Obstructive hydrocephalus associated with arachnoid cyst in the elderly.

We present a case of a symptomatic frontal arachnoid cyst associated with hydrocephalus in an elderly patient. It is well known that symptomatic arachnoid cysts usually develop at an early age. This condition is rarely observed in the elderly. The authors hypothesized that compression of the brain and obstructive hydrocephalus caused the arachnoid cyst to become symptomatic.