Intracranial peripheral primitive neuroectodermal tumor manifesting as abducens nerve palsy

Peripheral primitive neuroectodermal tumor (PNET) occurring as an extra-axial lesion within the intracranial space and extending to the subarachnoid space is extremely rare. An 18-month-old girl presented with an intracranial peripheral PNET manifesting as abducens nerve palsy. Magnetic resonance imaging on admission revealed a lesion affecting the trigeminal and abducens nerves. The tumor was partially removed via the subtemporal approach. Histological examination showed a high-grade, undifferentiated neoplasm of small cell type with positive immunostaining for MIC2. The histological diagnosis was peripheral PNET. Craniospinal radiotherapy reduced the tumor size, but adjuvant chemotherapy designed for Ewing's sarcomas and PNETs was not effective. She died 1 month after the last chemotherapy, despite whole craniospinal irradiation (total dose 53.2 Gy) and chemotherapy.