Familial Hemiplegic Migraine is a rare type of migraine typically characterized by weakness or even paralysis on one side of the body. It's been estimated that 0.01% of the population or less have this type of migraine. However, it's been studied more than many types, because certain characteristics (such as the genetic markers some patients have) are giving us early insights that may apply to other types of migraine as well.
Going to diagnosis and then successful treatment can be a long and challenging process. Part of the reason for this is that familial hemiplegic migraine (and the related sporadic hemiplegic migraine) can at first look like many other conditions. It's critical to rule out these conditions, but it can take time, and you may need a specialist (such as a neurologist with experience in migraine) to help you narrow things down.
Specialists use certain criteria to differentiate different types of migraine. When it comes to symptoms, this is what familial hemiplegic migraine (FHM) looks like:
FHM is a type of "migraine with aura". That means there are certain symptoms present other than headache that usually precede the "headache phase" (if there is headache pain).
First, the characteristic symptom of FHM is motor weakness. This is muscle weakness, almost always on one side of the body. This may be mild, or may even be paralysis - during an attack the person may not be able to walk.
The symptoms of FHM may be confused with the equally strange symptoms of basilar type migraine. But if there's motor weakness, a diagnosis of basilar type migraine will be ruled out.
To have a diagnosis of FHM, you'll have at least two of these symptoms:
These symptoms are temporary and typically develop gradually over 5+ minutes. Sometimes they come in succession - one after another. They usually last from 5 minutes to 24 hours, though they may last for days or longer. It's not uncommon for someone with familial hemiplegic migraine to experience all of these symptoms.
Usually if there's a headache it will start either during the aura or within an hour afterwards. The headache symptoms are like migraine headache symptoms, and have at least two of these characteristics: one-sided pain, throbbing/pulsating quality, moderate to severe pain, and aggravated by activity. Typically the patient will experience nausea and/or sensitivity to light and/or sound.
If the attack isn't treated, the pain typically lasts from a few hours to 3 days.
Other symptoms often accompany familial hemiplegic migraine, such as lethargy, fever, ataxia (loss of coordination), confusion and even a complete loss of consciousness (in very rare cases coma).
You can see why you would need to rule out other causes for these symptoms. Exact symptoms vary from patient to patient, but can look very much like stroke, epilepsy, meningitis, and various other kinds of migraine. The one-sided paralysis can be quite sudden, and the effects may linger.
FHM is very commonly mistaken for epilepsy, but of course the treatment doesn't fit the condition.
In some patients, the ataxia (loss of coordination) becomes chronic and progressive, not just during migraine attacks but all the time.
Familial Hemiplegic Migraine-
Genetic clues into strange symptoms
Though the symptoms are the same, one thing changes the diagnosis from sporadic hemiplegic migraine to familial hemiplegic migraine. That is, if a close family member is diagnosed with the same thing. Your doctor will ask you if you have a first or second degree relative with the same symptoms (particularly motor weakness)
We know that there are certain genetic markers that are more likely to be present in patients with FHM, and we expect there are more to be discovered.
These genetic markers have enabled us to "nail down" FHM in a way we haven't been able to with other types of migraine. It's still a mystery, to be sure, but this rare type of migraine has been a hot focus of research, because we hope it may give us early clues into the working of many other types of migraine as well.
For example, in July 2008 we talked about a gene that was being studied in relation to epilepsy. There is an indication that sodium channels in the body of some migraineurs may not work properly. Similarly, calcium channels were studied in relation to FHM, and are now the focus of a great deal of research.
Because Familial Hemiplegic Migraine can look like so many other conditions, it is critical to take the time to test for these other conditions. Depending on your situation, these are some of the tests that your doctor or specialist may call for:
There has been a lot of discussion about just how much impact migraine has on someone long-term. But there are even more concerns when it comes to FHM. Researchers are still trying to understand what long term problems may be caused by FHM. Are other conditions, such as stroke, simply more likely in patients with hemiplegic migraine, for example? Or can we lower the risk of stroke avoiding individual familial hemiplegic migraine attacks?
Depending on your symptoms, there are also concerns of personal safety. Sudden attacks of numbness, paralysis or imbalance can be a danger to you and others. So there is more emphasis in FHM on avoiding the attacks before they start - preventative medicine, whether that be drugs or other treatment.
References: Familial Hemiplegic Migraine by Dr Joanna C Jen, updated September 2009; Migraine and Other Headaches by Dr William B Young and Stephen D Silberstein, 2004; The Migraine Brain by Dr Carolyn Bernstein and Elain McArdle, 2008; Headache and Your Child by Dr Seymour Diamond and Amy Diamond, 2001; The International Classification of Headache Disorders 2nd Edition, International Headache Society, 2003; Hemiplegic Migraine Headaches: Symptoms, Causes, Treatments reviewed by Dr Matthew Hoffman October 2008