ELECTROPHYSIOLOGY AND NERVE BIOPSY - COMPARATIVE-STUDY IN FRIEDREICH ATAXIA AND FRIEDREICH ATAXIA PHENOTYPE WITH VITAMIN-E-DEFICIENCY

The authors report a comparative study of peripheral nerve conductions and nerve biopsy and somatosensory evoked potentials between 15 patie nts with Friedreich's ataxia and 15 patients with Friedreich's ataxia phenotype with selective vitamin E deficiency. The patients in the two groups are of similar age, age of onset, and clinical phenotype. Peri pheral motor nerve action potential amplitude, and conduction velociti es are within normal ranges in the two groups. In the Friedreich's ata xia group there is an early and severe peripheral sensory axonal neuro nopathy, characterised by an important reduction of the amplitude of s ensory action potential, and important loss of myelinated fibres with complete disappearance of large myelinated fibres without any regenera tive process. In the Friedreich's ataxia phenotype with selective vita min E deficiency group there is slight-to-moderate axonal sensory neur opathy with normal to moderate decrease of large myelinated fibre dens ity and important regeneration in nerve biopsy. Somatosensory evoked p otentials are markedly involved in the two groups asserting a severe i nvolvement of somatosensory pathway in lumbar, thoracic and cervical s pinal cord. These findings suggest that the pathological mechanism inv olved in the two diseases are different: central peripheral axonopathy in Friedreich's ataxia and central distal axonopathy in Friedreich's ataxia phenotype with selective vitamin E deficiency. (C) 1998 Elsevie r Science B.V. All rights reserved.