Visual hallucinations in blindness: the Charles Bonnet syndrome.

A 64-year-old woman developed complex visual hallucinations consisting of snakes crawling out of people's head and on her body. She had become blind 14 years before the onset of the hallucinations. Neurosurgical removal of a large suprasellar meningioma was followed by disappearance of her hallucinations. This case suggests that the complex hallucinations often encountered in blind subjects ("release hallucinations"), a phenomenon originally described by Charles Bonnet in 1769, are related to both sensory deprivation and an impairment in CNS functioning.