NEUROPHYSIOLOGICAL ASSESSMENT OF THE EARLY PHASES OF CARPAL TUNNEL SYNDROME WITH THE INCHING TECHNIQUE BEFORE AND DURING OPERATION

In 14 patients with early carpal tunnel syndrome, the diagnostic sensitivity of the measurement of the segmental sensory nerve conduction velocity at 1 cm. steps (“inching”) was compared with the distal sensory latency and the pre-operative wrist-digit and wrist-palm S.C.V. and with similar measurements made at operation immediately after surgical decompression of the nerve. Before operation, distal sensory latency and wrist-digit S.C.V. were normal in all cases, while wrist-palm S.C.V. was pathological in five patients and inching in all 14 patients. Moreover, inching allowed us to determine the site of the slowing across the carpal tunnel, this being between l-2 cm. from the distal wrist crease in 57 % and between 2-3 cm. in 21 % of cases. Focal slowing disappeared immediately after decompression in five patients, as is evident from the intra-operative recordings. Inching is, therefore, the most sensitive diagnostic method in early carpal tunnel syndrome. Journal of Hand Surgery (British Volume, 1991) 16B: 415-419 Surgical decompression is known to be the treatment of choice for carpal tunnel syndrome. Post-operative clinical recovery is variable, but it is accepted that patients with less severe carpal tunnel syndrome recover earlier. However, there are no reports on different recovery rates of patients operated on at different stages of the syndrome. To evaluate as homogenous a group of C.T.S. patients as possible, we selected those who corresponded to the “early stage ” (Spindler and Dellon, 1982; Lundborg, 1988). These patients have intermittent symptoms which occur during the night only, have no motor or sensory deficit (though there may be positive Phalen’s and Tinel’s signs) and have normal values in conventional electrodi-agnostic studies. In patients in this early stage, we compared the diagnostic sensitivity of the measurement of the segmen-tal sensory nerve conduction velocity at 1 cm. steps (Kimura, 1979), known as “inching”, with conventional and other more recent pre-operative electromyographi