Hemiplegic Migraine

Hemiplegic migraine is a rare subtype of migraine with aura, characterized by the presence of motor weakness as an aura manifestation at the time of migraine attack. Typically, migraine aura has visual symptoms as aura, but occasionally impairment in sensation or speech may also be seen. A hemiplegic migraine is a distinct condition in which motor weakness occurs.

Hemiplegic migraine may run in the family (familial hemiplegic migraine) or occur sporadically in an individual (sporadic hemiplegic migraine).

Familial Hemiplegic Migraine (FHM)

FHM is an autosomal-dominant subtype of hemiplegic migraine that runs in the family. The diagnostic criteria for familial hemiplegic migraine require that at least one first or second-degree relative has had attacks fulfilling the diagnostic criteria for hemiplegic migraine. International Classification of Headache Disorders-3 classifies FHM into four subtypes based on their genetic mutation.

1. FHM1 is associated with mutations in the CACNA1A gene on chromosome 19p13 that encodes the alpha-1A subunit of the P/Q-type calcium channel. FHM1 is the most common type and accounts for around 50% of cases of FHM. FHM1 is commonly associated with cerebellar degeneration.

2. Mutations in the ATP1A2 gene cause FHM2, accounting for less than 25% of cases of FHM.

3. Mutations in the SCN1A gene cause FHM 3.

4. FHM4 is diagnosed if no known genetic mutation linked to FHM is identified.

Sporadic Hemiplegic Migraine (SHM) occurs only in an individual without a family history of hemiplegic migraine. These individuals may or may not have a family history of migraine with aura.

Clinical Manifestations

The characteristic feature of hemiplegic migraine is the presence of unilateral motor weakness as aura manifestation in at least a few of the attacks. Motor weakness is, however, not the only type of aura present during the hemiplegic migraine attack. Other typical aura symptoms like visual field defects, scotoma, hemianopia, tingling, numbness, ataxia, fever, or lethargy may occur. Motor symptoms often start in the hand and gradually spread to the arm and face. The unilateral weakness may switch sides between or during attacks. Patients may rarely have a bilateral motor weakness either simultaneously or in succession.

The symptoms usually occur over 20 to 30 minutes, although, in rare instances, aura symptoms and motor weakness can develop acutely and mimic a stroke. The symptoms can last for a few hours to days and rarely can last up to 4 weeks. The symptoms resolve completely in a majority of the cases. Most patients with hemiplegic migraine have associated headaches. A headache usually occurs during the aura but can occur after the aura symptoms. Severe hemiplegic migraine attacks may be associated with encephalopathy or coma. Symptoms of a severe attack, including hemiplegia and impaired consciousness, can last for many days to months before they resolve completely. The motor symptoms may outlast a headache. Severe attacks rarely cause permanent brain injury, cerebral atrophy, infarction, cognitive decline, and death.

Seizures independent of hemiplegic migraine attacks have been reported in some patients with FHM, with higher rates in patients with FHM2.

Migraine attacks typically start in the first or second decade of life, with the frequency of attacks decreasing with age.