Multiple sclerosis presenting with progressive visual impairment independent of relapse activity: A case report

Visual impairment due to optic neuritis is one of the most common manifestations of multiple sclerosis (MS); however progressive visual loss without relapse is rare. Furthermore, the association of progression independent of relapse activity (PIRA) with visual impairment has not been largely explored. We report a rare case of MS associated with progressive visual loss, independent of relapse, with detailed follow-up data of visual acuity, critical flicker fusion frequency (CFF), and visual-evoked potential (VEP), which provided supporting evidence for monitoring visual function. A 44-year-old Japanese woman with MS presented with decreased visual acuity in both eyes. Her symptoms progressed slowly without relapse and did not respond to intravenous methylprednisolone or plasma exchange. Her CFF and VEP also showed gradual exacerbation. Magnetic resonance imaging revealed no new lesions of MS. Visual impairment was correlated with physical worsening, suggesting progression independent of relapse. After ofatumumab was initiated, her visual acuity mildly improved. We describe a patient with visual impairment that was considered the PIRA. Impairment of visual function, in addition to impaired walking ability and cognitive function, should be considered when assessing disability progression in MS. CFF and P100 latency of VEP may aid in the early diagnosis of PIRA, potentially leading to timely treatment.