What is familial hemiplegic migraine (FHM)?

Updated: Oct 16, 2019
  • Author: Rima M Dafer, MD, MPH, FAHA; Chief Editor: Helmi L Lutsep, MD  more...
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FHM is a genetically heterogeneous autosomal dominant disorder and a channelopathy; most of the affected families (FHM1) bear mutations in the CACNA1A gene (a defect linked to abnormal voltage-dependent P/Q-type calcium channel alpha-1A) on 19p13. [19, 20, 21, 22, 23, 24] In FHM type 2 (FHM2), mutation in ATP1A2 (R548H) on 1q23 was identified, encoding the alpha2-subunit of sodium/potassium pumps. [25, 26, 27, 28] A third novel mutation in sodium channel gene SCN1A has also been identified in FHM3. [29]

Genetic testing is available for FHM by using polymerase chain reaction (PCR) testing to detect point mutations in the CACNA1A and ATP1A2. DNA sequencing is also available. Positron emission tomography (PET) studies have shown glucose hypometabolism in the contralateral perisylvian region early during a hemiplegic migraine. [30]

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