Indications and Outcomes of Endoscopic Endonasal Approaches for Trigeminal Schwannoma Based on Tumor Characteristics: A Multicenter Case Series Study of 20 Cases

Introduction: Trigeminal schwannomas are rare tumors. It can involve various components of the trigeminal nerve throughout its course. Hence requiring complex surgical approaches. Initially, cranial approaches were the mainstay, then endoscopic skull base approaches were developed to be a valuable alternative. Endoscopic endonasal approaches (EEAs) and transorbital approaches can both be used to tackle this pathology. However, there is a need to further define the indication for the suitability of each approach based on specific tumor characteristics.

Methods: Multicenter case series from three tertiary centers Samsung Medical Center, Seoul National University Center, and Asan Medical Center. A total number of 20 cases were included. Analysis was done on tumor characteristics including modified Samii classification, extracranial extension, internal carotid artery displacement pattern, and sphenoid sinus pneumatization pattern. Outcome measures were gross total or near total resection (GNTR).

Results: Twenty cases were analyzed. D3 was the most common type 7 (35%). Gross or near-total resection (GNTR) was achieved in 15 cases (70%). An additional transorbital approach was performed prior to EEA in three cases (15%). Regarding tumor characteristics, 13 cases had extracranial extension (65%), nine cases had ICA displacement(45%). In the absence of all three factors (extracranial extension, lateral ICA displacement, and sphenoid sinus pneumatization) GNTR decreased significantly to 29%. GNTR was 100% in the presence of 1 and 3 factors and 86% in cases with 2 factors present. In the latter group, only one case out of seven had incomplete resection due to extensive bleeding from the tumor and resulting potential risk to underlying neurovascular structures.

Conclusion: EEAs can be considered as a valid option for trigeminal schwannomas. However, based on our series in the absence of extracranial extension, medial ICA displacement, and lack of sphenoid sinus pneumatization. The chances of GNTR were markedly decreased and an endoscopic transorbital approach should be considered.

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Artikel online veröffentlicht:
07. Februar 2025