Microsurgery of Koos I-II vestibular schwannomas: a case series of 100 consecutive patients.

Background: Treatment of small vestibular schwannomas (VS) depends on size, growth pattern, age, symptoms, co-morbidities. Watchful waiting, stereotactic radiosurgery and microsurgery are three valid options of treatment.

Methods: We reviewed clinical sheets, surgical data and results of 100 consecutive patients with Koos Grade I-II VS, operated at our department via a retrosigmoid microsurgical approach between September 2010 and July 2021. Extent of resection was assessed as total, near-total or subtotal. The course of facial nerve (FN) around the tumor was classified as anterior (A), anterior-inferior (AI), anterior-superior (AS) and dorsal (D). FN function was assessed according to House-Brackmann (HB) Scale and hearing level according to AAO-HNS Classification.

Results: Mean tumor size was 1.52 cm. FN course was mainly AS (46.0%) in the overall cohort; in Koos I VS, FN was AS in 83.3%. Postoperative FN function was HB I in 97% and HB II in 3% of cases. Hearing preservation (AAO-HNS class A-B) was possible in 63.2% of procedures. Total/near-total removal was achieved in 98%. Postoperative mortality was zero. Transient complications were observed in 8% of patients; permanent complications never occurred. Tumor remnant progression was observed in one case, 5 years after subtotal removal.

Conclusions: Microsurgery represents a valid option for management of VS, including Koos I-II grades, with an acceptable complication rate. In particular, in small VS long-term FN facial outcome, HP and total/near-total removal rate are favorable.