What Happens

In most cases, the child has normal early development, including normal development of speech and language. Onset of the disease is usually between three and nine years and the child experiences deterioration in speech and language ability. This loss may be abrupt or gradual over a period of weeks or months and is often initially mistaken for deafness. Many children compensate naturally for the loss of language by using visual cues and gesture, and may initially hide the extent of their difficulty. The deterioration in skills is often called a regression, as the child appears to have returned to an earlier stage in their development.

There are often associated behavioural changes including over-activity, reduced concentration span, irritability, tantrums and difficulties with social interaction. The child may also have problems with fine motor co-ordination and movement (for example, dribbling, messy eating, loss of speech clarity, clumsiness and tremor). These difficulties are thought to be a direct result of the disease process, and not simply an emotional reaction by the child to their loss of language.

Most of the children have clinically obvious seizures, and these often start before the initial regression.

The course of the illness is very variable. It isn’t usually life threatening, but can greatly affect a child’s functioning. Some children may recover spontaneously, while others may recover with the use of anti-epilepsy drugs (AEDs) including corticosteroids, or even brain surgery. Recovery may be complete but more often, children have some degree of persisting difficulties with language, behaviour or cognitive skills. The active phase of the disease often lasts some years until adolescence. During the active phase there may be repeated episodes of regression and recovery, and a child’s understanding and performance may be highly variable even within the same day. The variation can be related to the dose of corticosteroids and attempts to wean them. There is the impression that for many children, the first regression is the most severe, however it isn’t unusual for children to recover their skills, only to lose them again in a further regression.

Some children have the same EEG abnormality as in LKS, but lose skills in all areas (including general intelligence), not specifically in language. This broad group is usually referred to as Electrical Status Epilepticus during sleep (ESES) or continuous spike-and-wave discharges in sleep (CSWS). LKS (in which language is mainly affected) is effectively a specific type of ESES.

We recognise at least two variants of LKS:

Those who had a mild degree of early (developmental) language delay but who showed typical LKS regression later
Those with an abnormality on scan but otherwise a typical history

The diagnosis of LKS does not include children under the age of two years who regress as part of an autistic spectrum disorder, even if they have seizures or discharges on an EEG. This is because experience has shown that these children fit best within the autistic spectrum of disorders, and do not conform to the pattern of disorder seen in LKS.