The Terminology Guide

Glossary of Terms


Common term for unexplained loss of consciousness


Medical term for a blackout or ‘Transient Loss of Consciousness’ from any cause

Syncope (Greek word for faint)

A blackout/T-LoC arising from too little blood getting to the brain

There are three main reasons for blackouts/T-LoCs:

Cardiovascular (syncope)

When insufficient blood reaches the brain


In diseases such as epilepsy


Resulting from a psychological disorder


Relatively common disorder usually associated with collapse, resulting from a sudden reduction in blood supply to the brain. Affects 30-50% of population.


Relatively rare disorder of brain function characterized by recurrent sudden attacks of altered consciousness and abnormal movements caused by electrical disturbances in the brain. Affects <1% of population.

T-LoCs caused by epilepsy are also referred to as seizures. Epilepsy is frequently referred to as a “seizure disorder”. During a seizure, the sufferer might also suffer convulsions, abnormal limb or facial movements and loss of bladder control.

Key phrases used by patients to describe blackouts/T-LoCs:

  • Fits
  • Blackouts
  • Passing out
  • Collapses
  • Funny turns
  • Attacks
  • Seizures

Syncope terms and definitions

Syncope is technically defined as a transient, self-limited loss of consciousness, usually leading to collapse. The onset of syncope is relatively rapid, and the recovery is usually prompt. The underlying mechanism is transient global cerebral hypoperfusion.

In simple language, syncope is a sudden blackout/T-LoC which is normally brief but can last for several minutes and in some cases longer, does no permanent damage, and which arises from a temporary reduction in the blood supply to the brain. During a syncopal attack, jerking movements of the arms and legs and arching of the back are sometimes witnessed, along with snorting/clicking noises from the nose and throat. Upon regaining consciousness the patient is often emotional, disorientated and ‘hung-over’. It can take some time to recover completely – children often sleep for two or three hours after an attack and it can take adults two or three days to feel completely back to normal.

Additionally, the above medical definition takes no account of the mental distress and anxiety that syncope can cause. Simply knowing that another attack can take place at any time without warning leads to a dramatic reduction in freedom and quality of life, even with only one or two attacks a year.

Syncope can result from many cardiovascular causes:

  • Cardiac causes
  • Structural heart disease
  • Heart rhythm problems
  • Vascular causes
  • Reflex causes (explained below)
  • Situational causes (such as coughing, straining, passing urine, dehydration)
  • Postural causes (standing up to quickly)

Reflex syncope

The vast majority of syncope results from reflex vascular causes. To protect itself, the human body relies upon many nervous reflexes. These include blinking and sneezing. They are all spontaneous and involuntary. Among these reflexes are those that help to maintain blood pressure. These act on the muscles and blood vessels in our limbs. Upon detecting a sufficient drop in blood pressure, the nervous system fires the reflexes which cause these muscles and vessels to contract. This increases the pressure in the system and ensures that the brain has enough blood supply.These reflexes are transmitted via the vagus nerve. It has been suggested that reflex syncope arises when an over-sensitive vagus nerve ‘cuts out’ when something unexpected happens, such as a bump, fright or surprise. Among other things, the vagus nerve transmits heart beat information so, when it cuts out, the heart momentarily stops and blood ceases to reach the brain, resulting in syncope.

Toward ideal terminology

Traditionally, syncope has been given many names. Children are diagnosed with reflex anoxic seizures (also known as reflex asystolic syncope), whereas adults receive a diagnosis of vasovagal syncope (also known as neurocardiogenic syncope). There is a growing consensus among physicians and patients that these should be replaced with common and easy-to-understand terminology. A popular current term for this is reflex syncope.

Why “Reflex Syncope?

A failure in the system of vascular reflexes which results in reflex anoxic syncope. Upon failing:

  1. The protection system (reflex) doesn’t work
  2. The brain is left with insufficient oxygen from the blood (anoxia) and
  3. The sufferer blacks out (syncope)

Hence…Reflex Syncope

Current terminology

To illustrate the need for a simple term for reflex syncope, below is a list of many current terms used in the English-speaking world for syncope in a variety of patient groups:

  • Blood illness injury phobia
  • Bradycardia syndrome
  • Emotional fainting
  • Malignant vasovagal syncope
  • Neurally mediated hypotension
  • Neurally mediated syncope
  • Neurocardiogenic syncope
  • Pallid breath holding spells
  • Pallid infantile syncope
  • Pallid syncope
  • Reflex anoxic seizures
  • Reflex asystolic syncope
  • Reflex syncope
  • Valsalva syncope
  • Vasodepressor syncope
  • Vasovagal syncope (VVS)
  • White breath-holding