What Are Absence Seizures?

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An absence seizure causes you to blank out or stare into space for a few seconds. They can also be called petit mal seizures. Absence seizures are most common in children and typically don’t cause any long-term problems. These types of seizures are often set off by a period of hyperventilation.

Absence seizures usually occur in children between ages 4 to 14. A child may have 10, 50, or even 100 absence seizures in a given day and they may go unnoticed. Most children who have typical absence seizures are otherwise normal. However, absence seizures can get in the way of learning and affect concentration at school. This is why prompt treatment is important.

Absence seizures are a type of epilepsy, a condition that causes seizures. Seizures are caused by abnormal brain activity. These mixed messages confuse your brain and cause a seizure.

Not everyone who has a seizure has epilepsy. Usually, a diagnosis of epilepsy can be made after two or more seizures.

Absence seizures often occur along with other types of seizures that cause muscle jerking, twitching, and shaking. Absence seizures may be confused with other types of seizures. Doctors will pay close attention to your symptoms in order to make the right diagnosis. This is very important for effective and safe treatment of your seizures.

It’s uncommon for absence seizures to continue into adulthood, but it’s possible to have an absence seizure at any age.

Classification

The International League Against Epilepsy (ILAE) Commission on Classification and Terminology revised the concepts, terminology, and approaches for classifying seizures and epilepsy.

The classification of absence seizures has been simplified as follows:

  • Typical absence
  • Atypical absence
  • Myoclonic absence
  • Eyelid myoclonia
  • Patient education

Patients who are old enough to drive should be warned about driving and operating heavy machinery. Physicians should be familiar with state laws concerning driving with epilepsy; inform patients concerning these legal matters.

For patient education information, see the Brain and Nervous System Center, as well as Epilepsy.

Etiology

The etiology of idiopathic epilepsies with age-related onset is genetic. About 15-40% of patients with these epilepsies have a family history of epilepsy; overall concordance in monozygotic twins is 74%, with a 100% concordance during the peak age of phenotypic expression. Family members may have other forms of idiopathic or genetic epilepsy (eg, febrile convulsions, generalized tonic-clonic seizures).

The idiopathic generalized epilepsies are a group of primary generalized epilepsies with absence, myoclonic, and tonic-clonic seizures. Based on age of onset and seizure types, some can be grouped into well-recognized syndromes, such as childhood absence epilepsy, juvenile absence epilepsy, and juvenile myoclonic epilepsy.

However, patients with other syndromes, such as generalized epilepsy with febrile seizures plus (GEFS+), as well as patients who have childhood absence epilepsy that leads into juvenile myoclonic epilepsy, illustrate that these syndromes represent a genetically determined lower threshold to have seizures.

The idiopathic generalized epilepsies are best viewed as a spectrum of clinical syndromes with varied genetic causes that affect the function of ion channels.

Genetic studies have shown that these syndromes are channelopathies, but different gene mutations have been found in the same syndromes. Juvenile myoclonic epilepsy has been linked to chromosome 6, with linkage to chromosome 6p12 in Mexican families.Mutations in the EFHC1 gene have been found in Mexican and Italian families  with juvenile myoclonic epilepsy, but not in a group of Dutch families.

Childhood absence epilepsy with generalized tonic-clonic seizure has been linked to chromosome 8q24 in a 5-generation family from Bombay, India.

A mutation in the GABA(A) receptor gene GABRB3 was found in Mexican families with childhood absence epilepsy. Mutations showed hyperglycosylation in vitro, with reduced GABA-evoked current density from whole cells. Expression of this gene in the developing brain may help explain an age-related onset and remission in childhood absence epilepsy.

Pathophysiology

The pathophysiology of absence seizures is not fully understood. In 1947, Jasper and Droogleever-Fortuyn electrically stimulated nuclei in the thalami of cats at 3 Hz and produced bilaterally synchronous spike-and-wave discharges on EEG. In 1953, bilaterally synchronous spike-and-wave discharges were recorded by placing depth electrodes in the thalamus of a child with absence seizures.

In 1977, Gloor et al demonstrated that the bilaterally synchronous, 3-Hz spike-wave discharges in the feline penicillin model of absence seizures were generated in the cortex. This led to the corticoreticular theory of primarily generalized seizures.

Abnormal oscillatory rhythms are believed to develop in thalamocortical pathways. This involves gamma-aminobutyric acid (GABA)-B–mediated inhibition alternating with glutamate-mediated excitation.

The cellular mechanism is believed to involve T-type calcium currents. T channels of the GABAergic reticular thalamic nucleus neurons appear to play a major role in the spike-wave discharges of the GABAergic thalamic neurons.

GABA-B inhibition appears to be altered in absence seizures, and potentiation of GABA-B inhibition with tiagabine (Gabitril), vigabatrin (Sabril), and, possibly, gabapentin (Neurontin), results in exacerbation of absence seizures. Enhanced burst firing in selected corticothalamic networks may increase GABA-B receptor activation in the thalamus, leading to generalized spike-wave activity.

These data suggest that activity of thalamic networks is necessary for spike-wave discharge rhythmogenesis, and cortical hyperexcitability is necessary for their generation.

In symptomatic generalized epilepsies, absence seizures are due to a wide variety of causes that at an early stage of neural development, result in diffuse or multifocal brain damage. The causes and management of secondary generalized epilepsies, and the other seizure types that accompany them, are not discussed in this article.

Risk factors

After noncompliance with treatment, lack of sleep is the most frequent cause of seizure exacerbations. Drugs that lower the seizure threshold (eg, alcohol, cocaine, high-dose penicillin, isoniazid [INH] overdose, neuroleptics) are most likely to cause seizures in patients with epilepsy. Withdrawal of alcohol, benzodiazepines, and other sedatives are also common causes.

What causes absence seizures?

Like other kinds of seizures, absence seizures are caused by abnormal activity in a person’s brain. Doctors often don’t know why this happens. Most absence seizures are less than 15 seconds long. It’s rare for an absence seizure to last longer than 15 seconds. They can happen suddenly without any warning signs.

What are the symptoms of absence seizures?

The easiest way to spot an absence seizure is to look for a blank stare that lasts for a few seconds. People in the midst of having an absence seizure don’t speak, listen, or appear to understand. An absence seizure doesn’t typically cause you to fall down. You could be in the middle of making dinner, walking across the room, or typing an e-mail when you have the seizure. Then suddenly you snap out of it and continue as you were before the seizure.

These are other possible symptoms of an absence seizure:

  • Being very still
  • Smacking the lips or making a chewing motion with the mouth
  • Fluttering the eyelids
  • Stopping activity (suddenly not talking or moving)
  • Suddenly returning to activity when the seizure ends

If you experience jerking motions, it may be a sign of another type of seizure taking place along with the absence seizure.

How are absence seizures diagnosed?

You may have absence seizures repeatedly for years before heading to the doctor for a diagnosis. You may have “staring spells” without thinking of them as a medical problem or a seizure.

An EEG is a test most often used to diagnose absence seizures. This test records the brain’s electrical activity and spots any abnormalities that could indicate an absence seizure.

These tests also can help to diagnose absence seizures or rule out other conditions:

  • Blood tests
  • Tests of the kidneys and liver
  • CT or MRI scans
  • Spinal tap to test the cerebrospinal fluid

How are absence seizures treated?

Absence seizures can affect your ability to perform at work or school, so it’s a good idea to see your healthcare provider about treatment.

Absence seizures can be treated with a number of different antiseizure medicines. The type of medicine that your healthcare provider recommends you take will also depend on what other seizure disorder you may have. If you have more than one type of seizure disorder, you may need to take multiple medicines.

Can absence seizures be prevented?

Taking your medicines exactly as your doctor prescribed is one of the best ways to manage absence seizures. But you can also make some changes in your life to help prevent absence seizures from happening.

These include:

  • Get plenty of sleep each night.
  • Find ways to manage your stress.
  • Eat a healthy diet.
  • Exercise regularly.
  • Living with absence seizures

Most people with epilepsy live full and active lives with medicine and other lifestyle changes. But it can be challenging at times to manage large and small life events when you have epilepsy. Depending on your age and the severity and type of epilepsy, you may need support with the following:

Behavioral and emotional issues. It is important to get enough sleep and manage stress when you have epilepsy. Stress and lack of sleep can trigger seizures. If you have trouble sleeping, talk with your healthcare provider about how to make sure you get enough sleep. Learn coping techniques that will help you manage stress and anxiety.

Employment. With proper treatment, people with epilepsy can do just about any job safely and effectively. But, certain jobs in which there is a high risk to public safety may not be an option. Epilepsy is covered under the Americans with Disabilities Act. This law prohibits discrimination against people with epilepsy and other disabilities.

Coping with discrimination and stigma. Children and adults with epilepsy may face discrimination and struggle to overcome the stigma associated with this neurological condition. Help educate family, friends, co-workers, and classmates on your condition. Let them know what to expect and how to help during a seizure.

Education. Children with epilepsy may be entitled to special services under the Individuals with Disabilities Education Act (IDEA). Working closely with the child’s teacher and school nurse will help improve management of epilepsy at school. It’s important for parents of children with epilepsy to balance safety and fun. Allow your child to have some age-appropriate independence and participate in sports and other activities at school, when possible.

Driving. Each state has different driving laws for people with epilepsy. Licensing may depend on how severe seizures are and how well they are controlled. Consider public transportation where it is available. If you continue to have absence seizures, it may not be safe for you to drive.

Support and online resources. You may feel alone in dealing with day-to-day life with epilepsy, but be assured that many people have epilepsy. You can find local support groups through your healthcare provider or local hospital. Many online resources give tools and tips for managing this condition. Online social media support groups bring together people from all over the world who are managing their epilepsy. These groups provide support and encouragement.

If you have trouble managing your absence seizures, you may want to work more closely with your healthcare provider to find a better way to treat them.

Key points about absence seizures

Absence seizures are seizures that generally last just a few seconds, and are characterized by a blank or “absent” stare.

Absence seizures usually occur in children between ages 4 to 14, but it’s possible to have an absence seizure at any age.

Absence seizures are easy to miss, but tests and an evaluation of symptoms can diagnose them.

Healthcare providers can usually help find the right mix of medications and lifestyle changes to manage absence seizures.

Without treatment, school performance, work, and relationships can suffer.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

Know the reason for your visit and what you want to happen.

Before your visit, write down questions you want answered.

Bring someone with you to help you ask questions and remember what your healthcare provider tells you.

At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your healthcare provider gives you.

Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

Ask if your condition can be treated in other ways.

Know why a test or procedure is recommended and what the results could mean.

Know what to expect if you do not take the medicine or have the test or procedure.

If you have a follow-up appointment, write down the date, time, and purpose for that visit.

Know how you can contact your healthcare provider if you have questions.

What Are the Complications of Absence Seizures?

Absence seizures typically last between 10 to 15 seconds. The person returns to normal behavior after the seizure. The person usually doesn’t remember the past few moments or the seizure itself. Some absence seizures can last up to 20 seconds.

While absence seizures occur in the brain, they don’t cause brain damage. Absence seizures won’t have any effect on intelligence in most children. Some children may experience learning difficulties because of the lapses in consciousness. Others may think they’re daydreaming or not paying attention.

In most cases, the only long-term effects of an absence seizure occur if the person falls or gets injured. Falls aren’t typical during the seizure. A person can experience absence seizures a dozen or more times per day without any ill effects.

Other people are usually the first to notice absence seizures. This is because the patient is unaware that they’re experiencing a seizure.

Children with absence seizures often outgrow the condition. Absence seizures can continue, however. Some patients progress to longer or more intense seizures.

Call Your Doctor About Absence Seizures If:

You notice that your child is having spells of “being off in their own world” or staring spells or any other behaviors that may indicate absence seizures.

Your child’s teacher complains that your child is “tuning out” or “always daydreaming” in school. Have the teacher write down a detailed description of your child’s behavior, how many episodes he has per day, and how long the episodes last.

What do absence seizures look like?

There are two types of absence seizures that may look a bit different. Both types of seizures are short, and people often don’t notice them at first. They may come and go so quickly that no one noties anything wrong. Or observers may mistake the symptoms for simple daydreaming or not paying attention.

Typical Absence Seizures

  • These seizures are the most common.
  • The person suddenly stops all activity. It may look like he or she is staring off into space or just has a blank look.
  • The eyes may turn upwards and eyelids flutter.
  • The seizures usually last less than 10 seconds.
  • Atypical Absence Seizures

These absence seizures are called atypical because they may be longer, have a slower onset and offset, and involve different symptoms.

  • The seizure still starts with staring into space, usually with a blank look.
  • There is usually a change in muscle tone and movement. You may see
  • Blinking over and over that may look like fluttering of the eyelids
  • Smacking the lips or chewing movements
  • Rubbing fingers together or making other hand motions
  • An atypical absence seizure lasts longer, up to 20 seconds or more.

What’s it like to have an absence seizure?

When people have absence seizures, they are not aware of what is happening around them. For example, they will not notice if someone tries to speak to them during a seizure.

If a person is speaking when their seizure begins, they will stop talking, often in the middle of a sentence. It may seem like a pause to an observer.

Often a child may have many absence seizures in a row.

An observer may not see the beginning or end of a seizure. The person may just look confused and not know what has happened.

What happens after an absence seizure?

When an absence seizure ends, the person usually continues doing whatever they were doing before the seizure. They are almost always wide awake and able to think clearly. Generally, no first aid is needed for this type of seizure.

When absence seizures happen close together or a person has many in a day, the person may look or act confused and lose track of what has been going on. For children in school, they may not be aware of what has happened in the classroom, miss instructions from the teacher, or have incomplete work.

If someone has absence seizures, how often will they happen?

The number of absence seizures a person may have varies a lot.

Seizure medicines can control absence seizures in many children so they have rare seizures or none at all.

Other people may have hundreds of brief absence seizures a day.

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