Spontaneous Regression of Contralateral Vestibular Schwannomas after Resection of an Ipsilateral Tumor in Neurofibromatosis Type II

Objective: We report two cases of spontaneous marked regression of a contralateral vestibular schwannoma (VS) following resection of the ipsilateral VS in neurofibromatosis type 2 (NF2).

Method: Serial magnetic resonance imaging (MRI) was performed and the tumors were assessed linearly and volumetrically.

Results: Initially, following removal of the left VS in patient 1, the right VS appeared 2 to 3 mm larger at 3-month follow-up. Subsequent imaging at 6- to 12-month intervals revealed rapid, sustained spontaneous regression of the right VS of 77% of the maximum tumor volume over the subsequent 4 years. The largest posterior fossa diameter decreased from 30.1 mm to 18.6 mm during this interval. Patient 2 has had similar regression of a contralateral VS over a 7-year period even despite recurrence of the previously resected ipsilateral tumor.

Conclusions: These cases highlight the first well-documented, long-term, spontaneous VS regressions in NF2 patients. It underlines the importance of careful observation of tumors involving the only hearing ear in the management of bilateral VS to determine their natural growth pattern. The mechanism of the dramatic spontaneous tumor regression is uncertain.