Of 28 cases of intracranial arachnoidal cysts reported from the Clinica Las Condes, Santiago, Chile, 17 were located in the middle cranial fossa, 3 in the quadrigeminal cistern, 2 were parasagital, 3 suprasellar and 3 were in the posterior fossa. Of 23 (82%) treated surgically, 3 received craniotomy with fenestrations, 8 had shunts and 15 were treated by the insertion of cystoperitoneal drainage with excellent results. Twenty-one of the 22 treated cases are asymptomatic and leading a normal life. MRI or CT follow-up showed disappearance of cysts in 14 and marked reduction in size in 7. [1]

COMMENT. The diagnosis of intracranial arachnoidal cysts and reports in the literature have become more frequent since the routine use of neuroimaging. The danger of intracystic hemorrhage with a high possibility of secondary hydrocephalus following head injury has been quoted as a reason for surgical intervention, as a preventive measure in some cases. See Ped Neur Briefs Oct 1991, 5:80 for a report of 67 childhood arachnoidal cysts treated surgically and 1 report of spontaneous disappearance of a cyst. Small or medium sized cysts without clinical manifestations are not usually treated but are monitored carefully.