Hemiplegic migraine

There are two types of hemiplegic migraine (HM), which are distinguished based on the family history in affected people: familial hemiplegic migraine (FHM, in which at least one other close family member has the condition) and sporadic hemiplegic migraine (SHM, in which there is no family history).

FHM may be caused by changes (mutations) in the CACNA1A , ATP1A2 , SCN1A, and PRRT2 genes. The first three of these genes give the body instructions for making proteins involved in moving charged atoms (ions) across cell membranes. This process is important for for normal signaling between nerve cells (neurons) in the brain and other parts of the nervous system. Researchers think that mutations in these genes may upset the balance of ions in neurons, affecting the release and uptake of certain neurotransmitters in the brain. The exact function of the PRRT2 gene is not yet understood but is also thought to play a part in controlling signals between neurons. When the genes involved in FHM do not work correctly, the signaling abnormalities between neurons lead to the development of severe headaches and auras in affected people. The genetic cause in many families with FHM remains unknown.

While SHM occurs in people with no history of the condition in their family, most cases are due to new (de novo) mutations that occur for the first time in the affected person. Some people with SHM do inherit a mutation from a parent who has the mutation but is not affected. The ATP1A2 and CACNA1A genes have been found to cause SHM in addition to FHM. Many people with SHM do not have a mutation in one of these genes; however, researchers think that mutations in other, unidentified genes are also involved in the condition.

Hemiplegic migraine is diagnosed based on the presence of specific signs and symptoms. Genetic testing is not necessary for all affected people.

The diagnosis is based on the presence of having at least 2 attacks with:

• aura accompanied by fully reversible motor weakness and fully reversible visual, sensory, and/or speech/language symptoms; and
• at least 2 of the following 4 characteristics:
  • at least one aura symptom that spreads gradually over ≥5 minutes, and/or two or more symptoms that occur in succession
  • each individual non-motor aura symptom lasting 5 to 60 minutes, and motor symptoms lasting <72 hours
  • at least one unilateral (one-sided) aura symptom
  • the aura being accompanied by headache, or followed by headache within one hour

Additionally, all other potential causes for the symptoms need to be ruled out (such as transient ischemic attack and stroke). While the criteria requires fully reversible symptoms, it is known that some people with severe attacks may have permanent neurological problems.

A diagnosis of familial hemiplegic migraine also requires that at least one first or second degree relative has had attacks that meet the above diagnostic criteria. A diagnosis of sporadic hemiplegic migraine requires that no first or second degree relative has had attacks that meet the above criteria.

The known types of familial hemiplegic migraine (FHM) that are due to a mutation in the CACNA1A , ATP1A2 , or SCN1A genes are inherited in an autosomal dominant manner. When a person with an autosomal dominant condition has children, each child has a 50% (1 in 2) risk to inherit the mutated gene from the affected parent. FHM due to a mutation in one of these genes accounts for some, but not all, cases of FHM. It is likely that there are additional types of FHM caused by mutations in other genes.

People who are the first member of their family to have hemiplegic migraine are classified as having sporadic hemiplegic migraine (SHM). Some cases of SHM are caused by one of the genetic mutations that cause familial hemiplegic migraine (FHM), due to either having a new mutation, or from inheriting the condition from a parent with no signs or symptoms. In these cases, a person with SHM can still pass the condition on to a child.

Treatment of hemiplegic migraine varies depending on severity and which symptoms are most problematic for the patient. In general, treatments aim to manage symptoms. Drugs that are effective in the prevention of common migraines may be used in hemiplegic migraine. Prophylactic management is applied to patients with frequent, long lasting, or severe attacks. Examples of migraine drugs that have been tried with variable success in people with hemiplegic migraine, include oral verapamil, acetazolamide, lamotrigine.

There are a few articles describing the use of nasal administration of ketamine, intravenous verapamil, and triptans for treatment of aura in people with hemiplegic migraine. Use of triptans in hemiplegic migraine is controversial and may be contraindicated in people with severe attacks.

For further information on these and other treatments, we recommend that you speak with your healthcare provider.