neurocognitive and neuromuscular influences on concussion risk james t. eckner, m.d., m.s....
TRANSCRIPT
Neurocognitive and Neuromuscular Influences on Concussion Risk
James T. Eckner, M.D., M.S.University of Michigan
October 2, 2015
Disclosures
• No significant financial disclosures to report
• Research support:– US Department of Health and Human Services: 1 K23 HD078502-01A1– National Collegiate Athletic Association– National Collegiate Athletic Association & US Department of Defense– University of Michigan Injury Center– Foundation for Physical Medicine & Rehabilitation
• Co-Inventor on US Patent 8,657,295 issued to the University of Michigan on February 25, 2014 (no associated financial relationships)
Neurocognitive InfluencesIntroduction
Reaction Time
Neurocognitive InfluencesIntroduction
Reaction Time
Neurocognitive InfluencesReaction Time
Other Neurocognitive InfluencesVision, Processing, Attention…
Neurocognitive InfluencesWhat’s the evidence?
• No studies directly investigating neurocognitive risk factors for concussion in athletes
• Epidemiological study investigating cognitive function as a risk factors for mTBI in adult men
• Lab-based study investigating relationship between RT and a functional head protective response in recreational athletes
• Two field-based studies investigating relationship between visual/sensory performance and head impact exposure in athletes
Cognitive functionas a risk factor for mTBI
Nordstrom et al., 2013
• 305,885 Swedish adult males• Baseline cognitive testing upon enrollment:– Word recollection test– Visuospatial geometric perception test– Logical/inductive performance test– Theoretical/technical test– Calculated a single normalized cognitive score
• mTBI tracked in National Hospital Register• Median follow-up 19 years (0-22 years)
Nordstrom et al., 2013
• Results:– 5.6 % lower cognitive function in the 1,988 with
mTBI in the 2 yrs. prior to enrollment– Similar 5.3% lower cognitive function in the 2,214
with mTBI within 2 yrs. after enrollment– Moreover, 15.1% lower cognitive function in the
795 with two or more mTBIs during follow up
Nordstrom et al., 2013
Nordstrom et al., 2013
• Noteworthy limitations:– Non athlete, male population– Cognitive measures not sport-specific– Non sport-mTBI (fall, MVA, assault most common)– Hospital-based
• Conclusions:– Low cognitive function may be a risk factor for
mTBI
Relationship between RT and afunctional head-protective response
Eckner et al., 2011
• 26 adult recreational athletes– Completed clinical RT and a simulated sport-
related head protective response during a single laboratory testing session
Eckner et al., 2011
• Significant positive correlation was present(R = 0.725; p < .001)
• Conclusion: Clinical RT is predictive of a sport-protective response
Visual/Sensory performanceand head impact exposure
Visual/Sensory performanceand head impact exposure
• Prospective observational studies lasting 1 season
• Harpham: 38 collegiate football athletes• Schmidt: 37 high school football athletes
• Preseason Visual & Sensory Performance Assessments:– Nike SPARQ Sensory Station– Clinical RT (Harpham only)
• Instrumented with HITS
Visual/Sensory performanceand head impact exposure
• Nike SPARQ– Visual break, visual clarity,
contrast sensitivity, depth perception, near-far quickness, target capture, perception span, eye-hand coordination, go/no-go, RT
• HITS– Linear Acc, Rotational Acc, HITsp
ResultsHarpham et al., 2014
• Results:– Used 2 statistical approaches to compare high vs.
low performers on each task• Non-significant, or mixed findings for 30/45 relationships
studied• Lower impact magnitudes for high performers in 11
relationships– Depth Perception, Target Capture, Perception Span, Go/No-Go
tasks
• Higher impact magnitudes for high performers in 4 relationships– Near-Far, SPARQ RT tasks
ConclusionsHarpham et al., 2014
• Conclusions:– Head impact severity was significantly associated
with some visual and sensory performance measures (perception span, target capture, go/no-go, depth perception)
– Future work should involve identification of at-risk athletes and creation of preventive training interventions
ResultsSchmidt et al., 2014
• Analyses and Results:– Assessed odds of mild vs. moderate and mild vs.
severe head impacts in high vs. low performers on each task• Non-significant findings for 52/54 relationships studied• Greater odds of Moderate and Severe head impacts for
high performers on Near-Far Quickness task
ConclusionsSchmidt et al., 2014
• Conclusions– Better visual performance did not reduce the odds
of sustaining more severe head impacts in HS football players
– Results do not support use of visual training programs to reduce the odds of high magnitude head impacts in HS football players
– Additional research is needed
Visual/Sensory performanceand head impact exposure
• Study limitations:– Neither assessed intentional/unintentional
impacts or striking/struck athlete– Both involved uncontrolled conditions– Did not control for position (Harpham)– Accuracy of HITS for absolute magnitude
(Harpham)
Neurocognitive InfluencesTake-home points
• Neurocognitive factors may influence an athlete’s concussion risk– Stronger cognitive abilities do appear to be protective
for mTBI in adult males– Faster RT is probably protective in any given athletic
impact scenario– Additional factors likely modify the relationship
between neurocognitive factors and head impact severity in the field
– It is unclear whether “neurocognitive training” may modify an athlete’s risk for concussion
Neuromuscular influencesIntroduction
• Will focus on neck strength and related variables…
Neuromuscular influencesIntroduction
• Theoretical benefits:– Newton’s second law
F = ma
Neuromuscular influencesIntroduction
• Theoretical benefits:– Newton’s second law
F = ma
Neuromuscular influences What is the evidence?
• One epidemiological study does directly address this question in athletes
• Multiple biomechanical lab-based studies investigating relationships between neck variables and post-load head kinematics
• Two field-based studies investigating relationship between neck strength and head impact exposure in athletes
• One interventional study investigating the effect of a neck strengthening exercise program
Effect of neck strengthon concussion risk in athletes
Collins et al., 2014
• 6,662 male and female high school soccer, basketball, and lacrosse athletes– 51 schools in 25 states
• Observed over 2 years – High School Reporting Information Online (RIO)
Surveillance System
Collins et al., 2014
• Analyzed preseason neck measurements in 179 who did vs. 6,483 who did not sustain concussion– Circumference– Strength
• Flexion• Extension• R lateral bending• L lateral bending
Collins et al., 2014
• Results:– Overall, concussed athletes had smaller mean
neck circumference, smaller mean neck circumference to head circumference ratio, and smaller mean overall neck strength
Collins et al., 2014
• Results:– Adjusting for gender and sport, every one pound
increase in neck strength, decreased the odds of concussion by 5%
• Conclusion: neck strength may be used as a screening tool for concussion risk– Possible targeted intervention once identified
Biomechanicallab-based studies
Eckner et al., 2014
• 46 male and female athletes aged 8-30 years• Primary variables– Maximum isometric force generation– Changes in linear and angular velocity of the head– Measured in each plane of motion
Eckner et al., 2014
• Results:– Isometric neck strength was inversely associated
with changes in head linear and angular velocity across all planes of motion
Eckner et al., 2014
• Conclusion:– Greater neck strength can reduce the magnitude
of the head’s kinematic response• Generally consistent with other lab-based
research in this area
Neck strength andhead impact exposure
• Prospective observational studies lasting 1 season
• Mihalik: 37 youth ice hockey athletes• Schmidt: 49 high school and collegiate football athletes
• Preseason neck assessments:– Isometric strength (multiple-planes)– Cervical muscle cross-sectional area (Schmidt only)– Neck stiffness, angular displacement, and muscle onset latency
during perturbation (Schmidt only)• Instrumented with HITS
– Linear acceleration and HITsp– Rotational acceleration (Mihalik only)
Neck strength andhead impact exposure
Mihalik et al., 2011
• Analyses and results– Compared impact magnitudes between athletes in
3 tertiles of neck strength (in 5 directions)• No differences in impact magnitudes between the neck
strength groups for 14/15 analyses performed• Higher impact magnitude in the strong neck strength
group in one analysis– Higher HITsp in the strong group in “upper trapezius” direction
Mihalik et al., 2011
• Conclusions:– The notion that greater cervical muscle strength
mitigates head impact acceleration is not supported.
– Future work should consider dynamic strength testing methods
Schmidt et al., 2014
• Analyses and results– Compared odds of mild vs. moderate/severe head
impact magnitudes between high and low performers for each predictor variable• No relationship for 70/78 overall analyses and 154/176
positional subgroup analyses• Of significant findings:
– 4/4 overall analyses and 13/14 subgroup analyses found greater neck strength, faster rate of torque development, and larger cervical muscle cross-sectional area increased odds of moderate or severe head impacts
– 4/4 overall analyses and 6/8 subgroup analyses found greater stiffness, smaller angular displacement, and faster muscle onset latency decreased odds of moderate or severe head impacts
Schmidt et al., 2014
• Conclusions– Athletes with stronger and larger neck muscles did
not experience mitigated head impact severity– Greater cervical stiffness and less angular
displacement after perturbation reduced the odds of higher magnitude head impacts
Neck strength andhead impact exposure
• Study limitations:– Similar to limitations of field-based neurocognitive
studies• Neither assessed intentional/unintentional impacts or
striking/struck athlete• Both involved uncontrolled conditions• Both cite issues with neck strength testing• Did not control for position (Mihalik)• Accuracy of HITS for absolute magnitude (Mihalik)
Interventional study
Mansell et al., 2005
• Assigned 36 collegiate soccer players to an 8 week flexion/ extension neck strengthening program or control• Compared neck girth, strength, stiffness, and
head-neck kinematic responses pre and post intervention
Mansell et al., 2005
• Results summary:
• Potentially limited by highly selected study population and relatively small sample size
Variable Intervention Control
Neck Girth
Neck Strength
Neck Stiffness
Head-Neck Displacement
Head-Neck Acceleration
Mansell et al., 2005
• Conclusions:– The 8-week training program increased neck
strength and girth, but did not enhance head-neck-dynamic stabilization during force application
– Other neck muscle training programs should be considered in the future
Neuromuscular InfluencesTake-home points
• Thicker necks are stronger and stiffer• A thick, strong, stiff neck probably does
reduce the magnitude of the head’s kinematic response to any given external force– Additional factors likely modify the relationship
between neuromuscular factors and head impact severity in the field
• Optimal neck strengthening interventions for concussion risk mitigation are not known
Acknowledgements
• James A. Ashton-Miller, Ph.D.• Trina DeMott• Monica S. Joshi, M.S.• Hogene Kim, Ph.D.• Nick LeCursi• David B. Lipps, Ph.D.• Youkeun K. Oh, Ph.D.• Ryan Perkins• James K. Richardson, M.D.• Andrew Schuldt• Mark Shafer
