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11.16011-04042007.imIf 0.05). S y m p t o m s i n t h e m i d d l e finger c o r r e l a t e d w i t h M R I o f C 6 - 7 d i s k p r o t r u s i o n {P < D.OOl) a n d t h e s p i n a l c o r d i n v o l v e m e n t a t t h e m o s t u p p e r C 3 - 5 levels (P < 0 . 0 0 0 1 ) o n M R I . C o r r e l a t i o n w i t h M R I p a t h o l o g y o f C 6 - 7 r o o t channels w a s n o t signific a n t {P > 0 . 0 5 ) . S y m p t o m s i n t h e h t t l e finger showed significant positive correlation w i t h spinal cord involvement at C 5 - 6( P < 0.001) a n d C 3 - 5 {P < 0 . 0 0 0 1 ) l e v e l s a s w e l l a s w i t h C 6 - 7 d i s k p r o t r u s i o n {P < 0 , 0 0 0 1 ) o n M R I . D-SEP and MRl-lhQ results a r e presented i n T a b l e 3, w h e r e i t i s s h o w n t h a t d i g i t I - S E P (C6 sensory p a t h w a y ) a b n o r m a l i t y correlates w i t h C 5 - 6 i n t r a f o r a m i n a l c h a n g e s {P < 0 . 0 0 0 1 ) a n d spinal c o r d i n v o l v e m e n t at C 3 - 5 levels o n M R I (P < 0 . 0 0 0 1 ) . D i g i t I I I - S E P ( C 7 ) s h o w e d s i g n i f i cant correlation w i t h spinal cord i n v o l v e m e n t at C 3 - 5 a n d C 5 - 6 l e v e l s (P < 0 . 0 0 0 1 ) a n d w i t h C 6 - 7 i n t r a f o r a m i n a l n a r r o w i n g o n M R I (P < 0 . 0 1 ) . Digit V - S E P ( C 8 ) correlated with spinal cord i m p i n g e m e n t a t t h e u p p e r levels [C3-5, C 5 - 6 a n d C 6 - 7 ) o n M R I (P < 0 . 0 0 0 1 ) .
W e also f o u n d a positive correlation between general D - S E P a b n o r m a l i t y a n d the general a m o u n t o f p a t h o l o g y o n M R I (P < 0 . 0 0 1 ) . D-SEP and sensory symptoms - A c o m p a r i s o n o f D S E P abnormalities w i t h sensory s y m p t o m s i n t h e c o r r e s p o n d i n g finger s h o w e d t h a t 1 1 o f 1 5 a b n o r mal digit I - S E P (73Vo) were recorded following stimulation o f asymptomatic thumbs. F o r digit I I I S E P , t h e values w e r e 16 o f 2 8 ( 5 7 % ) a n d f o r digit V - S E P 11 o f 1 7 ( 6 5 % ) .
Discussion
Symptoms and M R I O u r pafients w i t h neck pain a n d pain radiating along the a r m represented a very heterogeneous group concerning age, onset a n d d u r a t i o n o f s y m p t o m s a s w e l l a s M R I findings. M R I s h o w e d o n l y a f e w severe compressions o f t h e spinal cord or i n t r a f o r a m i n a l n a r r o w i n g . W e f o u n d n o patients w i t h acute pure clinical m o n o - r a d i c u l o p a t h y o r pure myelopathy confirmed b y M R I . Therefore, i t a p p e a r s u n r e a s o n a b l e t o select c e r v i c a l m o n o r a d i c u l o p a t h y as a separate clinical e n t i t y a m o n g patients w i t h s y m p t o m a t i c C S D . This is usually d o n e m o s t l y i n cases o f l u m b o s a c r a l m o n o - r a d i culopathies where a n a t o m i c a l conditions a r e different. A p o o r c o r r e l a t i o n o f clinical signs a n d s y m p t o m s w i t h M R I findings o f r o o t c o m p r e s s i o n a t t h e corresponding cervical level i n radiculopathies is r e p o r t e d b y o t h e r s ( 1 , 2 , 8, 9, 11). I n o u r patients, we found a strong correlation o fsymptoms i n the fingers with spinal cord compression at t h e upper ( C 3 - 5 ) levels o n M R I , e v e n t h o u g h t h e grade o f a b n o r m a l i t y w a s assessed as m o d e r a t e t o severe i n only 5 o f t h e 2 0 patients. These data permit t h e c o n c l u s i o n t h a t s e n s o r y s y m p t o m s i n t h e fingers can be attributed n o tt o t h er o o t b u t t o t h e spinal cord c o m p r e s s i o n a t t h e u p p e r cervical levels. W e f o u n d a significant positive correlation o f M R I abnormality a t C 3 - 5 segments w i t h age. Disk 125
Kwast-Rabben et al. protrusions at l o w e r levels c a n be p a r t l y o r completely released a n d b e c o m e c l i n i c a l l y silent, while degenerative changes a t the upper C 3 - 4 and C4-5 segments c o m e w i t h age. A d d i t i o n a l c o m pression a t t h e upper cervical levels increases t h e severity o f injury and, therefore, can contribute t o D - S E P a b n o r m a l i t y a n d sensory symptoms. Regression o f m o s t herniated disks w i t h disappearance o f clinical symptoms w i t h time a n d w i t h o u t surgical i n t e r v e n t i o n , h a s been reported (12, 13). M o r e frequent i n v o l v e m e n t o f C 3 - 5 segments w i t h a g e as a reason f o r significant clinical d y s f u n c t i o n was also discussed b y others (14, 15). V o s k u h i a n d H i n t o n (14) described a g l o v e d i s t r i b u t i o n o f sensory loss i n t h e h a n d as being caused b y severe s p o n d y l o t i c compression o f the s p i n a l c o r d a t these t w o cervical levels i n their older patients (i.e. 4 8 - 8 3 years o l d ) . T h e y concluded that the presentation o f glove-distribution s e n s o r y loss s h o u l d a l w a y s raise a s u s p i c i o n o f a c e r v i c a l m y e l o p a t h y t h a t , i n t h e i r cases w a s s u r g i cally treatable. T a n i w i t h co-workers (15) f o u n d a high incidence o f c o n d u c t i o n block a t these upper cervical levels, w h i c h w a s a reason for significant clinical dysfunction i n elderly people. T h e authors a l s o f o u n d a n ' a g e - r e l a t e d s h i f t i n t h e p r i m a r y sites of involvement in cervical spondylotic myelopathy f r o m l o w e r t o upper levels'. Sensory s y m p t o m s correlated also w i t h t h e presence o f disk p r o t r u s i o n a t t h e corresponding spine level o n M R I , regardless o f i f it affected the r o o t i n its r o o t c h a n n e l o r t h e s p i n a l c o r d . T h e s e findings strongly suggest t h a t p a i n a n d paresthesia could depend o n factors other than o n l y compression o f t h e nerve. Local i n f l a m m a t i o n b y a ruptured disk o r vascular insufficiency have been demonstrated o r suggested b y others as possible significant factors t o generate t h e s y m p t o m s (14, 16). D-SEP In o u r group o f patients w i t h different severity and duration o f symptoms, conduction abnormality w a s detected b y D - S E P i n 5 2 % o f cases; a n d D - S E P appeared t o be m u c h m o r e sensitive t h a n S E P t o median nerve stimulation. T h e higher sensitivity o f D - S E P i n patients w i t h m u l t i p l e level a n d m u l t i p l e - r o o t c o m p a r e d w i t h a singlelevel i n v o l v e m e n t o n M R I (i.e. 6 2 % , 4 4 % a n d 3 0 % , respectively) c a n be explained b y a longer segment w i t h impaired conduction o r simply b y a m o r e severe i n j u r y . I n v o l v e m e n t o f t w o o r m o r e cervical levels also creates f a v o u r a b l e c o n d i t i o n s f o r d e t e c t i n g a b n o r m a l i t y i n cases w h e r e t w o n e r v e r o o t s i n n e r v a t e o n e finger. F o r t h e s a m e r e a s o n . 126
one can expect a l o w D - S E P sensitivity f o r detect i o n o f a single r o o t injury. L o w sensitivity o f D - S E P a n d its poor correlation w i t h clinical s y m p t o m s a n d r a d i o l o g i c a l findings w e r e e x p r e s s e d i n some p u b l i c a t i o n s ( 1 , 2 , 8, 9, 1 1 ) . U s i n g accurately prepared reference m a t e r i a l o f a healthy p o p u l a t i o n f o r D - S E P , increases sensitivity a n d specificity o f t h e m e t h o d b y d i m i n i s h i n g false n e g a t i v e a n d e l i m i n a t i n g false p o s i t i v e results. T h e h e a l t h y i n d i v i d u a l s w h i c h o u r reference values f o r D - S E P a r e based o n (10) have n o s y m p t o m s ; however, t h e presence o f M R I abnormalities cannot be excluded. Thus, with t h e absence o f a pure ' m o n o - r a d i c u l o p a t h y ' entity, using D - S E P for obtaining i n f o r m a t i o n about the level a n d t h e severity o f t h e i n v o l v e d sensory pathways in patients w i t h heterogeneous M R I and clinical picture can be even m o r e warranted. Analyses o f relationships between cervical a n d cortical responses following digital stimulation contribute t o t h e diagnostic localization o f t h e injury to the r o o t u pt o dorsal nucleus, spinal cord a b o v e t h e d o r s a l nucleus, o r t o b o t h levels. T h e p r i n c i p l e has been described i n the results. O b t a i n i n g o f a b n o r m a l i t y type three a l l o w e d u s to suggest that compression o f the sensory pathway above the dorsal nucleus m i g h t faciHtate t h e spinal component o f t h e cervical response, i f there a r e t w o c o m p o n e n t s ( 1 0 , I I , 17). T a n i et a l . (18) a n d H o s h i n o et al. (19) s h o w e d b y s t i m u l a t i o n o f the spinal cord that cervical potential was facilitated i f t h e c o m p r e s s i o n site is l o c a l i z e d i m m e d i a t e l y a b o v e t h e nucleus i n t h e d o r s a l c o l u m n . W e feel t h a t a physiological explanation f o r this p h e n o m e n o n c o u l d b e a decreased i n h i b i t o r y c o n t r o l o f t h e dorsal c o l u m n nucleus f r o m the compressed pyram i d a l tract. T h e m o r e frequent injury a t C 6 root level, compared w i t h other roots, localized b y D - S E P i n o u r r e s u l t s , m i g h t b e e x p l a i n e d b y t h e findings o f m o r e p r o n o u n c e d M R I abnormalities related t o C5-6 compared w i t h C6-7 root channel which was also f o u n d i n o u r data. Besides, compression o f the spinal c o r d a t the upper levels c a n also d a m a g e the grey m a t t e r (dorsal nucleus) itself, causing degene r a t i o n o f t h e nerve cells. I n j u r y o f C 8 sensory p a t h w a y s , as assessed b y D - S E P , m o r e o f t e n occurs o n t h e spinal c o r d level above i t s dorsal n u c l e u s . T h i s fits w e l l w i t h o u r r e s u l t s o f s i g n i f i c a n t correlation between digit I - S E P and intraforaminal changes o n M R I a n d between different D - S E P s a n d C 3 - 5 spinal c o r d c o m p r e s s i o n o nM R I as well as w i t h t h e c o m p l e x a n a t o m y o f the cervical spine area. T h u s , a disk compressing the spinal cord a t the C 5 - 6 level o n M R I can generate n o r m a l digit I-SEP, a b n o r m a l digit I I I - S E P w i t h localization o f
Relationship between the symptoms, D-SEP and M R I the lesion a tthe r o o t level, a n d even a b n o r m a l digit V - S E P s h o w i n g localization o f the injury above the dorsal nucleus. T h i s example, taken f r o m o n e o f o u r patients w i t h s y m p t o m s i nt h e l o n g a n d little finger a n d a single-level a b n o r m a l i t y o n M R I , c a n give a n i m p r e s s i o n o f a ' b a d ' c o r r e l a t i o n o f s y m p t o m s a n d D - S E P w i t h M R I findings, t h e r e b y g i v i n g a 'false p o s i t i v e ' digit I I I - a n d digit V - S E P results. H o w e v e r , i n o u r o p i n i o n , D - S E F f o l l o w i n g stimulation o f digit I , I I I a n d V ( C 6 , C 7 a n d C 8 sensory p a t h w a y s ) helps t o delineate t h e M R I findings, which a r e responsible f o r significant physiological abnormalities. Abnormal D-SEP found o ntheasymptomatic side r e p o r t e d i n o t h e r p a p e r s ( 1 , 2 , 8 , 9 , 11) w e r e explained b y t h e ability o f D - S E P t o detect subclinical a b n o r m a l i t i e s . O u r results were even more dramatic in showing that more than a half o f abnormal D-SEP w a sfound i n asymptomatic fingers ( 7 3 % , 5 7 % a n d 6 5 % f o r digit I - , digit I I I - a n ddigit V - S E P , respectively). Slowing o f c o n d u c t i o n o r r e d u c t i o n o f responses, caused b y d e m y e l i n a t i o n a n d a x o n a l damage as detected b y D - S E P , remains after regression o f herniated disks with disappearance o f clinical s y m p t o m s , w i t h time a n d w i t h o u t s u r g i c a l i n t e r v e n t i o n . T h i s stresses t h e value o f D - S E P e x a m i n a t i o n asc o m p l e m e n t i n g t h e clinical o n e f o r detection o f sub-clinical a n d chronic conduction abnormalities.
2.
3.
Considering t h e possible surgical treatment, t h e correct i n t e r p r e t a t i o n o f c o m m o n results o f different e x a m i n a t i o n s - M R I , clinical a n d electrophysiological - used for e v a l u a t i o n o f level a n d severity o f injury, s h o u l d be based o n the k n o w l e d g e o f the discussed r e l a t i o n s h i p s b e t w e e n t h e m , a n d o n c o n s i d e r a t i o n o f specific a n a t o m i c a l c o n d i t i o n s o f cervical spine area.
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