Absence seizures are a type of generalized seizure. They involve short periods of unresponsiveness, often many times a day. They usually begin in childhood, although they can occasionally begin in adolescence or adulthood; they are very rare in infants. There are several different types of absence seizures. The major subtypes are typical or atypical.
Once parents/caregivers or teachers become aware of absence seizures, they are usually quite easy to diagnose. However, if they have certain less typical features they may be confused with focal seizures with impaired awareness.
A diagnosis of absence seizures is made when parents/caregivers or teachers report that the child is having staring spells and a typical pattern is seen on the child’s electroencephalogram (EEG). Typical absence seizures can often be triggered in the health-care provider’s office by asking the child to hyperventilate (breathe fast and deeply).
Children with absence seizures may also have other seizure types for example, tonic-clonic seizures and myoclonic seizures. These are more common in adolescents who have absence seizures.
What are other terms for absence seizures?
Other terms for absence seizures include:
- petit mal seizures (older term for absence seizures)
- epileptic absence
- pyknolepsy
How can you tell if your child has absence seizures?
Typical absence seizures
Possible signs of an absence seizure include:
- staring
- the child suddenly stops what they are doing
- 10-20 seconds of unresponsiveness that can be confused with daydreaming
- lack of response when you touch your child
- immediate alertness after the seizure
- multiple seizures per day
Less common signs include:
- repetitive blinking
- eyes rolling up
- head bobbing
- automatisms such as licking, swallowing and hand movements
- autonomic symptoms such as dilated pupils, flushing, pallor (paleness), rapid heartbeat or salivation
Children usually do not know that they have had a seizure. Typical absence seizures begin and stop abruptly.
Absence seizures may be confused with focal seizures with impaired awareness. That is why it is important to record everything your child does during their seizures and discuss with their health-care provider.
The EEG shows a three per second “spike-and-wave” pattern during seizures. Typical absence seizures occur in children who are otherwise healthy, are developing normally and have no other neurological or developmental issues.
- An absence seizure with mild clonic components means there is mild, often subtle twitching of the eyelids, the corners of the mouth and sometimes the arms.
- In an absence seizure with atonic components, the child’s head or body may slump forward or objects may drop from their hand due to a sudden loss of muscle tone. It is rare for a child to fall during such a seizure.
- An absence seizure with tonic components may be symmetric (the same on both sides) or asymmetric (stronger on one side). With tonic activity, the muscles stiffen and contract suddenly, so a child that is standing may be pushed backward or their head or body may turn to one side.
- An absence seizure with automatisms may look a bit like a focal seizure with impaired awareness. The child does repetitive movements or behaviours that have no specific purpose such as raising their eyelids, licking, chewing, swallowing, and fiddling, patting or scratching with their hands.
- In an absence seizure with autonomic symptoms, the child may become pale around the mouth, their pupils may dilate, their face may become flushed, their heart may beat faster, they may get goosebumps, their mouth may water or they may wet themselves, however this is very rare.
Atypical absence seizures
Atypical absence seizures are harder to notice. The beginning and end of the staring spell are not as clear-cut as in typical absence seizures as they often begin and end gradually.
Unlike typical absence seizures, the child may be able to respond a bit during the seizure but is often confused after the seizure. The seizure usually lasts slightly longer than typical absence (often more than 10 seconds) and may include mild eyelid twitching, tonic or autonomic symptoms, automatisms, or loss of muscle tone causing the child to fall down. They are also more difficult to control with medication.
Atypical absence seizures are more often seen in children who have other neurological problems such as developmental disability. These children often have other seizure types as well. Their EEG does not show the typical three per second spike wave pattern seen in typical absence seizures, but slower one to two and a half per second spike wave pattern and also other abnormalities between seizures.
How many children have absence seizures?
About one child in 4,300 to 8,300 children under 15 years of age has absence epilepsy. The rates are usually higher in girls than in boys. Most children who experience absence seizures have their first seizure between six and eight years old. It is uncommon for absence seizures to begin after age 14.
What causes absence seizures?
Typical absence seizures are seen with childhood or juvenile absence epilepsy and juvenile myoclonic epilepsy. There is a genetic component to the development of these syndromes, however this does not mean the child inherited this from parents or will pass this along to their own children in the future. The brain appears normal on an MRI scan.
We know less about what causes atypical absence seizures. They are often seen in Lennox-Gastaut syndrome, generalized epilepsies with a known cause and developmental delay, myoclonic-astatic epilepsy, and when an EEG shows continuous spike waves in slow sleep. Some children with atypical absence seizures have obvious brain abnormalities while others have very small changes.
How are absence seizures treated?
Typical absence seizures can usually be controlled easily with anti-seizure medications. Atypical absence seizures are also treated with drugs, but often are not as easily controlled, and may require additional treatment methods, such as the ketogenic diet.
What should I do when my child has an absence seizure?
If your child is having an absence seizure:
- Don’t shout; they cannot hear you.
- If you are not sure whether they are having a seizure or just daydreaming, touch them gently on the arm.
- Ask them a simple question during the seizure, and check if they are able to respond to you or remember your question afterwards.
- No other intervention is usually needed.
What is the outlook for a child with absence seizures?
The outlook for a child with absence seizures depends on the underlying syndrome.
- In childhood absence epilepsy, the seizures can be controlled with medication in 80 per cent to 95 per cent of cases. Some researchers believe that earlier treatment improves the prognosis and reduces the chance of relapse. The seizures from childhood absence epilepsy usually stop two to five years after they begin. Usually, once the child has been free of seizures for two to three years, their anti-seizure medications can be gradually discontinued.
- The decision to discontinue the medication is different for each child and should be discussed with your child’s neurologist.
- Other syndromes with typical absence seizures, such as juvenile absence epilepsy and juvenile myoclonic epilepsy, may continue for the rest of the child’s life, although in 80 per cent to 90 per cent of cases the seizures can be controlled with medication.
- The prognosis for atypical absence seizures also depends on the underlying disorder. In Lennox-Gastaut syndrome, for instance, it is difficult to control the seizures and intellectual disability is common.