Electrophysiological studies of the visual system in myotonic dystrophy

Ocular signs and electroretinal alterations frequently occur in Myotonic Dystrophy (MD). Surprisingly few reports describe VEP abnormalities for this syndrome. Since the evaluation of cortical visual responses is linked to an understanding of preceding retinal changes, we conducted a systematic study of the visual system including ophthalmological and electrophysiological (EOG, ERG, PERG, VEP) investigation in 14 confirmed myotonic patients. The various tests revealed consistent abnormalities, the most frequent of these being PERG and VEP changes. These alterations seemed to occur independently of one another, suggesting impaired function at different levels of visual pathway. A generalized defect of cell membrane has recently been proposed as etiopathogenesis of typical EMG and systemic features of the disease. Such membrane dysfunction might account for the early and marked abnormalities in electrophysiological tests, even in the absence of neuro-ophthalmological changes.