Peroneal muscular atrophy. Part 1. Clinical and electrophysiological study

144 patients with the clinical syndrome of peroneal muscular atrophy or Charcot-Marie-Tooth disease were studied. Thirteen were recognized as the spinal form of the disease since all had normal motor nerve conduction velocity and sensory nerve action potential. The remaining patients could be classified according to their values of motor conduction velocity for the median nerve. Two main groups were therefore identified: 55 patients whose nerve conduction was below 30 m/s belonged to group I, which corresponds to the previously reported hypertrophic form or hereditary motor sensory neuropathy (HMSN) type I. Sixty-four patients whose nerve conduction was above 40 m/s belonged to group II which corresponds in the majority of cases to the neuronal form or HMSN type II. Twelve patients could not be classified since the motor nerve conduction velocity for median nerve ranged between 30 and 40 m/s. These could belong to either of the two main groups or might form an intermediate group, the existence of which is discussed. Clinical genetic and electrophysiological features of the two main groups are discussed and compared.