Dravet syndrome
- Article
- 2021-03-29
Formerly called severe childhood myoclonic epilepsy (SMEI), Dravet syndrome is an epilepsy syndrome that starts in childhood or early childhood and can include a spectrum of symptoms ranging from mild to severe. Children with Dravet syndrome initially exhibit focal (limited to one area) or generalized (by the brain) seizures that start before the age of 15 months (often before the age of one). These initial attacks are often long lasting and affect half of the body, with subsequent attacks that can switch to the other side of the body. These first attacks are often triggered by seizures or exposure to elevated temperatures or changes in temperature, such as getting out of a bath. Other types of seizures develop after 12 months of age and can vary considerably.
Children with Dravet syndrome usually have normal development in the first few years of life. As seizures increase, the rate of skill acquisition slows and developing children begin to lag behind their peers. Other symptoms may begin during childhood with changes in eating, appetite, balance, and a squatting gait (walking).
In at least 80 percent of cases, Dravet syndrome is caused by defects in a gene necessary for brain cells to function properly. Mutations in the SCN1A gene (a gene that codes as a sodium channel, part of the cell membrane involved in the functioning of the nervous system) are the main causes of Dravet syndrome. Borderline SMEI (SMEB) and another type of epilepsy in infants called generalized epilepsy with febrile seizures plus (GEFS +), but which is much less severe, are caused by defects in the same gene. Dravet syndrome is a lifelong condition.
Therapy
Seizures in Dravet syndrome are difficult to control but can be reduced by anticonvulsants. The United States Food and Drug Administration (FDA) has approved the drug fenfluramine to reduce the frequency of convulsive seizures with Dravet syndrome in people 2 years of age and older. A ketogenic diet that is high in fat and low in carbohydrates can also be helpful. Some anticonvulsant medications that bind to sodium channels (such as oxcarbazepine, carbamazepine, phenytoin, and lamotrigine) should not be used daily because they can make seizures worse.
In June 2018, the U.S. Food and Drug Administration approved cannabidiol (Epidolex, derived from marijuana) for the treatment of Dravet syndrome-related seizures in people 2 years of age and older. The drug contains only a small amount of the psychoactive element in marijuana and does not induce the euphoria associated with the drug. This is the first FDA-approved drug for Dravet syndrome.
Prognosis
As children with Dravet syndrome grow older, their decline in cognitive function stabilizes. The degree of intellectual disability varies widely from mild to severe, but most teens and adults with Dravet syndrome depend on health care providers. Gait abnormalities seem to worsen during adolescence. Seizures usually decrease in number and duration with age. Individuals with Dravet syndrome have a higher risk of sudden, unexpected death than the general population, but that risk is still low.
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