Intrapontine malignant nerve sheath tumor: MRI and MRS features.

The primary source of malignant intracerebral nerve sheath tumors is still unclear We report the imaging and MR spectroscopic findings in a 39-year-old man with a very rare brain stem tumor MR examination revealed the presence of intraaxial brain stem tumor with a partial exophytic growth. On pathological examination, the neoplasm appeared to be an intrapontine nerve sheath tumor originating most likely from the intrapontine segment of one of the cranial nerve fibres. The tumor showed exophytic growth, with consequent spread to adjacent subaracnoid space. MR spectroscopy revealed the presence of very high concentration of choline, associated with no creatine and N-acetyl aspartate resonance, suggesting non-glial origin of the intraaxial neoplastic infiltration. MR spectroscopy seems to be a helpful diagnostic modality not only in the estimation of the grade of astrocytomas that has been already confirmed in literature, but also in the diferentiation between glial and non-glial origin of primary intracranial neoplasms when MR imaging is not conclusive.