Syncope, a dizzy subject


What is syncope?

Syncope is transient fainting due to decreased blood flow towards the brain.


A drop in blood pressure


When the blood pressure drops below a certain level, the brain stops functioning and we lose consciousness. In general, we fall to the ground when this occurs.

When the victim is on the ground, the blood that was in the legs due to gravity before the loss of consciousness returns to the heart and the pressure balances again. The brain resumes and we wake up. This fainting lasts less than 2 minutes.

The symptoms felt are the same as those of a pre-syncope or lipothymia: by dizziness during the low-pressure period, possible blurred vision and short memory loss. These symptoms of pre-syncope vary in length from one individual to another and depend on the cause of the syncope. Some patients may have none of these symptoms.


Other causes of unconsciousness

A syncope can be distinguished from other conditions of loss of consciousness such as:

• Convulsion (caused by abnormal and excessive neurological activity),

• Coma (prolonged fainting caused by cerebral dysfunction)

• Pulmonary embolism (a clot blocking an artery in the lung).


A frequent cause of consultation

Syncope is a common reason for consultation, accounting for about 1% of emergency medical assessments each year.

This percentage underestimates the actual frequency of syncope since it is only a minority of victims who end up consulting.


Different types of syncope

Several conditions can lower blood pressure.

There are several types of syncope. The main ones are:

• Reflex syncope

Orthostatic syncope, or in other words, syncope secondary to a decrease in pressure when going from laying down to an upright position.

Heart syncope.


Reflex syncope


Reflex syncope is the most common cause of syncope in the population. Cardiac syncope and orthostatic syncope follow.

The reflex syncope gets its name because of an abnormal reflex of the brain in response to stimulation.

This reflex causes bradycardia, or, in other words, a slowing of the heart rate or asystole (the heart temporarily stops beating). Furthermore, a dilation of the blood vessels causes a drop in pressure and the syncope ensues.

"Reflex" syncopes are subdivided as follows:



Carotid sinus syndrome (sensors in the arteries of the neck)


Generality about all causes of syncope

Each of these types of syncope and the different reflex syncope will be reviewed.

The probabilities of syncope vary according to age, with cardiac and orthostatic causes being more common in the elderly. The tests performed and the treatments differ according to the identified or suspected cause of the syncope during the medical evaluation.

It is important to understand the importance of the doctor’s questionnaire when a person consults for a loss of consciousness.

The doctor wants to perfectly understand the events that preceded the syncope. All the details, as banal as they may seem, help the doctor in the search for the cause and guide him in his choice of investigation, if it is considered necessary.


In conclusion

In summary, syncope is a vast subject as there are many possible causes.

In general, syncope is benign and does not affect in any way the risk of cardiovascular diseases or mortality.

However, the risk of injury exists, but it is related to the fall.

The best way to prevent them is to change habits, according to the different types of syncope.

As for cardiac syncope, it often requires a more specific treatment.


There is a summary table of loss of consciousness: