M. Scott Perry, MD, reviews the prevalence, pathophysiology, signs and symptoms, and the diagnosis of Dravet syndrome.
M. Scott Perry, MD: What is Dravet Syndrome? It’s a rare genetic epileptic encephalopathy. It occurs in about 1 in 16,000 people. It’s a condition that presents in the first year of life, generally in the setting of seizures with fever, but not always seizures with fever.
Initial seizures are often of hemiclonic type, so one side of the body may be involved, or generalized tonic-clonic type where both sides are involved, though other seizure types can occur. Onset generally occurs around the age of 6 to 8 months, sometimes a little earlier in some, sometimes a little later, and the seizures oftentimes are very long in duration, especially if it’s in the setting of a febrile illness. Generally, the development of a child with Dravet syndrome is normal at onset, and oftentimes their EEG [electroencephalogram] is normal at onset when they’re first admitted, and as a result they are often diagnosed as having febrile seizures.
What generally happens is within several weeks or months they have another seizure. Some red flags people should consider in that first year of life are if a child, every time they have a seizure they have a fever, or if every time they have a fever they have a seizure, or the seizure is long each time they come in. Those are some definite red flags. After the age of 1, a lot of these kids will start to develop new types of seizures, so my myoclonic-type seizures may arise.
You may see atypical absence seizures more commonly at that point. Of course, generalized tonic-clonic and other focal seizures can also arise. The diagnosis of Dravet syndrome is one of recognizing the syndrome, so recognizing those red flags like I talked about, but also you can make the diagnosis through genetic testing. It is a syndrome based on clinical diagnosis, but the majority of patients, about 85% or so, will have a mutation in the SCN1A gene. That’s a gene that encodes the sodium channel that is highly expressed in the inhibitory network of the brain.
As I tell families, the way to think about this is that you’ve got 2 ways seizures happen in the brain. You either have too much electricity from the excitatory side, or you don’t have enough control of the electricity from the inhibitory side. In the case of Dravet syndrome, the problem is the inhibitory side does not work well, and as a result they are prone to these seizures.
After that first year of life, when you start to see these other seizure types arise, that is the time that you may see either a stagnation in development or sometimes a decline, especially after very long seizures after status epilepticus. It’s important to recognize this syndrome early on because the path of the treatment can be changed depending on this diagnosis.