(HM) is a rare type of migraine with aura that occurs with motor weakness during the aura. There are two types of HM which are distinguished based on the family history: familial hemiplegic migraine (FHM, in which at least one other family member has the condition) and sporadic hemiplegic migraine (SHM, in which there is no family history). Signs and symptoms vary but may include visual disturbances, sensory loss, difficulty with speech, weakness on one side of the body, confusion, and impaired consciousness. Severe attacks may occur in both types with prolonged hemiplegia, coma, fever and/or seizures. FHM may be caused by a mutation in any of several genes and is inherited in an autosomal dominant manner. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.