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multicentre trial comparing steroid and vigabatrin treatment for spasms not due to tuberous
sclerosis found evidence in favour of the former, although this must be balanced against the
potentially severe, even fatal adverse effects of steroids. Surgery has a role in cases due to
focal brain pathology.

The prognosis is generally, but not universally, poor: 1530% may become seizure free and
develop normally or near normally. However, around 60% are left with intractable seizures
(often Lennox-Gastaut syndrome) and two-thirds have severe learning difficulties and/or
behavioural problems.

Dravet syndrome (also called severe myoclonic epilepsy in infancy)
This epilepsy syndrome is increasingly recognised. It is more common in boys. It begins in
the first year of life and affected children are previously normal. The first seizure is usually
febrile. There may be nothing remarkable about the seizure but characteristically it is
complex, being prolonged and/or focal. Febrile status is common. In addition, the provoking
fever is often relatively mild. Indeed in some cases the child may simply be unwell without
clear evidence of a fever. The child recovers as expected but further similar seizures usually
occur, often becoming more and more frequent with time. Some are provoked by non-febrile
illnesses, immunisations, hot baths and even hot weather. During this stage of the condition,
development continues normally. A second stage then ensues, usually in the second or third
year of life, with a polymorphous epilepsy. Seizure types often include myoclonic seizures,
febrile and non-febrile convulsive seizures (tonic-clonic, clonic or hemiconvulsions), atypical
absences and focal seizures. Episodes of convulsive and non-convulsive status epilepticus
may occur. As well as temperature provoking seizures, some patients are photosensitive.
During this stage of the disease development stagnates and there is often a true regression.
Neurological signs, such as ataxia and pyramidal signs, commonly develop. Eventually all
children are left with severe, often profound, learning difficulties. In late childhood a final
stage ensues during which seizures tend to continue but are less frequent and development
plateaus.

At presentation the EEG in Dravet syndrome is initially normal, except that about one-fifth
of subjects show very early photosensitivity. With the onset of the polymorphous seizure
phase the EEG begins to slow and becomes dominated by diffuse theta and delta. Paroxysmal
abnormalities of polyspike and/or spikes and slow waves usually become frequent occurring
in brief bursts, which are often asymmetrical.

Genetic factors are very important in Dravet syndrome, but the condition rarely recurs in
families (although this is described) and it certainly does not follow simple Mendelian
inheritance. A family history of epilepsy (of various types) is very common. Probably more
than 80% of subjects with typical Dravet syndrome and a smaller, but still significant, number
of atypical cases have mutations on the SCN1A gene which codes for a sodium channel.
Given that the same mutations may be associated with much milder epilepsy phenotypes, it
is clear that other genetic or environmental factors must be involved in producing the Dravet
phenotype but these remain to be elucidated. Other investigations are expected to be normal,
though diffuse atrophy may develop on brain imaging.

Response to AEDs is poor, although temporarily good results can be obtained from a number
of agents. Carbamazepine, phenytoin and lamotrigine may exacerbate seizures and should be
avoided. Stiripentol in conjunction with sodium valproate and/or clobazam has been shown
to be beneficial in a double-blind, placebo-controlled trial. The ketogenic diet may be useful.