Dravet (Dra-vay) syndrome, previously known as Severe Myoclonic Epilepsy of Infancy (SMEI), is a neurodevelopmental disorder beginning in infancy and characterized by severe epilepsy that does not respond well to treatment. Estimates of the prevalence of this rare disorder have ranged from 1:20,000 to 1:40,000 births, though the incidence may be found to be greater as the syndrome becomes better recognized and new genetic evidence is discovered. It is thought to occur with similar frequency in both genders and knows no geographic or ethnic boundaries.

The course of Dravet syndrome is highly variable from person to person. Seizures begin during the first year of life and development is normal prior to their onset. In most cases, the first seizures occur with fever and are generalized tonic-clonic (grand mal) or unilateral (one-sided) convulsions. These seizures are often prolonged and may lead to status epilepticus, a medical emergency. In time, seizures increase in frequency and begin to occur without fever. Additional seizure types appear, most often these are myoclonic, atypical absence, and complex-partial seizures. MORE ABOUT SEIZURES

During the second to fourth year of life, varying degrees of developmental delay typically become apparent and can include regression of aquired skills. MORE ABOUT DEVELOPMENT

Additional features that are seen in significant numbers of patients with Dravet syndrome may include sensory integration disorders and other autism spectrum characteristics, orthopedic or movement disorders, frequent or chronic upper respiratory and ear infections, sleep disturbance, dysautonomia, and problems with growth and nutrition. MORE ABOUT SECONDARY FEATURES

 

The sodium channel gene SCN1A is currently the most most clinically relevant gene found to cause epilepsy and is a known contributor to a significant percentage (approximately 50-80%) of cases of Dravet syndrome. Researchers have documented many different mutations of the SCN1A gene, however the majority of them do not result in Dravet syndrome. SCN1A mutations most often lead to milder forms of epilepsy, including Generalized Epilepsy with Febrile Seizures (GEFS), Generalized Epilepsy with Febrile Seizures Plus (GEFS+), Intractable Childhood Epilepsy with Generalized Tonic-Clonic Seizures (ICEGTC), and Severe Myoclonic Epilepsy, Borderline (SMEB). Dravet syndrome is generally considered to be the severe end of a broad spectrum of SCN1A-related epilepsies.
                                                                                                                         
GEFS -------------- GEFS+ ----------- ICEGTC ------------ SMEB -------------- SMEI/Dravet syndrome

Mutations of the SCN1A gene have an autosomal dominant inheritance pattern, meaning that they can be passed from parent to child. However, in Dravet syndrome, although at least one-fourth of the affected individuals have some history of febrile seizures or epilepsy in their extended family, the gene mutation nearly always arises “de novo”, or new to the individual, meaning that neither parent tests positive for the gene mutation and it is thought to have occurred spontaneously after conception. Modifying genes and environmental factors likely play an important role in determining the severity of the resulting condition. Other genes have also recently been implicated in Dravet syndrome, including SCN9A and PCDH19. Much remains to be understood about the causes of Dravet syndrome and research is ongoing. FIND A GENETIC TESTING FACILITY

At this time, the treatments available for Dravet syndrome are focused on improving symptoms, primarily anticonvulsant medications to control seizures. Response to these medicines is variable, but often seizures persist despite treatment. While certain medications have been found to be generally useful for individuals with Dravet syndrome, others have been quite consistently found to have an aggravating effect. The helpfulness of other anticonvulsant therapies, such as the Ketogenic Diet and vagus nerve stimulation (VNS), are in ongoing evaluation. Once again, results tend to be highly variable from person to person.

 

Early implementation of global therapies is essential to support optimal development. Patients with Dravet syndrome should receive physical, occupational, speech, and social/play therapies and an enriched environment is encouraged. Treatments to address orthopedic, sleep, autonomic, immune and growth problems may be important considerations. MORE ABOUT CARE AND TREATMENT