Neuropsychological aspects of multiple sclerosis: a quantitative review.

Neuropsychological studies of multiple sclerosis (MS) from a 20-year period were reviewed using meta-analytic and vote-count techniques. Mean effect sizes comparing MS and healthy control groups on variables categorized by neuropsychological domain were small to moderate in magnitude; all were statistically significant (M(r) = .22 (.13) to .46 (.15), rW = .23 to .43, all p < .05). Interhemispheric transfer, general cognitive ability, and learning/memory were more highly related to MS than were visuoperceptual, visuospatial, and visuoconstructional ability, language and conceptual ability (all p < .05); other domains were generally intermediate. Despite previous reports to the contrary, disease subtype was not shown to be consistently related to neuropsychological status independently of other potential explanatory variables. Findings were interpreted with regard to future research and clinical activities involving patients with MS, including selection of tests for brief neuropsychological screening examinations.