Friedreich's ataxia. A light- and electron microscopic study of peripheral nerve biopsies.

Sural or superficial peroneal nerve biopsies of patients with clinical diagnosis of Friedreich's ataxia were studied. Patients were divided in two groups, typical and abortive forms: loss of fibers accompanied by axonal atrophy and segmental demyelination are the basic changes in both groups, although the decrease in number of myelinated fibers was most severe in typical FA. In the cases with slower progression there is a tendency to form onion bulb complexes.