Cognitive dysfunction occurs in many people with multiple sclerosis (MS), but the relationship between brain pathology and cognitive test scores is unclear. In a new study, researchers collected MRI and cognitive test data from 61 participants with MS. Cluster analysis of brain volume data divided participants into three clusters, and the cognitive test data indicated that participants in clusters 1, 2 and 3 were in the early, intermediate and late stages of MS, respectively. The findings suggest that cognitive function declines in conjunction with brain volume and provides information on how well different cognitive tests capture changes in brain pathology.