NORD gratefully acknowledges Michelle Welborn, PharmD, President/CEO of Intractable Childhood Epilepsy Alliance for the creation of this report; Charlotte Dravet, MD and Dr. Catherine Chiron, for assistance in the review of this report.
Dravet syndrome spectrum disorders are rare genetic epileptic encephalopathies (dysfunction of the brain) with onset during the first year of life in an otherwise healthy infant. There is a spectrum of severity ranging from no clinical symptoms, to simple febrile seizures, and extending to Dravet syndrome, which is the most severe. Mutations of the SCN1A gene cause 79% of diagnosed cases of Dravet syndrome. Frequently referred to as a sodium channelopathy, this intractable (uncontrollable) epilepsy is characterized by unilateral (one-sided) clonic or tonic clonic (grand mal) seizures that may be prolonged (> 5 minutes) or progress to status epilepticus (>30 minutes). Myoclonic seizures, often called myoclonic jerks, are common but not always present. Over time seizures present without fever, illness or heat triggers. Seizures are frequent and resistant to treatment. The first seizure is often associated with vaccine administration at six months of age. Infants eventually develop other seizure types including atypical absence, eyelid myoclonia and non-convulsive seizures. Multiple drug therapy is necessary for acceptable seizure control. Some anti-epileptic drugs exacerbate seizures and should be avoided. In most cases, surgery is not indicated. The initial EEG is normal but within the second or third year of life, brief generalized spike, polyspike, or polyspike-wave paroxysms appear. MRI and metabolic studies are normal. Developmental delays appear to varying degrees in most patients by age two years and ataxia (abnormal gait) is common. Appropriate and aggressive seizure management, and implementation of global therapies are necessary to improve the outcome of children affected with Dravet syndrome spectrum disorders.