Catching the Silent Seizure: EEG in Absence Seizures

How a quiet change in awareness becomes visible on the EEG

Picture two very different moments. A child pauses mid-sentence and stares blankly for a few seconds. Then the child keeps talking as if nothing happened. Across town, an older man goes quiet and distant. He struggles to follow a conversation he would normally have no trouble with. There is no tremor and no collapse. Nothing about either moment looks like a medical emergency, and that is exactly the problem. Absence seizures are quiet by nature. In older adults, a prolonged absence state can be mistaken for delirium, a medication side effect, or early dementia. An Electroencephalography (EEG) can cut through that confusion. It reveals the electrical signature behind a behavior that looks like nothing at all from the outside.

This blog explains how electroencephalography, or EEG, helps identify absence seizures in children and absence status epilepticus in older adults. The goal is not to teach you how to read an EEG trace. The goal is to explain why a neurologist might order this test when a patient has staring spells, sudden lapses in awareness, or unexplained confusion. Electrodes placed on the scalp detect voltage differences produced by the brain’s electrical activity over time (Jahangiri, 2026). It is a simple idea, and it becomes powerful once you realize how subtle the underlying signs can be. 

What EEG Actually Measures

Figure 1. EEG detects voltage differences at the scalp after synchronized cortical activity spreads through tissue layers. The thalamocortical loop helps shape rhythmic activity.

An EEG detects tiny voltage changes produced by groups of cortical neurons, recorded by small electrodes placed on the scalp. Most of what shows up on a scalp EEG reflects synchronized excitatory and inhibitory postsynaptic potentials in cortical pyramidal cells, an effect that is strongest when many neurons with similar orientations fire together (Jahangiri, 2026). The resulting signal is faint, typically between 10 and 100 microvolts, and it grows even fainter as it travels through the cerebrospinal fluid, skull, and scalp before it ever reaches an electrode.

That faintness is not really a weakness. EEG was never meant to capture a picture of brain structure. Instead, it tracks brain function as it happens, moment to moment. When a seizure occurs, the EEG can show a sudden, organized pattern that precisely coincides with the person’s lapse in awareness. In absence seizures, this often appears as generalized spike-and-wave activity, with both hemispheres moving together in a synchronized rhythm. For a worried parent, an observant teacher, or a puzzled clinician, that pattern can turn a vague concern into a clear neurological explanation.

What an Absence Seizure Can Look Like

An absence seizure is a brief break in awareness, nothing more and nothing less. The person might stop mid-sentence, stare ahead, blink rapidly, or make small, almost unconscious movements. The episode rarely lasts more than a few seconds. Once it passes, the person simply returns to what they were doing. There is no grogginess and no memory of the gap. That is why children with absence seizures are so often misread as daydreamers or as kids who are ignoring instructions on purpose. The difference is real. The child is not choosing to disengage. Their brain has been briefly caught in an abnormal electrical rhythm they cannot control.

On an EEG trace, classic childhood absence seizures show up as generalized spike-and-wave discharges, usually around 3 Hz. Bashiri and colleagues studied a group of children with childhood absence epilepsy. They found EEG patterns that were bilateral, symmetrical, and synchronous. Regular 3 Hz spike-and-wave complexes recurred in their results (Bashiri et al., 2022). This is a good reminder that absence epilepsy is what doctors call an electroclinical diagnosis. The behavior and the electrical pattern only tell the full story when they are read together.

Children: Why the EEG Test Sometimes Includes Deep Breathing

Figure 2. Hyperventilation during routine EEG can help provoke absence seizure activity in children with suspected childhood absence epilepsy.

If a child is being evaluated for suspected absence seizures, do not be surprised by an unusual request. The technologist may ask the child to breathe quickly and deeply for a few minutes. This is called hyperventilation. It might sound like an odd thing to do in a medical setting, but it is actually one of the most useful activation procedures for childhood absence epilepsy. The goal is simple: increase the chance of capturing the abnormal EEG pattern during a short routine test.

Rozenblat and colleagues studied this process further and asked whether a child’s position during hyperventilation affects the results. Their study found that hyperventilating while sitting upright provoked absence seizures more effectively than lying down (Rozenblat et al., 2020). That detail might seem small, but it carries real diagnostic weight. EEG quality does not depend solely on the machine. Testing conditions matter too, and something as simple as how a child sits during deep breathing can influence whether the seizure pattern appears on the recording.

Children: Why Early Recognition Matters

Childhood absence epilepsy often appears during the school years. A teacher may notice the first signs because episodes tend to happen during reading, writing, or other tasks that require sustained attention. A child may lose small pieces of information throughout the day and then struggle academically without understanding why. Too often, the child is simply told to pay better attention. The real issue is a string of brief, repeated seizures that no one has caught yet.

This is where EEG proves its value. It can separate ordinary inattention from real seizure activity, help classify the specific epilepsy syndrome, and give physicians a baseline to track treatment response. Bashiri and colleagues found that most children in their study gained clinical seizure control after treatment began. EEG patterns also normalized in a large share of that group (Bashiri et al., 2022). Not every case resolves this cleanly. Still, the finding shows why early diagnosis can change a child’s academic path.

Older Adults: When the Problem Looks Like Confusion

Absence seizures are usually associated with childhood. A related condition, absence status epilepticus, can appear much later in life. In older adults, it does not look like a few seconds of staring. It can stretch into prolonged confusion, reduced responsiveness, or behavior that is hard to explain. The person may seem awake but disconnected. They may answer slowly, repeat themselves, or drift in and out of awareness.

EEG becomes critical here because sudden confusion in an older adult has many possible causes. These include infection, stroke, a metabolic imbalance, medication effects, delirium, and dementia. A seizure is rarely the first explanation people consider. Fernández-Torre described a case that shows why this matters: an older patient developed late-onset absence status after lorazepam was withdrawn. Scalp video-EEG showed continuous generalized sharp-and-slow wave activity. Once treated, both the EEG and the patient’s clinical state improved (Fernández-Torre, 2001). The case makes a simple point. When a story does not fit a routine explanation, EEG deserves consideration.

Same Tool, Different Clinical Question

The same test can answer very different questions depending on who is being evaluated. For a child, the question might be simple: are these repeated staring spells actually absence seizures? For an older adult, the question looks different: is this unexplained confusion really nonconvulsive seizure activity? The questions sound different, but both depend on the same task: matching observed behavior with electrical activity in real time.

That is also why the phrase staring spell can be misleading. Staring is only the visible surface. The real issue is awareness. Can the person respond? Did the episode begin and end abruptly? Does an EEG pattern appear at the same time? These answers guide diagnosis and protect patients from being mislabeled as careless, inattentive, confused, or simply getting older.

What Families, Teachers, and Caregivers Can Watch For

Knowing what to look for can make a real difference. For children, watch for the following signs:

·        Repeated blank stares that interrupt an activity without warning

·        Sudden pauses during speech, reading, or writing

·        Eyelid fluttering or small automatic movements, such as lip smacking or hand fumbling

·        An immediate return to normal afterward, often with no memory that anything happened

These episodes are usually brief, but they may happen many times in a single day. A child may not remember them at all. That is why outside observation from parents and teachers matters so much.

For older adults, the warning signs look different. Watch for:

·        Sudden, unexplained confusion with no clear cause

·        Prolonged staring or a noticeable drop in responsiveness

·        A new inability to follow conversation

·        A significant change in behavior after a medication is stopped or adjusted

These symptoms need medical evaluation because they can have many causes. EEG is not the only test that matters, but it can still reveal seizure activity that would otherwise remain hidden.

What the EEG Experience Is Like

A routine EEG is usually simple and painless. A technologist measures the head and places electrodes using paste or adhesive while the patient rests. During the test, the patient may be asked to open and close their eyes, breathe deeply, or look at flashing lights. None of these steps are random. Each is designed to test how the brain responds, and each may help reveal patterns linked to specific seizure types.

In more complicated cases, video-EEG or prolonged monitoring may be needed. Video helps connect the electrical pattern to observed behavior, and longer monitoring increases the chance of recording an actual event. This matters because a short EEG can appear normal even when something is wrong. The abnormal activity simply may not occur during the test.

Conclusion

Absence seizures show why neurophysiology matters in everyday life. A seizure does not need to look dramatic to be real. In children, EEG can explain brief lapses that might otherwise be blamed on attention or behavior. In older adults, EEG can uncover nonconvulsive seizure activity behind confusion that might otherwise be blamed on aging or delirium.

The real strength of EEG is that it makes timing visible. It shows what the brain is doing the moment awareness changes. For absence seizures, that can be the difference between guessing and knowing. A quiet pause, a missed sentence, or a period of confusion can carry an electrical signature. EEG gives clinicians a way to find it.

About the Author:

Hafsa Omer is a graduate neuroscience student in the School of Behavioral and Brain Sciences at The University of Texas at Dallas (UT Dallas). She wrote this article as part of Professor Faisal R. Jahangiri’s Evoked Potentials course. Fascinated by how the brain’s electrical activity shapes our everyday experiences, Hafsa enjoys making complex neuroscience concepts easier to understand. Through her writing, she hopes to bring neuroscience beyond the classroom and make it engaging, approachable, and meaningful for everyone.

References

• Bashiri, F. A., Al Dosari, A., Hamad, M. H., Kentab, A. Y., & Alwadei, A. H. (2022). Childhood absence epilepsy: Electro-clinical manifestations, treatment options, and outcome in a tertiary educational center. International Journal of Pediatrics and Adolescent Medicine, 9(2), 131–135. https://doi.org/10.1016/j.ijpam.2021.11.003

• Fernández-Torre, J. L. (2001). De novo absence status of late onset following withdrawal of lorazepam: A case report. Seizure, 10(6), 433–437. https://doi.org/10.1053/seiz.2000.0510

• Jahangiri, F. R. (2026). Electroencephalogram (EEG) and electrocorticography (ECoG) [Lecture slides]. ACN 7372.

• Rozenblat, T., Kraus, D., Mahajnah, M., Goldberg-Stern, H., & Watemberg, N. (2020). Absence seizure provocation during routine EEG: Does position of the child during hyperventilation affect the diagnostic yield? Seizure, 79, 86–89. https://doi.org/10.1016/j.seizure.2020.03.013