THE SENSORY NEUROPATHY OF FRIEDREICHS ATAXIA - AN AUTOPSY STUDY OF A CASE WITH PROLONGED SURVIVAL

Observations have been made on a patient with Friedreich's ataxia who died 52 years after the onset of symptoms. The pathology of the brain and spinal cord was typical of this disorder. Apart from loss of dorsa l root ganglion cells. severe loss of secondary sensory neurons was ob served, including the nucleus dorsalis in the spinal cord, the spinal and principal trigeminal nuclei and, in particular, the mesencephalic trigeminal nucleus in the brain stem. Morphometric studies on the firs t sacral nerve root and on the sural nerve at levels from midthigh to ankle revealed a distally accentuated axonal loss that predominantly a ffected larger myelinated nerve fibres. Regenerative activity was seen , mainly in the spinal root and proximally in the sural nerve. Relativ e myelin thickness, assessed by g ratios, tended to be reduced. As tea sed fibre studies showed only limited evidence of demyelination/remyel ination and of axonal regeneration, this therefore suggests the presen ce of hypomyelination. The results confirm the presence of a distal ax onopathy and provide no evidence that this is preceded by axonal atrop hy.