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a metabolic disorder or periods of non-convulsive status, but investigation at the time of acute
deterioration may be the only way to differentiate between these.

The emergence of neurological signs in a child with epilepsy, in association with possible
cognitive decline, signals the need for investigation, particularly if signs are progressive.
These include a motor disorder with pyramidal or extrapyramidal signs and abnormalities of
eye movement. There remains the possibility that this is still epileptiform in origin; motor
disorders such as monoparesis or ataxia may revert with aggressive antiepileptic drug (AED)
treatment. However this does not preclude the need for exclusion of other causes, as the EEG
itself may be inconclusive. It is also unusual for epilepsy alone to present with hard
neurological findings on examination unless a known deficit has been previously established.

Epileptiform or non-epileptiform?

The mechanisms of cognitive/neurodevelopmental plateau or regression in certain epileptic
encephalopathies remain unclear. This is particularly true of the early onset epilepsy
syndromes, both those that are focal and those that are generalised in onset. Generalised
syndromes that are almost always associated with this include the early myoclonic
encephalopathies, West syndrome, Dravet syndrome and the Lennox-Gastaut syndrome.

West syndrome pertains to the triad of infantile spasms, hypsarrhythmia on the EEG, and
developmental plateau. The latter involves a regression in communication skills with poor
eye-to-eye interaction. Infantile spasms may occur in association with a variety of
pathologies, although the EEG and developmental pattern may be similar. Prognosis with
regard to initial seizure control is relatively good with vigabatrin or steroids, however it
remains poor with regard to developmental outcome, and the later development of further
seizures. Developmental outcome appears better in some infants who are treated early after
presentation and in whom there is a rapid resolution of seizures and EEG abnormality,
suggesting that the epileptic activity plays a major part in subsequent cognitive development.
However the underlying pathology is a strong indicator of future developmental outcome.

Focal seizure syndromes can also feature a similar clinical picture of neurodevelopmental
regression at presentation. Sturge-Weber syndrome is characterised by a facial capillary
haemangioma (port wine stain) involving the periorbital area, forehead or scalp, a venous
angioma of the leptomeninges and, in a proportion of cases, a choroidal angioma. Epilepsy is
reported in approximately 80% cases. However, these figures are derived from selected groups
of individuals with Sturge-Weber syndrome, and may therefore not be fully representative of all
cases. Seizures start in the first year of life in the majority. One study found that the onset of
epilepsy was within the first two years of life in 86%, and 95% by five years of age. Early-onset,
poorly controlled seizures tend to be associated with progressive hemiparesis and developmental
slowing; in such cases early resective surgery should be considered. The underlying
pathophysiology of the ‘encephalopathy’ is unclear, but may be related to ischaemia secondary
to venous hypertension within the angioma.

Landau-Kleffner syndrome is an age-related syndrome with a probable focal aetiology leading
to a more widespread encephalopathy. Typically, children have a period of normal language
development, followed by a period of language regression with auditory agnosia. There is a
marked associated behaviour disorder. Seizures may be infrequent, but a profound abnormality
is seen on the EEG, usually over the temporal regions. Some may demonstrate very little in the
waking state, however, but show almost continuous spike-wave activity in sleep (electrical status
epilepticus in slow sleep/continuous spike-wave in slow sleep). Although conventional AEDs
may have some benefit, there appears to be a particular role for steroids early in the treatment of
this disorder, in an attempt to reverse the language disorder.