Familial hemiplegic migraine (FHM)
is a form of migraine headache that runs in families. Migraines usually cause intense, throbbing pain in one area of the head, often accompanied by nausea, vomiting, and extreme sensitivity to light and sound. These recurrent headaches typically begin in childhood or adolescence and may last from a few hours to a few days. People with familial hemiplegic migraine experience an aura that comes before the headache. The most common symptoms associated with an aura are temporary visual changes such as blind spots (scotomas), flashing lights, zig-zagging lines, and double vision. In people with familial hemiplegic migraine, auras are also characterized by temporary numbness or weakness, often affecting one side of the body (hemiparesis). An aura typically develops gradually over a few minutes and lasts about an hour. Researchers have identified three forms of familial hemiplegic migraine known as FHM1, FHM2, and FHM3. Each of the three types is caused by mutations in a different gene. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.