Here is a story:
Joan was used to her visual auras. She had them since she was a child, seeing squiggly lines. Now at 27 years old, she was using triptans , had learned about her triggers, and was functioning well. But last week, her aura  was followed by tingling in her arm, then leg. And then…she could not move anymore. She stumbled to the sofa and panicked. The ambulance brought her to the ED, and she was treated like she had a stroke. The next day, the symptoms had completely cleared and she was told by the stroke team that this was «maybe hemiplegic migraine » and that she should not use triptans anymore. Joan had a ton of questions but was told that she would see a migraine  specialist. Then she learned it would be in a year!
What are auras?
Auras are neurological symptoms (vision, sensation, speech) caused by an abnormal electrical wave on the surface of the brain. The symptoms depend on where the wave goes. Auras have a strong genetic basis.
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What is hemiplegic migraine?
Hemiplegic means «paralyzed on one side». We use this term for people who develop weakness as part of their auras. Sometimes, people report «heaviness» as part of sensory auras, but no true weakness. It’s not always easy to clarify if true motor weakness is present. Testing the movement and strength of the affected limb during an attack can be helpful. Sometimes, the paralysis is very clear.
Is an aura different from a seizure?
Yes. Both are caused by abnormal electrical activity of the brain, but they are different. The electrical wave of the aura is slower and is usually not seen on EEG. Auras also come with a typical sequence of events and rarely involve loss of consciousness or abnormal movements that are typical in epilepsy.
Is hemiplegic migraine always a genetic disease?
There are three genes associated with hemiplegic migraine. They are named FHM1, FHM2 and FHM3. These genes influence how neurons function.
Up to 40% of people with hemiplegic migraine symptoms do not have these abnormal genes. Some people have members of their families affected (familial cases), other don’t (sporadic cases). If the gene testing is negative, it is still possible to have hemiplegic migraine. Research might discover new genes in the future.
Why do those genes cause auras with weakness?
These gene mutation change the way that neurons work. They become very excitable and prone to produce auras. Usually auras are mostly visual, because the electrical wave remains in the visual part of the brain. If the electrical mechanisms become «stronger», the electrical wave can reach the part of the brain that manages movement, and cause weakness.
Are there other symptoms associated with hemiplegic migraines?
Some hemiplegic attacks can be very severe. The brain can go under such an electrical and chemical storm that the person might have fever, seizures, confusion and even become comatose and require ICU management. Of course, in every case of such an attack there should be a complete medical workup done.
NEVER assume that a neurological symptom is an aura unless it has happened multiple times and has been investigated and diagnosed.
What about «confusional migraine»? Is it the same thing?
The term «confusional migraine» is not an official one, but many experts believe aura waves might go to the zones of the brain that manage language, memory and focus.That could explain symptoms of confusion. More research is needed in this area.
What should I do if I have auras with weakness?
Any person with hemiplegic migraine should be evaluated in Neurology, and ideally by a headache specialist. Specific tests need to be ordered, and treatments must be carefully adjusted. If you are using a headache diary, record your different types of migraines and auras.
Can the hemiplegic aura transform into a stroke?
Stroke after an aura (migrainous infarction) is reported, but extremely rare. Usually hemiplegic auras will resolve, but are sometimes longer than typical auras. Durations of many hours and even days have been reported.
Can I use triptans if I have hemiplegic migraine?
Physicians are instructed not to prescribe triptans to people with hemiplegic migraine. The idea is that triptans constrict blood vessels and that, during a severe aura, blood vessels are already constricted. Therefore, triptans could cause a stroke. A serious discussion with a headache specialist is needed to find the best treatment approach.
Are there better preventives for hemiplegic migraine?
Because hemiplegic migraine is very rare, we do not have studies on this group of migraine in particular and these patients are often excluded from pharmaceutical studies.
It is thought that medications that could be more effective for hemiplegic migraine prevention include magnesium , calcium channel blockers, topiramate , lamotrigine and acetazolamide. Botox has been effective in some patients.
Conclusion: the diagnosis and management of hemiplegic migraine requires a high level of expertise. If you think that you suffer from this condition, you should be evaluated by a headache specialist.
Russell MB, Ducros A. Sporadic and familial hemiplegic migraine: pathophysiological mechanisms, clinical characteristics, diagnosis, and management. Lancet Neurol. 2011;10(5):457-70.