Landau–Kleffner syndrome with onset at 18 months and an initial diagnosis of pervasive developmental disorder

We report one of the youngest and most intensively studied cases of Landau–Kleffner syndrome, with a follow-up of 5 years. The boy developed normally until the age of 18 months when he had two attacks, possibly epileptic. Electroencephalogram (EEG) was normal. Over the next 5 months he lost his six to ten words, did not engage with other children and became mute. When he was 34 months old a child-psychiatrist suggested a diagnosis of pervasive developmental disorder or developmental dysphasia. An EEG 3 months later showed abnormalities typical of Landau–Kleffner syndrome. His non-verbal abilities were normal as well as his neurological examination and brain magnetic resonance imaging (MRI). A trial of clobazam and vigabatrin was unsuccessful. When he was 4 years and 9 months old he was treated with corticosteroids and within 3 months his vocabulary increased from the standard for 112 years of age to that for 212 years of age. His language abilities continued to improve slowly until a stagnation period at the age of 6 years and 9 months. A second course of corticosteroids improved his comprehension and vocabulary to an almost normal level, and his EEG normalized. A total of 11 EEGs were obtained; all included sleep, but continuous spike and wave during slow sleep was never documented. This report illustrates that Landau–Kleffner syndrome should be considered as an alternative diagnosis in children diagnosed with developmental dysphasia. An EEG including sleep should be considered, and in the presence of abnormalities a trial of anti-epileptic drugs or corticosteroids should be undertaken.