Tumefactive Multiple Sclerosis Mimicking an Intracranial Mass in a 34-Year-Old Man: A Case Report.

Tumefactive multiple sclerosis (TMS) is a rare demyelinating variant of multiple sclerosis that can closely mimic intracranial malignancy or abscess on imaging. This case highlights diagnostic complexity when focal neurological deficits occur alongside a concurrent dermatomal rash. A 34-year-old man with no prior neurological history presented with three days of progressive left-sided weakness and numbness, preceded by ipsilateral neck pain and a pruritic vesicular rash, initially treated as herpes zoster. Brain imaging revealed a 3.5 cm right frontal ring-enhancing lesion with surrounding vasogenic edema and minimal mass effect. Cervical spine MRI demonstrated a concurrent enhancing lesion at C2 to C3. Cerebrospinal fluid showed mildly elevated protein and oligoclonal bands, supporting an inflammatory demyelinating process. He was treated with intravenous methylprednisolone (1 g daily for five days) followed by an oral prednisone taper, with complete clinical recovery at four-week follow-up. Brain biopsy was deferred after neurosurgical consultation. Integrating clinical context, MRI patterns, and CSF findings can support early recognition of TMS and help avoid unnecessary antimicrobial therapy or invasive diagnostic procedures.