Correlation of 1a afferent conduction with the ataxia of Fisher syndrome.

The pathophysiology of the ataxia in Fisher syndrome (the syndrome of acute ophthalmoplegia, ataxia, and areflexia) has been attributed to both peripheral nervous system pathology and cerebellar system dysfunction. Pathologic studies have demonstrated no consistent central nervous system abnormalities. We present a case in which abnormalities of 1a sensory conduction were found to correlate directly with the degree of ataxia, without impairment of motor or cutaneous sensory conduction. We propose that the ataxia seen in typical Fisher syndrome may be due to demyelination of 1a afferent fibers.