Neurological Disorders:Fainting

What is this condtion?

Fainting (medically known as syncope) is a commonly encountered health condition, and is characterized by a sudden and often temporary loss of consciousness mostly due to decreased blood supply to the brain.

Most often fainting results due to a reduction in blood supply to the brain which automatically deprives the brain of nutrients like glucose, oxygen etc; however sometimes blood supply is adequate but the severe deficiency of a particular nutrient in the blood like hypoglycemia (low blood glucose) is what causes it.

What are the Types?

Syncope can be broadly categorized as;

  • Cardiac (heart related) &
  • Non cardiac
This initial categorization is of paramount importance, as experience has shown that cardiac syncope is associated with increased risk of death while the other types generally not.

Causes of cardiac syncope include;

  • Obstructive valvular lesions like mitral valve stenosis
  • Irregular heart beats (cardiac arrhythmias)
  • CHF (congestive heart failure) etc.
Causes or types of non-cardiac syncope include;
  • Reflex type (neurally mediated)
  • Other causes (e.g. postural hypotension, hypoglycemic syncope etc)
The reflex (neurally) mediated type is further grouped as;
  • Vasovagal syncope
  • Situational syncope (e.g. while urinating, swallowing, defecating, shaving etc)
The reflex (neurally) mediated syncope is generally more frequent in young adults while the cardiac causes and postural hypotension are more frequent in older people.

How does syncope result?

For cardiac type, irrespective of the precipitating factor, the common immediate precursor to fainting is reduced cardiac out put. Decreased cardiac out put deprives the brain of its nutrients and results in syncope. There are several cardiac causes including few of them mentioned above and some more causes include;

  • Adams-stoke’s syndrome
  • Cardiomyopathies
  • Sick-sinus syndrome
  • Aortic dissection etc.
The vasovagal type involves a seemingly complex neural mechanism that results in the activation of so called ‘vasodepressor’ mechanism, which promotes abnormal pooling of blood in the peripheral vessels and diminished cardiac out put and this suppresses the brain perfusion and results in syncope.

Situational syncope is similar to vasovagal type except for an individual patient the syncope is coupled with a particular situation like;

  • Micturition syncope (during urination)
  • Deglutition syncope (during swallowing)
  • Defecation syncope (during passing bowels)
  • Cough syncope (during coughing) etc.
Another example for this type of syncope is carotid sinus syncope. Carotid sinus is the dilated proximal portion of internal carotid artery that supplies brain and is located in the neck. A pressure on this region can activate the vasodepressor mechanism and induce syncope. Wearing a tight collar, neck tie, or during shaving or massage of this area etc can induce syncope.

Postural hypotension may be caused when patient is dehydrated, or on medications that lower blood pressure or has neuropathies (nerve damage) that cause the dilatation of blood vessels in the legs promoting abnormal pooling of blood resulting in decreased cardiac out put.

How does patient present?

The episode of fainting (the actual passing out) is usually preceded by one or more of these symptoms;

  • Dizziness
  • Graying or blurring of vision
  • Feeling your heart beats (palpitation)
  • Abnormal Sweating
  • Cold & clammy feeling
  • Nausea & vomiting
  • Convulsive syncope (brief convulsive movements in few patients but not true fits)


Although the syncope episode is diagnosed clinically, but to find out what caused it, generally a bunch of investigations are necessary as below (these tests are ordered on case to case basis).

• CBC (complete blood cell count)
• Serum electrolytes like glucose, sodium etc
• ECG & sometimes a holter monitor
• Cardiac stress test
• Echo
• Cardiac enzymes like CPK, CPK MB
• CT and/ or Brain MRI scan
• EEG (Electroencephalogram)
• Carotid Duplex (ultrasound)
• MRA (magnetic resonance angiography)
• Tilt table test
• Massage of the carotid sinus etc


The treatment during or immediately after the syncope episode is to take the patient to ER (emergency room) and then if required to admit to the ICU (Intensive care unit) or to the regular ward floor. IVF (intravenous fluids) are given if low blood pressure is noted. Other measures may include intravenous glucose, nasal oxygen etc.

Once patient is out of acute danger and stable the long term treatment regime begins that focuses on preventive measures and includes;

• Avoiding the precipitating factors like seeing blood, surgery etc
• Maintaining adequate fluid intake (avoiding dehydration)
• Avoiding hypoglycemia, so eat adequately
• Avoiding undue stress as much as possible
• Avoiding sleep deprivations (long night outs etc)
• Daily and frequent leg exercises to facilitate return of blood to the heart
• Tight leg stockings (mainly useful for orthostatic hypotension)
• Medications like prozac (fluoxetine), (inderal) propranolol, midodrine, florinef (fludrocortisone)
• Wearing loose neck collar, ties, shaving precautions over the neck for patients with carotid sinus syncope
• Heart problems must be identified and treated aggressively as early as possible since there is a risk of death related with this type of fainting.

Surgical interventions:

If patient continues to experience these episodes despite the above measures then certain patients especially the one with the vasodepressor type may benefit from the placement of a cardiac pacemaker. If heart arrhythmias are the concern then a heart defibrillator is a consideration. Now-a-days there are hybrid devices that contain both defibrillators and pacemaker for those who need them.

A Neurologist is frequently involved in the care of these patients.

Fainting to Neurology Articles


Share this page:
Enjoy this page? Please carry it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.