A Challenging Uncommon Presentation of Steroid-Resistant Tumefactive Multiple Sclerosis: A Brainstem Crisis Resolved With Plasma Exchange and Ocrelizumab Maintenance

Tumefactive multiple sclerosis (TMS) is a rare variant of multiple sclerosis that presents large demyelinating lesions, often mimicking neoplasms or stroke. We report the case of a 32-year-old man who presented with progressive right-sided weakness, facial involvement and cranial nerve deficits. Neuroimaging revealed a demyelinating lesion in the left pons with additional older plaques. Despite initial treatment with high-dose corticosteroids, the patient showed no improvement. Subsequent plasma exchange led to significant neurological recovery and ocrelizumab was initiated for relapse prevention. This case highlights the diagnostic challenge of TMS presenting as a brainstem syndrome and the effective role of plasma exchange followed by ocrelizumab maintenance therapy.