Dravet Syndrome Spectrum Disorders - Experiences, Treatment and Outlook
Synopsis: Information regarding Dravet syndrome spectrum disorders a rare genetic epileptic encephalopathies or dysfunction of the brain with onset occurring during first year of life.1
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Main DigestDravet syndrome spectrum disorders are rare genetic,'epileptic encephalopathies,' or dysfunction of a person's brain, with onset occurring during the first year of life in infants who are otherwise healthy. There is a spectrum of severity ranging from no clinical symptoms to febrile seizures, extending to Dravet syndrome which is the most severe. Mutations of the SCN1A gene cause 79% of diagnosed instances of Dravet syndrome.
Often referred to as a, 'sodium chanelopathy,' this uncontrollable form of epilepsy is characterized by unilateral clonic or gran mal seizures that might be prolonged, or progress to status epilepticus. Myoclonic seizures, often times called, 'myoclonic jerks,' are common yet not always present. Over time seizures present without illness, fever or heat triggers. The seizures are frequent and resistant to treatment.
The first seizure is often associated with the administration of vaccines at 6 months of age. Infants eventually develop other types of seizures to include eyelid myoclonia, atypical absence and non-convulsive seizures. Multiple medication therapy is needed to control the seizures. Some anti-epileptic medications actually worsen seizures and should be avoided.
For most people with Dravet syndrome, surgery is not indicated. The person's initial EEG is average, yet within the second or third year of their life - brief generalized spike, polyspike, or polyspike-wave paroxysms appear. MRI and metabolic studies of the person appear average. Developmental delays appear to different degrees in the majority of people with Dravet syndrome by the age of 2 and ataxia or abnormal gait is common. Aggressive and appropriate seizure management, as well as implementation of global therapies, are needed to improve the outcome of children with Dravet syndrome spectrum disorders. Before the year 1989 Dravet syndrome was known as:
- Epilepsy with polymorphic seizures
- Polymorphic epilepsy in infancy (PMEI)
- Severe myoclonic epilepsy in infancy (SMEI)
Dravet syndrome starts in a person's infancy, yet is experienced for the duration of their life. Around 79% of people with the syndrome have a gene mutation that causes issues in the way that ion channels in their brain work. The mutation is most often not inherited from the person's parents, but is considered a, 'de novo,' or new mutation in the child. The seizures are, 'refractory,' or do not respond to seizure medications well in most instances.
The majority of children with Dravet syndrome develop some level of developmental disability and experience other conditions that are associated with the syndrome. Infants have average development at the time the seizures start. EEG and MRI tests are also average in the person's infancy. Dravet syndrome is commonly misdiagnosed.
The Experiences of Children with Dravet Syndrome
The seizures usually begin within the first year of a child with Dravet syndrome's life. The first seizure is many times associated with a fever and might be a tonic-clonic seizure, usually referred to as a, 'gran mal seizure,' or a seizure involving jerking movements on one side of the body. Myoclonic seizures appear between the ages of 1-5 in 85% of children with Dravet syndrome.
Chart showing other forms of seizures children with Dravet syndrome may experience
Seizures early in a person's life are often prolonged and last more than 2 minutes. They may be repetitive and can result in status epilepticus which is a life-threatening condition in which seizures last longer than 30 minutes. Children with Dravet syndrome may develop a number of different types of seizures:
- Atonic seizures
- Partial seizures
- Absence seizures
- Myoclonic seizures
- Tonic clonic seizures
- Atypical absence seizures
- Non-convulsive status epilepticus
Children with Dravet syndrome can experience seizures without a fever; however, these children are highly sensitive to infections and frequently have seizures when they are ill or have a fever. Seizures may also be triggered by slight changes in body temperature that are not caused by an infection - for example; warm or hot bath water, or hot weather. A number of children with Dravet syndrome have photosensitive seizures triggered by flashing lights, patterns, or similar photic triggers. Excitement or emotional stress may also trigger seizures in some children with Dravet syndrome.
Children with this syndrome usually develop averagely in their early years. After the age of 2, they might lose developmental milestones, or do not progress as rapidly as they age and experience more seizure activity. There appears to be a correlation between frequency of seizures, how often status epilepticus happens and the degree of developmental delay in children with the syndrome. Around the age of 6, cognitive issues in some children with Dravet syndrome might stabilize or even begin improving. The majority of children with Dravet syndrome; however, experience some degree of developmental disability that persists. Additional issues they may experience include the following:
Chart showing other conditions children with Dravet syndrome may experience
- Unsteady walking
- Chronic infections
- Low humoral immunity
- Growth and nutrition issues
- Issues with their autonomic nervous system
- Older children and adults might develop a crouched gait
- Low motor tone potentially leading to painful foot issues
- Developmental or behavioral issues such as autism spectrum disorder
It is not known how many people are affected by Dravet syndrome. Reports suggest that 1 in 20 to 1 in 40,000 people experience the syndrome. Between 3-8% of children who have their first seizure by the age of 12 months may have Dravet syndrome. Seizures that last longer than 10 minutes, seizures occurring on one side of the person's body, as well as seizures triggered by a warm bath in children younger than 12 months of age are considered to be significant risk factors for Dravet syndrome.
The most common gene mutation linked to Dravet syndrome is a gene called, 'SCN1A.' When this particular gene is not working as it should, sodium channels in the brain which help brain cells function do not work appropriately. A number of other gene mutations may affect sodium channels and cause Dravet syndrome as well. A blood test for the mutation can confirm the diagnosis. At times, a gene mutation is not found in testing, although the syndrome may be diagnosed based upon the symptoms the person is experiencing.
Treatment of Dravet Syndrome
Early achievement of a diagnosis is crucial to proper treatment and obtaining the best outcome. A multidisciplinary team is necessary to address the many ways that the syndrome may affect a child and their family members. Seizure treatment is aimed at discovering the best combination of medications to treat seizures chronically and both prevent and treat potential seizure emergencies.
Chart showing sodium channel blockers
Receiving the best seizure control possible is the goal, which could also help to improve the child's developmental abilities and decrease their mortality risk. Usually, 2 or more seizure medications are necessary to treat the multiple seizure types. It is important to avoid medications called, 'sodium channel blockers,' because they may actually worsen seizures associated with Dravet syndrome. Sodium channel blockers include:
In addition, the medications, 'tiagabine,' and, 'vigabatrin,' have the potential to increase the frequency of myoclonic seizures in Dravet syndrome and should be avoided. The, 'ketogenic diet,' has been helpful in some people with the syndrome. Vagal Nerve Stimulator (VNS) might be helpful in some people with Dravet syndrome.
Seizure response plans should include how to treat children with the syndrome when they experience illness or fever, use of seizure alerts and monitors, as well as emergency management of repeated or prolonged seizures. Developmental assessments should start as early as possible. People with Dravet syndrome should receive physical, speech, occupational and social therapies and an enriched environment is certainly encouraged.
Dravet Syndrome Outlook
Seizures are, 'refractory,' to medications, meaning medical treatment is highly complicated. Medications that are currently available are unable to achieve complete control of seizure activity in people with Dravet syndrome. Additional health issues need to be identified and treated early and affect a child's development and outlook. People with epilepsy that is:
- Hard to treat
- Combined with developmental delays
- Treated with multiple seizure medications
- Associated with tonic-clonic seizure activity
Also experience a higher risk of, 'Sudden Unexplained Death in Epilepsy (SUDEP). Additional causes of mortality associated with Dravet syndrome include consequences of status epilepticus and accidental death from drowning or injury. The diagnosis and consequences of Dravet syndrome can be catastrophic and the cause remains unknown. Hopefully, more research can be targeted to improve treatment.
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What is Dravet Syndrome
NINDS Dravet Syndrome Information Page
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