Reflex Anoxic Seizures

Also known as: Infantile Vasovagal Syncope; Reflex Asystolic Syncope


RAS is a particular type of convulsive syncope (transient loss of consciousness) with stiffening and or shaking. It is neither epileptic (see entry Epilepsy), nor due to deliberate breath-holding. It is a type of severe syncope or ‘faint’, caused by a temporary loss of the supply of blood carrying oxygen to the brain.


Last updated September 2020 by Dr W Whitehouse, Clinical Associate Professor and Consultant Paediatric Neurologist, University of Nottingham and Nottingham Children’s Hospital, Nottingham, UK.

Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information  provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.

What are the symptoms?

RAS can occur at any age. It is most common in toddlers, who usually grow out of it. However, it can reoccur in adolescence and adulthood as “cardio-inhibitory vasovagal syncope”.

Any unexpected pain, fear, fright or surprise can trigger an attack. During the RAS the heart stops, and typically the eyes roll, there is a deathly pallor (paleness) and clenching of the jaw. The body can stiffen, breathing becomes shallow or stops, and there may be jerking movements of the arms and legs.

After a few seconds to half a minute, the heart starts beating again and the body relaxes. The child may remain unconscious for a few minutes to a few hours afterwards, in a deep sleep.

The frequency of attacks varies, and most will have some attacks that seem unprovoked. They look frightening but are not life-threatening.

What are the causes?

It is a severe “neurally mediated” (reflex) syncope (transient loss of consciousness due to a temporary loss of the supply of blood carrying oxygen to the brain).

The reflex involves the vagus nerve which when activated slows the heart beat down, and can stop the heart beating (called “asystole”) for up to 30 seconds or more. However, it will always start beating again before any damage occurs. It is sometimes called “Reflex Asystolic Syncope”.

How is it diagnosed?

RAS is often misdiagnosed as breath holding (reflex expiratory apnoea syncope), temper tantrums, or epilepsy.

A good witness description of the attacks and the triggers is key. A GP may refer the child to a paediatrician, paediatric neurologist, or paediatric cardiologist. Sometimes the following tests are used:

  • ECG (electrocardiogram): wires placed on the chest so the heart rhythm can be monitored
  • EEG (electroencephalogram): wires placed on the head so the electrical activity of the brain can be monitored, usually combined with ECG
  • heart rhythm monitor: records ECG away from the hospital over hours or weeks.

How is it treated?

As RAS is not life threatening, the main thing is to provide information and support. The doctors will want to exclude any heart disease by their examination and a 12-lead ECG.

In a few rare cases the RAS is so severe or frequent that medical treatment is prescribed. We use antimuscarinic medicines, which block the ‘slow-down’ signal from the vagus to the heart, e.g. glycopyrronium. If these are ineffective or not tolerated, cardiac pacing may be appropriate in a few older children severely disabled by RAS.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
The genetics have not been established, but it does run in some families.

Prenatal diagnosis
There is no prenatal diagnosis at present.

Is there support?

STARS (Syncope Trust And Reflex anoxic Seizures)

Tel: 01789 867 503

The Trust is a Registered Charity in England and Wales No. 1084898. It provides information and support to individuals and families affected by syncope and Reflex Anoxic Seizures. The Trust holds regional, national and international meetings and patient days.

Group details last reviewed September 2020.

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