Alternative Names
Hemiplegic Migraine, Familial; Hemiplegic-ophthalmoplegic migraine
Symptoms & Characteristics
Familial hemiplegic migraine (FHM) is a form of migraine headache that runs in families. Migraines typically cause intense, throbbing pain in one area of the head that is often accompanied by nausea, vomiting, and extreme sensitivity to light and sound. These recurrent headaches usually begin in childhood or adolescence and can be triggered by certain foods, emotional stress, and minor head trauma. Each headache may last from a few hours to a few days.
In some types of migraine, including familial hemiplegic migraine, a pattern of neurological symptoms called an aura precedes 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 that often affects only one side of the body (hemiparesis). Additional features of an aura can include difficulty with speech, confusion, and drowsiness. An aura typically develops gradually over a few minutes and lasts about an hour. Unusually severe migraine episodes have been reported in some people with familial hemiplegic migraine. These episodes have included fever, seizures, prolonged weakness, coma, and, rarely, death. Although most people with familial hemiplegic migraine recover completely between episodes, neurological symptoms such as memory loss and problems with attention can last for weeks, even months. About 20% of people with this disorder develop mild but permanent difficulty coordinating movements (ataxia), which may worsen with time, and rapid, involuntary eye movements called nystagmus.
Treatment
Treatment of familial hemiplegic migraine may help to manage some of the symptoms.
How Common Is It?
The worldwide prevalence of familial hemiplegic migraine is unknown. In Denmark, studies suggest that the disorder affects about 1 in 10,000 people. Similar to other forms of migraine, familial hemiplegic migraine affects females more often than males.
Genetics & Inheritance
Researchers have identified three forms of familial hemiplegic migraine: FHM1, FHM2, and FHM3. Each of the three forms is caused by mutations in different genes.
- FHM1 is caused by mutations in the CACNA1A gene.
- FHM2 is caused by mutations in the ATP1A2 gene.
- FHM3 is caused by mutations in the SCN1A gene.
There is little evidence that mutations in these same genes play a role in common migraines, which affect millions of people each year. Researchers are searching for additional genetic changes that may underlie rare types of migraine, such as familial hemiplegic migraine, as well as the more common forms of migraine.
Familial hemiplegic migraine is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. By definition, everyone with familial hemiplegic migraine has at least one relative with the condition. In most cases, affected individuals have an affected parent.
Genetic Testing
Clinical genetic testing for familial hemiplegic migraine (FHM) may be available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
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