Acoustic schwannoma and petroclival meningioma occurring as collision tumours: a case report.

A case of a collision tumour comprising of an acoustic schwannoma and a petroclival meningioma in a 30-year old male patient is described. Both of these tumours were resected through a retrosigmoid route. The caudal portion of the mass was an acoustic schwannoma while the rostral portion was a distinct well-defined petroclival meningioma. The occurrence of an acoustic schwannoma and a petroclival meningioma in 'collision' has never been reported. The pathogenesis of such a rare entity is discussed and the relevant literature is briefly reviewed.