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Electrophysiological diagnosis of tarsal tunnel syndrome and interdigital neuropathy of the foot
S147
F238 MODIFICATIONOF OCULOMOTORPROGRAMMINGIN A PATIENT WITH CONGENITAL SQUINT OERTEL,W.H.*,FRIES,W.**,P~PPEL,E.**,LOGOTHETIS,N.**, AND STRUPPLER, A.* *Department of Neurology~Technical U n i v e r s i t y Munich and * * I n s t i t u t e f o r Medical Psychology, Ludwig-Maximilians-University~Munich, FRG We studied in a p a t i e n t with congenital squint (17°inward r o t a t i o n of the l e f t eye) to what extent visual experience can modify c o r t i cal and oculomotor visual f i e l d representation. At the age of 55 t h i s patient suffered an i n f a r c t in the l e f t o c c i p i t a l lobe. When the r i g h t eye was p e r i m e t r i c a l l y studied, the scotoma extended to the v e r t i c a l meridian in the loweroquadrant. In the squinting ( l e f t ) eye, t h i s border was shifted by 17 n a s a l l y from the f i x a t i o n spot but coincided with the anatomical v e r t i c a l meridian. Thus, the l i f e long experience of eye misalignment f a i l e d to induce a p e r i m e t r i c a l l y detectable r e t i n o t o p i c rearrangement in s t r i a t e cortex. In contrast, such rearrangements must have occured in the oculomotor system : We recorded horizontal eye movements of each eye independently ( i n f r a r e d sensitive corneal r e f l e c t i n g system). With the r i g h t eye excluded from v~sion, the l e f t eye could maintain a stable f i x a t i o n p o s i t i o n at 17 o f f the anatomical fovea and could perform r e l a t i v e l y normal saccades related to the functional pseudofovea both in amplitude and d i r e c t i o n . The saccades of the r i g h t eye were concordant with those of the l e f t , i n d i c a t i n g that a matching of noncorresponding r e t i n a l points had taken place in the oculomotor system. Thus, the visual f i e l d representation in the oculomotor centres is modif i a b l e , whereas that in the s t r i a t e cortex appears to be stable.
F239 ELECTROPHYSIOLOGICALDIAGNOSIS OF TARSAL TUNNEL SYNDROMEAND INTERDIGITAL NEUROPATHYOF THE FOOT OH,S.J., Dept. of Neurology, U n i v e r s i t y of Alabama/Birmingham, Birmingham, Alabama 35233, USA We have devised a method of sensory nerve conduction in the i n t e r d i g i t a l nerves of the foot. To assure the r e l i a b i l i t y of recording the small sensory compound nerve potential (CNAP), we used the near-nerve needle and signal averaging techniques. In 12 cases of tarsal tunnel syndrome (TTS) in lO p a t i e n t s , sensory nerve conduction was abnormal in I I cases (slow NCV in 7, dispersion in 7, and low amplitude in 6). Terminal latency was prolonged in 2 cases. In 5 cases of i n t e r d i g i t a l neuropathy (IDN), a selective decrease in amplitude of the CNAP in the involved i n t e r d i g i t a l nerve ("dip phenomenon") was the most c h a r a c t e r i s t i c electrophysiological f i n d i n g . The present technique is capable of recording the sensory CNAP in the i n t e r d i g i t a l nerves of the foot and of confirming the diagnosis of TTS and IDN.
F240 SPINAL CORD EVOKED POTENTIALS IN SPINAL CORD INJURY WITHOUT DISLOCATION OHMI,Y., TOHNO,S., HARATA,S., NAKANO,K., MURAOKA,M., Dept. of Orthopaedic Surgery, Hirosaki U n i v e r s i t y , School of Medicine, Aomori, Japan I t has become possible to i d e n t i f y the level of spinal cord lesions through morphological information by a roentgenologic examination such as myelography~ selective spinal cord angiogra~r~hy and CT scan.
F238 MODIFICATIONOF OCULOMOTORPROGRAMMINGIN A PATIENT WITH CONGENITAL SQUINT OERTEL,W.H.*,FRIES,W.**,P~PPEL,E.**,LOGOTHETIS,N.**, AND STRUPPLER, A.* *Department of Neurology~Technical U n i v e r s i t y Munich and * * I n s t i t u t e f o r Medical Psychology, Ludwig-Maximilians-University~Munich, FRG We studied in a p a t i e n t with congenital squint (17°inward r o t a t i o n of the l e f t eye) to what extent visual experience can modify c o r t i cal and oculomotor visual f i e l d representation. At the age of 55 t h i s patient suffered an i n f a r c t in the l e f t o c c i p i t a l lobe. When the r i g h t eye was p e r i m e t r i c a l l y studied, the scotoma extended to the v e r t i c a l meridian in the loweroquadrant. In the squinting ( l e f t ) eye, t h i s border was shifted by 17 n a s a l l y from the f i x a t i o n spot but coincided with the anatomical v e r t i c a l meridian. Thus, the l i f e long experience of eye misalignment f a i l e d to induce a p e r i m e t r i c a l l y detectable r e t i n o t o p i c rearrangement in s t r i a t e cortex. In contrast, such rearrangements must have occured in the oculomotor system : We recorded horizontal eye movements of each eye independently ( i n f r a r e d sensitive corneal r e f l e c t i n g system). With the r i g h t eye excluded from v~sion, the l e f t eye could maintain a stable f i x a t i o n p o s i t i o n at 17 o f f the anatomical fovea and could perform r e l a t i v e l y normal saccades related to the functional pseudofovea both in amplitude and d i r e c t i o n . The saccades of the r i g h t eye were concordant with those of the l e f t , i n d i c a t i n g that a matching of noncorresponding r e t i n a l points had taken place in the oculomotor system. Thus, the visual f i e l d representation in the oculomotor centres is modif i a b l e , whereas that in the s t r i a t e cortex appears to be stable.
F239 ELECTROPHYSIOLOGICALDIAGNOSIS OF TARSAL TUNNEL SYNDROMEAND INTERDIGITAL NEUROPATHYOF THE FOOT OH,S.J., Dept. of Neurology, U n i v e r s i t y of Alabama/Birmingham, Birmingham, Alabama 35233, USA We have devised a method of sensory nerve conduction in the i n t e r d i g i t a l nerves of the foot. To assure the r e l i a b i l i t y of recording the small sensory compound nerve potential (CNAP), we used the near-nerve needle and signal averaging techniques. In 12 cases of tarsal tunnel syndrome (TTS) in lO p a t i e n t s , sensory nerve conduction was abnormal in I I cases (slow NCV in 7, dispersion in 7, and low amplitude in 6). Terminal latency was prolonged in 2 cases. In 5 cases of i n t e r d i g i t a l neuropathy (IDN), a selective decrease in amplitude of the CNAP in the involved i n t e r d i g i t a l nerve ("dip phenomenon") was the most c h a r a c t e r i s t i c electrophysiological f i n d i n g . The present technique is capable of recording the sensory CNAP in the i n t e r d i g i t a l nerves of the foot and of confirming the diagnosis of TTS and IDN.
F240 SPINAL CORD EVOKED POTENTIALS IN SPINAL CORD INJURY WITHOUT DISLOCATION OHMI,Y., TOHNO,S., HARATA,S., NAKANO,K., MURAOKA,M., Dept. of Orthopaedic Surgery, Hirosaki U n i v e r s i t y , School of Medicine, Aomori, Japan I t has become possible to i d e n t i f y the level of spinal cord lesions through morphological information by a roentgenologic examination such as myelography~ selective spinal cord angiogra~r~hy and CT scan.