Metabolite findings in tumefactive demyelinating lesions utilizing short echo time proton magnetic resonance spectroscopy.

BACKGROUND AND PURPOSE To use MR spectroscopy to aid in the diagnosis of demyelinating disease and to help differentiate tumefactive demyelinating lesions from neoplastic processes. MATERIALS AND METHODS MR imaging of the brain was obtained in 4 patients who presented clinically with focal neurologic deficits. MR imaging initially revealed parenchymal mass lesions. Single-voxel MR spectroscopy was then performed utilizing a point-resolved spectroscopy sequence protocol with a short echo time (30 msec). RESULTS MR imaging revealed a focal ring-enhancing mass in one patient, multiple ring-enhancing lesions in the second patient, a large area of edema and mass effect without associated enhancement in the third patient, and multiple solid and peripherally enhancing lesions in the fourth patient. MR spectroscopic results in all 4 patients demonstrated marked elevation of the glutamate and glutamine peaks (2.1-2.5 ppm). Other nonspecific (and in a sense confounding) findings included elevation of the choline peak (3.2 ppm), elevation of the lactate peak (1.3 ppm), elevation of the lipid peak (0.5-1.5 ppm), and decrease in the N-acetylaspartate peak (2.0 ppm). All 4 patients were eventually given the diagnosis of multiple sclerosis based on CSF analysis, brain biopsy, and/or clinical follow-up. CONCLUSION MR spectroscopic metabolite information may be useful in the diagnosis of demyelinating disease by demonstrating elevation of the glutamate/glutamine peaks because elevation of these peaks is typically not seen in aggressive intra-axial neoplastic processes. This is particularly beneficial in the rarer cases of tumefactive demyelinating lesions, which are very difficult to differentiate from neoplasms by imaging findings alone.