Familial hemiplegic migraine


Disease Overview

Familial hemiplegic migraine (FHM) is an inherited form of hemiplegic migraine. Hemiplegic migraine is a type of migraine with aura that causes motor impairment (such as weakness) in addition to at least one visual, sensory, or speech disturbance (aura) that occurs before the migraine headache begins.[15140][494] FHM commonly begins during childhood or adolescence.[494] The symptoms of FHM can be scary and distressing.[15140]

FHM is currently classified into 4 subtypes, distinguished by their genetic cause:[15140][494]

  • FHM type 1 (the most common type) is caused by mutations in the CACNA1A gene and is commonly associated with cerebellar degeneration.
  • FHM type 2 is caused by mutations in the ATP1A2 gene and may be associated with seizures.
  • FHM type 3 is caused by mutations in the SCN1A gene.
  • FHM type 4 is diagnosed if no mutation currently known to cause FHM can be identified.

Inheritance of FHM is autosomal dominant, but not everyone who inherits a mutation responsible for FHM will have symptoms (a phenomenon called reduced penetrance).[15140][15141] The diagnosis of FHM requires that at least one first- or second-degree relative has also been diagnosed with hemiplegic migraine. Tests such as a CT scan or MRI of the brain, cerebrospinal fluid analysis, and EEG may be needed to rule out other potential causes of headache and neurological symptoms.[15140] Genetic testing may confirm the subtype of FHM in a family. Treatment of hemiplegic migraine involves medications to alleviate pain, stop the migraines, and prevent future migraines. Severe headache attacks may require hospitalization.[15140] In most people with hemiplegic migraines, aura symptoms completely go away in between migraines and the migraines become less frequent with age.[494] Rarely, hemiplegic migraines may cause permanent neurological symptoms, cognitive impairment, stroke, coma, or death.[15140][494]


  • FHM
  • Hemiplegic Migraine, Familial
  • Hemiplegic-ophthalmoplegic migraine

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National Organization for Rare Disorders