a critical assessment of clinical diagnosis of dis

7/27/2019 A Critical Assessment of Clinical Diagnosis of Dis

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Acta Neurochir (Wien) (1996) 138:4044 Acta Neurochirurgica9 Springer-Verlag1996Printed n Austria

A Cr i t i ca l As s es s m en t o f C l i n i ca l D i a g n o s i s o f D i s c H ern i a t i o n i n P a t ien t s w i t hM o n o ra d i cu l a r S c i a t i caM . J . A l b e c kUniversity Clinic of Neurosurgery, Rigshospitalet, Copenhagen

S u m m a r yThe diagnostic power or clinical parameters in the diagnosis of

lumbar disc herniation in patients with monoradicular pain wasevaluated in a prospective study with a 100% verification of thediagnosis.

Eighty patients with monoradicular pain corresponding to thefifth lumbar or the first sacral nerve root were included. Pre-opera-tively a number of clinical parameters were recorded and comparedto the intra-operative finding of a disc herniation. The parameterswere analysed by receiver operating characteristic (ROC) curves.Results from the available literature were analysed by ROC curvesfor comparison.

In 76% of the cases a disc herniation was discovered. The levelof the disc herniation was correctly predicted in 93% of these casesby the location of the pain alone or supplemented by neurologicalsigns. Apart from radicularly distributed pain, all parameters in thepresent study and in the literature had no or low diagnostic accura-cy.

Thus, in patients with monoradicular sciatica further clinicalparameters do not add to the diagnosis of lumbar disc herniation.

Keywords: Intervertebral disc displacement; neurologicalexamination; quality of test; receiver operating characteristicscurve.Int ro duct io n

The medical history and signs are important in thediagnostic clarifi cation of patients with low back painand sciatica and in the decision on imaging examina-tions and special ist referral [5].

Evidence of lumbar disc herniation is discoveredin 20-30% of asymptomatic persons on myelography,computed tomography and magnet ic resonance imag-ing. This indicates that the therapeutic decision inpatients with low back trouble and sciatica can not bebased on radio logical examina t ion a lone.

While m any s tudies have been published about thediagnostic potentials of radiological methods in the

recent years, this is not the case for clinical examina-tions. Most studies on clinical tests were made m anyyears ago, with different scientific traditions fromthose of today.

To establish the value of a diagnostic test the pop-ula t ion must be well-def ined . When applying noso-logical probabilities, the sensitivity and specificitymust be considered jointl y [1, 4]. A final diagnosis isoften only obtained in patients with positive tests,which introduced verific ation bias, a flaw in manystudies. In the present study all the patients had mono-radicular sciatica, and were all operated on indepen-dent of any imaging examination. The results wereassessed by receiver operating characteristic (ROC)curves to express the true positive fraction (TPF)equal to sens itivity as a func tion of the false positivefraction (FPF) equal to 1-specificity.M a t e r i a l a n d M e t h o d s

The prospective material comprises 80 patients (32 females and48 males) with monoradicular pain from 5th lumbar or 1st sacralroot. Conservative treatment should have failed. Patients with pre-vious low back surgery or age below 18 years and above 60 yearswere excluded, as were patients with the need for acute surgery.Pain should be present also without provocation from straight legraising.

Pain was accepted as evidence of L5 root compression whendistributed to the antero-lateral aspect of the calf and to the dorsumof foot, and as evidence of S 1 root compression when referred tothe posterior portion of the calf extending to the heel and the later-al aspect of the foot. If pain did not extend below the ankle, at leastone additional neurological sign was demanded for the patient to beincluded. These signs were for the L5 root: a) hypaesthesia in thedorsum of foot, b) weakness of dorsiflexion of foot or first toe, c)impaired medial hamstring reflex. For the S 1 root the signs were: a)hypaesthesia at the lateral aspect of the foot, b) weakness of theplantarflexion of the foot or first toe, c) impaired Achilles tendon


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M. J. Albeck: A Critical Asses sment of Clinical Diagnosis of Disc Herniation 41reflex. 57 patients were included on the basis of monoradicularpain referred to the foot alone and 23 on the basis of radicular painsin combination with other signs. The median age was 40 (21-59).

The medical history and clinical findings were carefully record-ed prior to surgery. Sciatica or simultaneous onse t of low back painand sciatica contrary to low back pain preceding sciatica were con-sidered indicative of disc herniation. Claims for workers compen-sation was regarded as speaking against a disc herniation providedexcept pain was positive if leg pain was aggravated by coughing,laughing or defaecation. Segmental spasm was the visual interpre-tation of impaired movement between the lower lumbar segments.Trunk list was examined with the patient in the standing position.The test was considered positive if there was a list of the trunk toeither side during flexion of the back. The f inger-f loor distance wasconsidered suggestive of disc herniation if it was only to the kneelevel or above. The straight leg raising test was described as posi-tive only if radicular pain was elicited. Hypaesthesia should have adermatomal distribution to be considered. Impaired reflexes werecompared with the nonsympt omatic side.

All the patients were investigated using myelography, CT- andMR-scanning. These examinations were available at surgery, butwere not included in the decision to include the patient in the study.The level according to the root syndrome was always explored. In9 cases the neighbouring disc level was explored as well, eitherbecause of a negative disc exploration at the clinical level orbecause paraclinical examination rendered suspicion of herniationat this level. The surgical findings were carefully recorded and con-sidered the definitive diagnosis. A disc herniation was defined asan extruded nucleus pulposus tissue through a defect in the annulusfibrosus. A bulging disc alone was not considered as a positivefinding.

S t a t i s t i c s : The true positive fraction, TPF (sensitivity) and thefalse positive fraction, FPF (1-specificity) was calculated as p {T +I D +} and p {T + I D-}, i.e., the probability of a positive test givenpresence and absence of a disc herniation, respectively. The ROCdiagram was plotted as TPF as a function of FPF for varying dec i-sion thresholds. For dichotomous variables only a single point wasplotted. Points c lose to the 45 ~ line from (0, 0) to (1, 1) are of nodiagnostic value. An optimal test will be close to the upper l eft cor-ner (0, 1) [20, 24].

To get the ROC for a combination of all the parameters wereadded. All positive parameters were weighted equally and assignedthe value one. The resulting ROC curve for varying decisionthresholds, i.e., number of positive parameters, was drawn. Thesignificance level was based on the Mann-Whitney statistic [14].As significance level X2 = 3.84, df = 1 corresp onding to a signifi-cance level of 0.05 was used [13].

Available values of sensitivity and specificity from the litera-ture [11, 12, 18, 19, 22] were plott ed in a ROC diagram. These fig-ures include sciatica, scoliosis, hypaesthesia, motor weakness, andstraight leg raising test.

The study design included informed consent and the patientsaccepted to be operated upon on the basis of clinical judgementalone, even if paraclinica! investigations showed no herniation. Thestudy was approved by the Scientific-Ethical Committee of Copen-hagen.

p r e d i c t e d i n 5 7 ( 9 3 % ) o f t h e s e 6 1 c a s e s . T h e f o u r c a s -e s i n w h o m t h e d i a g n o s i s w i t h r e g a r d t o l e v e l w a si n c o r r e c t w e r e t w o a t t h e 4 t h l u m b a r d i s c a n d t w o a tt h e 5 t h l u m b a r d i s c .

I n F ig . 1 t h e v a l u e s a r e p r e s e n t e d i n t h e R O C - d i a -g r a m . A l l v a l u e s a r e b e l o w o r c l o s e t o t h e X 2 = 3 .84c u r v e w h i c h i m p l i e s t h a t a l l t h e t e s ts h a v e n o o r v e r yl o w d i a g n o s t i c a c c u r a c y .

T h e R O C c u r v e a f t e r a d d i n g t h e n u m b e r o f p o s i -t i v e r e s u l ts f o r a l l t h e p a r a m e t e r s i n F ig . 1 i s d i s p l a y e di n F i g . 2 . T h i s c u r v e i s c l o s e t o t h e 4 5 ~ l i n e .

I f th e a n a l y s i s w a s r e s t r i c t e d t o th e 5 7 p a t i e n t s w h ow e r e i n c l u d e d o n t h e fi n d i n g s o f s c i a ti c a o n l y , th i sw o u l d n o t c h a n g e t h e r e s u l t s .

0 .8

True posit ive fract ion1

S ~ t u

0 . 4 / / / 0/

0. 2

o V" , , , , , ! , , . . . .0 0,2 0.4 0.6 0.8False posit ive fract ion

Fig. 1. Receiver operating characteristic (ROC) diagram of twelveclinical parameters in patients operated on for suspected lumbardisc herniation. Points above the dashed line are significantly diag-nostic (p < 0.05)

O n s e ti P r o v i d e d p a i nx W o r k e r s c o m p e n s a t i o n

S c o l i o s i s9 S e g m e n t a l s p a s mZ T r u n k l i s t9 F i n g e r - f l o o r d i s t a n c ev S t r a i g h t l e g r a i s i n g

P a r e s i sN M u s c l e w a s t i n g9 , i m p a i r e d r e f l e x-- H y p a e s t h e s i a

True posit ive fract ion1

0. 8

0 . 6 / / . . . -

0 . 4 / / / . "

0 r2 / ,'

0 0 .2 0 .4 0 .6 0 .8Fa lse pos i t ive fraction

Re su l t sA t o p e r a t i o n a d i s c h e r n i a ti o n w a s e x p o s e d i n 6 1c a s e s . T h e l e v e l o f th e d i s c h e r n i a t i o n w a s c o r r e c t l y

Fig. 2. Recei ver operating characteristic (ROC) curve (dotted line)of the combination of twelve clinical parameters in patients withsuspected lumbar disc herniation. The dashed line represent the p =0.05 limit


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42 M .J. Albeck: A Critical Assessmentof Clinical Diagnosis of D isc HerniationT r u e p o s i t i v e f r a c t i o n

1.0 -L

0. 8 X

0.6 + +

0.4

0.2

0 .0 . . . . . . 0 14 ' ' ' 0 16 ' ' 0 18 ' ' ' 1 . 00.0 0.2F a l s e p o s i t i v e f r a c t i o n

Fig. 3. R eceiver operating characteristic (RO C) diagram of fiveclinical parameters obtained rom the literature n patients with sus-pected lum bar disc herniation.

Straight leg raising+ Hypaesthesia:~ Paresis9 Scol iosisx Sciatica

T h e R O C d i a g r a m o f v a l u e s o f s e n s it i v it y a n ds p e c i f i c i t y f r o m t h e l i t e r a t u r e is s h o w n i n F i g . 3 . T h ev a l u e s f o r h y p a e s t h e s i a , m o t o r w e a k n e s s , s t r a i g h t l e gr a i s i n g a n d s c o l i o s i s a r e a l l c l o s e t o t h e 4 5 ~ l i n e . T h eo n l y p a r a m e t e r w h i c h i s s i t u a t e d i n th e u p p e r l e f t c o r -n e r i s s c i a t i c a .

D i s cu s s i o nT h e c l i n ic a l h i s to r y a n d p h y s i c a l e x a m i n a t i o n p l a y

a m a j o r r o l e i n t h e d e c i s i o n t o p e r f o r m s u r g e r y i np a t i e n t s w i t h r a d i o l o g i c a l l y c o n f i r m e d d i s c h e r n i a -t i o n . Y e t, t h e s c i e n t i fi c f o u n d a t i o n o f m o s t p a r a m e t e r si s d e f i c i e n t . C o m m o n f l a w s i n t h e c u r r e n t l i t e r a t u r ea r e : 1 ) t h e r e s u l t s o f t h e t e s t a re o n ly g iv e n f o rp a t i e n t s w h e r e a d i s c h e r n i a t i o n i s d i s c o v e r e d [7 , 1 7 ,1 8 , 22 , 2 6 ] ; 2 ) o n l y o p e r a t i v e f i n d i n g s f o r p a t i e n t sw i t h a p o s i t i v e t e s t a r e g i v e n [ 12 ] ; 3 ) n o f i n a l d i a g n o -s i s is o b t a in e d [ 2 ]; 4 ) o n ly p a t i e n t s w i th a p o s i t i v e t e s ta r e i n c l u d e d [ 2 1] ; 5 ) e x c l u s i v e l y a c c u r a c y o r s e n s i t i v -i t y a r e p r e s e n t e d .

W h e n p r e s e n ti n g t h e d i a g n o s t i c v a l u e o f a p a r a m e -t e r t h e s e n s i t i v i t y a n d s p e c i f i c i t y m u s t b e c o n s i d e r e dt o g e t h e r. I n t h e p r e s e n t s t u d y t h e c o n c l u s i o n f o r m o s to f th e p a r a m e t e r s w o u l d b e , t h a t t h e s e p a r a m e t e r s a r es u i t a b l e t o m a k e t h e d i a g n o s i s o f a d i s c h e r n i a t i o n( h i g h s e n s i t i v i t y ) a n d p o o r f o r e x c l u d i n g t h e d i a g n o -s i s (l o w s p e c i f i c i t y ) . W h e n l o o k e d a t i n t h e R O C - d i a -g r a m , i t i s a p p a r e n t t h a t t h e t e s t s h a v e n o o r a l o wd i a g n o s t i c p o w e r .

T h e p a t i e n t s a r e s e l e c t e d o n t h e b as i s o f m o n o r a -d i c u l a r s c i a t i c a a n d i t is c o n s e q u e n t l y n o t p o s s i b l e t oc a l c u l a t e t h e s p e c i f i c i t y o f t h i s s y m p t o m , b u t t h e h i g hi n c i d e n c e o f d i s c h e r n i a t i o n s u g g e s t s t h a t t h e p r e s -

e n c e o f s c i a t ic a h a s a h i g h p r e d i c t i v e v a l u e o f a d i s ch e r n i a t i o n . B u t i t i s n o t p o s s i b l e t o s a y a n y t h i n g a b o u tt h e n e g a t i v e p r e d i c t i v e v a l u e o f s c i a ti c a .

T o s e e i f t h e c o n c l u s i o n i s v a l i d f o r o t h e r s t u d i e s,c o r r e s p o n d i n g v a l u e s o f s e n s i t i v i t y a n d s p e c i f i c i t yf r o m t h e a v a i l a b l e l i t e r a t u r e w e r e p l o t t e d i n a R O Cd i a g r a m . I t w a s o n l y p o s s i b l e t o f i n d f e w v a l i d f i g -u r e s , a s e i t h e r t h e f i g u r e s f o r p a t i e n t s w i t h n e g a t i v et e s t w e r e n o t p r o v i d e d o r t h e f ig u r e s f o r t h e t e s t w e r en o t p r o v i d e d f o r p a t i e n t s w i t h n e g a t i v e d i s c e x p l o r a -t i o n . V a lu e s f o r s t r a ig h t l e g r a i s i n g s i g n [ 1 2 , 1 6 ], s e n -s o r y d i s t u r b a n c e s [ 1 6 , 1 9 ] , p a r e s i s [ 1 6 , 1 9 ], s c o l i o s i s[ 1 9 ], a n d s c i a t i c a [ 5 ] w e r e o b t a in e d . A s t h e s i z e o f t h ep o p u l a t i o n d i f f e r s b e t w e e n t h e v a r io u s s t u d i e s i t i s n o tp o s s i b l e t o p l o t a s i n g l e s i g n i f i c a n c e c u r v e , b u t i t i sa p p a r e n t t h a t a l l t e s t s , e x c e p t f o r s c i a t i c a , a r e c lo s e t ot h e 4 5 ~ l i n e , w h i c h m e a n s t h a t t h e y a r e d i a g n o s t i c a l l yu n i n f o r m a t i v e . T h e o n l y p a r a m e t e r p l a c e d i n t h eu p p e r l e f t c o r n e r i s s c i a t i c a [ 6 , 2 2 ] . A s t r o n g c o r r e l a -t i o n b e t w e e n r a d i c u l a r p a i n d i s t r i b u t i o n a n a m y e l o -g r a m i n d i c a ti v e o f d i sc h e r n i a t io n h a s b e e n d e m o n -s t r a te d b y p a i n d r a w i n g [ 25 ] .

W h e n t h e c l i n i c i a n e v a l u a t e s a p a t i e n t h e d o e s n o tr e l y o n a s i n g l e p a r a m e t e r a l o n e , b u t w i l l s u m m a r i z ee l e m e n t s f r o m t h e m e d i c a l h i s to r y a n d p h y s i c a l e x a m -i n a t i o n i n t o a n i m a g i n a r y l i k e l i h o o d t h a t t h e p a t i e n th a s a d i s c h e r n i a t i o n a n d w i l l b e n e f i t f r o m s u r g e r y .T h i s h a s r e s u l t e d i n c o n s t r u c t i o n o f s e v e r a l r a t i n gs c a le s w i t h a m o r e o r l e s s a r b i tr a r y w e i g h t i n g o f t h ep a r a m e te r s [ 8 , 15 , 2 3 ] . T h e r e l a t i v e w e ig h t o f e a c hp a r a m e t e r m a y v a r y a c c o r d i n g t o d i f f e r e n t c l i n i c ia n s ,b u t a s s u m i n g t h e w e i g h t o f o n e f o r e v e r y p a ra m e t e r i sp r o b a b l y c l o s e t o c o m m o n c l i n i ca l p r a ct i ce . W h e n t h ep a r a m e t e r s a r e s i m p l y a d d e d i t i s o b v i o u s f r o m t h eR O C d i a g r a m t h a t t h i s d o e s n o t i n c r e a s e t h e d i a g n o s -t i c a b i l i t y a s t h e r e s u l t i n g R O C p lo t i s c l o s e t o t h e 4 5 ~l i n e . A s a l l t h e p a r a m e t e r s h a v e a l o w d i a g n o s t i ca c c u r a c y , it i s u n l i k e l y t h a t a m o r e e l a b o r a t e d r a t i n gs c a l e w i l l b e b e t t e r .

V a l u e s o f s e n s i t i v i t y a n d s p e c i f i c i t y , i n c l u d i n gR O C c u r v es , m u s t a l w a y s b e c o n s i d e re d t o g e t h e r w i tht h e f r e q u e n c y o f d i s c h e r n ia t i o n a m o n g s t n e w c a s es i nt h e p o p u l a t i o n i n q u e s t i o n . I f t h e s e n s i t i v i t y o f s c i a ti -c a i s 0 .9 5 a n d t h e s p e c i f i c i t y is 0 . 8 8 [ 8 ], a n d t h e r e l a -t i v e f r e q u e n c y o f d i s c h e r n i a t i o n i s 7 5 % , w h i c h i sl i k e l y i n a n e u r o s u r g i c a l d e p a r t m e n t , t h e n t h e c o r r e -s p o n d i n g p o s i t i v e p r e d i c t i v e v a l u e w i l l b e 0 . 9 6 a n dt h e n e g a t i v e p r e d i c t i v e v a l u e 0 . 8 5. O n t h e o t h e r h a n d ,i f t h e p a t i e n t i s s e e n b y t h e g e n e r a l p r a c t i t i o n e r t h er e l a t i v e f re q u e n c y o f d is c h e r n i a t i o n c a n b e a s s u m e d


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M. J. A lbeck: A C ritical Assessment of Clinical Diagnosis of Disc Herniation 43t o b e 1 % a n d c o n s e q u e n t l y t h e p o s i t i v e p r e d i c t i v e v a l -u e w i l l b e 0 .0 7 a n d t h e n e g a t i v e p r e d i c t i v e v a l u e 0 . 9 9 .I n sp i te o f t h e s e l i m i t a t i o n s , R O C c u r v e s a r e v a l u a b l ef o r t e s t in g t h e r e l a t i v e a c c u r a c y o f d i f f e r e n t t e s ts .

I t m a y b e q u e s t i o n e d i f a d i f f e r e n t r e s u l t w o u l dh a v e b e e n f o u n d i n a p o p u l a t i o n w i t h o u t o b v i o u sm o n o r a d i c u l a r p a i n . T h e f i g u r e s f r o m t h e l it e r a tu r ea r e c o m p i l e d f r o m v a r i o u s p o p u l a t i o n s . I t h as b e e nd e m o n s t r a t e d b y H a k e l i u s [ 1 2] t h a t t h e r e is n o d i f f e r -e n c e i n th e i n c i d e n c e o f a d is c h e r n i a t i o n i n p a t i e n t sw i t h m o n o - a n d p o l y r a d i c u l a r s y n d r o m e s . I t is th u sl i k e l y t h a t t h e r e s u l t i s t r u e f o r m o s t p a t i e n t s w i t hs c i a ti c a . T h e s i t u a t io n m a y b e d i f f e r e n t f o r a p o p u l a -t i o n o f p a ti e n t s w i t h o u t l e g p a i n , b u t a s v i r tu a l l y a l lp a t i e n t s w h o a r e c a n d i d a t e s f o r s u r g e r y h a v e p a i n i nt h e l e gs , t hi s is o f s m a l l r e l e v a n c e . T w e n t y - t h r e e o ft h e p a t i e n t s i n t he p r e s e n t s t u d y w e r e i n c l u d e d o n t h eb a s i s o f l e g p a i n t o g e t h e r w i t h a t l e a s t o n e n e u r o l o g i -c a l s i g n , a s th e i r p a i n d i d n o t e x t e n d b e l o w t h e a n k l e .T h i s i n t r o d u c e s s o m e s e l e c t i o n bi a s . H o w e v e r ,e x c l u d i n g t h e s e p a t i e n t s f r o m t h e a n a l y s i s d i d n o tc h a n g e t h e r e s u l t s .

K o r t e l a i n e n [ 1 8 ] w a s a b l e to lo c a l i z e t h e le v e l o fd i s c h e r n i a t i o n i n 9 3 % b y p a i n p r o j e c t i o n a n d f o u n dt h a t p a i n r e f e r r e d t o t h e 5 t h lu m b a r d i s t r i b u t i o n w a sm o r e r e l i a b le f o r " l e v e l " d i a g n o s i s t h a n p a i n r e f e r re dt o t h e f i r s t s a c r a l d i s t r i b u t i o n . I n t h e p r e s e n t s t u d y i tw a s p o s s i b l e f r o m t h e p a in d i s t r i b u t io n t o p r e d i c t t h ec o r r e c t l e v e l i n 9 3 % o f p a ti e n t s w i t h a d i s c h e r n i a t i o n ,b u t t h e r e w a s n o d i f f e r e n c e i n t h e r e l ia b i l i t y i n l e v e lp r e d i c t i o n b e t w e e n t h e L 5 r o o t a n d t h e S 1 r o o t . O t h e ra u t h o r s s u g g e s t t h a t it i s n o t p o s s i b l e t o d i s t i n g u i s hb e t w e e n a n a f f e c t i o n o f t h e 5 t h l u m b a r a n d 1 s t s a c r a lr o o t f r o m t h e d i s t r i b u ti o n o f p a i n a l o n e [ 3, 1 0 ] .

T h e r e s u l ts o f th e t e s ts i n t h is a n d m o s t o t h e r s t u d -i e s r e f l e c t t h e e x a m i n e r s ' s u b j e c t i v e i n t e r p r e t a ti o n . Am o r e o b j e c t i v e e x a m i n a t i o n b y i ns t r u m e n t s m a yi m p r o v e t h e d i a g n o st i c a c c u r a c y o f s e n s o r y [ 26 ] a n dm o t o r c h a n g e [ 9 ], b u t a re t e s s s u i ta b l e f o r r o u t i n ee x a m i n a t i o n .

ConclusionT h e b e s t c l i n i c a l i n d i c a t o r o f a d i s c h e r n i a t i o n i s

s c i a ti c a . F u r t h e r c l i n i c a l e x a m i n a t i o n d o e s n o t a d ds i g n i f i c a n t l y t o t h e d i a g n o s i s . A l l p a t ie n t s w i t h s c i a t i -c a , w h o d o n o t r e s p o n d t o c o n s e r v a t i v e t r e a tm e n t ,s h o u l d b e r e f e r r e d f o r C T o r M R I . P a t i e nt s w i t h m o n o -r a d i c u l a r le g p a i n a n d a p o s i t i v e i m a g i n g e x a m i n a t i o nc a n s a f e l y b e r e f e r r e d f o r s u r g e r y e v e n i f t h e r e a r e n op o s i t i v e s i g n s , u n l e s s , e . g . n o n - o r g a n i c s i g n s s p e a k

a g a i n s t i t. E v e n t h o u g h i t d o e s n o t a d d t o t he d i a g n o -s is o f a d i s c h e r n i a t i o n , t h e m e d i c a l h i s t o r y s h o u l d b eo b t a i n e d a n d a p r e c i s e c l i n i c a l e x a m i n a t i o n c a r r i e do u t to u n c o v e r o t h e r d i s o rd e r s l i k e n e o p l a s m a n d p o l -y n e u r o p a t h y a n d t o e x p o s e n o n - o r g a n i c p r o b l e m s .

AcknowledgementSupported by K athrine & Vigo Skovgaards Foundation and TheDanish Hospital Foundation for Medical Research, Region of

Copenhagen, The Faroe Islands and Greenland.

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Correspondence: Michael J. Albeck, M.D., 431 NeurosurgicalDepartment, Hvidovre University Hospital, Ketteg~rds All~ 30,DK-2650 Hvidovre, Denmark.

a critical assessment of clinical diagnosis of dis

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