Tumefactive Demyelinating Lesion Differentiated from a Brain Tumor Using a Combination of Magnetic Resonance Imaging and (11)C-methionine Positron Emission Tomography.

A 37-year-old woman gradually developed a gait disturbance due to sensory loss in the left lower extremity three years after being diagnosed with clinically isolated syndrome. Brain magnetic resonance imaging (MRI) demonstrated an incomplete ring-enhanced lesion with perifocal edema in the subcortex of the right parietal lobe. (11)C-methionine positron emission tomography (MET-PET) showed an insignificant uptake in the lesion. The patient was noninvasively diagnosed with tumefactive multiple sclerosis and treated with corticosteroids, and her neurological symptoms and MRI findings improved with treatment. The combination of MRI findings and insignificant uptake on MET-PET is useful for noninvasively differentiating tumefactive demyelinating lesions from brain tumors.