Suprasellar arachnoid cyst diagnosed preoperatively by computerized tomographic scanning.

True arachnoid cysts of the suprasellar region are uncommon and have rarely been diagnosed pre-operatively. An histologically verified suprasellar arachnoid cyst producing hydrocephalus and visual loss in a 19-year-old man was diagnosed by a combination of pneumoencephalography and computerized tomographic (CT) scanning prior to surgery. The incidence, pathogenesis, signs, and treatment of suprasellar arachnoid cysts are discussed.