Background and Aim: Multiple sclerosis (MS) is characterized with inflammation, demyelization and gliosis. It may be relapsing, remitting, or progressive. Cognitive impairment is relatively prevalent in patients wit h multiple sclerosis and as duration of disease is longer as cognition impairment is more. To understand the cognitive impairment, event related potential can be considered as a valuable tool. This study aimed to investigate the influence of duration of disease and expanded disability status scale (EDSS) on the amplitude and latency of the event related potentials of P300 in patients with multiple sclerosis.

Methods: In this cross-sectional and non-intervention study, 21 patients with multiple sclerosis with mean age of 27.8 with SD 7.1 years (between 18 to 50 years) were enrolled. The patients were selected randomly. The correlation of P300 event-related potential and oddball paradigm was assessed, using two 1000 and 2000 Hz tone burst stimulus.

Results: There was a significant correlation between the latency of P300 wave and duration of disease and expanded disability status scale (p < 0.05) there was high correlation in both electrode sites (r>0.50). The correlation of amplitude of P300 and duration of disease and expanded disability status scale was not significant (p>0.05).

Conclusion: Significant correlation between the latency of P300 and the duration of multiple sclerosis and expanded disability status scale can be a sign of central nervous system changes. Besides, there is a relation between physical disability and cognitive impairments.