WAIS
data was analyzed to control for practice effects.
In both studies, Mandleberg found that VIQ abilities were related to PTA duration
only at three months, while PIQ was related to PTA duration at three and six montiis. In
other words, performance abilities were slower to recover. Mandleberg reported that
despite PTA level, all participants' IQ levels were indistinguishable after six months. He
also indicated that practice effects were not found in the second investigation. Finally,
Mandleberg concluded that PTA was not related to long-term cognitive outcome and
added that these findings were consistent with his earlier findings.
Levin et al. (1979) studied the relationship between indices of severity and
outcome. Their subjects (N = 27) were selected from over 700 CHI cases referred for
neurosurgery to find the most severe cases that had recovered to a testable level.
Obviously, these participants are a small subset of the CHI population and this limits the
generalizability of any findings. Participants were excluded with a history of head injury,
alcoholism, dmg abuse, or neuropsychiatric disorder, and if they were under 16 or over
50 years-old. Severity of injury was determined by GCS and duration of coma, and only
patients with GCS scores of eight or less were included in the study. Measures used in
this investigation included the GCS, Glasgow Outcome Scale (GOS), Brief Psychiatric
77
Ratmg Scale, WAIS, a "selective reminding technique" described as an unconventional
method to assess memory, Multilingual Aphasia Examination, Controlled Word
Association, Token Test, Auditory Comprehension of Words and Phrases, Reading
Comprehension, and selected subtests from the Neurosensory Center Comprehensive
Examination for Aphasia.
Levin et al. concluded that the relationship between severity level and outcome
was "not invariable." Nevertheless, level of outcome, as determined by the GOS, was
significantly related to level of cognitive deficit. These authors added that, compared to
Mandleberg and Brooks (1975), their patients demonstrated heterogeneity of intellectual
recovery following CHI. Specifically, they found that marked intellectual impairment, as
measured by the WAIS, was present after intervals as long as three years. In summary,
they stated that neuropsychological assessments should be conducted at numerous points
over an extended period to evaluate treatment protocols for CHI patients.
Brooks et al. (1980) acknowledged the discrepancies in the research literature
regarding measures of severity level and cognitive outcome. Therefore, they hoped to
clear up these discrepancies by examining a number of severity indices in relation to
cognitive outcome across the domains of intellectual/cognitive functioning, memory,
language, and visuospatial/constmctive tasks. Their participants (N = 89) were those
referred to the Neurosurgical Unit of the Institute of Neurological Sciences, Glascow for
"operable lesions such as intracranial haematoma." This is a small subset of all CHI
patients. Hence, the generalizability of any findings is limited to only severe CHI
patients with similar medical maladies. Moreover, inclusion/exclusion criteria regarding
78
a history of head trauma, alcoholism, dmg abuse, psychiatric problems, and/or neurologic
problems were lacking. This lack of control over the participants used in the study
potentially adds error variance, obscures findings, and renders any found results
questionable. Brooks et al.'s severity measures of brain damage included coma duration
as measured by the GCS, duration of PTA, presence of hematoma, skull fracture, and age
(p.530). All participants' inteUigence was reportedly measured using the Raven's
Progressive Matrices and the Mill Hill Vocabulary Scale. Other measures included part
of the Logical Memory subtest, Story 1 of Form 1, from the WMS, the Inglis Paired
Associate Learning test, Rey Picture, "three measures of word fluency," Part 5 of the De-
Renzi and Vignolo Token Test, a copy condition of the Rey Picture, and the WAIS Block
Design Subtest.
Brooks et al. reported that all one-way ANOVAS between severity level, as
determined by the GCS, and cognitive outcome measures were insignificant.
Specifically, they stated that "there was no statistically significant influence of coma
duration on later cognitive outcome" (p. 531). However, increased PTA duration was
significantly related to the part of the Logical Memory subtest investigated. Associate
Leaming (only the delayed portion), one word fluency condition out of three (the letter j),
and the Rey Picture (immediate and delay conditions only). Overall, PTA duration was
the only measure of brain severity that had a consistent relationship on a small subset of
the neuropsychological measures. Finally, it should be noted that these authors
completed at least seventy ANOVAS, but no mention was made for correction of
79
familywise error rate. This could result in spuriously finding results that are not tmly
statistically significant.
Alexandre et al. (1983) investigated the possibility of predicting cognitive
outcome in individual patients. Their participants (N = 100) were unrepresentative of the
entire range of CHI individuals because they were all referred for neurosurgical
interventions for the removal of extradural clot, acute subdural hematoma, or
combination of hematoma, cerebral contusion, and laceration. This limits the
generaUzability of their fmdings to only severe CHI patients with similar neurological
problems; these individuals are only a subset of the possible range of all CHI sufferers.
Moreover, inclusion/exclusion criteria regarding a history of previous head trauma,
alcoholism, dmg abuse, psychiatric problems, and/or neurologic problems were lacking.
This lack of control over the participants used in the study potentially adds error variance,
obscures findings, and renders any found resuhs questionable. All participants were
evaluated with the GCS, and PTA duration was determined for each patient. Participants
were divided into groups using an unorthodox system based upon initial performance on
the neuropsychological measures of this experiment to determine severity level.
Specifically, participants completed the Wechsler-Bellevue Form 1, Benton's test of
visual memory, Rey's test for verbal leaming, Corsi's test for spatial memory, Kimura's
test for recognition memory, and the Token test. Assessments were conducted once
participants cleared from PTA, and then their severity level was determined by their
performance on the above measures. All participants were assessed again at one and two
year intervals.
80
The GCS was reliable in predicting the outcome of survival, but the GCS was not
accurate for patients with initial GCS scores of five, six, or seven. Moreover, no
significant relationships were found between PTA duration and cognitive performance.
However, the failure to find significance could be related to the unusual severity level
classification system employed. Overall, using such a system limits the ability to
compare this investigation's results to other research and places question on their
findings.
Paniak et al. (1992) wanted to discover the generalizability of the WAIS findings
to the WAIS-R. Specifically, they wanted to discover if PIQ was more sensitive than
VIQ to CHI effects, if left-hemisphere mass lesions resulted in lower VIQ than PIQ, if
right-hemisphere mass lesions resulted in lower PIQ than VIQ or bilateral mass lesions.
Additionally, they wanted to investigate whether severity was related to WAIS-R
performance, and if CHI subjects produced greater intersubtest scatter than normals.
Their participants were (N = 71) all right-handed aduhs, several months to years post
insult that were more severely impaired than usual given the "clinical nature" of their
referrals. Using an unrepresentative sample limits the generalizability of these findings
to only those individuals with similar circumstances. Duration of PTA was available for
some subjects (n = 63) as was CT scan data (n = 57). However, these authors
acknowledged that CT scanning often fails to detect lesions that MRI might find.
Paniak et al. found that Digit Symbol was the only WAIS-R subtest that
correlated with severity of injury, as determined by PTA duration. These authors also
reported that there is little practical applicability for VIQ/PIQ discrepancies for individual
81
CHI patients. Only 27% produced a VIQ that exceeded a PIQ by more tiian 10 points
although these were all severe CHI patients. Furthermore, they stated that contrary to
"clinical lore," there was no evidence of greater WAIS-R subtest scatter in the CHI
sample versus the WAIS-R standardization sample. These authors also failed to find
VIQ/PIQ or Vocabulary-Block Design discrepancies in CHI patients with lateralized
mass lesion. Overall, Paniak et al. concluded that only some WAIS findings can be
generalized to the WAIS-R.
Paniak et al. admitted that CT scan procedures, with limited resolution, might
have missed diffuse lesions that generally characterize CHI. If this occurred, then
participants would be incorrectly classified by severity level and this would add error
variance to the results and obscure findings. No GCS scores were reported, some PTA
data was missing, as was some CT scan data all used to document the CHI severity. This
again could result in incorrect classifications and cause problems as discussed above.
Moreover, the average time from injury to assessment was 504 days, but more
surprisingly, the standard deviation was almost three years. Hence, there was wide
variability in recovery time before the first assessment; this was not a study designed to
longitudinally look at outcome. Furthermore, some investigators have reported that
longer time from injury until IQ assessment resuhs in recovery of cognitive deficits to
normal levels regardless of injury severity (Mandleberg, 1976; Mandleberg & Brooks,
1975). Paniak et al.'s assessment of CHI participants' so long after injury could have
contributed to their failure to find significant results between severity level and cognitive
outcome. These authors also did not list any inclusion/exclusion criteria screening for
82
history of alcohol or dmg abuse, previous head trauma, psychiatric problems, or
neurologic conditions. Missing data, large variability between insult and first assessment,
lack of exclusion for conditions known to effect test performance all confound
assessment results and places questions on any significant findings.
Although it is well established that CHI patients have deficits on a wide range of
cognitive tasks, difficulties with memory and attention/concentration are two of the most
commonly reported problems following CHI (Bennett-Levy, 1984; Geffen, Butterworth,
Forrester, & Geffen, 1994; Ponsford and Kinsella, 1992). Therefore, it seems clear that a
literature review on the relationship between severity level and cognitive deficits would
be incomplete if an examination of the research regarding attention/concentration and/or
memory, and severity level was not conducted.
In order to ascertain the relationship between severity level and recognition
memory following CHI, Brooks (1974) tested (n = 34) aduUs on a recognition memory
procedure that involved the identification of eight recurring shapes out of a series of 160.
In addition, he used a control group consisting of orthopedic outpatients undergoing
rehabilitation for injuries of the lower limbs. Brooks did not report whether any
participants were excluded for a history of previous head trauma, dmg abuse, alcoholism,
neurological, and/or neuropsychiatric problems. Failure to exclude these individuals
from either group can potentially add error variance to the results and obscure findings.
All head-injured participants were tested after transfer to the Division of Neurosurgery at
the Institute of Neurological Sciences, Glasgow. Therefore, these individuals are a
distinct subgroup of the total CHI population and the results of this investigation have
83
limited generalizability. Brooks reported that all participants were tested only after they
were fully out of PTA and had received a neurological examination before memory
testing. The Continuous Recognition Test by Kimura (as cited in Brooks, 1974) was
given to all participants to examine the amount of correct responses, false positives, and
false negatives by group.
According to Brooks, significant differences were found between the CHI group
and the control group on the total amount correct, number of false negatives, but not on
the amount of false positives. Furthermore, duration of PTA was correlated significantly
with the amount correct and the number of false positives. This is surprising because no
significant correlation was found between amount of false negatives and severity,
although the amount of false negatives was significant by group. Brooks' resuhs were
also unexpected since there was not a significant difference by group on false positives.
Nevertheless, an examination within the head-injured group for false positives (moderate-
severe neurologically impaired participants versus mild neurologically impaired
participants) was also significant. Specifically, the more severely injured participants
provided more false positives. However, Brooks wamed that when age is taken into
account, the relationship between PTA and memory deficits becomes less clear because
PTA duration bears a stronger relationship with memory in older (over 30 years-old) than
younger (15-30 years-old) participants. Overall, Brooks concluded that there was no
association between memory and persisting neurological signs or skull fracture, but
added that fijrther work was needed to clarify these findings.
84
Brooks (1976) attempted to further his previous work and clarify tiie relationship
between severity of injury, severity of persisting neurological signs, skull fracture, time
post-injury, age, and memory performance. The focus here will be on injury severity,
age, and memory performance. His CHI group consisted of (N = 82) patients that had
PTA duration of at least two days. Part of his CHI group (n = 30) were neurosurgical
cases while the others (n = 52) were referred for examination of cognitive recovery
following CHI. The author stated that these two subgroups did not significantly differ by
memory test performance. Hence, their data was combined. Control participants were (n
= 34) orthopedic patients with "primarily fractures of the lower limbs." Brooks clearly
stated that no member of the control group had suffered a head injury. Nevertheless, the
author did not indicate whether CHI participants were excluded for previous head injury,
dmg abuse history, alcoholism, neurological conditions, and/or psychiatric problems.
Moreover, Brooks did not report whether the control participants were excluded for
history of dmg abuse, alcoholism, neurologic conditions, and/or psychiatric problems.
Failure to exclude these individuals from either group can potentially add error variance
to the results and obscure findings. Brooks indicated that memory was tested on the
WMS "a scale that is far from ideal." Specifically, he did not agree that the Memory
Quotient produced by the WMS was efficacious, but he added that few clinical batteries
of memory tests were available.
Brooks reported that CHI participants performed significantly worse than controls
on six of the eight subtests. Specifically, the groups did not differ on Mental Control
(errors) and Digits Forward. To examine the effects of severity level on WMS
85
performance, Brooks subdivided the CHI group into subgroups based upon duration of
PTA. Specifically, his groups were PTA of (1) seven days or less (n = 14), (2) PTA
between eight and fourteen days (n = 14), (3) PTA of fifteen to twenty-eight days (n =
22), and (4) PTA greater than twenty-nine days (n = 32). Brooks did not find
significance between the CHI subgroups on Information, Orientation, Mental Control
(errors and time), Digits Forward, Digits Backwards, and Visual Reproduction.
However, CHI subgroup 1 performed significantly better than subgroups 3 and 4 on
Logical Memory (LM). Therefore, Brooks reported a "significant association" between
LM and PTA duration with a "threshold" above PTA of approximately four weeks, after
which PTA duration was less important. On Associate Leaming, (AL) CHI subgroup 1
significantly differed from 4. Brooks' resuhs did not support that longer PTA duration
detrimentally affects older participants' memory performance significantly more than
younger participants'. Overall, Brooks' findings were supported that severe CHI
individuals demonstrate marked memory deficits many months post-injury.
Gronwall and Wrightson (1981) examined the relationship between the PTA
duration and performance on memory and attention tests in two experiments.
Specifically, (N = 71) participants for experiment one were between 17 and 30 years-old.
They were administered the WMS, the PASAT, and the Quick Test (QT). Participants
were excluded for skull fracture, intracranial hematoma, "localising neurological signs, or
other complications." However, it was not reported whether participants were excluded
for a history of previous head trauma, alcoholism, dmg abuse, or psychiatric problems.
Failure to exclude these conditions can add additional error variance and obscure results
86
because these conditions can detrimentally affect neuropsychological testing
performance. Length of PTA and PASAT performance was used to determine
participants' severity level. Specifically, CHI subgroups were formed for PTA duration
of less than one hour (n = 20) [Mild]; see Appendix B), PTA duration of one to twenty-
four hours (n = 38 [Moderate]), and PTA of greater than one day (n = 13 [Severe]). The
classification of participants by time on the PASAT and PTA duration is unusual but was
based upon "grades." Specifically, Gronwall and Wrightson assigned participants into
three "grades" based upon their time to completion on the PASAT. Specifically, grade 1
was comprised of individuals who performed the task in less than 3.5 seconds (PTA < 1
hour), grade 2 between 3.6 and 5.5 seconds (PTA 1-24 hours), and grade 3 greater tiian
5.6 seconds (PTA > Iday). For further information on his classification strategy, the
interested reader is referred to Gronwall and Wrightson (1981) page 890.
Gronwall and Wrightson failed to find significance on WMS Mental Quotient
(MQ) between the mild CHI group versus moderate CHI group, and mild CHI group
versus severe CHI group. However, the MQ difference between the moderate CHI group
versus severe CHI group was significant. Overall, these authors indicated that the MQ
had obscured findings. They also submitted all moderate and severe CHI participants' (n
= 51) assessment data to a "Varimax rotated factor solution" and three factors emerged.
Factor 1 reportedly loaded on the PASAT and Mental Control (MC) subtest of the WMS,
Factor 2 on the WMS Associate Leaming (AL) subtest, and Factor 3 on the QT as well as
Information and Orientation subtests from the WMS. The duration of PTA's loadings on
all three factors was reportedly low. Overall, PTA duration was moderately, but
87
significanfly correlated with performance on the PASAT (L=.30), MC (L=.35) , and AL (r
=.28). Overall, Gronwall and Wrightson stated that he was surprised with the low
loading of PTA on Factor 2 (reportedly a leaming and memory factor), hence, he ran a
second study to further examine this relationship with additional memory assessment
devices.
Gronwall and Wrightson's second investigation included CHI participants (n =
20) whose CHI was in the moderate to severe range as determined by duration of PTA
(range 2-56 hours) and that met the same age and injury inclusion criteria of experiment
one. These investigators also included a control group (n = 30) in the second
investigation comprised of hospital staff and university students. No inclusion/exclusion
criteria were reported. Therefore, they did not screen either group for a history of
previous head injury, dmg abuse, alcoholism, neurological conditions, or psychiatric
disorders. Again, these conditions could have added error variance to his findings as
discussed in experiment one, and obscured differences by group. In the second study, all
participants completed the PASAT, the Selective Reminding Task, and the Visual
Sequential Memory subtest of the Illinois Test of Psycholinguistic Abilities (a full
description of these instmments is provided in the article).
Grownwall and Wrightson found significant correlations between the PASAT and
PTA duration, but severity level was not associated with performance on the Visual
Sequential Memory test. These authors reported that the Selective Reminding Task
yields three measures, total number correct, cumulative number of words in memory
storage, and consistent retrieval. Severity level, as measured by PTA duration, was
88
significantly related to the total amount correct for the CHI participants. No statistically
significant group mean differences were found between the control group and the CHI
group on the cumulative number of words in memory storage. Nevertheless, PTA
duration was correlated significantly with cumulative number of words in memory
storage for the CHI group. Severity level, as measured by PTA duration, was not
significantly related to consistent retrieval for the CHI participants. Based upon tiie
results of both investigations, these investigators stated that it appeared tiiat PTA duration
did not predict degree of impairment on memory tasks. However, these authors indicated
that the ability to place information into long-term memory store was related to either
PTA duration or time between injury and testing, and that PTA duration did predict
impairment in the ability to retrieve information from memory once it was stored.
Bennett-Levy (1984) noted that investigations examining the relationship between
severity level and cognitive outcome had produced varying results. Therefore, he wanted
to examine the relationship between CHI severity and "memory and related functions"
two to five years post-insult. Specifically, he attempted to discover if there was a
"threshold of brain damage" near PTA duration of three weeks, above which patients
would incur long-term cognitive deficits. Head-injured participants (n = 39) were
individuals that sustained head-injuries between 1976-1978. They were all between 17
and 35 years-old, had PTA duration of greater than one week "as determined by the
neurosurgeons," and an estimated pre-morbid IQ of 80 or greater. Selecting only CHI
participants between the age of 17 and 35 limits this investigation's generalizability to
only young CHI individuals. Head-injured participants were excluded for a history of
89
alcoholism, dmg abuse, or a neurological disorder. Nevertheless, Bennett-Levy did not
exclude participants for a history of previous head trauma or neuropsychiatric problems.
Control participants (n = 32) were orthopedic patients "under assessment for surgical
intervention from limb injuries." Control participants were excluded if they had a history
of head trauma or epilepsy, but the authors did not report excluding these individuals for
a history of alcoholism, dmg abuse, or psychiatric problems. Failure to exclude
participants from either group with conditions known to detrimentally affect
neuropsychological assessment performance could add error variance to the results and
obscure findings.
The control group was assessed in the hospital while the CHI participants were
tested between two to five years post-injury. Head-injured participants were divided into
two subgroups based upon their PTA duration. The first group (CHIl) was comprised of
participants whose PTA duration was between one and three weeks, the second group
(CHI2) had PTA duration of more than three weeks. All participants' IQ was estimated
with the National Adult Reading Test (NART) and the Schonell Graded Word Reading
Test. Furthermore, all participants completed the Logical Memory (LM) subtest of the
WMS, Face-Naming Leaming Test, Word Recognition (an admittedly unpublished test).
Keeping Track, Famous Personalities Test, Figure-Ground Test of Discrimination,
Mooney Faces, Recurring Faces Test, Rey-Osterrieth Complex Figure Test, Speed of
Information Processing test adapted from the British Abilities Scale, and the Subjective
Memory Questionnaire (these relatively unknown instmments are fully described in the
article pp. 288-290).
90
Bennett-Levy reported that CHI2 group performed significantly worse on the LM
subtest and the Keeping Track test than the control group, whereas tiie CHIl group did
not. Significant differences by severity level, as determined by PTA duration, were only
evident for LM (delayed recall & percent forgetting conditions), the Keeping Track test,
and the Rey-Osterrieth (recall condition). No other significant differences were obtained
between CHIl versus CHI2 on any other assessment devices or conditions. In other
words, severity level was not related to performance on other measures except the ones
noted above. Moreover, no significant differences were produced by group (CHIl, CHI2,
and control) on Word Recognition, Face-Name Leaming Test, and the Famous
Personalities Test. Furthermore, he stated that severity of injury, as determined by PTA
duration, was not related to performance on the Speed of Processing Task across any of
the five conditions. Bennett-Levy concluded that "the increasing task demands in no way
differentially affected the head-injured patients since both the patient groups' and the
controls' mean times increased by constant amounts" (p. 293). Surprisingly, age was
only significantly correlated with one test, the Famous Personality Test, and the older
patients performed better. Therefore, because of the lack of significant correlations
between age and Bennett-Levy's measures combined with the finding that older subjects
performed better on the Famous Personality Test, this author concluded that, within the
age range of this investigation, there was no evidence that older patients are affected
more by head injury than younger patients. In closing, this Bennett-Levy stated that the
results of his investigation do not support that individuals classified as "very severe" by
PTA duration suffer permanent cognitive impairment.
91
Vilkki et al. (1988) noted that PTA duration was found to be related to memory
performance in some investigations, whereas coma duration had even less proven
consistency in relation to the severity of residual memory deficits. Therefore, these
investigators wanted to demonstrate that CHI creates a memory deficit that is not
secondary to perceptual or conceptual analysis of the to be remembered material and that
is related to coma duration in patients without intracranial hematoma. Their participants
(N = 51) were patients admitted to the Neurosurgical Clinic of Helsinki following CHI
that had also been comatose immediately after injury for a measurable period. They
excluded participants who were confused, disoriented, or unable to cooperate sufficiently
during the psychological examination as well as participants who underwent operation
for intracranial hematoma. Vilkki et al. admitted that their group of participants was a
"biased sample." Specifically, participants were only those referred to the neurosurgical
unit and who had experienced a loss of consciousness (LOC); not all CHI patients
experience a LOC. Furthermore, these authors did not report that the participants were
out of the acute or post-acute phase before testing ensued. In fact, they stated that some
participants were given a neuropsychological assessment only five days following CHI
with LOC. These investigators also did not exclude CHI participants with a history of
previous head trauma, alcoholism, dmg abuse, neurological conditions, or psychiatric
problems. Overall, because of the limited generalizability of their findings, lack of
documentation that their participants were out of the acute or post-acute phases, and
failure to exclude participants with conditions known to detrimentally affect
neuropsychological test performance, their results should be interpreted cautiously.
92
Vilkki et al.'s participants were subdivided into two groups. The Short Coma
Group (SCG; n = 25) consisted of participants who experienced a LOC of less tiian six
hours. The Long Coma Group (LCG; n = 26) was comprised of individuals whose LOC
was greater than six hours. All participants completed the WAIS subtests of Digit Span,
Similarities, and Block Design as well as free and cued recall conditions of Similarities.
Furthermore, all participants completed the BVRT with homogeneous interference.
Coma duration was not found to be related to performance on the WAIS subtests
or the Immediate Reproduction of the BVRT. This was evident by the lack of
significance between subgroups on these measures. However, the LCG was significantly
inferior to the SCG on the free and cued recall condition of Similarities, and the
forgetting percentage of the BVRT. Overall, Vilkki et al. concluded that the effects of
CHI on verbal and visual memory was related to coma duration, but not secondary to
deficient conceptual or perceptual analysis of the material to be remembered.
Crosson et al. (1988) investigated CHI patients' memory performance on the
CVLT because it provides insight into the qualitative aspects of memory impairment.
Moreover, they were concemed with examining the relationship between severity of
injury, as determined by coma duration and length of PTA, and performance on the
CVLT. Crosson et al.'s CHI participants (n = 33) were individuals whose medical
records indicated that had experienced a "blunt-head trauma," had a documented period
of unconsciousness and/or CT scan indicating brain damage, and that had completed the
CVLT. Nevertheless, these authors stated that they were unable to establish an estimate
of coma or PTA duration for only one case, but that they had established this for all of the
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other twenty-four subjects (p. 756). Therefore, it is unclear whether their CHI group was
comprised of thirty-three or twenty-four CHI participants. All CHI participants in this
investigation were reportedly in the severely injured range. Head-injured participants
were excluded if they were abusing dmgs or alcohol at the time of the investigation
and/or if they had experienced a penetrating head wound.
The control group was made up of "neurologically normal adults" that were paid
participants (except for five participants) obtained through advertisement. However,
Crosson et al. did not report the sample size of the control group in the body of tiie
article, but stated that the size was thirty-three in the abstt-act. Crosson et al.'s only
exclusion criterion for the control group was history of a central nervous system disorder
before admission. Therefore, they did not exclude control participants with a history of
alcoholism, dmg abuse, or psychiatric problems. Failure to exclude individuals from
either group for conditions known to detrimentally affect neuropsychological assessment
performance potentially adds error variance to the results, obscures findings, and places
question on any significant results.
Crosson and colleagues found that CHI participants demonstrated lower scores
than controls across leaming trials. Moreover, there were significant differences between
groups and leaming trials for correct responses. Furthermore, they found that head-
injured participants produced more intmsions and a lower level of semantic cluster
responses. Crosson et al. noted that previous investigations had demonstrated
relationships between indices of injury severity (e.g., length of coma, or length of PTA)
and performance on verbal memory measures. Overall, these authors reported using
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Spearman's rho and finding a consistent absence of significant relationship between
CVLT performance and severity level.
Haut and Shutty (1992) reported that recent advances in cognitive psychology
made it possible to examine specific memory processes, and successftilly delineate
deficits. They added that although previous sttidies have demonstt-ated deficits in the rate
of leaming of normal contt-ols versus CHI patients, they "are aware of no other sttidies
that have explored within-group differences in leaming and memory after CHI" (p. 56).
Hence, the purposes of their investigation was to further explore subgroup differences in
verbal leaming following a CHI, and to explore differences in memory performance
according to indices of prior functioning and severity level. Their subjects (N = 70) were
men (n = 54) and women (n = 16) who were referred for a neuropsychological
evaluation. They classified these participants' severity level with the GCS. No other
inclusion/exclusion criteria were reported. Finally, all participants completed the WAIS-
R, WMS-R Logical Memory subtest, and CVLT.
Their results revealed three distinct pattems of verbal leaming and memory on the
CVLT following CHI. Haut and Shutty reported that these pattems differed by leaming
rate, amount leamed, amount recalled following a delay, and retroactive interference.
Moreover, they indicated that the groups demonstrated "clear differences" on concurrent
cognitive measures (e.g., LM subtest). Specifically, they reported that poor CVLT
performance was associated with lower IQ, attention, and semantic memory. However,
they added that they found a lack of differentiation across subgroups on variables
believed to be associated with severity level. For instance, they failed to find a
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significant relationship between severity of injury, as determined by tiie GCS, and CVLT
or WAIS-R performance. Therefore, they concluded that the GCS was not sophisticated
enough to differentiate "long-term higher level variations in cognitive performance." In
other words, despite different severity levels as determined by the GCS, it did not
discriminate between subgroups' WAIS-R or CVLT performances. Overall, these
authors called for fiittire research that combines the GCS with other variables, such as the
duration of PTA, to sttidy CHI severity and pattems of memory performance.
This study was important at identifying leaming pattems in CHI sufferers.
However, it had some methodological difficulties. First, Haut and Shutty did not report
whether participants were excluded with a history of alcoholism, dmg abuse, previous
head trauma, psychiatric problem, or neurological disorders. These conditions are known
to adversely affect neuropsychological assessment performance, especially memory
testing. Hence, by not excluding participants for these conditions can potentially add
error variance and obscure findings. Haut and Shutty also did not classify their subjects
according to the standardized and accepted GCS criteria. Specifically, they classified
individuals as moderate if they had a GCS score of 13, but GCS scores of 13 are
considered mild head injuries according to standard GCS criteria (see Appendix B;
Lezak, 1995). These authors stated in the conclusion that the GCS severity ratings failed
to differentiate CVLT performance, but they did not follow standard classification
criteria. Therefore, this statement seems premature. Overall, by failing to follow
standardized classification criteria their findings cannot be compared to other
investigations.
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Reid and Kelly (1993) assessed the vahdity of the WMS-R in a group of CHI
patients. Specifically, they examined the relationship between WMS-R performance and
CHI, severity of injury, and day-to-day memory performance. Their participants
included (n = 20) inpatients from a rehabilitation unit and "neurologically normal"
volunteer participants (n = 20). Inclusion criteria specified that the participants were
between 16-74 years-old, with an eighth grade education, no history of a diagnosed
leaming disability, psychiatric problems, and had reportedly not abused alcohol or dmgs
for at least one month pre-testing. No significant differences were found between the
groups on demographic variables. Their admission GCS score and amount of PTA as
measured by the GOAT determined all CHI patients' severity levels. Staff occupational
therapists completed the Inpatient Memory Impairment Scale (IMIS) for each CHI
participant to assess their day-to-day memory functioning. All participants completed a
full WMS-R. The authors hypothesized that CHI individuals would perform more poorly
on the WMS-R than controls. Moreover, they postulated that CHI patients would
evidence more deficits on measures of long-term memory (LTM) than controls. Finally,
they also expected that more severe injuries as determined by the GCS and duration of
PTA would perform more poorly on the WMS-R indices.
Reid and Kelly's (1993) results supported their contentions that contt-ols would
outperform CHI patients on overall memory performance and LTM. In particular, CHI
patients had difficulty with the delayed memory component of the WMS-R. However,
severity level, as determined by both the GCS and duration of PTA, reportedly was not
significantly related to WMS-R performance. Overall, Reid and Kelly found support for
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the construct validity of the WMS-R by comparing scores on its indices to the MIS
ratings.
Reid and Kelly acknowledged that their sample sizes were small by group (n =
20) and that the generalizability of their findings was limited. These investigators also
included individuals in their sttidy if they had abused substances (i.e., alcohol and dmgs)
if it had been more than one month since they "abused" these substances. Overall, a
history of dmg and/or alcohol abuse has been associated with impaired performance on
neuropsychological assessment devices. Therefore, by not excluding all individuals with
a history of substance abuse and/or alcoholism these authors may be adding error
variance to their data and obscuring findings on the WMS-R overall and specifically in
relation to severity level.
Geffen et al. (1994) wanted to examine how the RAVLT performance varied by
severity level, as determined by the PTA duration, and compare the differences between
matched controls and CHI participants on individual RAVLT items. Their participants
included (n = 18) CHI patients referred for neuropsychological assessment and (n = 23)
matched controls. Specifically, they were matched on age, estimated IQ, education, and
occupational level. Estimates of full-scale IQ were computed with the NART for most of
the participants. No inclusion/exclusion criteria were provided. Failure to exclude
participants with a history of head trauma, alcoholism, dmg abuse, neurological
disorders, or psychiatric problems is problematic because these conditions are known to
affect neuropsychological test performance. Consequently, this may add error variance
to results and occlude findings. Ten of the CHI participants and all controls were tested
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individually on Form 1 of the RAVLT, while the remaining CHI participants were
examined with an altemative form of the RAVLT, Form 4. It should also be noted that
the delayed-recall trial, trial eight, of the RAVLT was not administered to most of tiie
CHI participants. Therefore, this ttial was excluded from analyses.
Geffen et al. reported that a two-way ANOVA, Group by Trial, revealed
significant main effects for Group and Trial, but the interaction was not significant. They
stated that this indicated that the two groups leamed at a similar rate despite poorer
overall performance by CHI participants. A series of one-way ANOVAs for total recall
and the first seven trials, and the recognition measures revealed that the control group
significantly performed at a superior level. Moreover, the CHI participants demonsttated
significantly more retroactive interference, but did not differ from the conttols on
proactive interference. Pearson correlation coefficients were used to assess the effects of
injury severity on recall and recognition performance. Only trial seven was significantly
correlated with severity of injury, as determined by PTA duration. In other words, no
other RAVLT recall or recognition measures were correlated with CHI severity.
Haslam et al. (1994) examined the relationship between early GCS scores,
duration of coma or unconsciousness, PTA duration, the presence and evacuation of
hematoma, post-coma disturbance (PCD) on cognitive outcome. They defined PCD as
the period between a patient's emergence from coma and the regaining of continuous
day-to-day memory. These authors stated that there is considerable variation in
researchers' definitions of cognitive outcome. Therefore, they attempted to predict
outcome on two specific areas of cognitive deficit, recent memory functioning and speed
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of information processing. Their sample (N = 57) was comprised of individuals over the
age of 15 with documented severe head injury by the GCS. Nevertheless, Haslam et al.
did not report excluding individuals with a history of previous head ttauma, alcoholism,
dmg abuse, neurological disease, or neuropsychiattic disttirbance. Failure to exclude
participants with these conditions known to detrimentally affect neuropsychological
assessment performance may add error variance to the resuhs and obscure findings.
Furthermore, they admittedly chose individuals for inclusion that had made good or
moderate outcomes, as measured by their GOS score, to complete cognitive assessment.
This inclusion hurts their generalizability because they cannot generalize results to those
who do not make do not have good or moderate recovery.
Following admission all subjects were reportedly assessed with these neurological
indices the GCS, Coma duration, CT scan. Surgery, Length of PTA, PCD, and nature of
the trauma (pp. 522-523). Twelve months following admission, these participants
underwent a cognitive assessment that included the PASAT, SDMT, RAVLT, and the
Vocabulary subtest of the WAIS-R as a measure of pre-morbid intelligence. Haslam et
al. conducted a principal-components analysis to reduce these cognitive assessment
variables to discrete factors. The first factor, PSYl, was reported to be primarily a
measure of recent memory while factor two, PSY2, was reported to be an index of speed
of information processing. Next, they transformed the PCD and PTA by a square root
transformation. Then, they conducted a stepwise regression to determine which
neurologic variable or combination of variables best-predicted scores on the cognitive
factors.
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Haslam et al. reported that PTA and transformed PTA were significant predictors
of performance on PSYl (recent memory). However, the combination of ttansformed
PCD and presence of subarachnoid hemorrhage reportedly best predicted performance on
this factor. They also indicated that only two factors, tt-ansformed PTA and PCD were
significant predictors for performance on PSY2 (speed of information processing).
Overall, these authors concluded that the predictive power of PTA and PCD could be
significantly improved by controlling for their non-linearity.
Haslam et al. (1995) reported that previous investigations have varied
considerably in their ability to demonstrate consistent relationships between neurological
indices (e.g., PTA duration and the GCS) and cognitive variables for CHI patients.
Nevertheless, they investigated the relationship between early neurologic variables and
cognitive outcome in a sample of head-injured patients two years post-insult. Their head-
injured sample (N = 77) included forty participants from their original study (Haslam et
al., 1994). All participants had a documented history of severe head injury by the GCS.
However, in this investigation the authors excluded individuals with a history of previous
head trauma, psychiatric disturbance, or alcohol abuse. Haslam et al. admittedly had a
sample skewed towards those judged to have made a good recovery because they only
chose individuals for inclusion that had made good or moderate outcomes as determined
by the GOS to participate. This exclusion hurts their generalizability because they cannot
generalize results to those who do not make do not make this type of recovery.
Following hospital admission, all subjects were reportedly assessed with these
neurological indices the GCS, Coma duration, CT scan. Surgery, Length of PTA, PCD,
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and nattire of the tt-auma. Twenty-four montiis post-admission, these participants
underwent a cognitive assessment that included the PASAT, SDMT, RAVLT, and the
Vocabulary subtest of the WAIS-R as a measure of pre-morbid intelligence. Haslam et
al. also performed a principal component factor analysis on the cognitive measures and a
square root tt-ansformation on two of the neurological indices, PTA duration and PCD.
These authors obtained three factors PSYFACl, reportedly a recent memory factor,
PSYFAC2, reportedly a factor tapping into information processing speed, and PSYFAC3,
reportedly a measure of vocabulary and education.
Haslam et al. reported that five neurological variables, tt-ansformed PCD, PTA,
ttansformed PTA, PCD, and coma duration were significantly related to PSYIFACI
(recent memory). Transformed PTA, ttansformed PCD, coma duration, and surgical
evacuation of exttadural hematoma were reported as significant predictors for
performance on the second factor PSYFAC2 (information processing speed). No
significant correlations were obtained for the third factor PSYFAC3 (vocabulary).
Overall, reportedly 20% more variance in prediction of cognitive outcome was accounted
for with ttansformed PTA and PCD above what was found with these same
untransformed variables.
Gupta and Ghai (1996) investigated memory and information processing capacity
impairment following CHI. Specifically, they examined the effect of severity, as
determined by PTA duration, on information processing and memory performance. Their
participants (N = 48) were all males between 17-50 years-old. They noted that all CHI
patients (n = 24) that participated were alert, oriented, and unequivocally out of PTA at
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the time of testing as judged by the attending physician and psychologist. Duration of
PTA was determined by rettospective questioning. All patients reportedly suffered from
"simple" closed head injury, that is, none evidenced inttacranial hematoma, skull
fracture, or any other neurological complications. Exclusionary criteria for CHI patients
included history of alcoholism, cerebral disease, psychiattic ilhiess, and motor
disturbance or communication problem. A matched sample (n = 24) was obtained, but
the inclusion/exclusion criteria were not reported. Reportedly, information processing
was assessed by the PASAT, while verbal and non-verbal memory was tested three
subtests of the WMS, Digit Span, Associate Leaming, and Visual Reproduction. They
added that these WMS subtests were selected for their abilities to assess attention, verbal,
and visual memory respectively. All materials were in Hindi and presented in the same
order for all participants.
These authors reported that the CHI group performed significantly poorer across
all measures. They added that "deficient performance" by the CHI group on Digit Span
and on the PASAT might have been due to reduced encoding capacity, poor
attention/concenttation, or centtal executive dysfunctioning. To address whether severity
of injury played a role in compromised performance, the authors divided their subjects
into two groups, mild head injury (n = 12) and severe head injury (n = 12). Finally,
Gupta and Ghai found no significant differences on severity by group except for Visual
Reproduction in which the severe CHI group performed worse.
Although Gupta and Ghai covered their bases in regards to inclusion/exclusion
criteria with the CHI group, they did not exclude control participants for a history of head
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ttauma, alcoholism, dmg abuse, neurological conditions, or psychiattic problems. Failure
to exclude individuals with conditions known to adversely affect neuropsychological
assessment performance potentially adds error variance, obscures findings, and makes
any found significant results questionable. Moreover, they only demonsttated what was
already known, that is that CHI individuals perform significantly worse than matched
controls on cognitive measures. These authors also stated the obvious in their
conclusion, that many different independent systems may be involved in visual and
verbal memory, attention/concenttation, and executive fiinctioning. Finally, they failed
to demonstrate a relationship between severity level and these "independent systems" that
affect cognitive outcome.
Loken et al. (1995) assessed severe CHI patients' ability to sustain attention on a
visual continuous performance task "of sufficient ease and duration to assess stability of
performance over time" (p. 593) and compared these performances to severity of injury
as measured by duration of PTA. These investigators used two groups, a severe CHI
group (n = 20) referred from a rehabilitation hospital once they were out of the acute
phase of injury (mean time since injury = 2.9 months), and a conttol group (n = 20)
recmited from the university subject pool and matched for age, education, and gender.
Duration of PTA and severity of injury was determined with the GOAT for the CHI
group. Head injury participants were excluded for history of former head injury or
neurologic insult, but not for alcoholism, substance abuse, or psychiatric history. Control
participants were excluded for previous neurologic insult or psychiatric illness, but not
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for dmg abuse or alcoholism. All participants were administered a computerized version
of a visual continuous performance task.
Loken et al. (1995) reported that their investigation demonsttated that attentional
performance following a severe CHI is impaired in terms of "sustained allocation of
attention over time" and overall vigilance. However, the CHI and conttol groups did not
differ on the amount of errors of commission or omission. These authors also did not
find a significant relationship between CPT performance and severity of injury as
determined by duration of PTA. However, these investigators did not exclude
participants across groups with the same exclusion criteria. Moreover, they included a
healthy conttol group comprised of currently enrolled college students. This is
potentially problematic because of non-equivalence of groups. In other words, the two
groups are qualitatively and perhaps quantitatively different. Overall, failure to follow
standard exclusionary criteria and potential non-equivalence of groups is problematic
because of the potential to add error variance to findings and obscures results.
In summary, review of this body of literature has revealed great inconsistencies
between investigations' findings. The GCS and PTA duration have been related to
measures of cognitive outcome in some investigations, but not others. The lack of
consistent resuhs could be due to the fact that most investigations reviewed failed to
exclude individuals for conditions known to adversely affect neuropsychological test
performance (Alexandre et al., 1983; Bennett-Levy, 1984; Brooks, 1974; Brooks et al.,
1980; Crosson et al, 1988; Geffen et al., 1994; Gupta & Ghai, 1996; Haslam et al., 1994;
Haut & Shutty, 1992; Loken et al, 1995; Mandleberg, 1976; Mandleberg & Brooks,
105
1975; Paniak et al, 1992; Reid & Kelly, 1993; Vilkki et al, 1988). Only one reviewed
investigation (Haslam et al. 1995) implemented exclusion criteria for a history of
previous head injury, neurological condition, psychiattic problems, alcoholism, and dmg
abuse. It is also difficuh to obtain consistent and comparable when there is wide
variation of measures used to assess cognitive outcome across studies (Levin et al,
1990). Another potential contributor to the variability in findings may be attributable to
some investigations' failure to use standardized severity classification criteria (e.g.,
Alexandre et al, 1983; Bennett-Levy, 1984; Haut & Shutty, 1992; Wrightson, 1981).
Failure to use standardized classification methods puts any obtained significance at
question, and limits the usefuhiess on any investigation because the results cannot be
compared across investigations. Finally, many reviewed studies had low sample size per
group (e.g., Gupta & Ghai, 1996), therefore, low power to detect relationships that may
have also contributed to the failure to obtain consistent results.
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APPENDIX B
SEVERITY CLASSIFICATION CRITERIA
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Posttraumatic Amnesia-Severitv Classification Criteria
PTA duration
<5 minutes 5-60 minutes 1-24 hours 1-7 days 1-4 weeks More than 4 weeks
Severity Classification
Very mild Mild Moderate Severe Very severe Exttemely severe
Glascow Coma Scale-Severity Classification Criteria
GCS Coma duration Severity Classification
>13 or <20 minutes Mild
9-12 or <6 hours of admission Moderate
<8 or >6 hours of admission Severe
Both the Posttraumatic Amnesia-Severity Classification Criteria and the Glascow Coma Scale-Severity Classification Criteria were adapted from Lezak (1995).
Lezak, M.D. (1995). Neuroosvcholopical Assessment. (3'^ ed.). New York: Oxford University Press.
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