Absence seizure is a type of epilepsy (fits) disorder manifesting as sudden, brief spells (usually less than 15 seconds) of staring or lapse of consciousness. This kind of seizure is more commonly seen in children than in adults and are caused because of abnormal electrical activity in the brain.
The nerve cells in the brain normally produce electrical impulses to communicate with different parts of the nervous system. Seizures are caused because of abnormal electrical discharges from the brain. During the episodes of absence seizures, these altered electrical waves typically occur at the rate of three spike/wave discharges per second pattern. Altered levels of brain neurotransmitters (chemical messengers) may also be present in those with seizures.
Absence seizures are seen mostly under the age of 20, usually in children aged 6-12 years. It can present in older teens and adults, but the incidence is very low.
No underlying cause can be identified in most cases of absence seizures. There may be a genetic predisposition in many children. In some patients, the seizures may be triggered by flashing lights or when the person breathes faster than usual (hyperventilates).
Some children with absence seizures may also experience other types of seizures such as full seizures (tonic-clonic seizures), twitches or jerks (myoclonus), or sudden loss of muscle power (atonic seizures).
Simple absence seizures. Most absence seizures present as staring episodes lasting less than 15 seconds (simple absence seizures). The person may stop talking mid-sentence or stop doing some activity and start again after a few seconds.
Complex absence seizures. In addition to staring, some additional movements may be seen such as fluttering eyelid, lip smacking, chewing movement, finger rubbing and hand gestures.
After the seizure, the person recovers fully without any subsequent confusion, headache or drowsiness. The person usually continues whatever they were doing before the seizure and may not have any memory of what happened to them during the seizure.
During the episode, they may not notice someone when they try to talk to them. If the affected individuals were talking, they might stop mid-sentence. It may take years before they realise that something is wrong.
They may stop giving attention for short periods in school or home. Such episodes may happen multiple times daily and interfere with daily activities or school.
Your doctor will elicit a detailed history, perform a physical examination and look at the nervous system functioning in detail. The tests that may be ordered include:
- EEG (electroencephalogram). This test measures the electrical activity in the brain. People with seizures often have abnormal electrical discharges. In some cases, the test will also pick the specific area of the brain affected. The EEG may come as normal after seizures or between seizures.
- Brain scans. Brain imaging scans such as magnetic resonance imaging (MRI) or computerised tomography (CT) scan may be done to produce images of the brain and rule out other problems.
- Blood tests. To look for other health problems that can cause seizures.
Your doctor will start an anti-seizure medicine in a low dose in the beginning and increase the dose as needed to keep the seizures under control. The medications need to be continued as long as recommended by the doctor. Once the child is seizure-free for two years, the doctor may suggest tapering of the medications under supervision.
Absence seizures do not cause any damage to the brain and it does not affect the intelligence of most children.
If the absence seizures episodes repeatedly occur while at the school, the child may experience learning difficulties due to the lapses in concentration.
Other kids or adults may notice the child during the attack and think that they are not paying attention or daydreaming. There are chances of the child having behavioural problems or experiencing social isolation when they or others become aware of the condition.
As they grow, most children will outgrow the absence seizures. However, in some cases, the absence seizures may continue even into the adulthood and persist for long and in some convert to full blown generalised tonic-clonic seizures.
If you feel that your child is having absence seizures, consult a doctor right away.
Some of the points that help to differentiate absence seizures from daydreaming include:
- It can happen anytime but more commonly occurs when the child is bored
- Seizures come on suddenly
- Seizures cannot be interrupted (child can be woken up from daydream) and
- Seizure ends on its own within about 20 seconds (daydreams can continue longer).
Children with the absence seizures can sometimes have full-seizures (generalised tonic-clonic convulsions). It is important to identify this type of seizures and get them treated. During a generalised tonic-clonic attack, individuals become rigid followed by loss of consciousness and violent contractions.
During this attack move hard or sharp objects away, and place the child on a side, so as to keep the airway clear (this prevents tongue or secretions from blocking the windpipe). Do not try to restrain the child or try to stop the movements. Look at the watch and record the duration of the seizure. Once the seizure ends, take the child to the doctor.
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- Medline Plus. Medical encyclopedia –Absence seizures. Accessed at https://www.nlm.nih.gov/medlineplus/ency/article/000696.htm on 21 June 2016.
- The Johns Hopkins University. Health Library – Absence Seizures. Accessed at http://www.hopkinsmedicine.org/healthlibrary/conditions/nervous_system_disorders/absence_seizures_134,16/ on 21 June 2016.
- Epilepsy Action. Childhood absence epilepsy (CAE). Accessed at https://www.epilepsy.org.uk/info/syndromes/childhood-absence-epilepsy on 22 June 2016.