Peroneal muscular atrophy. Part 2. Nerve biopsy studies.

The present study used the nerve pathology, studied by quantitative light microscopy, as the sole basis for classification of peroneal muscular atrophy (PMA). The findings in biopsies of superficial peroneal nerves of 20 patients were compared with normal values obtained from 8 controls. Three homogeneous groups comprising 17 out of 20 patients were clearly identified. The hypertrophic type (7 cases) was characterized by (1) many multilamellated onion bulb formations; (2) extensive loss of MF with both involvement of the largest and smallest fibers; (3) lack of significant cluster formation. The neuronal sensori-motor type (5 cases) was characterized by (1) absence of any OB; (2) elective loss of large MF; (3) abundance of clusters with significant increase of the small MF population. The neuronal motor type (5 cases) showed a virtually normal sensory nerve except for fairly numerous clusters in some cases. Comparing this classification based on histomorphometric grounds, with the electrophysiological data it appears that 14 patients out of 17 would be correctly classified as hypertrophic or neuronal with respect to the motor nerve conduction velocity of the median nerve alone. Three cases were not classified in the previous groups since they differed notably in one or more parameters from the typical cases. A possible intermediate group is discussed.