Hemiplegic migraine (HM) is a rare variety of migraine with aura characterized by the presence of a motor weakness during the aura. Hemiplegic migraine has two main forms depending on the familial history: patients with at least one first- or second-degree relative who has aura including motor weakness have familial hemiplegic migraine (FHM); patients without such familial history have sporadic hemiplegic migraine (SHM).
The prevalence of HM is one in 10,000, with FHM and SHM being equally frequent.
Typical HM attacks are characterised by motor weakness that is always associated with other aura symptoms, the most frequent being sensory, visual and speech disorders. In addition, basilar-type symptoms occur in up to 70% of patients. Severe attacks may occur in both FHM and SHM with prolonged hemiplegia, confusion, coma, fever and seizures. The clinical spectrum also includes permanent cerebellar signs (nystagmus, ataxia, dysarthria) and less frequently various types of seizures and intellectual deficit.
The three causative genes identified so far encode ion-transporters (CACNA1A, ATP1A2 and SCNA1). Molecular diagnosis is now possible through screening of these three genes.
FHM is transmitted in an autosomal dominant manner.
Treatment involves the same approaches used for other varieties of migraine with aura, with the exception that triptans are contraindicated in MHF/MHS. Based on new pathophysiological insights, preventive treatments using various antiepileptic agents seem promising.
Prognosis is usually good.
- Dr Anne DUCROS