Large demyelinating brain lesion mimicking a herniating tumor.

We describe the case of a large brain lesion whose computed tomography appearance and clinical evolution mimicked a herniating tumor. The patient progressed to coma within 6 days of hospitalization despite high-dose steroid treatment. Emergency excision of the lesion was carried out. Histological analysis showed massive demyelination, axon preservation and no tumor cells. No lesion recurrence was seen during a 55-month follow-up. Recognition of such lesions through magnetic resonance imaging or spectroscopy may spare unnecessary surgery or biopsy. However, our case shows that such lesions may still require resection in the face of a rapid clinical progression and poor response to medical treatment.