Sudden cochlear hearing loss as presenting symptom of arachnoid cyst of the posterior fossa.

Arachnoid cysts account for almost 1% of neoformations located in the cerebellopontine angle. The aetiopathogenesis is unknown. Arachnoid cysts of the cranial posterior fossa may produce symptoms typical of a tumour such as headache, dizziness, tinnitus and progressive sensorineural hearing loss. Management of these lesions is still controversial; if the arachnoid cyst is symptomatic, surgical treatment is usually recommended. The case is described of an adult female with sudden unilateral cochlear hearing loss as presenting symptom of an arachnoid cyst in the cranial posterior fossa.