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).