What are the other Names for this Condition? (Also known as/Synonyms)

• FHM (Familial Hemiplegic Migraine)

What is Familial Hemiplegic Migraine? (Definition/Background Information)

• Familial Hemiplegic Migraine (FHM) is a subtype of hemiplegic migraine that is characterized by migraine with aura observed along-with motor weaknesses during the episodic attacks
• Familial Hemiplegic Migraine is inherited in an autosomal dominant manner and a positive family history of the condition is recognized. Mild injuries to the head may trigger the migraine attacks
• Chronic and worsening cerebellar ataxia and neurodegeneration of brain cells causing loss of body movement control is observed in nearly half of the families with Familial Hemiplegic Migraine, independent of the migraine attacks 
• The presentation of symptoms typically occurs in childhood. Children of both genders, and belonging to all racial and ethnic groups may be affected
• Familial Hemiplegic Migraine is characterized by mutations involving any of the following genes:
  • CACNA1A gene
  • ATP1A2 gene
  • SCN1A gene
  • There may be other genes involved that are yet identified; however, some experts believe that the PRRT2 gene may also be causative
• Based on these genes, there are four forms of Familial Hemiplegic Migraine that include:
  • Familial Hemiplegic Migraine type 1 (FHM1)
  • Familial Hemiplegic Migraine type 2 (FHM2)
  • Familial Hemiplegic Migraine type 3 (FHM3)
  • Familial Hemiplegic Migraine, other loci

Molecular genetic testing to check for or confirm known causative gene mutation(s) is important to establish a diagnosis of Familial Hemiplegic Migraine, apart from having at least one family member with the FHM, per diagnostic criteria below.

The criteria for diagnosis of Familial Hemiplegic Migraine as outlined by the International Headache Society (IHS) is given below:

• Attacks fulfilling criteria for “hemiplegic migraine” and the criterion below
• At least one first- or second-degree relative has had attacks fulfilling criteria for hemiplegic migraine

(Source: International Headache Society Classification ICHD-3, London, United Kingdom)

Differential diagnosis: It is reported that the Familial Hemiplegic Migraine attack is frequently confused for an epileptic seizure and inappropriate treatment may be inadvertently provided.