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Benefit of carbamazepine in a patient with hemiplegic migraine associated with PRRT2 mutation

SIR–Mutations in the PRRT2 gene have been proven to be a major cause of paroxysmal neurological disorders, particularly paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy, and infantile convulsions and choreoathetosis (ICCA). Examination of the spectrum of neurological disorders associated with PRRT2 mutations has shown that 1–4% of hemiplegic migraine patients have PRRT2 mutations. PRRT2 mutations can be associated with pleiotropy, and we have previously described a family with heterogeneous paroxysmal disorders with PKD, paroxysmal torticollis, infantile epilepsy, and hemiplegic migraine occurring in members with the common PRRT2 mutation, c.649dupC. Here we describe a previously undescribed child from this family with hemiplegic migraine and his beneficial response to carbamazepine. The patient is a 9-year-old male, whose father has hemiplegic migraine, as previously described. The patient had no history of epilepsy but does have dyslexia. His first hemiplegic migraine episode occurred during Christmas 2009 and he has had three to four episodes per year, totalling 10 episodes over the following 2 years and 7 months. All episodes were stereotypical, and the family have identified chocolate and excessive physical exertion as exacerbating features. His paroxysmal events are always hemiplegic migraine and affect the left side more than the right. The onset of the event is left-foot numbness described as being like a ‘dental anaesthetic’ that then migrates all over the unilateral side of his body. By the time the numbness migrates to his trunk and arm, he begins to feel nauseous and vomits, and then the numbness migrates to his face and sometimes his tongue. This sensory migration can take as long as 2 hours, but is usually much shorter. Once the sensory phenomena are fully evolved, he will start to have a headache which is bilateral, bitemporal, and throbbing, and is associated with photophobia and phonophobia but no visual phenomena. During the onset of the headache, he will evolve ipsilateral weakness, manifest by dragging of the ipsilateral foot and he loses strength in his ipsilateral hand. He will look white during an episode, will need to lie down, and sleep reduces the duration of an attack. He will remain ‘groggy’ and have a headache for between 12 hours and 2 days. He finds the attacks scary and upsetting, and was motivated to try a prophylactic medication. He was confirmed to have the familial PRRT2 mutation, c.649dupC. Paroxysmal kinesigenic dyskinesia and benign infantile epilepsy are typically highly responsive to low-dose carbamazepine, and his cousin with the same PRRT2 mutation had therapeutic benefit from carbamazepine for the infantile epilepsy. He was therefore started on 50mg twice a day increasing to 100mg twice a day after 2 weeks (4mg/kg/d). He has been taking the medication for 1 year and 7 months with diligent compliance, and has not had an attack during this time. This is the first report to describe a therapeutic benefit of carbamazepine in hemiplegic migraine associated with mutations in PRRT2. Certain antiepileptic drugs can be useful in patients with migraine, although the evidence for carbamazepine is lacking, as discussed in a recent systematic review. Although prolonged follow-up of this case and further cases are required to strengthen this finding, we believe this case provides a scientific rationale for the widespread testing of the PRRT2 gene and the use of antiepileptic drugs in hemiplegic migraine. Carbamazepine should be considered in patients with hemiplegic migraine with proven PRRT2 mutations, or in patients with hemiplegic migraine with a personal or family history of infantile epilepsy or PKD.