Surgical Resection of an Optic Nerve Sheath Meningioma: Relevance of Endoscopic Endonasal Approaches to the Optic Canal

Abstract

Optic nerve sheath meningiomas (ONSMs) account for less than 2% of meningiomas and 1.7% of orbital tumors. Although rare, the management of these tumors is important as unilateral blindness often results in untreated cases. Radiotherapy has emerged as the preferred treatment. However, therapies for ONSMs are controversial due to the variable natural history of the disease and limitations of surgical and radiotherapy options. A 60-year-old woman presented with monocular left diminished color perception and blurred vision. Magnetic resonance imaging demonstrated a homogenously enhancing 5-mm left optic nerve mass with evidence of nerve compression. Conservative management was advised. However, 1 month after diagnosis her visual acuity deteriorated further. Because of the small focal location of the tumor within the optic canal, surgery was considered. Given the tumor's location inferomedial to the optic nerve, an endoscopic endonasal approach to the optic canal was performed. This patient recovered fully with resolution of visual symptoms immediately following surgery. Postoperative imaging 24 hours after surgery demonstrated gross total resection of the tumor; 1 year postoperatively the patient has a normal ophthalmologic examination. This report highlights the value of endoscopic endonasal approaches in the management of select optic canal pathology, otherwise inaccessible via transcranial approaches.

Keywords: endoscopic endonasal; meningioma; minimally invasive; optic canal; optic nerve sheath; skull base.

Fig. 1

Automated visual field of the left eye shows a worsening superior arcuate visual field deficit (A) one month preoperatively and (B) two days preoperatively. Postoperative testing demonstrated an improvement in fields. (C) Two weeks postoperatively. (D) Ten months postoperatively.

Fig. 2

Pre- and postoperative MRI. (A) Preoperative coronal MRI T1 weighted with contrast demonstrates a small intracanalicular lesion inferomedial to the left optic nerve. (B) Postoperative coronal MRI T1 weighted with contrast demonstrates gross total resection. (C) Postoperative coronal CT demonstrating decompression of the optic canal. Arrow, tumor; circle, optic nerve/canal.

Fig. 3

Intraoperative images during endonasal endoscopic resection. (A) Initial exposure of the entire length of the optic canal prior to sheath opening. (B) Visualization of the tumor along the inferomedial surface of the nerve after sheath incision. (C) Sharp dissection of the tumor away from the optic nerve. (D) Sharp excision of the dural attachment of the tumor. (E) Visualization of the optic nerve at the completion of tumor resection. Sup., superior; Inf., inferior; Med., medial; Lat., lateral; solid line, optic nerve; *, cavernous sinus; ^, orbital apex.