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more common in boys. It consists of a triad of: an acquired language problem; epileptic
seizures; and behavioural problems. The language problem is initially auditory verbal agnosia
such that the children find difficulty in attributing semantic value to speech. This is often very
severe, causing the children to stop responding initially to the spoken word and sometimes to
environmental noises as well. They are often suspected of being deaf. A secondary motor
aphasia commonly develops. Epileptic seizures occur in three-quarters of patients with LKS.
The seizures can be of different types including GTCS and focal seizures. They are often, but
not always, infrequent. The behavioural problems, often severe, include hyperactivity and
attention deficits and autistic behaviours. The language problems, behavioural problems and
seizures often fluctuate in their severity and this may correlate with the EEG findings.

The EEG is characterised by mainly posterior temporal lobe foci of sharp slow-wave
complexes that are often multi-focal and bisynchronous. The awake EEG may be normal but
non-REM sleep nearly always markedly increases the epileptiform abnormalities, such that
they often occupy at least 85% of non-REM sleep. This constitutes electrical status
epilepticus during slow wave sleep (ESES). Although ESES is very common in LKS it is not
a prerequisite and its presence may vary between EEGs.

Structural imaging in LKS is usually normal. Functional imaging often implicates the
superior temporal gyrus, on one side or the other.

The LKS nearly always eventually remits. Occasionally this can be after only a few weeks or
months. More often it continues for some years and adults are usually left with persistent
language and cognitive problems, although these are often milder than would be anticipated
during the active stage of the condition.

Seizures in LKS often respond well to conventional AEDs but often without improvement in
language function or behaviour. However, sodium valproate is often used first line and both
ethosuximide and benzodiazepines can be helpful. Some children respond very well to
treatment with steroids. If medical treatment fails the neurosurgical technique of multiple
subpial transections over Wernicke’s area has been reported to be helpful. It requires the area
of cortex ‘driving’ the problem to be identified. Multiple cortical cuts are made tangentially
to the surface disrupting horizontal fibres responsible for seizure propagation whilst leaving
vertical fibres responsible for normal functioning intact. Evaluation is detailed, and evidence
for true benefit limited.

Epilepsy with continuous spike and waves during slow-wave sleep (CSWS) is a related and
overlapping epilepsy syndrome which can start from two months to 12 years. Many children
are neurodevelopmentally normal prior to the onset of seizure but others have a variety of
developmental problems, including cerebral palsy and learning difficulties. The condition
usually starts with seizures which are often nocturnal and hemi-convulsive in type. They may
be prolonged constituting status epilepticus. Usually after months or years the seizures
increase in frequency and become polymorphous. Indeed all types of seizures may occur
during this stage, except probably tonic seizures. With the increase in seizures
neuropsychological regression occurs and may be severe. There may be, in addition, acquired
motor deficits such as ataxia, hemiparesis and dyspraxia. An opercular syndrome with
drooling, feeding problems and dysarthria can occur.

The EEG hallmark of ECSWS is continuous (i.e. >85%), bilateral and diffuse spike and
waves during non-REM sleep (Figure 5).