What is Dravet Syndrome?
Dravet Syndrome (previously called severe myoclonic epilepsy of infancy, SMEI), is an epilepsy that usually starts in the first year of life with frequent febrile convulsions that are often prolonged. In the second year of life a febrile generalised seizures appear – commonly myoclonic jerks and absence seizures.
Although previously the term Dravet syndrome was used to describe children with this seizure pattern and a severe intellectual and developmental disability, it is now recognised that there are children with this syndrome who have variable seizure severity and variable developmental and learning impacts and the term Dravet syndrome is now used for all these situations (previously terms such as severe myoclonic epilepsy – borderline, SMEB, were used).
What types of seizures are seen?
Children with Dravet syndrome typically start having seizures in the context of febrile illnesses in the first year of life. Unlike other children with febrile convulsions, febrile seizures in children with Dravet syndrome can be prolonged and may be hemiclonic (jerking involving only one side of the body). The side of the body involved in a hemiclonic convulsion can vary from febrile seizure to febrile seizure. This variation of the hemiclonic seizure from side to side is a useful indicator for Dravet syndrome.
In the second year of life, afebrile seizures start and these are often in the form of myoclonic and absence seizures. Generalised tonic-clonic and even focal seizures can occur. Status epilepticus is also seen (prolonged seizures or clusters of frequent seizures requiring medication to terminate the seizures).
Seizures in Dravet syndrome can be difficult to control with medication. It is well known that certain medications can in fact aggravate seizures – carbamazepine, oxcarbazepine and lamotrigine should be avoided for this reason, phenytoin should be used with caution. The best medications to use are combinations of valproate, topiramate and benzodiazepines. If these fail to control seizures then a special medication can be ordered from overseas, stiripentol.
When stiripentol is commenced, doses of the other medications need to be reduced significantly to avoid sedation. If stiripentol does not control seizures then the ketogenic or modified atkins diet can be helpful.
Seizures in Dravet syndrome can be increased by heat (hot days, hot showers or exercise) and in some (not all) children by visual stimulation (flickering lights or patterns).
What effects are there on learning?
Children with Dravet syndrome are at risk of developmental and intellectual delays. This may not be seen in the first year of life but may become apparent in the second year of life or later, and appears to be linked to frequency of seizures and to prolonged seizures. Early assessment and the support of early intervention services and therapy are important in a child with Dravet syndrome because of the high risk of developmental or intellectual difficulties. Most children with Dravet Syndrome will need a modified curriculum and an individual education plan (IEP).
What effects are there on behavior?
Children with Dravet syndrome can have behavioral difficulties. Dravet syndrome, and the medications use to treat seizures, can be associated with problems with attention and concentration, with processing information and with understanding information. These factors can result in a child who appears not to comply with instruction. Having a good understanding of a child’s developmental and intellectual abilities is therefore important in understanding and managing any apparent behavior.
In some situations specific medications can assist with improving behavior, such as the use of medications to improve attention and concentration.
What causes Dravet syndrome?
The majority of children with Dravet syndrome have a gene defect in the SCN1A gene. However testing this gene may not reveal an abnormality in 20% of cases, in these children the syndrome is likely due to another gene. SCN1A testing is available clinically, if this test is negative then it may be possible to test for other related genes – discuss this with your doctor. Most children with an identified gene abnormality have this as a new change in the child themselves i.e. the gene abnormality is not inherited from a parent. However, in some instances the gene abnormality can be inherited, and discussion with a genetic counsellor is warranted to consider of other family members should be tested.
How common is it?
This is a rare childhood epilepsy. Out of 500 children with epilepsy, only one, or at most, two children are likely to have this form of epilepsy.
What is the long-term outlook?
As children with Dravet syndrome get older, their condition generally stabilises and their seizures reduce in frequency and severity. Periods of status epilepticus are generally less common. When children grow, in adolescence, they can develop an unusual way of walking.
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Information reviewed by Dr. Kate Riney, Mater Hospital Brisbane.
Updated August 2013. To be reviewed August 2015.