1. Alternating hemiplegia of childhood into adulthood (AHCA): Case series and literature update

Abstract

Objective To describe the clinical and electrophysiological characteristics of 3 cases of AHC, including novel treatment (off-label use). Study design We report three patients with AHCA. The clinical phenotype comprises of episodes of hemiplegia that moves from one side of the body to the other. The onset of the weakness usually occurs in the first few months of life. Movement disorder such as dystonia can also accompany the hemiplegic attacks in 2/3 cases. Intellectual impairment and epilepsy have been reported in these patients. However, the onset of seizures is usually in the age range between 3 and 4 years. Half the children with AHC have epilepsy, and these seizures are usually quite distinct from AHC attacks in their manifestations, although they may occur simultaneously. If an EEG is recorded during the seizure it usually shows an appropriate abnormality, but between seizures the EEG is normal. Seizures may be prolonged in two forms: epilepsia partialis continua or a more generalized convulsive status epilepticus. There is no agreed specific drug for seizure prevention in AHCA, and indeed, the epilepsy is often resistant to treatment. It is usual to give antiepilepsy drugs (AEDs) if the child has epilepsy, but one should monitor their effect and not continue in the face of side effects and poor efficacy. The management of these cases is challenging. The only drug with some efficacy is flunarizine and AEDs for seizure control. A trial of gamma-hydroxy butyrate (GHB) in N = 1 study had some efficacy and lateralised EEG changes contralateral to the side of hemiplegia, reversing with GHB. Results The diagnosis of AHCA was confirmed by the finding of ATP1A3 gene mutation in all 3 patients. In 2/3 cases the disorder extended into adulthood necessitating a name change: AHCA for the same genotype. Discussion The mutation found to be associated with AHCA is the ATP1A3 gene in 3/3 cases, reported in a majority of AHCA patients, with some familial cases. Conclusion AHCA is very uncommon, likely underdiagnosed clinically but with a high index of suspicion for early diagnosis and appropriate therapy, may ameliorate outcome and long-term prognosis in a larger RCT study.