Familial hemiplegic migraine

Familial hemiplegic migraine (FHM) is an autosomal dominant type of hemiplegic migraine that typically includes weakness of half the body which can last for hours, days, or weeks. It can be accompanied by other symptoms, such as ataxia, coma, and paralysis. Migraine attacks may be provoked by minor head trauma. Some cases of minor head trauma in patients with hemiplegic migraine can develop into delayed cerebral edema, a life-threatening medical emergency. Clinical overlap occurs in some FHM patients with episodic ataxia type 2 and spinocerebellar ataxia type 6, benign familial infantile epilepsy, and alternating hemiplegia of childhood.FHM signs overlap significantly with those of migraine with aura. In short, FHM is typified by migraine with aura associated with hemiparesis, and in FHM1, cerebellar degeneration, which can result in episodic or progressive ataxia. FHM can also present with the same signs as benign familial infantile convulsions and alternating hemiplegia of childhood. Other symptoms are altered consciousness (in fact, some cases seem related to head trauma), gaze-evoked nystagmus, and coma. Aura symptoms, such as numbness and blurring of vision, typically persist for 30–60 minutes, but can last for weeks to months. An attack resembles a stroke, but unlike a stroke, it resolves in time. These signs typically first manifest themselves in the first or second decade of life.See the equivalent section in the main migraine article.The first discovered FHM locus was the CACNA1A gene (originally named CACNL1A4), which encodes the P/Q-type calcium channel CaV2.1. Currently, 17 mutations in this channel are known (table 1), and these mutations are distributed throughout the channel. Some of these mutations result in patients with notable cerebellar degeneration or other dysfunction, including one mutation (S218L), which may be related to severe responses to mild concussion, up to and including delayed cerebral edema, coma, and death. Fifteeen of these mutants have received at least some further analysis at the electrophysiological level to attempt to determine how they might lead to the FHM1 phenotype. Contradiction in the literature is increasing as to the end result of these mutations on channel kinetics and neuronal excitability.Diagnosis of FHM is made according to these criteria:Prenatal screening is not typically done for FHM, but it may be performed if requested. As penetrance is high, individuals found to carry mutations should be expected to develop signs of FHM at some point in life.See the equivalent section in the main migraine article.Migraine itself is a very common disorder, occurring in 15–20% of the population. Hemiplegic migraine, be it familial or spontaneous, is less prevalent, at 0.01% prevalence according to one report. Women are three times more likely to be affected than males.Also caused by calcium channel mutations: