Recognizing febrile seizures (FS) is important in the diagnosis of Dravet Spectrum Disorders. Febrile seizures are caused by a high or rapidly rising temperature, often due to illness or vaccination. These are usually tonic clonic or hemiclonic seizures. Tonic clonic seizures involve a stiffening of the arms and legs (tonic phase), followed by jerking of the arms, legs, and head (clonic phase). Hemiclonic seizures are similar, though only one side of the body convulses.

While these seizures are frightening to watch, febrile seizures usually last only a few seconds to a few minutes and end without need for medical intervention. Febrile seizures are very common in childhood, and usually are not associated with a genetic form of epilepsy. However, some children have febrile seizures that are genetically inherited in families and represent the mildest form of epilepsy (FS) in the Dravet Spectrum Disorders.

The first clue that a Dravet Spectrum Disorder may be involved is when the first febrile seizure happens in infancy and the seizure lasts more than five minutes. Recurring febrile seizures followed by spontaneous seizures of increasing severity is the hallmark of the more severe Dravet Syndrome Disorders, including GEFS+ and SMEI. Genetic testing will help confirm a genetic form of epilepsy caused by mutations in the SCN1A gene. Knowing the genetic basis can help explain the cause of the disease and give parents the information they need to know what to expect as the disease progresses and to find the best treatment.  

For general information on gene mutations:

• Home Reference: What Kind of Gene Mutations are Possible?
• See Genetics Section

Summary of FS

• Febrile seizures
• Tonic clonic seizures or hemiclonic seizures
• Common in childhood
• Severe seizures only in subset
• Gene mutations only in subset