Abnormalities in sensory and mixed evoked potentials in ataxia-telangiectasia

SUMMARY Electromyography, motor, sensory and mixed nerve conduction velocity, and H reflex were studied in four patients with ataxia-telangiectasia. The earliest and most striking electrophysio-logical finding was the reduced amplitude of evoked nerve potentials. In the oldest patient, findings suggestive of spinal atrophy and mild reduction of the motor and sensory nerve conduction velocities were found. Reduced amplitude in the evoked nerve potentials can be observed without clinical evidence of peripheral neuropathy. Electrophysiological abnormalities are more severe in older than in young patients. Sural nerve biopsy in one patient showed mild changes: loss of the largest myelin-ated fibres and demyelination of some fibres. The ratio between maximum conduction velocity of the sural nerve and the diameter of the largest fibres was in the lower limits of the normal range. The resemblance between electrophysiological abnormalities in Friedreich's ataxia and ataxia-telangiec-tasia is discussed. Ataxia-telangiectasia is a heredofamilial syndrome, transmitted by an autosomal recessive gene (Tadjoedin and Fraser, 1965), and described first by Syllaba and Henner (1926) and Louis-Bar (1941). Later this syndrome was separated from other ataxias and considered as a new entity (Boder and Sedgwick, 1957, 1958). The disease begins in infancy, and the main clinical features are progressive cerebellar ataxia, oculo-cutaneous telangiectasia, and frequent sinopul-monary infections. Other symptoms which may be observed are choreoathetosis, dysarthria, apraxia of eye movements, characteristic facies, and growth retardation. An immunological defect is constant: dysgammaglobulinaemia with decreased or absent serum IgA (Fireman et al., 1964), atrophic thymus, and impairment of delayed hypersensitivity responses (Peterson et al., 1963). Necropsy reveals cerebellar degeneration (Boder and Sedgwick, 1957), loss of myelinated nerve fibres in the posterior columns of the spinal cord (Boder an