Vestibular schwannomas occur in schwannomatosis and should not be considered an exclusion criterion for clinical diagnosis

Abstract

Schwannomatosis is a recently delineated inherited condition that has clinical overlap with neurofibromatosis type 2 (NF2). Diagnostic criteria have been developed to distinguish schwannomatosis from NF2, but the existence of mosaic NF2, which may closely mimic schwannomatosis, makes even these criteria problematic. In particular, it is not clear why there is a relative sparing of the cranial nerves from schwannomas in schwannomatosis. We have identified two individuals with schwannomatosis and a unilateral vestibular schwannoma (VS), where a diagnosis of NF2 has been excluded. A third case with an identified SMARCB1 mutation was reported by two radiologists to have a VS, but this was later confirmed as a jugular schwannoma. These cases question whether the current exclusion of a VS from the clinical diagnosis of schwannomatosis is justified.