Regrowth Rate after Resection of Small Vestibular Schwannomas (Koos Grade I to III) and Prognostic Factors

To preserve facial and cochlear function, subtotal resection may be selected for vestibular schwannoma surgery. Prognosis of residual tumors should be considered for treatment selection. We have investigated postoperative regrowth rate and prognostic factors of small vestibular schwannomas.

Subjects and Methods: We included 130 patients with vestibular schwannomas of Koos grade I to III, who underwent their first surgery in our institute from 1998 to 2006 (mean follow-up period, 4.7 years). Patients were divided into three groups according to Gd-enhancement of MR images studied 6 months after surgery: (1) no enhancement, (2) string-like enhancement showing linear enhancement with width < 4 mm, or (3) tubercular or nodular enhancement (TN) with any size.

Result: Among 130 patients, tumor regrowth was observed in 6 patients, and 4 underwent additional treatment, including surgical resection (2 patients) and stereotactic radiosurgery (3; 1 underwent both). The rate of reoperation 7 years after surgery was 0.8% and that for additional treatments was 2.9%. Recurrence was observed only in the TN group. The one patient with reoperation underwent subtotal removal for cranial nerve preservation, and the other showed 5.2% of MIB1 index. In the TN group, the 7-year reoperation rate was 2.0% and that for additional treatment was 7.6%, while there were no additional treatments required in the other groups (p < 0.05). There were no other factors significantly related to recurrence.

Conclusion: The recurrence rate of small vestibular schwannoma is not so high as to consider immediate further treatments. Careful observation may be important for cases with high MIB1 indices and nodular enhancement.