Profound Cognitive Impairment as a Salient Feature of Multiple Sclerosis: A Case Report

ABSTRACT Background Cognitive impairment affects up to two‐thirds of patients with multiple sclerosis (MS); however, profound global deficits, defined as a full‐scale IQ below 70, are uncommon and rarely constitute the primary symptom. Case Presentation We describe a 27‐year‐old woman with severe multidomain cognitive impairment due to MS. Neuropsychological testing showed marked slowing of processing speed and perceptual reasoning, while verbal abilities remained relatively preserved. Although such profound dysfunction is atypical, the cognitive profile remained typical of MS: prominent deficits in processing speed and perceptual reasoning with sparing of verbal abilities. Conclusions This case suggests that atypical MS with unrecognized cognitive dysfunction presents a diagnostic challenge.