Hemiplegic migraine (HM) is a rare variant of migraine with motor aura (migraine accompanied by transient hemiparesis). A family history can discriminate cases of familial hemiplegic migraine (FHM) with at least one 1st or 2nd-degree relative suffering from the same problem, and cases of sporadic hemiplegic migraine (SHM) with no relatives affected.
Typical HM attacks include a motor deficit, always associated with at least one other sign of aura, the most frequent being sensory or visual disorders and language difficulties. Basilar symptoms are also frequent i.e. vertigo, loss of balance and tinnitus. Severe HM attacks can occur in both FHM and SHM; they include prolonged loss of motor ability, confusion or coma, fever and epilepsy. The clinical signs may also include permanent cerebellar signs (nystagmus, ataxia, dysarthria) and, less frequently, epilepsy and mental retardation.
FHM is the only type of autosomal dominant hemiplegic migraine. The three known genes (CACNA1A, ATP1A2 and SCN1A) encode for ionic channels and the mutations cause cerebral hyperexcitability. Genetic screening is currently available.
In most cases, the prognosis is good. The medical treatments are those used in other types of migraine with aura, except for triptans which remain contraindicated for FHM/SHM.