Hemiplegic migraine

A rare type of migraine involving temporary weakness on one side of the body

What is hemiplegic migraine?

The word hemiplegic means paralysis on one side of the body.


A person with hemiplegic migraine will experience a temporary weakness on one side of their body as part of their migraine attack.

The weakness may be in addition to some more common aura symptoms such as:

  • Visual disturbances – changes in eyesight in both eyes, such as coloured spots, zig-zags or sparkles
  • Speech difficulties – slurring words or not being able to speak clearly
  • Communication difficulties – it can affect your ability to write and understand language which can cause problems with reading, listening, speaking and writing

People may also experience:

  • dizziness or vertigo (a sensation of movement)
  • hearing problems or ringing in the ears
  • confusion

This can be a frightening experience as the symptoms are similar to those of a stroke. The weakness may last from one hour to several days, but usually goes within 24 hours. A headache may follow the weakness, though it may occur before it or not at all.

There are two types of hemiplegic migraine:

  1. Familial hemiplegic migraine: Familial hemiplegic migraine or FHM, is the form that runs in families. When this occurs, at least two or more people in the same family experience weakness on one side of the body as a symptom with their migraine. On average 50% of children who have a parent with hemiplegic migraine will develop this disorder. There are three identified gene mutations found in Hemiplegic Migraine – CACNA1A, ATP1A2 and SCN1A. This causes the related calcium channel in nerve cells to work incorrectly from time to time, and when it does, this results in a hemiplegic migraine attack. However, these specific mutations are not present in all families diagnosed with FHM.
  2. Sporadic hemiplegic migraine: Sporadic Hemiplegic Migraine or SHM is diagnosed when someone experiences all the physical symptoms of FHM but doesn’t have a known family or inherited connection. The cause of SHM is unknown but probably due to new or ‘sporadic’ gene mutations. People with SHM usually also experience the more common aura symptoms with their attacks. For the most people the aura symptoms last around an hour to a day but can last longer.

What causes hemiplegic migraine?

The brain and nervous system depend on a combination of electrical and chemical signals to function. When a nerve impulse (electrical) of sufficient strength passes down from one nerve cell towards another, it opens a so-called ‘channel’ which acts like a ‘gate’. This process releases neurotransmitters (or chemical messengers) which contact the neighbouring cells and tell them how to respond.

When a channel in the brain is not working properly, neurotransmitters, such as serotonin, may be released in an abnormal way. In hemiplegic migraine, the way some channels dysfunction, results in these symptoms.

Diagnosing hemiplegic migraine

If you have symptoms of either type of hemiplegic migraine, it is important that a diagnosis is made. You may need specialist medical advice to explain the sudden onset of one-sided weakness or numbness. The SHM and FHM diagnosis must always be based on a thorough evaluation of your symptoms and include a full family history.

Treatment options for hemiplegic migraine

If you have suspected hemiplegic migraine specialist advice is recommended. This helps to make sure you are given the most appropriate treatments. Triptans, for example, are best avoided during the aura phase of SHM or FHM and a specialist should assess whether it is safe to use during the headache phase.

As with other types of migraine, there isn’t a single ‘best’ treatment. A specialist will consider your medical history, individual symptoms and use their clinical experience to recommend preventive treatments such as flunarizine (limited access in the UK), topiramate or others.