Cognition in multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disorder of the central nervous system characterized by demyelination and neurodegeneration. Cognitive impairment is a common sign and symptom that impacts patients’ independence, job status, and quality of life. Among the various validated neuropsychological tools applied to characterize cognitive dysfunction in MS, the symbol digit modalities test (SDMT) stands as a gold-standard cognitive test with superior sensitivity, reliability, and external validity. Recently, the SDMT revealed the phenomenon of cognitive relapse wherein cognition acutely declines during MS relapse. Early work suggests that this can occur in the absence of other neurological signs, implying a key role for cognition in defining disease activity. Routine screening with the SDMT is now recommended for all adult MS patients, and it serves as an endpoint in clinical trials. Applied alongside magnetic resonance imaging techniques, neuropsychological research suggests that pathology-induced dysfunction of specific brain networks contributes to cognitive impairment in MS.