Absence seizure

An absence seizure is a brief seizure that causes a sudden lapse in awareness. The person may stop what they are doing, stare, and then quickly return to normal. These episodes are caused by a temporary burst of abnormal electrical activity involving both sides of the brain.

Absence seizures are a type of generalized seizure, meaning the abnormal activity begins across networks on both sides of the brain at about the same time. They are most common in children but can continue into adolescence or adulthood. Some people also have other seizure types.

A typical absence seizure usually lasts only a few seconds. Because there may be no fall or large body movement, the episode can look like daydreaming or inattention. Some people have many episodes in one day. Frequent interruptions in awareness can affect learning, conversations, and safety even when each seizure is brief.

Absence seizures may be part of an epilepsy syndrome. Childhood absence epilepsy generally starts during childhood and often causes frequent absence seizures. Juvenile absence epilepsy begins later and is more likely to occur with generalized tonic-clonic seizures, which cause loss of consciousness and body stiffening and shaking. An accurate syndrome diagnosis helps guide treatment and follow-up.

A typical absence seizure begins and ends suddenly. The person usually resumes their activity without confusion and may not know that anything happened.

Possible signs include:

• A blank stare and loss of response for several seconds
• Stopping speech or activity in the middle of a sentence or task
• Small, repeated eyelid movements
• Brief eye rolling or upward eye movement
• Subtle chewing, lip smacking, or hand movements
• A slight change in muscle tone
• Immediate return to the previous activity

The person generally cannot respond normally during the seizure. Unlike ordinary daydreaming, the episode may not stop when someone calls their name or gently tries to get their attention. However, staring alone does not prove that a seizure occurred.

Atypical absence seizures often last longer, begin and end less abruptly, and cause more noticeable changes in muscle tone. They are more commonly associated with developmental difficulties and certain complex epilepsy syndromes.

Other conditions can resemble absence seizures. These include daydreaming, attention problems, sleepiness, tics, fainting, and focal impaired-awareness seizures. Focal seizures begin in one area of the brain and may cause a longer period of confusion afterward.

Keeping a written description or a safely recorded video may help a clinician assess a suspected episode. A video should be made only when it can be done without delaying care or putting the person at risk.

Absence seizures usually result from a tendency of brain networks to produce generalized seizure activity. Genetics often play a role, but inheritance is complex. A child may develop absence epilepsy without having a parent or sibling with the condition.

Risk factors and related features include:

• Childhood or adolescent age
• A family history of epilepsy or generalized seizures
• Having a generalized epilepsy syndrome
• Developmental or neurological conditions in some people with atypical absence seizures
• A personal history of other generalized seizure types

In typical childhood absence epilepsy, brain structure is usually normal. A visible brain injury or lesion is not the usual cause. Atypical episodes or examination findings may lead a clinician to look for another neurological condition.

Certain situations can make seizures more likely in someone who is already susceptible. These are triggers rather than underlying causes. They may include missed antiseizure medicine, inadequate sleep, illness, stress, and, for some people, flashing lights. Rapid deep breathing, called hyperventilation, can provoke typical absence activity and is sometimes used under clinical supervision during testing.

Diagnosis usually begins with a detailed account of the episodes. The clinician may ask when they started, how long they last, how often they happen, and whether awareness returns immediately. Information from a parent, teacher, partner, or other witness can be important because the person having the seizure may not notice it.

The main diagnostic test is an electroencephalogram, or EEG. An EEG uses small sensors placed on the scalp to record the brain’s electrical activity. Typical absence seizures commonly produce a characteristic generalized spike-and-wave pattern. The classic pattern occurs about three times per second, although the exact appearance can vary by seizure type and epilepsy syndrome.

During an EEG, a trained professional may ask the patient to breathe deeply and rapidly for several minutes. This can bring out absence seizure activity and improve the chance of recording an episode. Hyperventilation testing is not appropriate for everyone and should be directed by the clinical team.

A routine EEG can be normal when no abnormal activity occurs during the recording. If the history remains concerning, a clinician may recommend a longer EEG, sleep-deprived EEG, or video EEG monitoring.

Brain imaging is not always needed when the history, examination, and EEG clearly show a typical generalized absence epilepsy. Magnetic resonance imaging, or MRI, may be considered when symptoms are unusual, development or neurological examination is abnormal, the EEG suggests a focal problem, or seizures do not respond as expected.

Blood tests do not diagnose absence epilepsy. They may be used to look for other causes of altered awareness or to monitor certain medicines.

The goal of treatment is to prevent seizures while limiting medicine side effects. The choice depends on the epilepsy syndrome, whether other seizure types are present, the person’s age and health, and pregnancy-related considerations.

Ethosuximide is commonly used when absence seizures are the only seizure type. In a major clinical trial involving childhood absence epilepsy, ethosuximide and valproic acid controlled seizures more often than lamotrigine during initial treatment. Ethosuximide caused fewer attention-related effects than valproic acid in that trial. It does not treat every generalized seizure type, so it may not be appropriate when generalized tonic-clonic seizures also occur.

Valproic acid, also called valproate, can treat absence seizures and other generalized seizure types. It has important risks, including serious fetal harm when taken during pregnancy. It can also affect the liver, pancreas, blood cells, and body weight. Its use requires an individualized discussion, especially for anyone who could become pregnant.

Lamotrigine may be considered in some situations. It must usually be increased gradually because raising the dose too quickly can increase the risk of a serious skin reaction. Other medicines may be considered by an epilepsy specialist if initial options are ineffective or poorly tolerated.

Common treatment principles include:

• Take medicine consistently and follow the prescribed schedule.
• Do not stop an antiseizure medicine suddenly unless a clinician directs it.
• Report troublesome side effects rather than changing the dose independently.
• Tell the care team about all medicines, supplements, pregnancy plans, and contraception.
• Keep a record of suspected seizures, missed doses, illnesses, and side effects.

Follow-up EEG testing may sometimes help assess seizure control, since absence seizures can occur without being noticed. Blood tests may be needed with certain medicines, but monitoring requirements differ.

People whose seizures continue despite appropriate medicine trials may be referred to an epilepsy specialist. The specialist can confirm the seizure type and discuss additional medicines or, in selected difficult-to-treat epilepsies, dietary therapy. Surgery is generally not used for typical generalized absence epilepsy because the seizures do not begin in one removable area of the brain.

Practical safety steps matter while seizures are not fully controlled. A school seizure action plan can explain what staff should observe and when to seek help. Extra supervision may be needed around water, heights, traffic, open flames, or machinery. Showers are generally safer than bathing alone. Swimming should involve close supervision by someone who knows about the seizures.

Driving rules differ by location and may require a seizure-free period or clinician reporting. A healthcare professional can explain the applicable rules.

The brief seizure itself usually does not cause lasting brain injury. The main concern is the effect of repeated interruptions in awareness. A child who has many seizures may miss parts of lessons, instructions, or conversations. This can appear to be poor attention or a learning problem.

Absence seizures can also affect confidence, social participation, school performance, and independence. Injuries are less common than with seizures that cause falling, but an absence at the wrong moment can still be dangerous during swimming, cycling, cooking, driving, or crossing a road.

Some people develop or already have generalized tonic-clonic seizures. Others continue to have absence seizures into adolescence or adulthood. The outlook depends partly on the specific epilepsy syndrome and response to treatment.

Treatment can cause side effects, ranging from stomach upset and tiredness to less common but serious reactions. Regular review helps balance seizure control against these risks.

A prolonged period of reduced awareness with repeated or continuous absence activity is called absence status epilepticus. It may cause ongoing confusion, slowed behavior, or unusual responsiveness rather than a single short stare. This requires prompt medical assessment.

Routine follow-up is used to review seizure control, school or work effects, medicine adherence, side effects, and safety. Children may need support from both healthcare and school teams. As a child grows, medicine doses and the epilepsy diagnosis may need review.

Contact the treating clinician sooner if:

• Suspected seizures continue or become more frequent
• A new type of event occurs, especially stiffening, shaking, falling, or prolonged confusion
• Medicine causes persistent vomiting, severe tiredness, behavior changes, or other concerning effects
• School performance or attention changes noticeably
• Pregnancy is planned or occurs while taking an antiseizure medicine

Do not stop treatment without medical guidance. A clinician may consider reducing medicine after a sustained seizure-free period, but the timing and process depend on the epilepsy syndrome, EEG findings, and individual history.

Call emergency services if a seizure lasts five minutes or longer, seizures repeat without recovery, breathing is difficult, a serious injury occurs, or the event happens in water. Emergency help is also appropriate for a first convulsive seizure or a prolonged, unexplained change in awareness. Follow an established seizure action plan when one is available.