Discrimination of speech sounds in a boy with Landau-Kleffner syndrome: an intraoperative event-related potential study.

A 7-year-old boy with severe acquired epileptic aphasia (Landau-Kleffner syndrome) was treated by multiple subpial transections to the left temporal lobe. In the course of electrocorticography, event-related potentials (ERP) were recorded to the phonemes /ba/ and /ga/; /ba/ occurred 72.5% of the time and /ga/ 27.5%, in a pseudo-random sequence. The ERPs were distributed over the middle and inferior temporal gyri and there was a marked overlap with the area of maximal spiking detected on the electrocorticogram. Repetition of the frequent syllable /ba/ was associated with diminution of the prominent negative component of the ERP culminating around 550 ms suggesting habituation. Presentation of the novel syllable /ga/ restored the amplitude of this negative component, showing that discrimination was preserved despite the apparent global aphasia. This finding supports clinical evidence that some children with epileptic aphasia can still process auditory speech input. Intraoperative ERP recording may help improve our understanding of the relationship between epileptiform activity and aspects of language processing in Landau-Kleffner syndrome where lack of cooperation precludes detailed clinical testing.