Dravet syndrome is a very rare form of childhood epilepsy. Out of 500 children with epilepsy, only one, or at most two, children are likely to have this form of epilepsy. The epilepsy usually starts with seizures that may seem to be very similar to febrile convulsions. The more typical features of Dravet syndrome usually become more obvious during the second year of life.
Epilepsy Action has more information about febrile convulsions.
Other names for Dravet syndrome
Severe myoclonic epilepsy in infancy (SMEI)
The seizures begin in the first year of life, usually at 6-10 months of age. They are most often associated with a high temperature (febrile seizure or febrile convulsion). They often involve just one side of the body, although both sides of the body may be involved. The seizures are characterised by stiffness and jerking (called a tonic-clonic seizure), or just repeated jerking (called a clonic seizure). Febrile convulsions in Dravet syndrome are usually quite long, sometimes lasting for 15 or 30 minutes, or even longer. This is called febrile status epilepticus and is common in the first year of life. However, at this time it can be difficult to differentiate these children from others with briefer febrile convulsions, who do not go on and develop other types of seizure. In the past, Dravet syndrome has been misdiagnosed in some children as a severe reaction, called an ‘encephalopathy’, to some early childhood vaccinations and particularly whooping cough (pertussis) vaccine.
During the second year of life the seizures become more frequent and persistent, and are often more obviously focal (also called partial) involving one part of the body. They may happen with or without a fever, and at any time of day and night. In addition to the tonic-clonic seizures, myoclonic seizures (‘myo’ meaning muscle, and ‘clonus’ meaning jerk) and focal seizures become common. Often the children are photosensitive (have seizures brought on by flashing or flickering lights or even certain patterns such as checked materials). A few children are very sensitive to these patterns. Seizures may also sometimes be brought on by hot environments or hot showers or baths.
The early development of children with Dravet syndrome is usually normal. However, the child’s development starts to slow down and children may lose skills towards the middle or end of the second year of life. The child’s speech and language is particularly affected. Their manner of walking (called ‘gait’) is also abnormal and is quite fast and unsteady (called ‘ataxia’).
A full history and description of the seizures that have happened in the past and at the time the child attends their hospital appointment is very important. It is also important for parents to give the doctor a detailed account of their child’s development.
The EEG, which records the electrical activity in the brain, is usually normal early on in this condition. By the time the child is 18 months old, the EEG shows evidence of epileptic activity, with spike and wave or polyspike discharges. These happen either as a single event, or in bursts. They may be generalised involving the whole brain, or happening just from one small area of the brain. Some, but not all, children with Dravet syndrome show EEG evidence of sensitivity to flashing or flickering lights, called photosensitivity. Brain scans in children with Dravet syndrome are usually normal.
A specific genetic abnormality, called a ‘mutation’ has been found in at least 8 out of 10 children with Dravet syndrome. This mutation is known as the ‘SCN1A’ mutation. Many different types of mutation have been found in people with Dravet syndrome. A mutation can be looked for in a simple blood test. The discovery of this mutation has been very helpful in making or confirming a diagnosis of this epilepsy syndrome. About 90% of mutations are new or ‘de novo’ mutations. This means that the mutation has not been inherited from a parent, but it is a new mutation in the child. Because of this, it is very un-common for the same parents to have another child with Dravet syndrome. However, if a twin develops Dravet syndrome and their twin is identical, then it is very likely that this other twin will also have the condition.
In some families a mutation in the SCN1A gene may cause a different form of epilepsy.
Dravet syndrome is one of the epilepsy syndromes that are most resistant to epilepsy medicines. Sodium valproate (Epilim) or topiramate (Topamax) are usually tried first. Other medicines which are helpful include clobazam (Frisium) and stiripentol (Diacomit). There are also some NICE guidelines about this. NICE, the National Institute for Health and Care Excellence, is an independent organisation that provides guidelines for treatment and care for people using the NHS in England, Northern Ireland and Wales.
Here are the NICE guidelines, in section 1.9.9 about treatment for Dravet syndrome:
Do not offer carbamazepine, gabapentin, lamotrigine, oxcarbazepine, phenytoin, pregabalin, tiagabine or vigabatrin [to people with Dravet syndrome].
Many children with Dravet syndrome seem to respond best to a specific combination of 3 epilepsy medicines. This combination is sodium valproate, stiripentol and clobazam. It is very important that only specialist epilepsy doctors, called paediatric neurologists, prescribe this combination of medicines. Other treatments that might be helpful include clonazepam (Rivotril), topiramate (Topmax) and zonisamide (Zonegram). A course of a steroid (called prednisolone) may also be helpful for a few weeks if a child’s epilepsy is going through a difficult time. The ketogenic diet may also be helpful but it may take a number of weeks to be effective. The diet will usually have to be given with at least one epilepsy medicine.
A child is very likely to have prolonged or repeated seizures as part of Dravet syndrome. The hospital doctor (paediatrician or paediatric neurologist) will discuss a ‘rescue’ or emergency care plan to treat any prolonged or repeated seizures that may happen at home. This rescue or emergency care plan is important for the child.
Because children with Dravet syndrome always have some degree of learning disability, they will also need a full educational assessment and support.
Information about treatments for children can be found on the Medicines for Children website.
There has been – and continues to be – a lot of research into Dravet syndrome. This research includes different medicines and treatments. You could ask your child’s hospital doctor about this and they will be able to discuss this with you.
The seizures continue to be very difficult to control, throughout childhood. Learning difficulties are very common and can range from mild to very severe. These difficulties usually persist and only rarely improve. As the condition progresses most children become more unsteady (ataxic) on their feet. Children with Dravet syndrome will need to be cared for throughout their lives. Usually by the age of 14 or 16 years, the seizures tend to become less frequent but they still happen.
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Dravet Syndrome UK
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What is a syndrome?
A syndrome is a group of signs and symptoms that, added together, suggest a particular medical condition. In epilepsy, examples of these signs and symptoms would be things like the age at which seizures begin, the type of seizures, whether the child is male or female and whether they have physical or learning disabilities, or both. The results of an electroencephalogram (EEG) are also used to help identify epilepsy syndromes.
If you would like to know more about an epilepsy syndrome, please speak to your doctor. If you would like to know more about epilepsy in general, please contact Epilepsy Action.
Epilepsy Action would like to thank Dr Richard Appleton, consultant paediatric neurologist at Alder Hey Children’s Hospital, Liverpool, UK for preparing this information.