Congenital Arachnoid cysts (AC) have been reported to account for roughly 1% of atraumatic intracranial mass lesions. Sylvian fissure cysts can manifest clinically at any age, but they become symptomatic more frequently in children and adolescents than in adults, and in most series infants and toddlers account for about a quarter of the cases. The incidence of epilepsy in AC patients has been reported to be between 7.5% and 42.4%; conversely MRI screening studies in epileptic patients have showed that AC are incidentally found in up to 2% of the cases. Single photon emission computed tomography (SPECT) studies proved more sensitive than increased intracranial pressure (ICP) monitoring in children with unspecific clinic radiologic correlation. Open cyst marsupialization is considered the preferable surgical procedure. Cyst extrathecal diversions are obviously safer, but are accompanied by a high incidence of additional surgical procedures and the stigma of lifelong shunt dependency.