Dravet syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 15, 2016
StartDiseasesDravet syndrome

Dravet syndrome, or severe myoclonic epilepsy of infancy, is a rare form of epilepsy. About 1 in 16,000 to 1 in 20,000 children have it, though some studies put the number at 1 in 20,000 to 1 in 40,000. It is incurable and lifelong.

Contents

Definition & Facts

Dravet syndrome is a genetic disorder that causes brain dysfunction that usually begins in the first year of life in a baby that is otherwise healthy and developing normally. It is caused by a mutation in a gene or genes that causes the sodium channels in the brain to malfunction.

Though Dravet syndrome is genetic, it is not necessarily inherited from the child’s parents and is considered a de novo mutation. The seizures of Dravet syndrome are prolonged and do not respond well to the usual medications used to treat epilepsy. Indeed, some of these medications can make the seizures worse.

Symptoms & Complaints

The symptoms of Dravet syndrome often begin when the baby has a fever. The seizures are either grand mal (tonic-clonic seizures) or they affect one side of the child’s body. They usually last more than two minutes and can deteriorate into a condition called status epilepticus, where the seizures can last as long as a half an hour and become life-threatening. People with Dravet syndrome are subject to a variety of seizures besides tonic-clonic seizures, including:

  • Myoclonic. This form presents as brief seizures in a group of muscles. It is comparable to the muscles receiving an electric shock.
  • Absence seizures. This is where the child appears to be daydreaming or staring off into space. Sometimes these seizures are so brief that they are not noticeable.
  • Atypical absence seizures. The child still stares off into space, but is somewhat responsive.
  • Non-convulsive status epilepticus. In this type of seizure, the patient may seem confused or unable to respond fully. They may twitch and blink their eyes. This condition can last for hours or even days.
  • Partial seizures. These seizures only involve one hemisphere of the brain. They can be simple or complex.
  • Atonic seizures. This is the loss of muscle tone. The patient can drop to the floor, giving this type of epilepsy the name “drop attack.” Sometimes only the head droops.

Patients with Dravet syndrome are subject to infections, problems with their growth, malnutrition, and problems with their autonomic nervous system. This is the system that controls involuntary actions in the body such as breathing and digestion. Other symptoms are pronated feet that lead to an unsteady gait. As they get older, people with Dravet syndrome may walk in a hunched-over position.

Dravet syndrome patients sometimes have autism. Patients are more at risk for sudden unexpected death in epilepsy, or SUDEP. They can be seriously injured or killed by accidents or injuries caused by seizures.

Children with Dravet syndrome develop normally until they are about two years old, then their development slows in comparison to their peers. Researchers have found a relationship between the frequency of the child’s seizures, the type of developmental delay, and status epilepticus. Some children improve after they’re six years old, but most experience some kind of disability for the rest of their lives.

Causes

Researchers have found that there are at least 400 genetic mutations that can lead to Dravet syndrome, though the commonest cause is a mutation on the SCN1A gene. Other gene mutations that can lead to Dravet syndrome are those on the following genes: FEB1, FEB2, and FEB4, SCN1B, and GABRG2. Vaccines do not cause Dravet syndrome.

For those who have Dravet syndrome, slight changes in body temperature can bring on a seizure. Patients have seizures when exposed to hot weather or even if they are taking a hot bath. Flashing lights can trigger seizures, as can stress or excitement.

Diagnosis & Tests

Genetic testing and blood tests can find the mutated SCN1A gene, though it is sometimes not present in a person with Dravet syndrome. Doctors diagnose the condition through medical history and the parents’ observation of the child’s symptoms.

Medical imaging tests like computed tomography (CT) scans and magnetic resonance imaging (MRI)s as well EEGs (electroencephalography) may be used to examine the brain and confirm diagnosis. It is important that the disease be diagnosed early so a treatment team can be set up to manage it.

Treatment & Therapy

Dravet syndrome is notoriously hard to treat, and patients need a combination of medications to contain their seizures. The best medications for Dravet syndrome are valproic acid, stiripentol, and clobazam. Stiripentol has not been approved by the FDA as of 2016, but families can obtain special permission to buy it. Other drugs that can mitigate symptoms are topirimate, zonisamide, and levetiracetam.

Some patients have been helped by a ketogenic diet. This is a high-fat, low-carbohydrate diet that puts the body into a ketogenic state. This allows the body to burn fat for fuel with great efficiency. The diet lowers the levels of insulin and glucose and converts fat in the liver to ketones. This creates energy for the brain.

Other patients benefit from vagus nerve stimulation. Most Dravet syndrome patients don’t need surgery. Teams of experts in physical therapy, speech therapy, occupational therapy, and other therapies are needed to help both the child and the family cope with the disease.

There are also drugs to avoid, which include the following:

Sometmes, EMTs want to give some of these medications to a Dravet syndrome patient during a status epilepticus emergency. They must be warned against doing so.

Prevention & Prophylaxis

Though Dravet syndrome can’t be prevented, the seizures can be monitored and their effects lessened. The patient will need to have blood, metabolic, genetic and medical imaging tests throughout their life to chart their disease.

The family needs to invest in seizure monitors, helmets, and cool vests to keep the patient’s body temperature from rising and generating seizures. Some patients wear colored glasses to avoid seizures that are triggered by light. The family must be vigilant to keep the child away from triggers and to treat fevers promptly. Medicines such as benzodiazepam can serve as emergency aids if a patient has status epilepticus.