Use of serial proton magnetic resonance spectroscopy to differentiate low grade glioma from tumefactive plaque in a patient with multiple sclerosis.

We report on the use of serial proton MR spectroscopy ((1)H MRS) to differentiate between glioma and tumefactive plaque in a known multiple sclerosis (MS) patient who developed a symptomatic cerebral space occupying lesion. Gliomas and acute MS plaques may have indistinguishable chemical resonance spectra, whereas that of chronic plaque is distinct. In our case (1)H MRS demonstrated elevated concentrations of choline, lactate and lipid, with reduced N-acetyl aspartate, a pattern consistent with either low grade glioma or acute demyelinating plaque. A repeat study 4 months later showed no change, this was felt to be incompatible with the natural history of an acute plaque and low grade glioma was diagnosed. Surgical removal of the lesion revealed an oligodendroglioma, confirming the imaging findings.