This is a common epilepsy syndrome starting in early childhood. Absence seizures can happen in many different epilepsy syndromes of childhood and adolescence. The most common epilepsy syndrome in which they happen is childhood absence epilepsy. This information refers specifically to the syndrome of childhood absence epilepsy.
The seizures of childhood absence epilepsy usually start between 4 and 7 years of age; rarely the seizures may start under 4, and as late as 8 years of age. They happen slightly more often in girls than boys. They can also happen many times a day, from 10 and up to over 100. They are sometimes divided into ‘typical’ and ‘atypical’ absence seizures.
A typical absence seizure consists of a sudden loss of awareness. The child will suddenly stop talking or what they are doing and stare blankly into space. They will not respond to people talking to them. The seizure is sometimes associated with slight repetitive, purposeless movements of the fingers, hands or mouth, such as some lip-smacking. These are called automatisms. There may also be eyelid flickering or fluttering.
A seizure usually lasts between 5 and 15 seconds and usually stops as suddenly as it starts, with the child resuming their normal activities. The child may behave as though nothing has happened or might appear a little confused, but only for a couple of seconds.
Absences that last longer than 15 or 20 seconds or that have a lot of automatisms or brief jerks of the head are usually called ‘atypical’ absences.
Absence seizures tend to happen more commonly when the child is bored, sitting quietly or when they are tired or unwell. They happen less often when the child is busy or focused on an activity that they enjoy.
Children with CAE usually develop and learn normally, although uncontrolled absence seizures that happen many times a day and over many weeks or months, may cause some learning difficulties. Sometimes a child’s concentration and memory are thought to be poor before the diagnosis of the childhood absence epilepsy is made – and improves after treatment is started.
The cause of CAE is not known. However, it is very likely to be caused by a mutation (a change in the way the gene is made up or ‘sequenced’) in one or more genes. CAE is one of the epilepsy syndromes that is in the group of epilepsies called, ‘idiopathic generalised epilepsy (IGE)’ or a ‘genetic generalised epilepsy (GGE)’.
The diagnosis is usually suggested by the history. The doctor may ask the child to hyperventilate (over-breathe) for 3 to 4 minutes while counting out loud and sometimes with their eyes shut. If an absence seizure happens, the child will stop hyperventilating and will usually open their eyes. Hyperventilation will trigger an absence seizure in over 9 in every 10 children with typical CAE. This is important in making the diagnosis. Hyperventilation can also be done in the outpatient clinic.
An EEG test is useful in confirming the diagnosis. The EEG may also be used to monitor response to treatment. No other tests such as a brain scan are required in CAE. If the absences are not controlled with treatment and continue to happen may times a day, or if there are lots of atypical features, children may need to have a magnetic resonance imaging (MRI) brain scan or genetic tests to make sure the diagnosis of CAE is the right one.
CAE usually responds very well to treatment. The epilepsy medicines of choice are ethosuximide (Zarontin), sodium valproate (Epilim) and lamotrigine (Lamictal). Occasionally a combination of two of these medicines may be required to completely control absences. Rarely, the medicines topiramate (Topamax) and zonisamide (Zonegran) might be helpful. Some children may also benefit from the ketogenic diet if their absences are not controlled by any combination of epilepsy medicines.
Information about treatments for children can be found on the Medicines for Children website.
There may be research studies open that are relevant to this epilepsy syndrome. Your child’s doctor will be able to discuss this with you.
The outlook of typical CAE is excellent, with the majority of children becoming seizure free as they pass through puberty.
About 7 out of 10 children with CAE will have their absence seizures completely controlled with one or two epilepsy medicines.
Approximately one in 10 children will develop other seizure types in adolescence, usually generalised tonic-clonic seizures. However these seizures are infrequent and usually respond to treatment with sodium valproate (Epilim) or lamotrigine (Lamictal).
Some children with CAE may also develop other seizure types such as myoclonic seizures (sudden, brief jerks of the head, limbs or body). When looked at in more detail these children will almost certainly not have CAE but instead have a different epilepsy syndrome such as juvenile absence epilepsy, juvenile myoclonic epilepsy, epilepsy with myoclonic absences or an ‘atypical’ absence epilepsy.
What is a syndrome?
A syndrome is a group of signs and symptoms that, added together, suggest a particular medical condition. In epilepsy, examples of these signs and symptoms would be things like the age at which seizures begin, the type of seizures, whether the child is male or female and whether they have physical or learning disabilities, or both. The results of an EEG are also used to help identify epilepsy syndromes.
If you would like to know more about an epilepsy syndrome, please speak to your doctor. If you would like to know more about epilepsy in general, please contact the Epilepsy Action Helpline.
Epilepsy Action would like to thank Dr Richard Appleton, consultant paediatric neurologist and honorary professor in paediatric neurology at Alder Hey Children’s Hospital, Liverpool, UK for preparing this information.