How does it Happen

All children with LKS can be shown to have seizure activity during the active phase, that usually affects both sides of the brain (although one side may seem more affected), and is often concentrated in areas known to be important for language (centro-temporal region). Some of this activity results in actual seizures but much of it does not, that is, it is ‘sub-clinical’. EEG recordings show that there is a particularly high rate of subclinical epileptiform activity in sleep, which often amounts to nearly continuous spike-and-wave (CSWS) discharges (Electrical Status Epilepticus during sleep or ESES) during the active phase of the disease.

It is thought that regression and impairments are related to these epileptiform discharges during sleep, and that these electrical seizures ‘short-circuit’ the normal wiring so certain functions of the brain are prevented. This seizure activity, which is often-widespread, prevents the child from using his or her brain normally so they regress in abilities. Initially, the brain is not ‘damaged’ in the conventional sense, but rather caught up in an ‘electrical storm’ that blocks certain brain functions (especially language, attention, social functioning). Stopping seizure activity may restore these functions.

LKS mainly affects a child’s language abilities, and this is probably related to the common location of recorded discharges over the key language areas (centro-temporal region). It was initially thought to be specific to language, but certainly current experience is that other higher functions are also commonly affected, including attention, social interaction, behaviour and motor control. Non-verbal cognitive skills are usually relatively spared, although not always, and it is not unusual to have specific or more general learning difficulties.

Unlike physical injury where brain ‘plasticity’ allows other areas of the brain to take up important functions, in LKS, the brain’s capacity and reserves appear to be limited by the electrical activity. Consequently, relocation of skills (such as language) to other brain areas is not generally possible.

The active phase of the disease relates to the period of sub-clinical seizure activity and appears to be time-limited, starting after the age of three, and ‘burning out’ by early adolescence. The visible, clinical seizures are generally short and do not show a close relationship with the effects on language and other areas of development.

This ‘seizure mechanism’ that produces the deficits, makes LKS (and related epilepsies) quite unlike more common developmental disabilities, which are usually present from birth with static deficits affecting all aspects of learning evenly. LKS is also quite different from traumatic brain injury where there is actual damage to brain substance, usually visible on a brain scan, with predictable loss of abilities related to the damaged areas. The brain-injured child usually makes steady progress once they have recovered from the immediate injury, and in some cases, the uninjured brain areas may take over the lost skills.

LKS and related severe seizure disorders are unique in causing extreme fluctuation because of the variable nature of the electrical activity. A child’s understanding and abilities may change dramatically (for better or worse) over short periods of time, and for some children, there may be obvious variation even within a day. This poses a major challenge for those supporting the child particularly in the classroom.