Cognitive event-related potentials in multiple sclerosis

Twenty-three patients with multiple sclerosis (MS) and 1 patient with isolated optic neuritis (mean age 37.5 yrs, average duration of disease 10 yrs) were tested with auditory and visual cognitive event-related potentials (ERPs) using an oddball paradigm. The results were compared with data from 19 age-matched healthy controls. All patients had magnetic resonance imaging (MRI) head scans and 19 had comprehensive neuropsychological testing. The stimulus-related components of the ERPs were normal for nearly all patients, but 10 showed abnormalities of the later cognitive-related components and another 3 had waveforms in which the cognitive components could not be identified. These abnormalities were found mainly for the auditory test. Of these 13 patients, 11 had significantly prolonged reaction times (RT) or reduced target recognition performance. Five of 8 MS patients with normal IQ and memory function tests had abnormal ERPs with the reverse being true for 4 of 10 patients. Patients with abnormal ERPs showed a higher MRI cerebral lesion score and had a longer duration of illness and greater physical disability than patients with normal ERPs. It is concluded that the generation of ERPs is in part dependent on the integrity of cerebral white matter and that ERPs may indicate subtle degrees of cognitive dysfunction not always detected by standard tests of intellect.