Contribution of NMR spectroscopy to the differential diagnosis of a recurrent cranial mass 7 years after irradiation for a pediatric ependymoma.

CASE REPORT: We describe the case of a 5-year-old-boy who underwent surgery and focal radiotherapy for an anaplastic ependymoma of the fourth ventricle. One year later, a spinal metastasis was treated the same way. Six years later, a 16-mm lesion was found on a control MRI in the posterior fossa. To help the differential diagnosis between a relapse, a radio-induced modification, and a new tumor, magnetic resonance spectroscopy was performed. The main findings were a peak at the expected resonance frequency of reduced glutathione, a prominent peak of glutamate/glutamine compounds, a low N-acetylaspartate, and the absence of elevated choline. These findings were suggestive of a meningioma, although the latency between irradiation and development of the lesion was quite short. The diagnosis was confirmed by the pathological examination.
CONCLUSION: This case exemplifies the fact that magnetic resonance spectroscopy provides useful biochemical information in such a clinical setting.