Dravet syndrome

What Dravet syndrome is

Dravet syndrome — first described by Charlotte Dravet in 1978 and once called severe myoclonic epilepsy of infancy — is a developmental and epileptic encephalopathy. This means that both the frequent seizures and the underlying brain difference contribute to how a child develops over time.

It usually begins between 1 and 20 months of age (most often around 5–6 months) in an infant who had been developing normally. The first seizures are commonly long, may be triggered by fever, and often affect one side of the body — or alternate sides from one seizure to the next.

The genetic cause (SCN1A)

In more than 90% of children, Dravet syndrome is caused by a loss-of-function variant in the SCN1A gene. SCN1A carries the instructions for the NaV1.1 sodium channel, which is especially important for inhibitory (GABAergic) neurons that normally help calm electrical activity in the brain. When the channel does not work well, there is too little inhibition — which predisposes to seizures.

Most SCN1A variants in Dravet syndrome arise new in the child (de novo). However, in around 10% of seemingly de novo cases a parent carries the change in a small proportion of their cells (mosaicism), which can raise the chance of recurrence in a future child. For this reason, careful genetic testing of parents and genetic counselling are an important part of the picture.

Two cautions matter: not every SCN1A change causes Dravet syndrome (milder changes can cause genetic epilepsy with febrile seizures plus), and gain-of-function SCN1A changes cause a different, neonatal-onset condition that is managed differently.

How it presents

• Onset in the first year or two of life in a previously healthy infant
• Long convulsive seizures, often with fever; recurrent prolonged seizures (status epilepticus) are common
• Triggers can include fever or illness, warm temperatures, vaccination and excitement
• Other seizure types (myoclonic, absence, atonic, focal) often appear later in childhood
• Seizures are typically resistant to medication and lifelong, although the burden often eases somewhat with age

Beyond seizures: development and comorbidities

Development is usually typical at first, with slowing most often noticed in the second year of life. Over time most children have some degree of intellectual disability, and many have difficulties with speech and language, movement (including a characteristic crouched gait), sleep and behaviour.

Autism spectrum and attention difficulties are common. Importantly, these developmental effects can occur independently of how well seizures are controlled — one reason the field is so interested in therapies that address the underlying cause.

Current management

There is no cure yet, and complete seizure freedom is rarely achievable, so the goals of care focus on reducing seizures — especially long ones — and on supporting development, behaviour and quality of life. Most children need more than one medicine, chosen carefully to balance benefit and side effects, together with a home rescue medication and a written seizure action plan.

• First-line medicines are usually valproate and clobazam
• Dravet-specific add-on therapies with strong (class 1) trial evidence include fenfluramine, stiripentol and pharmaceutical-grade cannabidiol
• Other options include topiramate and the ketogenic diet; vagus nerve stimulation is sometimes considered
• Certain sodium-channel-blocking medicines (for example phenytoin, carbamazepine and lamotrigine) are generally avoided, because they can make seizures worse in Dravet syndrome

The genetic pipeline: precision and disease-modifying therapies

For the first time, treatments designed to correct the underlying SCN1A problem — rather than only suppress seizures — are being tested in children. Because the SCN1A gene is too large to simply replace with standard gene therapy, researchers are instead trying to boost the body's own healthy SCN1A copy. Several approaches have reached clinical trials; all remain investigational and are not yet approved as standard care.

• Zorevunersen (STK-001) — an antisense oligonucleotide given into the spinal fluid that increases NaV1.1 production from the working SCN1A copy. Early-phase and extension studies have shown durable seizure reductions alongside gains in cognition, behaviour and quality of life; in March 2026 the first data suggesting disease modification were published in the New England Journal of Medicine. The global Phase 3 EMPEROR study (Stoke Therapeutics / Biogen) is enrolling children aged 2 to under 18 across the US, UK, Japan and Europe, with a readout expected in 2027.
• ETX101 (Encoded Therapeutics) — a one-time AAV9 gene-regulation therapy that selectively targets inhibitory interneurons to raise the child's own SCN1A output. Interim results from the POLARIS Phase 1/2 programme (ENDEAVOR in the US, EXPEDITION in the UK, WAYFINDER in Australia) have suggested seizure reductions and early developmental gains; the pivotal ENDEAVOR Part 2 study began dosing in 2026.
• Newer serotonergic medicines that avoid the heart-valve receptor (such as bexicaserin, in the Phase 3 DEEp SEA study) and other targeted or repurposed drugs are also in trials, while some candidates (for example soticlestat and lorcaserin) have been discontinued.
• Earlier-stage (preclinical) research includes CRISPR-based activation of SCN1A and engineered tRNA / mRNA approaches.

How an educational review can help

A Dravet diagnosis brings a great deal of complex information at once — genetic results, EEG and MRI reports, a changing medication list and, increasingly, questions about whether a trial might be relevant. An educational review can translate these documents into plain language, explain how the current plan fits established guidance, and help you prepare focused questions for your treating team.

It is an educational second opinion — not a diagnosis, treatment or prescription — and it does not replace the care of your child's own clinicians.