Hemiplegic migraine (HM) is a rare variant of migraine with aura that presents with episodic and reversible attacks of headache and unilateral motor weakness, usually beginning as an aura prior to the headache. Patients may also present with impaired level of consciousness, ataxia, sensory loss, vision changes, or brainstem symptoms. Symptoms typically last from hours to days, and neurologic symptoms may outlast the associated headache. Symptoms typically occur over 10-30 minutes but may present acutely and mimic an acute stroke.

To diagnose HM, patients must have episodic, unilateral, reversible motor weakness as a migraine aura, as well as at least one other type of aura. Between attacks, patients typically have a normal neurologic examination.

HM is a rare condition occurring with a prevalence of 0.01%. HM is more prevalent in women than men (3:1), with an age of onset in the teenage years. HM has been associated with mutations in CACNA1A, ATP1A2, and SCN1A genes, which can be sporadic or familial. Inheritance in familial HM is autosomal dominant, although penetrance is incomplete. Patients with HM, cerebellar findings, and developmental delay should be tested for CACNA1A gene mutations. Patients with HM and associated epilepsy should be tested for ATP1A2 gene mutations. Many patients with HM do not demonstrate any of these known gene mutations.