Tumefactive Multiple Sclerosis Masquerading as High Grade Glioma.

Tumefactive multiple sclerosis is a demyelinating lesion that can radiographically mimic high-grade gliomas during acute episodes, thus affecting clinical decision making. A delay in appropriate diagnoses can result in unnecessary invasive resections. The following case is a patient with unilateral weakness and radiologic findings that were concerning for a high-grade glioma. Peripheral studies were equivocal. The decision was made to proceed with a stereotactic biopsy, yielding a definitive diagnosis of tumefactive demyelinating lesion (TDL). The patient responded robustly to medical management and made a full clinical recovery. While TDLs and gliomas may look radiologically identical during acute demyelinating episodes, unlike gliomas, TDLs will demonstrate evolvement over serial imaging and robust clinical response to high dose steroids. Clinicians should proceed with caution when considering invasive procedures with such lesions. Conservative medical management is often sufficient as seen in this patient. This case highlights the importance of timely diagnosis and management of TDLs.