Cystic vestibular schwannoma: surgical outcome.

Abstract

We investigated the proportion of the cystic form of vestibular schwannoma and assessed the results of surgery in this subtype of the condition. The definition of cystic vestibular schwannomas was based on the following criteria: per-operative identification of cystic components; occurrence of the hypodense/hypointense areas on computed tomography (CT) and/or magnetic resonance (MR); and histological verification of S-100 protein membrane-like structures. In a study of 773 Danish patients with vestibular schwannomas, 44 (5.7 per cent) displayed cystic components. The outcome of surgery on 44 cystic vestibular schwannoma (mean tumour size 39 mm) was evaluated and compared with that for 151 solid grant vestibular schwannoma (mean tumour size 49.8 mm). Per-operatively, we found a substantially higher adherence to different intracranial structures in the solid giant vestibular schwannoma compared with the cystic vestibular (95 per cent vs 70 per cent for brainstem, 91 per cent vs 59 per cent for trigeminal nerve, 85 per cent vs 45 per cent for cranial nerves X and XI, 67 per cent vs 32 per cent for dura). Nevertheless, the preservation of the facial nerve function was much better in patients with solid giant vestibular schwannoma compared with those with cystic vestibular schwannoma (House-Brackmann facial nerve dysfunction grade 6 (one year post-operative): 27 per cent vs 41 per cent, respectively p < 0.04). We conclude that the cystic components in vestibular schwannoma are associated with a less favourable surgical outcome, probably due to the rapid tumour growth and symptoms caused by compression of the posterior fossa structures.