Tumefactive demyelinating lesions or tumefactive multiple sclerosis (TMS) constitute a unique presentation of demyelinating disease that frequently mimics intracranial neoplasm, infection or other, nondemyelinating intracranial pathology. Consequently, these lesions, which are larger than typical multiple sclerosis plaques and are generally characterized by certain MRI features including edema and incomplete ring enhancement, pose a serious diagnostic challenge that frequently prompts biopsy in initial evaluation. Biopsy can be averted when imaging features for TMS are seen on MRI. We present a biopsy-proven case of TMS with atypical imaging features, evaluated using MRI and diffusion-tensor imaging.