Antisaccade performance in patients with multiple sclerosis

Commonly used measures of disability in patients with Multiple sclerosis (MS) inadequately reflect disease severity and progression. Further, cognitive deficits experienced by up to 70% of patients, are poorly represented by these measures. Saccadic eye movements may provide a powerful tool for the analysis of cognitive changes in MS, providing a surrogate measure of performance that extends more conventional measures. The cognitive control of eye movements has not previously been investigated in patients with MS. We studied antisaccade (AS) performance in 25 patients with MS and compared the results with 25 age matched healthy controls, to evaluate the resolution of response conflict between volitional and automatic processes. Experimental measures were also correlated with a battery of neuropsychological tests evaluating attention, working memory and executive processes, the most commonly reported cognitive deficits in MS. Compared to controls, patients with MS generated significantly more prosaccade errors, and AS latencies were prolonged and more variable. Error rates correlated significantly with scores on the commonly used PASAT. MS patients also exhibited poor spatial accuracy, with mean absolute error significantly larger and more variable than control subjects. The sensitivity of this task in dissociating function in MS, as well as clear correlation with a key measure of cognition, suggests that eye movements, may provide a surrogate measure of cognitive function in MS, with the potential to sensitively assess disease severity and progression.