The utility of MRI techniques to monitor cognitive impairment progression in MS over time and to assess treatment is reviewed by researchers at University Hospital, San Raffaele, Milan, Italy; State University of New York, Buffalo; University of New Jersey, Newark; Leiden Institute for Brain and Cognition, the Netherlands; and University College and Institute of Neurology, Queen Square, London, UK. Focal white matter lesions play a role by disruption of crucial tracts, but the effect of T2-visible lesions on MS-related cognitive impairment is limited. Detection of cortical lesions in critical brain areas is important, and cerebral atrophy is robustly associated with cognitive deficits. Brain volume measures are correlated better with cognitive performance than T2 and T1 lesion volumes. The value of fMRI in measurement of benefits of therapeutic interventions in MS requires multicenter studies. 
COMMENT. Cognitive impairment occurs in 40% to 70% of patients with MS. Deficits involve chiefly information processing speed and episodic memory (repetition or recall of verbal or visual information presented over successive learning trials, after an interval of 20-30 minutes). Two validated test batteries are accepted: the Rao Brief Repeatable Neurosychological Battery (BRNB) and the Minimal Assessment of Cognitive Function in Multiple Sclerosis (MACFIMS). The Symbol Digit Modalities Test (SDMT) requires only 5 minutes and is proposed as a reliable and sensitive test in MS, correlating with MRI findings.