For centuries, physicians have been fascinated by the visual hallucinations, or auras, which often precede a migraine and which are similar to those induced by hallucinogenic drugs or deliria. This study of migraine has been revised and expanded to include a new chapter, illustrated with startling full-colour paintings by migraine sufferers. Dr Sacks draws on recent advances in chaos theory and neural simulation to describe these "hallucinatory constants" and what they reveal about the working of the brain. Another addition to the 1992 edition discusses newly developed drug therapies for migraine, as well as alternative, non-drug approaches.