Visual evoked Response Anomalies in a Patient with Friedreich’s Ataxia

Abstract

Steady state visual evoked responses were studied in a patient with the clinical diagnosis of Friedreich’s ataxia. Ophthalmologic examination revealed no anomalies including visual acuity of 6/6 in both eyes, full visual field in both eyes, normal screening color vision, absence of optic atrophy and absence of nystagmus. Steady state VER revealed a monocular moderately attenuated signal in the left eye at 12 and 16 Hz and a markedly attenuated signal at 20 and 25 Hz. This contrasted with a normal VER in the right eye. The patient died of cardiac failure secondary to cardiomyopathy associated with Friedreich’s ataxia. Autopsy examination of the brain revealed a number of structural changes. The spinal cord had the usual severe demyelination and axonal changes associated with Friedreich’s ataxia. Histologic examination of the optic nerves showed no abnormality in the right nerve but focal axonal swelling, and some evidence of demyelination in the left optic nerve.