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Dr. Alessandro Giardini
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One of the most anxiety-provoking moments in the aftermath of a child's collapse is not knowing whether what happened was a faint or a seizure. The two can look remarkably similar to a frightened parent watching from a few feet away. Getting the distinction right is important, not just because the causes are different, but because the investigations, the specialists involved, and the management pathways are entirely different too.
Dr Alessandro Giardini, Consultant Paediatric Cardiologist at Great Ormond Street Hospital and the Portland Hospital, is regularly asked this question in clinic. This post explains the key differences between syncope and seizure, why the confusion happens, and what features help distinguish between the two.
The confusion is understandable and extremely common, even among healthcare professionals. Syncope, particularly vasovagal syncope, can produce brief involuntary movements that look like fitting. When blood flow to the brain drops sharply, the brain can generate rhythmic jerking of the limbs for a few seconds. This is called convulsive syncope, and it happens in roughly one in ten fainting episodes.
It is not a seizure. The mechanism is different. But to a parent who has never seen it before, a child who drops to the floor and briefly jerks their arms and legs is an extremely frightening thing to witness, and the natural assumption is that something neurological and serious has occurred. That assumption is frequently wrong.
Certain features in the history are strongly associated with a fainting episode rather than a seizure. The setting and context are often the most revealing. A child who collapses in a warm, crowded environment, a school hall, a queue, a sports changing room, has a very different history from one who has a sudden unexplained episode at home while sitting quietly.
A prodrome before the episode strongly favours syncope. Most children who faint have several seconds to a minute of warning: light-headedness, nausea, greying of vision, muffled hearing, and a feeling of warmth. This prodrome reflects the gradual drop in blood pressure that precedes loss of consciousness. Seizures usually begin abruptly, without this kind of warning, though some have their own aura which can feel broadly similar.
Pallor during the episode is characteristic of syncope. The child goes pale, often sweaty, and limp. Seizures more typically involve maintained muscle tone and sometimes a bluish tinge around the lips from breath-holding or abnormal breathing patterns during the episode.
Recovery is a particularly useful discriminator. After a vasovagal faint, children recover quickly, usually within a minute or two, and although they may feel tired, pale, and nauseous, they are orientated and know where they are. After a seizure, there is usually a post-ictal phase: a period of confusion, disorientation, and sometimes deep sleep that can last many minutes to hours. A child who is back to normal within two or three minutes of an episode is much more likely to have fainted than to have had a seizure.
Duration of the abnormal movements is important. The jerking that occurs in convulsive syncope is brief, typically a few seconds, coinciding with the period of lowest blood flow to the brain. Sustained rhythmic convulsive activity lasting more than thirty seconds, or generalised tonic-clonic movements from the outset, is more consistent with a seizure.
Tongue biting during an episode is a classic feature of generalised seizures. It does not occur in fainting. Incontinence of urine can happen in both, so it is less discriminating, but it is associated more frequently with prolonged seizures than with typical vasovagal episodes.
The context is again important on the seizure side. An episode that occurs during sleep, from a lying or sitting position with no obvious trigger, in the absence of any prodrome, is more concerning for a seizure or a cardiac arrhythmia than for vasovagal syncope.
There is a third category that parents and clinicians sometimes miss. Certain cardiac arrhythmias, particularly those associated with Long QT syndrome, Brugada syndrome, or other inherited channelopathies, can cause collapse that is rapid, without prodrome, and may include brief convulsive activity. These episodes can be misdiagnosed as seizures when the underlying cause is actually a dangerous cardiac rhythm disturbance.
This is why a 12-lead ECG is a recommended part of the initial assessment for any child who has had an unexplained loss of consciousness, even when the working diagnosis is epilepsy. An abnormal QTc interval, a Brugada pattern, or other ECG changes can point towards a cardiac cause that would otherwise be missed. The implications for treatment and safety are entirely different in that situation.
Dr Giardini regularly sees children who have been referred with a diagnosis of epilepsy, where a detailed cardiac assessment reveals an underlying arrhythmia syndrome as the true explanation for their episodes. This is not a criticism of referring clinicians. It reflects how genuinely difficult these cases can be, and underscores the importance of paediatric cardiac assessment in any child with unexplained episodic loss of consciousness.
When a child presents with a history of unexplained collapse, the evaluation at Dr Giardini's clinic begins with a detailed account of the episode itself, ideally from both the child and any witnesses. The position the child was in, what they were doing, whether there was a prodrome, what the movements looked like, how long recovery took, and how they felt afterwards are all clinically important details.
A 12-lead ECG is performed at every initial assessment. An echocardiogram allows assessment of the heart's structure and function. In children where the history is ambiguous or where an arrhythmia is suspected, ambulatory ECG monitoring may be arranged. For some children, a tilt table test can help reproduce the haemodynamic conditions that provoke vasovagal episodes in a controlled environment.
The aim is to reach a clear diagnosis rather than leaving families in the uncertainty of a working diagnosis that nobody is confident in.
If you witness your child collapsing, try to note the following as clearly as you can: how long the episode lasted, whether there were any movements and what they looked like, whether the child was pale or blue, how quickly they recovered, and how they seemed in the minutes afterwards. A brief video on a mobile phone, if it is safe to do so, can be enormously useful to the clinician reviewing the case. It is not always possible in the moment, but it can make a material difference to how quickly a diagnosis is reached.
Do not move a child who is unconscious unless they are in immediate danger. Place them on their side if there is any concern about vomiting. Call an ambulance if the episode lasts more than three minutes, if they do not recover quickly, or if you are unsure what has happened.
After the event, seek a medical assessment even if the child appears completely well. A single unexplained loss of consciousness in a child always warrants investigation. Most will have a straightforward explanation.
Not necessarily. Brief jerking movements during a faint, known as convulsive syncope, are common and do not indicate epilepsy. They are caused by the temporary reduction in blood flow to the brain and usually last only a few seconds. A specialist assessment will help clarify the diagnosis.
Yes. The two are not mutually exclusive, and some children have both conditions. This is one of the reasons a full assessment, including both cardiac and neurological evaluation where appropriate, is important.
A normal ECG is reassuring, but paediatric ECG interpretation requires specific expertise. Some important abnormalities, such as a borderline QTc interval or subtle Brugada pattern, can be missed without experience in paediatric traces. If there is ongoing clinical concern, a specialist review is worthwhile.
In many cases, both are worth seeing. A good starting point is a paediatric cardiology assessment to exclude a cardiac cause, as this has important safety implications. If the cardiac assessment is normal and the history remains suggestive of seizure, neurology input is the appropriate next step.
Not necessarily. Many children with epilepsy have a normal MRI. The diagnosis of epilepsy is primarily clinical and based on the EEG alongside the history. MRI looks for structural causes and may not show abnormalities in primary generalised epilepsies.
Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist
Written 13/07/2026
Last reviewed 13/07/2026