Endoscope-assisted microsurgical resection of a primary oculomotor nerve schwannoma involving the cavernous sinus via a pterional approach: a case report with narrative review.

Primary oculomotor nerve schwannomas that involving the cavernous sinus represent an exceptionally rare entity. The surgical management of these tumors is complicated by the need to maximize resection while safeguarding oculomotor function. We report a middle-aged female who presented with headache, dizziness, and visual decline. Examination showed right ptosis and decreased visual acuity. MRI demonstrated a lesion in the right parasellar region that involved the cavernous sinus, circumferentially surrounded the cavernous segment of the internal carotid artery, and extended into the optic canal. A right pterional craniotomy was performed with a microsurgical resection under endoscope assistance. Following microsurgical debulking through the oculomotor trigone and supratrochlear triangle, neuroendoscopy was used to explore and curette deep residual tumor within the cavernous sinus. Histopathology confirmed schwannoma of Schwann cell origin. Postoperatively, ptosis showed partial improvement and visual acuity showed mild improvement, with oculomotor and pupillary function preserved without postoperative deterioration. Postoperative MRI obtained within 72 hours confirmed an intentional subtotal resection with a minimal residual enhancing focus, for which adjuvant stereotactic radiosurgery has been recommended. In this patient, endoscopic visualization facilitated inspection of areas not directly visible through the microscope and supported an intentional function-preserving resection. The surgical strategy illustrated in this case may inform the management of this rare pathology, although long-term outcomes remain to be evaluated.