Autonomic Seizures

Seizure semiology

Seizures can change automatic body functions: heart rate, breathing, sweating, skin colour, nausea, abdominal sensations, vomiting, pupils, goosebumps and urinary symptoms. These autonomic features may be subtle, may occur without dramatic movement, and can easily be mistaken for panic, fainting, stomach illness or another medical problem.

What does “autonomic” mean?

The autonomic nervous system controls body functions that normally happen automatically, including heart rate, blood pressure, breathing, digestion, sweating, pupil size, temperature regulation and bladder function.

Seizure activity can temporarily disturb the brain networks that regulate these functions.

Autonomic features are part of seizure semiology

The International League Against Epilepsy updated seizure classification in 2025. Rather than treating every visible feature as a separate seizure type, the expanded classification describes seizures in chronological sequence using semiology descriptors.

Autonomic manifestations are included among observable seizure features. A seizure might therefore be described by a sequence such as an epigastric sensation followed by another focal feature and then impaired consciousness.

Read more: Seizure Types →

A rising or strange stomach sensation

One of the best-known autonomic seizure symptoms is an epigastric sensation — often described as a rising feeling in the stomach, nausea, abdominal discomfort, queasiness or an unusual internal sensation moving upward.

These symptoms are particularly recognised in focal seizures involving temporal-lobe networks, although one symptom alone does not identify a seizure location with certainty.

Nausea, retching and vomiting

Nausea, retching and vomiting can occur during focal seizures. In some childhood epilepsies, vomiting is especially prominent.

The ILAE describes self-limited epilepsy with autonomic seizures in childhood, formerly widely known as Panayiotopoulos syndrome. In this syndrome, vomiting is the most frequent autonomic manifestation and may occur with pallor, flushing, nausea, malaise or abdominal pain.

Repeated stereotyped vomiting with altered responsiveness or other seizure features should not automatically be assumed to be a stomach bug.

Heart-rate changes

Seizures can speed up or slow down the heart. Tachycardia — a faster heart rate — is much more common than ictal bradycardia or asystole.

A person may feel palpitations, pounding in the chest or a sudden awareness of their heartbeat. Sometimes heart-rate change is visible only on ECG or physiological monitoring.

Because palpitations also occur with panic, arrhythmia, medication effects and many other conditions, context and repeated stereotyped episodes matter.

Rare slowing or stopping of the heart

Ictal bradycardia and ictal asystole are uncommon but recognised seizure-related phenomena. They can contribute to collapse or fainting and require specialist assessment.

When unexplained collapse occurs alongside suspected epilepsy, clinicians may sometimes need both EEG and cardiac monitoring because epileptic and cardiac causes can mimic one another.

Sweating

Sudden sweating can occur during focal seizures, either locally or more generally. It may accompany nausea, flushing, pallor or a feeling of internal heat.

Sweating by itself is not specific to epilepsy, but recurrent stereotyped episodes occurring with other seizure features can be diagnostically useful.

Pallor and flushing

A seizure can make the face or skin suddenly pale or flushed. These colour changes reflect autonomic effects on blood vessels and circulation.

A 2026 systematic review found that ictal pallor and flushing can sometimes provide localising information in focal epilepsy, but the evidence base is small and these signs should be interpreted with the rest of the seizure semiology.

Goosebumps or piloerection

Goosebumps occurring suddenly without cold or emotion can be an ictal autonomic sign. This is sometimes called piloerection or a pilomotor seizure feature.

The 2026 systematic review of cutaneous ictal signs found piloerection strongly associated with temporal-lobe involvement in the published cases, although it remains an uncommon manifestation overall.

Pupil changes

Pupils can change size during seizures. Dilatation is reported more often, but pupillary changes are difficult to notice reliably without close observation or video.

Pupil size should never be used alone to decide whether an event was epileptic.

Breathing changes

Breathing may speed up, slow down, become irregular or pause during seizures. Respiratory autonomic changes can occur in focal as well as convulsive seizures.

Persistent breathing difficulty after a seizure, cyanosis or failure to recover normally is an emergency.

Read more: Breathing and Seizures →

Urinary symptoms

Autonomic seizure manifestations can include urinary urge and, less commonly, other bladder-related sensations. These are different from urinary incontinence occurring because consciousness and motor control are lost during a larger seizure.

A sudden stereotyped urge to urinate as part of a recurring seizure sequence may be clinically informative, but bladder symptoms have many non-epileptic causes.

Bowel and gastrointestinal sensations

Autonomic seizures can produce abdominal pain, cramping, nausea, retching, vomiting and other gastrointestinal sensations. Rare reports also describe bowel-related urgency or defaecation phenomena.

Because gastrointestinal symptoms are common in everyday illness, the strongest clue is often a repeated, highly stereotyped sequence linked to other seizure features.

Salivation, drooling and swallowing

Changes in salivation can accompany seizures, although drooling can also result from impaired swallowing or facial/oral motor activity rather than a purely autonomic mechanism.

The exact sequence matters: hypersalivation, swallowing automatisms, oral movements and impaired responsiveness can occur together but describe different aspects of the seizure.

Temperature and chills

Some seizures are accompanied by sensations of heat, cold, shivering or changes in skin temperature. These symptoms are less specific and need careful correlation with the rest of the event.

Fever itself can also provoke seizures in susceptible children, so a feeling of heat during a seizure should not be confused with actual febrile illness.

Autonomic seizures can happen with preserved consciousness

A person can experience a focal seizure with autonomic features while remaining aware and responsive. This is one reason such seizures may go unrecognised for months or years.

They may be dismissed as panic attacks, indigestion, hot flushes, palpitations or “just feeling strange”.

They can also evolve into other seizure features

An autonomic sensation may be only the first part of a seizure. It can be followed by behavioural arrest, automatisms, impaired consciousness, motor signs or focal-to-bilateral tonic-clonic activity.

The ILAE 2025 classification specifically encourages describing this chronological evolution rather than recording only the first symptom.

Autonomic seizure or panic attack?

Both can involve palpitations, sweating, nausea, fear, flushing, shaking and altered breathing. Features that can raise suspicion of a seizure include:

• very brief, stereotyped episodes
• the same sequence occurring repeatedly
• abrupt onset and ending
• associated impaired responsiveness
• automatisms or other focal seizure signs
• postictal confusion or fatigue

None of these features proves epilepsy by itself, and panic disorder and epilepsy can coexist.

Autonomic seizure or fainting?

Fainting can also cause pallor, sweating, nausea, visual dimming and loss of consciousness. Syncope may even include brief jerking movements.

The history before, during and after the event is therefore crucial. ECG is part of first-seizure assessment because cardiac causes can mimic epilepsy.

Read more: Diagnosis and Tests →

Autonomic seizure or stomach illness?

Nausea, vomiting and abdominal pain usually have non-neurological causes. Epilepsy becomes more plausible when episodes are stereotyped, recurrent, brief or linked to changes in responsiveness, eye/head deviation, pallor, other focal signs or a clear postictal state.

In children, prolonged autonomic seizures with vomiting can be particularly confusing and may initially look like gastroenteritis, migraine or syncope.

Self-limited epilepsy with autonomic seizures

The ILAE recognises self-limited epilepsy with autonomic seizures (SeLEAS) as a childhood epilepsy syndrome. Onset is usually between 3 and 6 years, although the recognised range is wider.

Focal autonomic seizures are mandatory for diagnosis. Seizures are often prolonged, vomiting is common, and EEG abnormalities can occur in different locations and are often activated by sleep.

Despite sometimes dramatic seizures, the syndrome is usually self-limited and remission typically occurs within a few years.

Read more: Epilepsy Syndromes →

What these symptoms can tell clinicians

Autonomic signs can sometimes help localise seizure networks, especially when combined with other semiology, EEG, imaging and video.

Temporal and limbic networks are particularly important in autonomic seizure physiology, but individual signs should not be treated as a simple map of “this symptom equals this lobe”. Seizure activity can spread rapidly between networks.

Why video and detailed witness descriptions matter

Autonomic signs are often subtle. A witness may notice colour change, sweating, repeated swallowing, retching, pupil change or altered breathing before the person themselves remembers anything unusual.

If safe, video can preserve details that are difficult to describe later. Clinical safety always comes before filming.

What to write in a seizure diary

Record autonomic symptoms in order, including:

• stomach or abdominal sensation
• nausea, retching or vomiting
• heart pounding or slowing
• pallor or flushing
• sweating
• goosebumps
• pupil changes
• breathing changes
• urinary urge
• what happened next
• whether awareness and responsiveness changed
• recovery afterwards

The sequence is often more informative than any isolated symptom.

Read more: Seizure Diaries and Recording Seizures →

Autonomic symptoms and SUDEP

Cardiac and respiratory autonomic changes are important in SUDEP research, but most autonomic seizure symptoms are benign and self-limiting.

Having nausea, sweating, pallor or another autonomic symptom does not by itself mean a person is at high risk of SUDEP.

Read more: SUDEP — Straight Facts →

When autonomic symptoms need urgent assessment

Urgent medical help is needed when an event includes:

• persistent severe breathing difficulty
• prolonged cyanosis
• collapse with suspected serious arrhythmia
• failure to recover normally
• prolonged seizure activity
• repeated seizures without recovery
• significant injury

New unexplained cardiac symptoms should not automatically be attributed to epilepsy.

The central point

Seizures do not have to look motor. A sudden wave of nausea, pallor, sweating, goosebumps, heart-rate change or another automatic body response can be part of a focal seizure.

The strongest clues are repetition, stereotyped timing, chronological evolution and correlation with the rest of the person’s clinical history.

Where next?

Auras and Focal Seizures →
Seizure Types →
Breathing and Seizures →
Diagnosis and Tests →
Back to Understanding Epilepsy →

Sources

• International League Against Epilepsy — Updated classification of epileptic seizures (2025)
• ILAE — Classification and definition of epilepsy syndromes with onset in childhood
• Baumgartner C et al. Epidemiology and pathophysiology of autonomic seizures: a systematic review. 2019
• Thijs RD et al. Autonomic manifestations of epilepsy: emerging pathways to sudden death? Nature Reviews Neurology. 2021
• Localizing value of cutaneous ictal phenomena: A systematic review. 2026

Medical note: Autonomic symptoms have many possible causes. Recurrent or unexplained episodes should be assessed clinically rather than assumed to be epileptic from one symptom alone.