The carpal tunnel syndrome: a clinical and electrophysiological study of 250 patients.

Clinical and electrophysiological studies were performed on 250 patients with carpal tunnel syndrome. Acroparaesthesia was often referred to all digits (64%) and proximal pain was not uncommon (46%). The male patients as a group differed from the female in that nocturnal acroparaesthesia was less frequent and a causal of predisposing factor was identifiable in the majority (76%). The most common associated condition in the females was trigger finger (11%). An associated ulnar nerve lesion was rare. Delay in diagnosis was attributable to cultural factors or lack of awareness of the occurrence of diffuse acroparaesthesia and proximal pain in the syndrome. Sensory signs were commoner (85%) than motor (53%). The most useful clinical finding was digital sensory 'splitting' (ring finger) which was present in 58% of hands and clearly distinguished the condition from a radiculopathy, myelopathy or a diffuse polyneuropathy. In general, the diagnostic yield of any test depends on the duration of the disease. Of the various electrodiagnostic tests employing surface electrodes, the most sensitive was the comparison of the median (index finger) to ulnar (little finger) sensory amplitude. This was abnormal in 73% of hands and was found to be particularly useful in patients with a probable background of polyneuropathy or suspected cervical rib syndrome. Slowing of sensory conduction was demonstrable in 67% of hands, decreased sensory amplitude in 44% and prolonged motor latency 35 to 32%. A combination of the various electrodiagnostic tests yielded a positive result in 91%. Decompression resulted in complete recovery in 85% and some improvement in all the remaining patients. The outcome was adversely affected by the presence of several neurological deficits but apparently not by the presence of a coexisting disease.