A case of meningioma originating from the oculomotor nerve

ABSTRACT A 22-year-old woman presented with a unique case of meningioma originating from the oculomotor nerve manifesting as periorbital pain and diplopia beginning 4 months previously. Oculomotor nerve schwannoma was suggested by several pre-treatment examinations. Tumor resection was considered risky for preservation of the oculomotor nerve function, so gamma knife surgery (GKS) was performed. Six months later, she suffered right complete ptosis and worsened blurry vision. Corticosteroid was administered, but her symptoms did not improve. Magnetic resonance imaging showed the tumor lesion had grown larger. We decided to resect the tumor lesion due to her uncontrolled periorbital pain. The tumor had occupied the oculomotor cistern and was gross totally removed. Histological diagnosis was surprisingly transitional meningioma. The tumor lesion occupied the oculomotor cistern and was refractory to GKS, with a progressive clinical course, which are more suggestive of meningioma than schwannoma, although extremely rare. Her periorbital pain and blurry vision gradually regressed whereas complete oculomotor nerve palsy persisted. In such a case, tumor resection after GKS should be considered.