Diagnosing Dravet Syndrome

Dravet Syndrome is a clinical diagnosis. This means it’s diagnosed from reported signs and symptoms, rather than diagnostic tests.

In the UK, the clinical diagnosis for Dravet Syndrome is based on:

• what type of seizures someone has
• how the condition develops
• the results of an electroencephalographic (EEG) test or scan, a recording of electrical activity in the brain.

However, diagnosing Dravet Syndrome from signs and symptoms alone is not always straightforward. Some symptoms are shared with other types of epilepsy, and others can take several years to be noticeable.

The good news is that there is a genetic test available that can help confirm a Dravet Syndrome diagnosis. Today, a genetic test, together with a clinical history (a record of when seizures and other symptoms occurred) means doctors can diagnose Dravet Syndrome with a high degree of accuracy.  

Healthcare professionals who are not familiar with Dravet Syndrome can find out more about diagnosing the condition here.

What characteristics will a doctor look for to make a clinical diagnosis of Dravet Syndrome?  

A first seizure as a baby or infant

A child with Dravet Syndrome will usually have their first seizure when they are between three to nine months old, with an average of around six months of age. Rare cases can happen as early as one month old, or as late as 20 months. Before the first seizure, a child will probably have been developing normally.

The first seizure might be:

• triggered by a fever, either from an illness that causes a high temperature or from a childhood vaccination. Sudden change in temperature from hot to cold or cold to hot, such as getting in or out of a warm bath, is another common trigger
• ‘Hemiclonic’ where only one side of the body convulses or ‘Generalised tonic-clonic’ where the body suddenly becomes stiff and then jerks rhythmically
• prolonged, possibly more than 30 minutes in length, and perhaps with multiple seizures happening close together (status epilepticus, which is either an individual seizure that lasts longer than five minutes, or a cluster of them that happen close together, without recovery time in-between).

Find out about more about initial seizures in Dravet Syndrome.

A child develops normally in their first year of life, then development slows down

Dravet Syndrome is not just epilepsy. It also includes a spectrum of conditions (or ‘comorbidities’) that become noticeable in early childhood. Initial development appears normal, but then it will start to slow. For example, a child might walk a little later (around 17 to 18 months of age) and take longer to speak.

Children aged one to four years old might have an abnormal EEG scan or test

Around 50% of children with Dravet Syndrome, who are between one and four years old, will have an abnormal EEG.

After the age of two, the child experiences other seizures

During the second year of life seizures become more frequent and persistent. They may happen with or without a fever, and at any time of day and night.

They can include: myoclonic seizures, focal impaired awareness seizures, atypical absence seizures, atonic seizures.

Visit the seizures section of our website to find out more about patterns of seizures in early and later childhood.

Seizure patterns change over time

Generally, as children get older, typically around four years of age, status seizures begin to settle. However, people with Dravet Syndrome remain prone to status seizures, particularly when they are ill or have an infection.

Another change is that children may begin to experience their seizures at night (‘nocturnal seizures’), particularly as they transition through nightly sleep phases.

During the first 10 years of their lives, a child with Dravet Syndrome will experience a huge number of seizures – in some cases averaging 50 to 100 per day. These include:

• myoclonic seizures. These involve one part of, or the whole, body. They can be subtle or mild and may cause a fall. Myoclonic seizures are brief but can happen in clusters, close together. They often happen shortly after someone wakes up. As a child gets older, they can have more of these types of seizures.
• focal impaired awareness seizures. These seizures usually involve loss of awareness and extra movements, such as lip smacking, fumbling or fiddling with the hands. They typically last more than 30 seconds, with a further period of time needed for someone to fully recover.
• atypical absence seizures. Absence seizures last up to 30 seconds, at most. The person can become blank and unresponsive for a few seconds and may appear to be ‘daydreaming’. They can be accompanied by head nodding or jerks. ‘Atypical’ refers to the EEG test or scan result when someone has this type of seizure.
• atonic seizures. In this type of seizure, the person’s muscles suddenly relax and become floppy. If they are standing, they can fall (often forwards) and may injure the front of their head or face. Atonic seizures tend to be brief and happen without warning. People usually recover quickly, but may sustain seizure-related injuries that take longer to heal.

The child will have less ‘convulsive status epilepticus seizures’. ‘Status epilepticus’ is either an individual seizure that lasts longer than five minutes, or a cluster of them that happen close together, without recovery time in-between.

Developmental delay and other difficulties become noticeable in early childhood

If a child is living with Dravet Syndrome, varying degrees of ‘developmental delay’ will become noticeable between the ages of two and four. The term 'developmental delay' is used when a child takes longer to reach certain development milestones than others of their age. These milestones cover four areas – motor (or movement) skills, speech and language, cognitive skills and social/emotional skills. A child has Global Developmental Delay (GDD) if they haven’t reached two or more milestones in all areas of development.

In Dravet Syndrome, development generally continues to be impaired – some early skills and abilities may be lost, and the comparative gaps with neurotypical peers continue to widen throughout childhood.

All children and adults living with Dravet Syndrome therefore have some degree of intellectual (or learning) disability, ranging from moderate to severe. In addition, they may develop other associated conditions, such as autism, ADHD and challenging behaviour, and difficulties with mobility, speech, eating and sleep. These can become apparent in early childhood, and continue to evolve as a child grows into adulthood.  

You can find out more about these in our non-seizure aspects of Dravet Syndrome section.

An adult who has intellectual disability and epilepsy

Dravet Syndrome is a life-long condition. The early signs and symptoms of the condition might be lost from someone’s medical history or they may have been misdiagnosed. An adult who has intellectual disability and epilepsy may have Dravet Syndrome, which could be diagnosed by a genetic test.

If you suspect someone you know or care for could have Dravet Syndrome, share our ‘Could it be Dravet?’ diagnosis guide for healthcare professionals with their medical team.

What do I do if I suspect Dravet Syndrome?

If you’re concerned that someone you know might have Dravet Syndrome, speak to a doctor without delay. Any child with suspected Dravet Syndrome should be assessed by a paediatrician with expertise in epilepsy, or a child neurologist. 

As Dravet Syndrome is a life-long condition, a diagnosis can be beneficial at any age. Ask the health professional involved in your child or adult’s care, to carry out a genetic test for Dravet Syndrome.

Healthcare professionals who are not familiar with Dravet Syndrome can find out more about diagnosing the condition here.