Chapters Three through Five Summary and Analysis

Sacks next addresses the subject of the "aura" of a migraine. The aura traditionally refers to the "sensory illusions" prior to an epileptic seizure. Sacks notes that an aura that is not followed immediately by the headache may be confusing and misinterpreted. There were early accounts of these phenomenon, but would be some time before the aura is connected to migraines. There are five areas of aural symptoms identified though Sacks cautions that the five are not exclusive of each other as combinations of symptoms may very well occur. The categories are sensory hallucinations, changes in the "sensory threshold," changes in the "level of consciousness," changes in mood, and disorders in perception, speech and memory.

Visual sensory hallucinations may be in the form of flashing lights, stars, or geometric figures across the line of vision...