The predominant feature of Dravet syndrome is severe and intractable seizures. Seizures occur when the normal rhythm of electrical activity in the brain is disrupted by the abnormal firing of brain cells, resulting in a change in the individual’s consciousness and/or behavior. In Dravet syndrome, the onset of seizures occurs within the first year of life, most often between the ages of three and nine months. The first seizure is frequently associated with a fever and is a generalized or unilateral (one-sided, possibly changing sides) tonic clonic seizure. It may be brief, but is often prolonged. These are often followed by a second febrile convulsive seizure after approximately six to eight weeks that may be quite prolonged and lead to convulsive status epilepticus. In time these seizures may occur without fever and the frequency of seizures will increase. Additional seizure types are likely to appear. (Dravet, 2003)

The next seizure type to appear is usually myoclonic seizures. These are typically a generalized seizure, a quick full body jerk that looks like a startle reflex, often with rather dramatic involvement of the limbs. Sometimes, however, at the beginning they may have a focus. These partial myoclonic seizures may be initially limited to one limb, the head, or even as eye-blinks, and may generalize. Myoclonic jerks tend to be frequent and these seizures may occur several times a day. Myoclonic obtundation status may also occur, during which consciousness may be altered to varying degrees and fragmentary segmental myoclonias are observed over a prolonged period. Convulsive seizures may occur at the beginning, during, or at the end of these episodes.  Without intervention, myoclonic obtundation status may last for hours or even days. The prominence of myoclonic seizures in this syndrome led to it previously being called Severe Myoclonic Epilepsy of Infancy (SMEI), however investigators began to document unusual cases that met the other clinical diagnositic criteria, but did not have myoclonic seizures. As this came to be supported by genetic studies, the name was changed to Dravet syndrome. (Dravet, 2003)

A third type of seizure that is characteristic of Dravet syndrome is complex partial seizures. Partial seizures involve only part of the brain and the corresponding part of the body. Simple partial seizures do not impair consciousness. In the case of complex partial seizures, consciousness is altered, though this may be difficult for the observer to discern. Aimless repetitive motor activity known as automatism is usually observed and may include chewing, playing with hair, picking at clothes, or wandering. In Dravet syndrome atonic or autonomic phenomena may also be observed.(Dravet, 2003) These episodes may be preceded by a generalized seizure, but more commonly they secondarily generalize. Typically complex partial seizures are relatively brief, however in Dravet syndrome they can be prolonged or occur in clusters, and without intervention they may evolve into nonconvulsive status epilepticus sometimes referred to as complex partial status.

A fourth type of seizure observed in children with Dravet syndrome is atypical absence.
Typical absence seizures are brief generalized seizures involving the sudden loss and return of consciousness over a period of a few seconds. In the case of atypical absence seizures consciousness is altered, but the individual may be semi-responsive. These begin and end gradually and are usually relatively brief. The child may experience staring or eye deviations to the left or right as well as twitching of facial muscles. Some children with Dravet syndrome have been observed to experience clusters of atypical absence seizures for prolonged periods of time.

Seizures in Dravet syndrome are very resistant to current methods of treatment. Status epilepticus can be frequent. Though seizure activity may begin to stabilize after the age of four, there have been no cases of remission. The seizures are never outgrown.

A variety of stimuli that are part of daily living can provoke seizures in children with Dravet syndrome. Sensitivity to these varies from child to child. Potential seizure triggers can include hyperthermia (whether due to fever, exertion, or environmental conditions), hypothermia/shivering, sudden changes of temperature, illness (even without fever), bathwater/water poured over the head, various types of environmental light (photosensitivity), fatigue, startle, and excitement/anxiety.