Pattern-reversal visual evoked potentials in late-onset progressive multiple sclerosis

This report describes five cases of presumed progressive multiple sclerosis (MS) of late onset, four of them with predominantly or exclusively spinal manifestations, in which abnormal pattern-reversal visual evoked potentials (VEP) showed evidence of subclinical optic nerve involvement despite the absence of visual symptoms and normal neuro-opthalmological examinations. VEP measurement should be included in the evaluation of patients with myelopathy or encephalopathy of unkown etiology.