Supratentorial convexity schwannoma unrelated to cranial nerves: Case report and review of the literature.

Background: Intracranial schwannoma not related to cranial nerves is rare entity, and difficult to be diagnosed preoperatively. Here, we experienced a case of convexity schwannoma mimicking convexity meningioma, and discuss about the characteristics of such cases based on the past published reports.

Case Description: A 48-year-old man presented with a sudden onset of seizures. Brain magnetic resonance image (MRI) revealed a small mass lesion in the peripheral aspect of the right parieto-frontal lobe. The mass was isointense on T1-weighted and hyperintense on T2-weighted MRI, with homogenous enhancement after contrast medium administration. After the feeder embolization on the previous day, removal of the tumor was performed. The tumor revealed a well-demarcated, firm, spherical tumor beyond, and beneath the dura and was relatively easy to be separated from the brain. Histologically, the tumor was observed to be in subarachnoid space extending to outer space of dura-mater, intimately attached to the pia mater. The histological diagnosis was schwannoma.

Conclusion: In our case, MRI findings are similar to convexity meningioma; however, the pathological diagnosis was schwannoma. Cerebral convexity is an extremely rare location for schwannoma. We emphasize that schwannoma, not related to cranial nerves, may arise in the subdural convexity space.