Hypertrophic neuropathy in spinocerebellar degeneration. Morphological study of the superficial peroneal nerve in fourteen cases.

Fourteen patients belonging to eight families were studied. At least one member of each family presented a clinical picture of spinocerebellar degeneration (SCD) and lowered motor nerve conduction velocity (MNCV). Muscular atrophy of the Charcot-Marie-Tooth type was found in 11 cases. The average MNCV of the median nerve was less than half the value in the controls (P less than 0.001). Morphometric analysis of the superficial peroneal nerve showed a considerable reduction (P less than 0.001) in myelinated fibres, primarily those of large diameter (P less than 0.001), a high average density of onion bulb formations, and a large percentage (P less than 0.001) of teased fibres showing aspects of segmental demyelination, with or without remyelination. These results indicate the presence of a hypertrophic neuropathy (HN) associated with the SCD. In most cases, this HN bore the electrophysiological and morphological features of type I hereditary motor and sensory neuropathy. In certain cases, however, there was an individual and intra-familial discordance of the electrophysiological and histological aspects, which may correspond to a difference in phenotypic expression, or to mutant genes. It is possible that a single disease is involved, assuming the clinical appearance of both SCD and HN, the biochemical support of which remains to be determined.