Familial hemiplegic migraine (FHM) is an inherited form of the condition, which causes severe headaches and reduced motor function preceded by visual or speech disturbances.

Familial hemiplegic migraine (FHM) is a type of migraine passed from parents to children. Although migraine is a common condition, FHM is rare.

This article explores the causes, symptoms, and treatment for inherited hemiplegic migraine.

The main signs of a hemiplegic migraine include:

  • Aura: A migraine aura can cause vision problems, sensitivity to light and sound, difficulty speaking, confusion, numbness, tingling, fever, chills, nausea, and vomiting.
  • Hemiplegia: Hemiplegia refers to muscle weakness that affects only one side of the body.
  • Head pain: People typically describe migraine pain as throbbing, pounding, or stabbing that affects one side of the head.

There are four FHM types, each linked to a different genetic mutation:

FHM typeGenetic mutationOther features
1CACNA1A• accounts for approximately half of all cases of FHM
• sometimes also associated with deterioration of the cerebellum, a part of the brain linked to muscle control
2ATP1A2• accounts for less than 25% of all cases of FHM
• sometimes also associated with polymicrogyria, which occurs when the brain develops too many folds
3SCN1A• often also associated with epilepsy
4Unknown• diagnosed when doctors can’t identify the responsible mutation

Researchers have identified mutations in other genes that may cause hemiplegic migraine, but these are rarer.

To diagnose FHM, a doctor will ask about your medical history and symptoms. They’ll also ask if you have a relative who experiences migraine with aura and muscle weakness on one side of the body.

It’s possible to have hemiplegic migraine if none of your family members has it. However, an FHM diagnosis requires you to have at least one close relative who also experiences hemiplegic migraine.

A doctor might suggest additional tests to confirm the diagnosis and rule out other potential conditions. These can include:

Is there a genetic test for familial hemiplegic migraine?

Genetic testing for FHM looks for genetic mutations linked to the condition. These include mutations in CACNA1A, ATP1A2, and SCN1A, genes involved in making proteins required for nerve cell signaling.

If a doctor suspects a particular mutation based on your family history, they might test a single gene. Otherwise, they’ll analyze a panel of several genes or your entire genome.

It may be possible to have FHM even if a test can’t identify a known genetic mutation, particularly if you have a close relative who experiences similar attacks.

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Common treatments for FHM include medication to stop migraine symptoms, known as abortive medication, and medication to prevent future migraine attacks.

These may include one or more of the following:

If you have FHM type 1, a doctor may prescribe acetazolamide, a diuretic. Doctors don’t use acetazolamide to treat other headache types, but it seems to have positive results in people with FHM. Experts don’t fully understand why.

Some people find that their environment, emotional state, or everyday activities can bring on migraine headaches. Specific FHM triggers can include:

  • bright lights
  • bumping your head
  • intense emotions
  • physical exertion
  • sleeping too little or too much
  • stress

Keep in mind, though, that not everyone experiences migraine triggers.

Can diet affect hemiplegic migraine?

Some people find that specific foods and beverages can bring on a hemiplegic migraine. These foods include those high in nitrates, a preservative commonly added to hot dogs, bacon, and deli meats.

Other dietary migraine triggers include caffeine and alcohol.

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Familial hemiplegic migraine is an autosomal dominant condition. That means anyone with the genetic mutation for FHM can pass it on to their child.

In other words, if one of your parents has a single gene mutation that causes FHM, there’s a 50% chance they’ll pass that gene down to you.

However, it’s possible to have the genetic mutation without experiencing symptoms.

Migraine can seriously affect your quality of life, and people with FHM may be at an increased risk of severe attacks. Although most people with FHM feel as they typically do between episodes, some have reported lingering complications such as problems with memory, attention, and coordination.

If you think you might have FHM, consult a doctor right away. Medication and lifestyle changes can help prevent migraine attacks and reduce their intensity.

FHM is a rare genetic condition. It typically causes aura and one-sided muscle weakness before a migraine headache.

FHM is linked to at least three known genetic mutations, and your doctor might suggest genetic testing to confirm a diagnosis. Most people with FHM have a first-degree relative who also has it.

Treatments for FHM include preventive and abortive medication, and sometimes lifestyle changes to avoid migraine triggers. Consult a doctor to learn more about available treatments.