What is Landau- Kleffner Syndrome?
Landau–Kleffner Syndrome (LKS) is a rare childhood epilepsy accompanied by acquired aphasia. The first LKS cases were described by Landau and Kleffner (1957). They reported five children with a gradual regression of language abilities showing paroxysmal unilateral or bilateral spike-and-wave discharges, which were characteristically localized in the temporo-parietal brain regions. The syndrome is relatively uncommon: in a review Ansink et al. (1989) report about 170 known LKS cases, and since then, this number has not increased considerably. In a recent paper, Smith and Hoeppner (2003) mention 198 published cases. The question arises whether the low number of LKS patients is due to the lack of proper diagnosis. The diagnosis is rather problematic given that the epileptic activity does not always manifest itself in clinical seizures and the language impairment might be diagnosed and treated as a developmental disorder (i.e. dysphasia, or specific language impairment) or deafness.
One of the main features of the syndrome is the language regression. It is primarily related to auditory comprehension, and thought to be specific to phonological processing. Expressive disorders are present as well, but in most cases they occur later than the comprehension deficits and are therefore considered secondary.
Language regression may be gradual or rapid, and it is not necessarily accompanied by abnormal neurological signs or seizures. However, a special EEG pattern, namely an almost continuous spike-and- wave activity in slow-wave sleep, and sometimes in wakefulness, is always present in LKS children. The onset peak of the disorder is between the ages of 3 and 8 years, and twice as many boys are affected relative to girls (Pearl et al., 2001).
The outcome of the syndrome is rather benign: a complete spontaneous recovery from the epilepsy is likely at the beginning of adolescence, which is not the case for the acquired language disorder. A severe residual language deficit may remain, and the onset of the syndrome is of a major effect on the outcome: the younger the child at the onset, the worse the chance of recovery (Bishop, 1985).