Familial/Sporadic hemiplegic migraine type 2 (FHM2/SHM2) is a rare disorder. Overall hemiplegic migraine has an estimated prevalence of 0.01%. Clinical diagnosis can be made based on the ICHD criteria of the International Headache Society (IHS) together with physical examination in order to exclude other disorders. Clinical diagnosis together with a mutation in the ATP1A2 gene confirm the diagnosis of FHM2/SHM2. FHM2/SHM2 is inherited in an autosomal dominant manner. The average attack frequency of FHM2/SHM2 lies around 3 attacks per year.
ICHD-III criteria
Attacks fulfilling the following criteria:
- At least two attacks fulfilling criteria two and three.
- Aura consisting of both of the following:
- fully reversible motor weakness1,2
- fully reversible visual, sensory and/or speech/language symptoms
- At least three of the following six characteristics:
- at least one aura symptom spreads gradually over ≥5 minutes
- two or more aura symptoms occur in succession
- each individual aura symptom lasts 5-60 minutes
- at least one aura symptom is unilateral
- at least one aura symptom is positive
- the aura is accompanied, or followed within 60 minutes, by headache
- Not better accounted for by another ICHD-3 diagnosis.
FHM
- At least one first- or second-degree relative has had attacks fulfilling the criteria above.
SHM
- No first- or second-degree relative fulfils the criteria above.
1 The term plegic means paralysis in most languages, but most attacks are characterized by motor weakness.
2 Motor symptoms generally last less than 72 hours but, in some patients, motor weakness may persist for weeks.