Cognitive impairment in early-onset multiple sclerosis. Pattern, predictors, and impact on everyday life in a 4-year follow-up

Objectives: To assess the evolution of cognitive dysfunction in early-onset multiple sclerosis, to identify clinical predictors of mental decline, and to determine its impact on a patient's everyday life. Design: The cognitive performance of 50 patients with multiple sclerosis on a neuropsychological battery was compared with that of 70 control subjects initially and again after a 4-year interval. Clinical predictors of cognitive impairment and its effect on daily life were analyzed by stepwise linear regression. Setting: The research clinic of a university department of neurology. Participants: A consecutive sample of 50 inpatients and outpatients with multiple sclerosis (mean disease duration, 1.58 years) and 70 demographically matched healthy control subjects selected from the patients' relatives and friends. Main Outcome Measures: Mean psychometric test scores of both groups at the initial and follow-up testing. Regression coefficients measuring the relationship between clinical parameters and cognitive capacity and between mental decline and performance of common tasks measured by the Environmental and the Incapacity Status scales. Results: Multiple sclerosis—related deficits in verbal memory and abstract reasoning on initial testing remained more or less stable on the retest, at which time linguistic disturbances on the Set and Token tests also emerged. A patient's initial disability level predicted decreased performance on only four of 13 cognitive variables, and disease duration did so on only two. Extent of intellectual decline on initial testing, initial disability level, and progressive course were independent determinants of handicap in a patient's work and social activities. Conclusions: Cognitive and neurological deficits appear not to develop in parallel. Yet cognitive dysfunction proves to be a predictor of handicap in everyday life, even in patients in the incipient phase of multiple sclerosis.