Intellectual impairment and cognitive evoked potentials in myotonic dystrophy.

Twenty-seven patients with myotonic dystrophy (MD) and 20 control subjects were tested using neuropsychological and electrophysiological measures. MD patients reported significantly lower scores on the Wechsler Adult Intelligence Scale and the Mini-Mental State Examination. P3 amplitude of auditory event-related potentials was significantly reduced in 14 patients. P3 latency was normal. In 13 patients, P3 was not elicited. Our results clearly show the presence of a significant impairment of cognitive functioning, as assessed by psychometric measures, in more than 50% of MD patients. Discriminant function correctly classified 92% of patients, using event-related potentials and neuropsychological variables.