A 71-year-old woman presented with recurrent episodes of headache accompanied by hemihypoesthesia, fever, aphasia, reduced consciousness and worsening of pre-existing ataxia. Brain imaging revealed atrophy of the cerebellum. The white cell count in the cerebrospinal fluid was slightly increased. The patient had a family history of migraine and cerebellar ataxia. DNA testing revealed a missense mutation in the CACNA1A gene, confirming the diagnosis of familial hemiplegic migraine. Familial hemiplegic migraine is a rare subtype of migraine with aura. It follows an autosomal dominant pattern of inheritance. Patients with familial hemiplegic migraine exhibit a wide spectrum of symptoms, which can hinder the diagnosis. If a patient presents with recurrent coma or encephalitis with or without cerebellar ataxia, familial hemiplegic migraine should be included in the differential diagnosis.