[Medulloblastoma originating from the superior cerebellar peduncle: a case report].

A rare case of medulloblastoma originating from the superior cerebellar peduncle is reported. After tilting her neck to the right, a 4-year-old girl experienced a left-side hemiparesis for 3 months. Computed tomography (CT) scan and magnetic resonance image (MRI) showed an enhanced mass in the left tentorial incisura. The preoperative diagnosis was trochlear nerve neurinoma or tentorial meningioma, while the postoperative pathological diagnosis was medulloblastoma. Since medulloblastoma is thought to originate from the external granular layer, it is speculated that the external granular layer migrated through the superior cerebellar peduncle and changed to medulloblastoma.