INTRODUCTION Alternating hemiplegia of childhood (AHC) is a rare disease characterised by repeated episodes of hemiplegia that alternately affect one side of the body. Onset is usually before the age of 18 months, the episodes last anywhere from a few minutes to several days. In some cases these episodes may even render the early infant quadriplegic for some time if one begins before the previous one has finished or if they occur at the same time. The clinical description includes, in addition to these paralysing attacks, other paroxysmal manifestations that are present in practically all the children diagnosed with this condition and which, moreover, appear earlier. Such manifestations consist in tonic attacks, dystonic attacks, abnormal eye movements and autonomic disorders. The fact that these symptoms precede the typical clinical signs and symptoms often leads to delays in the final diagnosis.

CASE REPORT We report the case of a male, aged one year and nine months, who initially presented a clinical picture of tonic seizures at the age of two weeks, which then went on to episodes of hemiplegia that appeared alternately at the age of 11 months. The patient also presented retarded overall psychomotor development. In the early stages of the symptoms he was diagnosed with epilepsy, failed to respond to multiple antiepileptic drugs, and the electroencephalogram, neuroimaging and complementary blood and urine tests were all normal/negative. The patient responded well to flunarizine.

CONCLUSIONS This is the first patient with AHC reported in El Salvador. The early and accurate diagnosis of AHC is essential to be able to establish drug therapy and improve the prognosis and the quality of life of patients and their families.