Unilateral Expanded Endoscopic Endonasal Surgery for Olfactory Schwannoma of Anterior Cranial Base in a Patient with Hereditary Hemorrhagic Telangiectasia

Background and Importance: Olfactory schwannomas of the anterior skull base (ASB) are rare tumors and their association with hereditary hemorrhagic telangiectasia (HHT) has not previously been described. The majority of ASB schwannomas arise from the sinonasal tracts, and may demonstrate intracranial extension. We report a case with an olfactory schwannoma of the ASB with subpial involvement of the frontal lobe. Complete tumor resection was performed through a unilateral extended endonasal endoscopic approach with preservation of the contralateral olfactory bulb. Anterior cranial base repair was achieved with a unilateral contralateral mucoperichondrial vascularized pedicled nasoseptal flap.

Clinical Presentation: A twenty-five–year–old female with a history of migraines with progressive worsening. Patient had a history of HHT and epistaxis. Nasal endoscopy showed mild telangiectasias, but no clear evidence of a mass. The computed tomography scan (CT scan) showed a large left-sided anterior cranial base mass and expansive lesion in the left ethmoid area. Magnetic resonance images (MRI) with contrast showed a lesion with ASB invasion frontal lobe and the adjacent left orbit. Angiography was performed, without an intense vascular blush.

Conclusion: We report a rare case of HTT and olfactory schwannoma completely resected with a unilateral extended endoscopic endonasal approach. Reconstruction was performed with a contralateral nasoseptal flap. This is the first reported single stage fully endoscopic endonasal unilateral approach for resection of an olfactory schwannoma with preservation of the contralateral olfactory cleft. The sense of smell and taste is preserved postoperatively.