Absence seizures involve brief, sudden lapses of consciousness. They're more common in children than in adults.
Someone having an absence seizure may look like he or she is staring blankly into space for a few seconds. Then, there is a quick return to a normal level of alertness. This type of seizure usually doesn't lead to physical injury.
Absence seizures usually can be controlled with anti-seizure medications. Some children who have them also develop other seizures. Many children outgrow absence seizures in their teens.
An indication of simple absence seizure is a vacant stare, which may be mistaken for a lapse in attention that lasts about 10 seconds, though it may last as long as 20 seconds, without any confusion, headache or drowsiness afterward. Signs and symptoms of absence seizures include:
Sudden stop in motion without falling
Small movements of both hands
Afterward, there's no memory of the incident. Some people have many episodes daily, which interfere with school or daily activities.
A child may have absence seizures for some time before an adult notices the seizures, because they're so brief. A decline in a child's learning ability may be the first sign of this disorder. Teachers may comment about a child's inability to pay attention or that a child is often daydreaming.
Contact your doctor:
The first time you notice a seizure
If this is a new type of seizure
If the seizures continue to occur despite taking anti-seizure medication
Your doctor will ask for a detailed description of the seizures and conduct a physical exam. Tests may include:
Electroencephalography (EEG). This painless procedure measures waves of electrical activity in the brain. Brain waves are transmitted to the EEG machine via small electrodes attached to the scalp with paste or an elastic cap.
Rapid breathing (hyperventilation) during an EEG study can trigger an absence seizure. During a seizure, the pattern on the EEG differs from the normal pattern.
Brain scans. In absence seizures, brain-imaging studies, such as magnetic resonance imaging (MRI), will be normal. But tests such as MRI can produce detailed images of the brain, which can help rule out other problems, such as a stroke or a brain tumor. Because your child will need to hold still for long periods, talk with your doctor about the possible use of sedation.
Your doctor likely will start at the lowest dose of anti-seizure medication possible and increase the dosage as needed to control the seizures. Children may be able to taper off anti-seizure medications, under a doctor's supervision, after they've been seizure-free for two years.
Drugs prescribed for absence seizure include:
Ethosuximide (Zarontin). This is the drug most doctors start with for absence seizures. In most cases, seizures respond well to this drug. Possible side effects include nausea, vomiting, sleepiness, trouble sleeping, hyperactivity.
Valproic acid (Depakene). Girls who continue to need medication into adulthood should discuss potential risks of valproic acid with their doctors. Valproic acid has been associated with higher risk of birth defects in babies, and doctors advise women against using it during pregnancy or while trying to conceive.
Doctors may recommend the use of valproic acid in children who have both absence and grand mal (tonic-clonic) seizures.
Lamotrigine (Lamictal). Some studies show this drug to be less effective than ethosuximide or valproic acid, but it has fewer side effects. Side effects may include rash and nausea.
Many children appear to have a genetic predisposition to absence seizures.
In general, seizures are caused by abnormal electrical impulses from nerve cells (neurons) in the brain. The brain's nerve cells normally send electrical and chemical signals across the synapses that connect them.
In people who have seizures, the brain's usual electrical activity is altered. During an absence seizure, these electrical signals repeat themselves over and over in a three-second pattern.
People who have seizures may also have altered levels of the chemical messengers that help the nerve cells communicate with one another (neurotransmitters).
Certain factors are common to children who have absence seizures, including:
Age: Absence seizures are more common in children between the ages of 4 and 14.
Sex: Absence seizures are more common in girls.
Family members who have seizures: Nearly half of children with absence seizures have a close relative who has seizures.
While most children outgrow absence seizures, some:
Must take anti-seizure medications throughout life to prevent seizures
Eventually have full convulsions, such as generalized tonic-clonic seizures