216 Indications and Outcome of Endoscopic Transorbital Surgery for Trigeminal Schwannoma Based on the Classification: A multicenter Study With 50 cases (Korean Society of Endoscopic Neurosurgery - 009)

Abstract

INTRODUCTION: Trigeminal schwannoma is a rare central nervous system tumor and involves multi-compartmental skull base. Recently, endoscopic transorbital approach (ETOA) has been emerging technique as a minimally invasive surgery. METHODS: Between Sep. 2016 and Feb. 2022, we performed ETOA in 50 patients with trigeminal schwannoma at four tertiary hospitals. There were 15 men and 35 women with the mean age of 46.9 years. All tumors were classified type A (mainly involving the middle cranial fossa), type B (mainly posterior cranial fossa), type C (dumbbell-shaped tumor involving middle and posterior fossa), type D (Extracranial type). Type D tumors were also classified the ophthalmic division (D1), maxillary division (D2), mandibular division (D3). RESULTS: In this study, overall gross or near total resection was performed in 45 of 50 patients (90.0%). Median follow-up period was 21.9 months ranging from 1 to 61.7 months. There was no regrowing or recurrence during the follow-up period. Based on the classification, there were 17 tumors with type A, 1 type B, 19 type C and 13 type D. In particular, seven tumors were belong to D1, one D2, and five D3. For type A tumors, GTR/NTR was achieved with ETOA in 16 of 17 patients (94.1%). 18 of 20 patients with type C received GTR/NTR. For type D tumors, GTR was achieved in 5 of 7 patients who underwent ETOA. CONCLUSIONS: This study showed that trigeminal schwannomas can be effectively treated with a minimally invasive ETOA in all types of tumor except tumors mainly involving posterior fossa (type B). Especially, trigeminal schwannoma involving orbit (D1) or infratemporal fossa (D3) can be successfully removed with ETOA alone or combined ETOA with the endoscopic endonasal approach.