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Dravet syndrome
This condition is characterised by prolonged seizures, often triggered by fever, which can be challenging to manage. It can affect a child's development and behaviour, and generally requires lifelong specialist care.
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Overview
Dravet syndrome is a rare and severe form of epilepsy, an electrical disorder of the brain, which usually starts during infancy. It is also known as Severe Myoclonic Epilepsy of Infancy (SMEI). Children with Dravet syndrome experience a variety of seizure types, which are often prolonged and resistant to standard epilepsy treatments [PMID:31536202].
Symptoms typically appear within the first year of life, often with seizures triggered by fever or hot temperatures. Beyond the seizures, individuals with Dravet syndrome may also experience developmental delays, movement difficulties, and behavioural challenges as they grow older. This condition is lifelong and requires ongoing medical care and support.
Symptoms & clinical features
The initial symptoms of Dravet syndrome usually involve seizures that start during the first year of life, generally between 5 and 8 months of age. These early seizures are frequently prolonged and affect one side of the body, or generalise to both sides. They are often triggered by fever, vaccinations, or changes in body temperature like going from a warm bath to a cooler room.
As the condition progresses, a wider range of seizure types may develop. These can include myoclonic seizures (brief, shock-like jerks), atypical absence seizures (staring spells), focal seizures (affecting one part of the brain), and generalised tonic-clonic seizures. Many children also experience developmental delays, which can become more noticeable in the second year of life. Other associated symptoms may include difficulties with coordination and balance, and behavioural challenges such as hyperactivity or features of autism spectrum disorder [PMID:31536202].
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Affected organs
Dravet syndrome primarily affects the brain, which is the organ responsible for controlling all body functions, thoughts, and emotions. The seizures arise from abnormal electrical activity in the brain. Beyond the immediate effects of seizures, long-term impacts can include developmental delays affecting cognitive function and motor skills. This can lead to difficulties with learning, speech, and movement.
Secondary effects may involve difficulties with sleep, eating, and various behavioural issues, all stemming from the neurological impact of the condition. The recurrent seizures can also place stress on the cardiovascular and respiratory systems during an event, though these are not primarily affected organs in the disease mechanism.
Risks & severity
Dravet syndrome is considered a severe and challenging form of epilepsy. The seizures are often frequent and resistant to medication, which can impact brain development. The severity of developmental, cognitive, and behavioural challenges can vary among individuals, but most experience some degree of impairment. The condition also carries an increased risk of sudden unexpected death in epilepsy (SUDEP), alongside seizure-related injuries [PMID:37554900].
The lifelong impacts mean that individuals with Dravet syndrome often require significant medical, educational, and social support. Seizure control often improves somewhat with age, but seizures typically continue into adulthood. The prevalence of Dravet syndrome is estimated to be between 1 in 15,000 and 1 in 40,000 live births, making it a rare condition.
Genetic causes
Dravet syndrome is most frequently caused by changes in the SCN1A (sodium voltage-gated channel alpha subunit 1) gene. This gene provides instructions for making a protein that forms part of a sodium channel. Sodium channels are crucial for the proper functioning of nerve cells (neurons) in the brain, controlling the electrical signals that allow neurons to communicate.
Pathogenic variants in SCN1A typically lead to a reduction in the number or function of these sodium channels. This disruption primarily affects inhibitory neurons, which are responsible for calming brain activity. When these inhibitory neurons do not function correctly, it leads to an imbalance in brain signalling, making the brain more prone to uncontrolled electrical activity, resulting in seizures [PMID:31536202]. While SCN1A variants account for the majority of cases, a small percentage of individuals with Dravet syndrome-like symptoms may have changes in other genes or no identifiable genetic cause.
- SCN1A sodium voltage-gated channel alpha subunit 1
Inheritance pattern
Dravet syndrome is typically inherited in an autosomal dominant pattern. This means that a condition can result from a pathogenic variant in only one of the two copies of a particular gene. In the vast majority of Dravet syndrome cases (around 90%), the genetic change is a 'de novo' variant. This means it occurs spontaneously in the affected individual and is not inherited from either parent. In such cases, neither parent carries the pathogenic variant in their cells.
When a de novo variant causes Dravet syndrome, the chance of another child in the family being affected is very low for future pregnancies, though the possibility of germline mosaicism (where a parent carries the variant in some reproductive cells but not others) can sometimes lead to a very small recurrence risk. If one parent does carry the variant, there is a 50% chance of passing it on with each pregnancy.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosing Dravet syndrome typically involves a combination of clinical observation and genetic testing. A paediatric neurologist will consider the characteristic clinical features, such as seizure type, age of onset, and triggers (e.g., fever sensitivity). An electroencephalogram (EEG) may be used to record brain activity, although early EEG results in Dravet syndrome can sometimes appear normal or show non-specific abnormalities.
Confirmation of Dravet syndrome usually relies on genetic testing to identify a pathogenic variant in the SCN1A gene. This testing is often performed through an NHS Genomic Medicine Service (GMS) pathway, typically initiated by a clinical geneticist or neurologist. The relevant NHS R-code for testing for severe epilepsies, which includes SCN1A, can facilitate this process. Genetic counsellors play a crucial role in explaining the testing process and interpreting the results for families.
Management & lifestyle
The management of Dravet syndrome focuses on reducing the frequency and severity of seizures, as well as supporting developmental progress and addressing associated challenges. There is no cure for Dravet syndrome, but treatment aims to improve quality of life. Management often involves a multidisciplinary team, including paediatric neurologists, physiotherapists, occupational therapists, speech and language therapists, and educational psychologists.
Several anti-epileptic medications are used, some of which are specifically effective in Dravet syndrome, though seizures can be difficult to control. Non-pharmacological treatments like ketogenic diet therapy may also be considered. Families receive support through NHS care pathways, often linking with specialist epilepsy centres. Regular monitoring for developmental progress and associated conditions is important. Genetic counsellors can provide essential support and information regarding the genetic aspects and inheritance patterns.
UK care pathway
In the UK, individuals suspected of having Dravet syndrome typically enter the NHS Genomic Medicine Service (GMS) pathway. Referral to a clinical geneticist or paediatric neurologist is crucial. These specialists can assess the clinical picture and determine if genetic testing is appropriate. The testing is vital for confirming the diagnosis and informing ongoing management and family planning.
Genetic testing for severe epilepsies, including SCN1A-related conditions, is available through the GMS with specific R-codes (NHS National Genomic Test Directory reference codes) that guide the testing strategy. Genetic counsellors are an integral part of this pathway, providing information, support, and guidance to families before, during, and after genetic testing.
Frequently asked questions
What is the typical age of onset for Dravet syndrome?
Dravet syndrome generally begins in the first year of life, often between 5 and 8 months of age, with the first seizures appearing during this period.
Are seizures in Dravet syndrome always triggered by fever?
Early seizures in Dravet syndrome are very often triggered by fever or changes in body temperature, but as the condition progresses, seizures may occur without a fever trigger as well.
Can Dravet syndrome be inherited from parents?
In the majority of cases, Dravet syndrome is caused by a new genetic change (de novo variant) that is not inherited from either parent. However, in a small number of families, it can be passed on in an autosomal dominant pattern if a parent carries the genetic variant.
Is there a cure for Dravet syndrome?
Currently, there is no cure for Dravet syndrome. Management focuses on controlling seizures and supporting development, often with a combination of medications and other therapies.
Where can I find support for Dravet syndrome in the UK?
In the UK, support is available through specialist epilepsy services and organisations like Dravet Syndrome UK. Your clinical genetics team or neurologist can also provide guidance on local and national support networks.
References
- Dravet C. Dravet syndrome history. Developmental medicine and child neurology. 2011. PMID: 21504424
- Incorpora G. Dravet syndrome. Italian journal of pediatrics. 2009. PMID: 19737414
- Anwar A, Saleem S, Patel UK. Dravet Syndrome: An Overview. Cureus. 2019. PMID: 31497436
- Connolly MB. Dravet Syndrome: Diagnosis and Long-Term Course. The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques. 2016. PMID: 27264139
- Xu X, Yang X, Wu Q. Amplicon Resequencing Identified Parental Mosaicism for Approximately 10% of "de novo" SCN1A Mutations in Children with Dravet Syndrome. Human mutation. 2015. PMID: 26096185
- Wirrell EC. Treatment of Dravet Syndrome. The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques. 2016. PMID: 27264138
- Nickels KC, Wirrell EC. Dravet Syndrome: Don't Hesitate, Just Vaccinate! Neurology. 2023. PMID: 36323523
- Liu YH, Kuo CY, Chou IC. Dravet Syndrome: Past, Present, and Future. Acta neurologica Taiwanica. 2025. PMID: 41020456