What are Dravet Spectrum Disorders:

The purpose of this section is to help families understand what seizures are, why seizures happen in Dravet Spectrum Disorders, and how seizures appear to observers.

What are seizures? 

Seizures are a symptom of a problem in the brain.They happen because of a sudden, abnormal burst of electrical activity in the brain. Typically, seizures last a few seconds or a few minutes. There are many types of seizures – what a seizure looks like depends on the area of the brain affected.

Why do seizures happen in Dravet Spectrum Disorders?

The brain is the ‘command center’ to the body. Electrically charged chemical signals in the brain pass along a network of cells called neurons. Signals go to and from the neurons which function in networks, or groups of cells, allowing the brain to allow us to experience sensations and emotions, think, and control our muscles.

Ion channels are the openings in the outer cell membrane that let ions, electrically charged chemicals, into and out of the neuron. If charged chemicals do not move in and out of the neuron properly, the electrical signals may not switch off when they should, resulting in seizures. The SCN1A gene is the gene that tells the cell how to make sodium ion channels. SCN1A gene mutations, or changes, are a common feature of Dravet Spectrum Disorders. Other genes are involved in Dravet syndrome and related spectrum disorders.

What is status epilepticus?

Status epilepticus is defined as seizures that last 30 minutes or more, or seizures that occur in clusters without the patient recovering normal consciousness between seizures. Status epilepticus often happens in Dravet syndrome, though it can happen in any seizure disorder. Status epilepticus is a medical emergency and requires immediate medical attention.

What are the different types of seizures?

Sacks, Oliver Ph.D, Creativity and the Brain, Wright University Honors Institute Lecture Series, March 9, 2006. View Source.

The brain is consists of the upper portion: the cerebrum, a lower portion: the cerebellum, and the brain stem. The cerebrum’s outer layer is the cortex. Seizures are cortically based. We each have two hemispheres or halves of our cerebrum : the right hemisphere and the left hemisphere. The right hemisphere controls the left side of the body. The left hemisphere controls the right side of the body. Seizures involving both sides of the brain are called generalized seizures. Seizures involving one side or part of the brain are called focal or partial seizures.

Types of seizures seen in Dravet Spectrum Disorders include:

• Tonic clonic seizures
• Clonic or hemi clonic these are very similar to tonic clonic, but only involve jerking/twitching, not stiffening. Sometimes they are seen on only one side of the body.
• Myoclonic seizures (myoclonus)
• Partial seizures
• Absence seizures/atypical absence seizures

Tonic clonic seizures (grand mal) or Clonic seizures: Tonic clonic seizures are generalized, involving on both sides of the body. Tonic clonic seizures begin with stiffening of the arms and legs (tonic phase), then follow with jerking of arms, legs, and head (clonic phase). The person having the seizure is not aware of what is going on. Tonic clonic seizures can happen in any of the Dravet Spectrum Disorders, at any age. Clonic seizures involve jerking but not stiffening. They may be partial, involving only one side of the body.

Myoclonic seizures (myoclonus): These are usually generalized seizures, involving both sides of the brain.  Myoclonic seizures look like a startle reflex, similar to normal leg jerks that happen upon falling asleep. A person having a myoclonic seizure will have quick jerks or spasms involving head, neck, arms, and/or legs. Jerks can be dramatic, causing the person to drop a held object. Jerks can be subtle, looking like a twitch in the extremities. Myoclonic seizures can be focal, involving only one side of the brain, causing jerking motions of just the head, or just the arm, for instance. They can even be eye-blinks, or "flutters". A person who has myoclonic seizures may or may not be aware of what is going on.

Partial seizures: These seizures involve only one side of the brain and the part of the body controlled by that side. Repetitive movements or irrational movements with no obvious purpose are typical in complex partial seizures. Such movements might include things like chewing, playing with hair, picking at clothes, or wandering. The person having a complex partial seizure is only partly aware or not at all aware of what is going on, though this may not be obvious to others. Simple partial seizures are very similar to complex partial seizures. However, the person having a simple partial seizure knows what is going on but has no control of seizure-related movements or behaviors.

Absence seizures (petit mal): These seizures are generalized, involving both sides of the brain. The person having an absence seizure will suddenly lose and regain consciousness. An absence seizure looks like a blank stare to the observer. There may be eye blinking, chewing, and twitching of facial muscles as well. If the person having an absence seizure is somewhat aware and responsive, or if the absence seizure lasts longer than the typical few seconds, the seizure may be called an atypical absence seizure.