Dravet syndrome is a rare, severe epilepsy syndrome that begins during the first year of life in otherwise healthy infants. It was previously called severe myoclonic epilepsy of infancy. Dravet syndrome is marked by long, frequent seizures that are often triggered by fever or overheating. Most cases are caused by a mutation (change) in the SCN1A gene, which helps control electrical signals in the brain. However, the disease can occur without this mutation.

Dravet syndrome occurs in about 1 in every 15,000 to 40,000 people. Seizures typically start between the ages of 1 and 18 months, with the average age of onset being 5.2 months. This severe form of epilepsy is also known as developmental and epileptic encephalopathy because the seizures and abnormal brain activity are associated with developmental delays and cognitive challenges (difficulties with thinking, learning, and memory).

What Is Dravet Syndrome Life Expectancy?

Dravet syndrome is associated with a higher mortality (death) rate than many other forms of epilepsy. Studies estimate that cumulatively, 15 percent to 20 percent of individuals with Dravet syndrome die during childhood or adolescence. Most of these deaths occur before age 10.

While around 85 percent of children with Dravet syndrome survive into adulthood, most require lifelong care.

The leading cause is sudden unexpected death in epilepsy (SUDEP), accounting for about 49 percent of deaths, followed by status epilepticus and seizure-related accidents. While around 85 percent of children with Dravet syndrome survive into adulthood, most require lifelong care.

Symptoms of Dravet Syndrome and Seizure Types

Children with Dravet syndrome may experience several different types of seizures that become more frequent and longer with age.

Febrile Seizures

Febrile seizures can occur in children with or without Dravet syndrome and are typically triggered by a high body temperature or childhood illness. They are usually the first seizures a child with Dravet syndrome may experience. Febrile seizures may involve tonic-clonic seizures (stiffening and jerking) or clonic seizures (repeated jerking).

In children without Dravet syndrome, most febrile seizures last from a few seconds to as long as 15 minutes and only occur once every 24 hours. In those with Dravet syndrome, though, febrile seizures frequently last more than 15 minutes and usually continue for 30 minutes or longer. These prolonged seizures increase the risk of developing epilepsy.

Myoclonic seizures often develop in children with Dravet syndrome, frequently around the age of 4 or 5, although they can appear earlier. Febrile seizures in Dravet can be unusual from the beginning — they can last a long time and may affect only one side of the body.

Myoclonic Seizures

Myoclonic seizures appear as sudden, brief jerking movements of a muscle or group of muscles, which can be subtle or quite forceful. They occur in about 85 percent of children with Dravet syndrome and often appear before age 2. Myoclonic seizures can affect the entire body or just one part of the body. They usually last a fraction of a second, though some people experience them in clusters, where multiple jerks happen close together.

Focal Aware or Impaired Awareness Seizure

Focal seizures, which involve one side of the brain, commonly develop in children with Dravet syndrome around age 2. During these seizures, the person may remain aware or partially aware of their surroundings but may be unable to move or respond. Automatic movements, such as lip smacking or hand fumbling, may occur. Focal seizures can spread and become tonic-clonic seizures.

Atypical Absence Seizures

Atypical absence seizures cause brief periods of “blanking out” or staring into space, usually lasting less than 30 seconds. These seizures typically appear after age 2. Unlike typical absence seizures, atypical ones may involve falls or loss of muscle control during the event. Atypical absence seizures are usually resistant to typical absence medication.

Atonic Seizures

Atonic seizures, also called “drop attacks,” involve a sudden loss of muscle tone (the muscles' ability to stay firm and support the body). These seizures are brief, usually lasting under 15 seconds. They may cause a person to drop their head or fall to the ground. Atonic seizures can also temporarily paralyze part of the body.

Status Epilepticus

Status epilepticus refers to seizures that last longer than five minutes or occur so close together that the person doesn’t recover between them. This condition can involve either convulsive seizures (stiffening and jerking movements) or nonconvulsive seizures (altered awareness with minimal body movement). Both types are life-threatening emergencies and require immediate medical attention.

Seizure Triggers

Common seizure triggers among children with Dravet syndrome include:

• Temperature changes, both hot and cold — This may include getting out of a hot bath, overheating, or going outside on a cold day after being in a warm environment.
• Emotional stress or excitement — These can overstimulate the brain.
• Flashing lights, images, or patterns, like those on TV or computer screens — These can cause photosensitive seizures (seizures triggered by light).

Dangers of Seizures With Dravet Syndrome

Seizures can have life-threatening consequences for people with Dravet syndrome. The risk of SUDEP in Dravet syndrome is higher than in most other types of epilepsy. Additionally, status epilepticus and accidental injuries, such as drowning, are common causes of death.

Temperature changes, both hot and cold, can be a seizure trigger for people with Dravet syndrome.

The best way to reduce the risk of SUDEP and status epilepticus is by working with your medical team to control seizures as much as possible. Effective seizure control through a combination of appropriate medications, dietary therapies (like the ketogenic diet), vagus nerve stimulation (VNS), and other interventions is crucial for minimizing the risks of SUDEP and status epilepticus. Children with Dravet syndrome often require 24-hour supervision to stay safe and manage emergencies.

Developmental Delays With Dravet Syndrome

Children with Dravet syndrome usually develop normally during their first year of life. However, as seizures become more frequent and severe, their development often slows. They may begin showing signs of cognitive impairment. By ages 2 or 3, speech delays are common, and cognitive challenges tend to worsen.

Gait problems (issues with walking) are also common. They may include crouched walking or ataxia (poor coordination), which can reduce mobility with age, especially during adolescence.

Physical, occupational, and speech therapy are recommended for developmental support. Children with Dravet syndrome may also have autism spectrum disorder or attention-deficit/hyperactivity disorder (ADHD), which may be treated with behavioral interventions and social skills training. Early and ongoing intervention with physical, occupational, and speech therapy is essential for maximizing developmental potential.

Other Health Issues With Dravet Syndrome

Many people with Dravet syndrome experience dysautonomia, which is a problem with the autonomic nervous system (the system that controls automatic body functions like heart rate, digestion, and temperature). Symptoms of dysautonomia include:

• Problems with temperature regulation, such as overheating or difficulty staying warm
• Decreased sweating, which can make it harder to cool down
• Tachycardia (fast heart rate)
• Sluggish digestion and blood circulation, which may cause bloating, constipation, or cold hands and feet

About 60 percent of children with Dravet syndrome experience challenges with growth and nutrition, according to Dravet Syndrome UK. These may include:

• Trouble swallowing, eating, or maintaining a healthy appetite
• Poor nutrient absorption or difficulty gaining weight
• Weak bones due to osteopenia (low bone density)
• Scoliosis (curvature of the spine)

Causes of Dravet Syndrome

About 80 percent to 90 percent of children with Dravet have a mutation of the SCN1A gene. A mutation on the SCN1A gene prevents sodium channels in neurons of the brain from working correctly.

Other genetic mutations may be associated with Dravet syndrome too. About 90 percent of gene mutations are de novo (new) mutations. This means the mutation has not been inherited from a parent, but is a new, first-time mutation in the child. In families with inherited SCN1A mutations, the risk of each additional child being born with Dravet syndrome is 50 percent.

Dravet Syndrome Diagnosis

If your child has seizures, a pediatric neurologist (a doctor specializing in children’s brain health) may be involved in their care. Diagnosing Dravet syndrome typically begins with a thorough medical history and may include tests such as:

• Electroencephalogram (EEG) to measure electrical activity in the brain
• An MRI to look for structural abnormalities in the brain
• A genetic blood test to check for mutations in the SCN1A gene, especially if Dravet syndrome is suspected

Many children with Dravet syndrome are initially misdiagnosed. That is because EEG and MRI results typically appear normal in babies with Dravet syndrome and may not show abnormal activity until the child is 18 months old.

Dravet syndrome may also be mistaken for common childhood febrile seizures. Some studies suggest that it can take almost five years from seizure onset to get a diagnosis of Dravet syndrome.

Genetic testing can help diagnose Dravet syndrome. Guidelines recommend genetic testing for Dravet syndrome if children experience one or more of the following symptoms:

• At least two prolonged seizures by age 1
• One prolonged seizure and sustained, rhythmic jerking of one side of the body (hemiclonic seizures) by age 1
• Two seizures that affect alternating sides of the body
• Seizures before 18 months and myoclonic or absence seizures later on

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