Conventional and Quantitative Magnetic Resonance Imaging and Cognitive Impairment in Multiple Sclerosis

Abstract

An estimated 30–70% of patients with multiple sclerosis (MS) have some cognitive impairment. Cognitive function depends on a spectrum of faculties including information processing speed, sustained attention, recent memory and executive function. The broad definition of cognition has resulted in different assessments of function, and repeatable batteries of tests have been devised to gain an overall and repeatable view of cognition in MS. Many studies have attempted to find an association between cognitive function and MS pathology using magnetic resonance imaging (MRI). Conventional MRI has been used to show the relationship between cognitive impairment and MS lesion volume and/or brain volume (reflecting atrophy). Studies using quantitative MRI to estimate the degree of abnormality in tissue that is normal-appearing on conventional MRI have also found correlations with cognitive function. Longitudinally, cognitive decline has been found to correlate with changing MRI-detectable pathology in some studies. However, consistency between studies has been lacking, and the large number of cognitive tests available makes direct comparison of different studies difficult. Focus on specific cognitive domains may alleviate this issue in future studies.