Disease at a Glance

Familial hemiplegic migraine (FHM) is an inherited form of hemiplegic migraine. Hemiplegic migraine is a type of migraine with aura that causes motor impairment (such as weakness) in addition to at least one visual, sensory, or speech disturbance (aura) that occurs before the migraine headache begins. FHM commonly begins during childhood or adolescence. FHM is currently classified into 4 subtypes, distinguished by their genetic cause: FHM type 1 (the most common type) is caused by genetic changes in the CACNA1A gene and is commonly associated with cerebellar degeneration. FHM type 2 is caused by genetic changes in the ATP1A2 gene and may be associated with seizures. FHM type 3 is caused by genetic changes in the SCN1A gene. FHM type 4 is diagnosed if no genetic change currently known to cause FHM can be identified. Inheritance of FHM is autosomal dominant, but not everyone who inherits a genetic change responsible for FHM will have symptoms (a phenomenon called reduced penetrance). The diagnosis of FHM requires that at least one first- or second-degree relative has also been diagnosed with hemiplegic migraine. Tests such as a CT scan or MRI of the brain, cerebrospinal fluid analysis, and EEG may be needed to rule out other potential causes of headache and neurological symptoms. Genetic testing may confirm the subtype of FHM in a family.
Estimated Number of People with this Disease

This section is currently in development.

What Information Does GARD Have For This Disease?

Many rare diseases have limited information. Currently GARD is able to provide the following information for this disease:

*Data may be currently unavailable to GARD at this time.
When do symptoms of this disease begin?
This section is currently in development. 


This section is currently in development. We recommend speaking with a doctor to learn more about this disease. 


This section is currently in development. 

Next Steps

Talking with the Medical Team

Good communication between the patient, family, and medical team can lead to an accurate diagnosis. In addition, health care decisions can be made together which improves the patient’s well-being and quality of life.

Describing Symptoms

Describe details about the symptoms. Because there may be many different causes for a single symptom, it is best not to make a conclusion about the diagnosis. The detailed descriptions help the medical provider determine the correct diagnosis.

To help describe a symptom:

  • Use a smartphone or a notebook to record each symptom before the appointment
  • Describe each symptom by answering the following questions:
    • When did the symptom start?
    • How often does it happen?
    • Does anything make it better or worse?
  • Tell the medical team whether any symptoms affect daily activities

Preparing for the First Visit

Working with a medical team to find a diagnosis can be a long process that will require more than one appointment. Make better health decisions by being prepared for the first visit with each member of the medical team.

    Make informed decisions about health care: 
    • Prepare a list of questions and concerns before the appointment
    • List the most important questions first, not all questions may be answered in the first visit
    • Ask questions about symptoms, possible diagnoses, tests, and treatment options
    For future appointments:
    • Discuss what was not addressed at the last visit
    • Discuss changes in the quality of life for the patient, family, and caregivers
    • Discuss health goals and other issues in the patient’s and family’s life that may affect the health care decisions
    Take notes during the appointments to help remember what was discussed.

    Last Updated: Nov. 8, 2021