Cystathionine Detection via Proton Magnetic Resonance Spectroscopy (¹H-MRS) for the Diagnosis of Oligodendroglioma: A Case Report.

Oligodendroglioma, IDH-mutant and 1p/19q-codeleted, is a subtype of adult-type diffuse gliomas that demonstrates a favorable prognosis and chemosensitivity. Typical imaging findings include a location in the frontal lobe and calcification on computed tomography (CT). However, differentiating it from other gliomas, such as glioblastoma, can be difficult when characteristic imaging features, like calcification, are absent. We present a case of a woman in her 30s with a ring-enhancing lesion in the right frontal lobe, initially suggestive of glioblastoma. Proton magnetic resonance spectroscopy (1H-MRS) was performed using a single-voxel, point-resolved spectroscopy sequence (PRESS) with an echo time of 97 ms. Spectral data were analyzed with LCModel (Stephen Provencher, Inc., Oakville, Canada), which revealed a distinct cystathionine peak at 2.7 ppm. This finding raised the suspicion of oligodendroglioma, which was confirmed by histopathological and molecular analyses. Cystathionine accumulation is attributed to the co-deletion of chromosome arm 1p, leading to downregulation of phosphoglycerate dehydrogenase and cystathionine gamma-lyase, and a metabolic shift toward the transsulfuration pathway. Although glioblastomas may also upregulate this pathway to resist ferroptosis, a previous study showed higher cystathionine levels in oligodendrogliomas. This case suggests that cystathionine detection by 1H-MRS could serve as a useful radiological clue in gliomas with atypical imaging features, which are a ring enhancement without calcification, assisting in the differential diagnosis.