Identification of a Predominant Cognitive Phenotype in Patients with Multiple Sclerosis

BACKGROUND AND PURPOSE: Cognitive impairment occurs frequently in multiple sclerosis (MS). However, the prevalence and clinical characteristics of cognitive MS phenotype are not well established. The aim of the study was to characterize the clinical course and neurocognitive impairment of patients with MS meeting an Expanded Disability Status Scale (EDSS)-defined cognitive phenotype. METHODS: A total of 2302 patients from the Comprehensive Longitudinal Investigation of Multiple Sclerosis at Brigham and Women's Hospital (CLIMB) study were studied. Predominant cognitive MS phenotype was defined as EDSS Cerebral Functional System (FS) subscore >/=3 and remaining EDSS FS subscores /=2 throughout all follow-up. However, predominant cognitive phenotype subjects with clinical neuropsychiatric testing [n = 39/60 (65%)] frequently had cognitive impairment (1.5 SD below mean) in >/=1 domain [n = 30/39 (77%) of subjects] affecting memory, attention/executive function and processing speed. A total of 11 of 39 (28%) patients had severe-range cognitive impairment (3.0 SD below mean). Cognitive phenotype designation was associated with low rate of employment at last clinical assessment. CONCLUSION: Predominant cognitive MS phenotype is rare, although an EDSS-based definition identifies patients with multidomain cognitive impairment and may serve as a practical screen for identification of patients who might warrant close monitoring of neurocognitive status.