Dravet Syndrome

Dravet syndrome is a developmental and epileptic encephalopathy that usually begins in the first year of life with prolonged convulsive seizures in a previously normally developing infant. It is strongly associated with pathogenic variants in SCN1A, although the diagnosis is clinical and electroclinical rather than being defined by one gene result alone.

Dravet syndrome is important to recognise early because seizure type, medication choice, fever sensitivity, emergency planning, developmental monitoring and genetic counselling are all affected by the diagnosis.

Where Dravet syndrome fits in the modern ILAE classification

The International League Against Epilepsy classifies Dravet syndrome among the developmental and epileptic encephalopathies with onset in infancy. In these disorders, developmental difficulties can reflect both the underlying cause and the effects of severe epileptic activity.

The ILAE syndrome framework uses mandatory features, alerts and exclusionary criteria rather than a single laboratory test. This helps clinicians distinguish a classic syndrome from conditions that can look similar.

Typical age at onset

The ILAE diagnostic framework places seizure onset between 1 and 20 months, with onset most commonly in the first year of life. Very early onset at 1–2 months or later onset near the upper end of that range should prompt careful review for alternative or overlapping diagnoses.

Development is typically normal before seizures begin. Developmental slowing, plateau or regression usually becomes apparent later rather than being clearly present at seizure onset.

The first seizures

Early seizures are often prolonged hemiclonic seizures, focal to bilateral tonic-clonic seizures or generalised tonic-clonic seizures. Hemiclonic seizures may alternate sides from one event to another.

Fever is a common precipitant, but the syndrome is not simply “febrile seizures that continue for longer”. Seizures can also be triggered by illness, heat, vaccination-related fever, hot baths, sudden temperature change, visual stimulation or other physiological stress in some people.

Why prolonged seizures matter

Long convulsive seizures and status epilepticus are characteristic early features. A history in which seizures are never prolonged should make clinicians reconsider whether the syndrome fits the classic Dravet pattern.

Because prolonged seizures can recur, families are often given an individual emergency plan and prescribed rescue medication where locally available and clinically appropriate.

How the seizure pattern evolves

Additional seizure types usually appear over time. These can include myoclonic seizures, atypical absence seizures, focal impaired-awareness seizures and other generalised or focal seizures.

The mixture of focal and generalised features is one reason Dravet syndrome historically caused classification difficulty. The syndrome is now understood as a network epilepsy rather than a simple focal or simple generalised epilepsy.

EEG

The EEG can be normal early in the disorder. Interictal epileptiform abnormalities often become more evident later and may include generalised spike-wave, polyspike-wave or multifocal abnormalities.

Photosensitivity can occur. The absence of epileptiform activity on an early routine EEG does not exclude Dravet syndrome.

MRI

Brain MRI is often normal at onset and is not required to make the diagnosis. It is nevertheless strongly recommended where available to exclude a structural cause that could better explain the seizures.

A clear causal focal lesion on MRI is exclusionary for classic Dravet syndrome under the ILAE diagnostic framework.

SCN1A and genetics

Most people with classic Dravet syndrome have a pathogenic variant in SCN1A, which encodes a neuronal voltage-gated sodium-channel subunit. Many variants arise de novo rather than being inherited from an affected parent.

However, not every SCN1A variant causes Dravet syndrome, and not every clinically convincing Dravet case has an identified SCN1A variant. Other genes and mechanisms can produce Dravet-like phenotypes.

Why genetic testing matters

Early molecular diagnosis can shorten the diagnostic journey, support treatment choices, help avoid medicines that may aggravate seizures in classic Dravet syndrome, and inform genetic counselling.

Testing may be performed using an epilepsy gene panel, exome sequencing or genome sequencing depending on the health system and clinical context.

Medication choice matters

International consensus recommends broad-spectrum antiseizure treatment. Commonly used options include valproate, clobazam, stiripentol, cannabidiol and fenfluramine, with availability and regulatory approval differing by country.

No single treatment works for everyone, and combination therapy is common.

Sodium-channel blockers can worsen classic Dravet syndrome

Prophylactic sodium-channel-blocking medicines such as carbamazepine and oxcarbazepine can aggravate seizures in classic Dravet syndrome. Lamotrigine can also worsen seizures in some affected people.

This is one reason early syndrome recognition is clinically important. A medicine that is appropriate for another focal epilepsy may be a poor choice in Dravet syndrome.

Important nuance: emergency phenytoin is a different question

The concern about chronic sodium-channel-blocking therapy should not be oversimplified into “phenytoin can never be used”. Emergency treatment of status epilepticus is a separate clinical situation and local protocols may include agents that would not be selected for long-term maintenance therapy.

Emergency medication decisions should follow an individual rescue plan or acute-care protocol.

Ketogenic dietary therapy

Ketogenic dietary therapy can reduce seizure burden in some people with Dravet syndrome and may be considered when seizures remain difficult to control.

It requires specialist dietetic and medical supervision and is not a general home diet.

Development, learning and behaviour

Developmental slowing usually becomes apparent after seizure onset. Intellectual disability ranges from mild to severe.

Attention difficulties, autistic features, behavioural differences and executive-function problems are common. Speech and language development can be affected.

Movement and gait

Older children and adults can develop gait abnormalities, crouched gait, balance problems or other motor difficulties. These are not necessarily caused by seizures alone and may reflect the underlying channelopathy, repeated injuries, medication effects or broader neurological involvement.

Sleep and autonomic issues

Sleep problems are common and can interact with seizure susceptibility. Autonomic disturbances, temperature sensitivity and altered heart-rate regulation have also been reported.

SUDEP and mortality

Dravet syndrome carries an increased risk of premature mortality, including sudden unexpected death in epilepsy (SUDEP), status epilepticus and seizure-related accidents.

Risk should be discussed without implying that an individual outcome can be predicted. Seizure control, night-time supervision strategies where appropriate, rescue planning and general epilepsy safety remain important.

Vaccination and Dravet syndrome

Some first seizures occur after vaccination because fever can trigger seizures in a susceptible infant. Vaccination does not create the underlying genetic disorder.

International expert consensus supports routine vaccination in most children with Dravet syndrome, with an individual fever and seizure-management plan where needed. Country-specific vaccine schedules and clinical advice vary.

Adulthood

Dravet syndrome is lifelong. Convulsive seizure frequency may change with age, but epilepsy, cognitive impairment, mobility difficulties and the need for support can continue into adulthood.

Transition from paediatric to adult neurology should include seizure management, rescue medication, mobility, communication, mental health, sleep, bone health and social-care needs.

Diagnosis in resource-limited settings

The ILAE specifically recognises that genetic testing, MRI and specialist EEG are not universally available. A clinically convincing diagnosis can still be made when mandatory clinical features are present and exclusionary features are absent.

This matters worldwide because insisting on genetic confirmation as a prerequisite would exclude many people living in regions without genomic services.

The central point

Dravet syndrome is not simply severe febrile epilepsy. It is a developmental and epileptic encephalopathy with a characteristic age-dependent seizure pattern, strong association with SCN1A, important medication implications and lifelong neurological consequences.

Sources

Medical note: treatment recommendations depend on age, seizure type, current medicines, comorbidities and local drug availability. Antiseizure medicines should not be stopped suddenly.

Evidence checked: September 2026.