Dravet syndrome is a rare and severe type of epilepsy typically caused by mutations in the SCN1A gene. Symptoms usually appear in the first year of life with long, uncontrollable seizures. This is accompanied by developmental delays and disabilities in the following years.

It may take time to make an accurate diagnosis of Dravet syndrome because the symptoms progress in time and the initial diagnosis depends mainly on the patient’s medical history.

Medical history

A detailed medical history of the patient is essential for the physician to diagnose Dravet syndrome based on the signs and symptoms. This includes information about the time the seizures started, the frequency, duration, and possible triggers of the seizures, and observations on the development of the patient.

Some common characteristics of seizures associated with Dravet syndrome are that they last longer than five minutes, that they cannot be controlled with anti-epilepsy medications, that they usually occur on one side of the body, and that they can be triggered by a warm bath, a mild illness, or a fever.

Vaccines do not cause Dravet syndrome and they do not change the course of the disease. However, seizures often start shortly after the child receives his or her first vaccine around 6 months of age, probably because vaccines sometimes cause a fever.

Genetic testing

Mutations in SCN1A gene are responsible for almost 80 percent of Dravet syndrome cases. A simple blood test can detect whether the patient has a mutation in this gene.

Some SCN1A mutations can cause other forms of epilepsy than Dravet syndrome. Therefore, genetic testing alone is not always conclusive and should be interpreted in the context of other findings.

The remaining 20 percent of patients with Dravet syndrome may have mutations in different genes, most of which are yet to be identified.

Electroencephalogram (EEG)

EEG is a method to measure the electrical signals that the brain produces. In Dravet patients, these look normal at first, but become unusual starting from when the patient is 18 months old. Abnormal signals can be single events or bursts of waves and spikes.

Imaging scans

Magnetic resonance imaging (MRI) can be used complementary to other exams. In a small number of Dravet syndrome patients, MRI scans show degeneration of the brain, abnormal growth of the cortex (the outer layer of the brain), and nerve damage in another region of the brain called the hippocampus (hippocampal sclerosis).

Other imaging methods, such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) are under investigation as diagnostic methods for Dravet syndrome.

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