Arachnoid cysts of the posterior fossa

Abstract

Intracranial arachnoid cysts (AC) are presumably congenital malformations which are supposed to form by the splitting of the arachnoid membrane due to a circumscribed increased pulsation of the cerebrospinal fl uid (CSF) [ 4, 12, 13, 21 ]. They represent only 1 % of all intracranial lesions and are most commonly found in the middle fossa [ 2, 4, 20, 40 ]. AC involving the posterior fossa, especially the cerebellopontine angle (CPA), represent the second most common location and are found in 10-11 % of all the cases [ 17, 31, 39 ]. Despite modern diagnostic imaging (MRI), a defi nitive preoperative diagnosis is sometimes still controversial [ 17, 38 ]. AC involving the posterior fossa may be asymptomatic or may produce a wide variety of posterior fossa symptoms with little specifi city like headache, ataxia, dizziness, tinnitus and hearing loss. Patients affected are usually between the fourth and fi fth decades of life. Different methods of surgical treatment have been proposed for the management of intracranial AC [ 10 ]. Stereotactic punction, cystoperitoneal shunting, cyst fenestration or marsupialisation into the subarachnoid space and radical resection of the cyst are the most common procedures [ 2, 10, 24 ].