Morphometric study of the sensory nerve in classical (or Charcot disease) and juvenile amyotrophic lateral sclerosis.

Analysis of the superficial peroneal nerve sampled in 9 cases of classical amyotrophic lateral sclerosis (classical ALS, Charcot disease) and compared with 8 age-matched controls showed a very significant reduction of all myelinated fibres (P less than 0.001), affecting small-diameter (P less than 0.01) and large-diameter (P less than 0.02) fibres. Moreover, the small-diameter unmyelinated fibres were very significantly reduced (P less than 0.001) and the large-diameter fibres were highly increased (P less than 0.01). These results suggest a phenomenon of chronic axonal degeneration. Analysis of the same nerve in 7 patients suffering from juvenile ALS and compared with 4 age-matched controls showed a significant reduction (P less than 0.05) of myelinated fibres. The small-diameter and overall unmyelinated fibres were not significantly reduced while the large-diameter fibres, were significantly increased (P less than 0.01). The same analysis of 4 patients presenting an early-onset ALS compared with 3 controls showed lesions of a severity half-way between that of the classical and the juvenile form. Our study showed that the lesions of the sensory nerve are of the same type in classical ALS and in juvenile ALS, but of differing severity. The nosologic place of juvenile ALS compared with classical ALS and with heredodegenerative diseases of the nervous system is discussed.