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Migrating focal seizures of infancy (also called malignant migrating partial seizures in
infancy)
This rare syndrome starts any time between birth and about seven months in previously
normal children. It is characterised by focal seizures with motor and prominent autonomic
symptoms and with secondary generalised seizures. Seizures vary in their intensity and
duration; episodes of status are common. The seizures tend to increase in frequency,
becoming virtually continuous. EEG background is slow with varying side emphasis and
multifocal spikes develop. Ictal discharges involve multiple independent sites, moving from
one cortical area to another. Investigations, except EEG are normal. It is likely to be genetic
in origin; a recent study suggested up to 50% may be due to a mutation in the KCNT1 gene.
Response to treatment is poor and there is a high mortality.

Severe epilepsy syndromes of childhood

The following epilepsy syndromes in childhood are often severe, constituting epileptic
encephalopathies: Lennox-Gastaut syndrome; Doose syndrome; Landau-Kleffner syndrome
and the related disorder of epilepsy with continuous spike and waves during slow-wave sleep;
and myoclonic absence epilepsy. Note that the propensity of these syndromes to act as
epileptic encephalopathies varies: Landau-Kleffner syndrome always does so whilst Doose
syndrome, which is classified as an idiopathic generalised epilepsy, sometimes does but often
does not.

Lennox-Gastaut syndrome
Probably no syndrome diagnosis is more abused and misunderstood than Lennox-Gastaut
syndrome (LGS). Some authorities, particularly in the United States, classify virtually all
drug-resistant epilepsies characterised by multiple seizure types as LGS. Used in this way,
the diagnosis is of little use in helping management. The alternative, much favoured in Europe
and increasingly in the UK, is to use a narrower definition of the syndrome. This approach
will be used here. LGS usually begins between three and five years of age, but can start as
early as one year or as late as adolescence. Its incidence is said to be 2.8 per 10,000 live births
but because of its intractable nature its prevalence in children with seizures may be up to 5%.
It is characterised by seizures of multiple, mainly generalised, type and learning difficulties.

The three most characteristic seizure types are tonic (particularly axial tonic seizures), atonic
and atypical absence seizures. However, other seizure types may occur, including GTCS and
focal seizures. Myoclonic seizures are not usually prominent, although they can occur. A so-
called myoclonic variant of LGS is described in which myoclonic seizures are prominent.
However, children with this may be better classified as Doose syndrome. Tonic seizures can
occur both when awake and in sleep, but the latter are a particular feature of LGS. Tonic,
atonic and to a lesser extent, myoclonic seizures frequently cause astatic seizures (i.e. drop
attacks) in LGS. Finally, episodes of non-convulsive status epilepticus are common.

The background EEG in LGS is usually diffusely slow. Two main paroxysmal EEG features
help in the diagnosis. These are (Figure 3):

 Slow (<2.5 Hz) spike and wave discharges which are usually generalised and
symmetrical but can be asymmetrical, unilateral or even regional. They can be inter-
ictal or ictal. If the latter they can be associated with atypical absences or atonic
seizures.

 Fast rhythms or rhythmic rapid spikes at frequencies of 10–20 Hz which are usually
seen in slow wave sleep. These may accompany tonic seizures.