A 42-year-old woman presents to her neurologist for routine follow-up. She was diagnosed with relapsing remitting multiple sclerosis (RRMS) at age 29 years. Before her diagnosis, she experienced paresthesia of her right hand for several days but recovered fully and had no lingering deficits. She was placed on Interferon beta-1b therapy. For the 10 years after her diagnosis, she had two additional episodes: one with a weakness in her left leg, the other where she experienced diplopia, both of which resolved completely. She had and maintained an Expanded Disability Status Scale (EDSS) score of 1.0.

She presents now with reports of fatigue, both general and exertional, and significant sleep disturbance as well as occasional urinary incontinence. She reports muscle cramping, weakness, and sensory loss in her legs and right arm in addition to visual disturbances. She states that her symptoms are increasingly affecting her daily activities. In addition to her ambulatory deficits, she reports trouble with her attention, memory, and executive function.

Physical exam shows prominent ataxia, gait dysfunction, and facial myokymia. Her EDSS is now 6.0, and she requires a cane to be able to walk steadily. Complete blood count is performed, and results are unremarkable.