What is “Syncope” & “Orthostatic Hypotension”?

What is “Syncope”?

“Syncope” means loss of consciousness due to decreased blood supply to the brain. “Syncope” is the most important and common Seizure Mimic.

Some events look almost precisely like seizures but are not seizures. These events are called “Seizure Mimics”, and may be mistaken for seizures.

There is NO electrical surge in the brain with any of these “Seizure Mimics”.

If an episode of  Syncope is mistaken for a Seizure, two things happen: Unnecessary treatment with anti-epileptics, and lack of treatment for the “true” condition (e.g. cardiac arrhythmia).

Which problems cause “Syncope”?

Lets quickly summarize how blood goes to the brain: The heart receives oxygenated blood from the lungs. It pumps this blood to the brain through large blood vessels in the neck.

The heart takes oxygenated blood from the lungs and pumps it to the brain.

4 Groups of problems can cause Syncope:

4 Problems causing Syncope
– Heart problems
– Overactivity of the vagal nerve
– A sudden drop in BP on standing up (Orthostatic Hypotension)
– Problems with blood vessels going to the brain

Which heart problems can cause Syncope?

  • If the heart has become weak (for example due to multiple heart attacks) and not able to pump enough blood, the patient may occasionally lose consciousness. This cause is not very common.
    A weak heart can cause episodes of unconciousness (syncope)
  • More common is an obstruction to blood flow in the heart.
    Valves in the heart usually keep blood moving in only one direction. They can open and close as needed. Sometimes the heart valves (especially a valve called the Aortic Valve) may become damaged and incapable of opening completely – this decreases blood flow to the brain. Sometimes, the heart wall around the Aortic Valve may become thickened producing the same effect – this condition is called “Hypertrophic Sub-Aortic Stenosis”.
    An echocardiogram quickly & easily detects these structural problems.
    Valve problems in the heart may obstruct the flow of blood and cause episodes of unconciousness (syncope)
  • A straightforward problem to miss is Cardiac Arrhythmia. Usually, the heart beats regularly, almost like a clock. But if the wiring system of the heart develops problems, it may have episodes where it suddenly stops beating or starts beating very rapidly without pumping any blood. This condition is called a cardiac Arrhythmia (A = lack of – rhythm).
    Since these rhythm problems occur only once in a while, a single ECG may miss them. Therefore, an EEG machine that is stuck to your chest and records your heart rhythm for many days (A Holter Monitor) may be required. Newer devices called External Loop Recorders (ELDs) can record your heart rhythms for many months at one time!
    You may require a pacemaker if you have a severe cardiac arrhythmia.
    An irregularly beating heart can cause unconciousness (syncope)

What do you mean by overactivity of the Vagal Nerve?

The vagal nerve is a long nerve from the brain to the heart. When it is active, it can decrease the heart rate.

The vagus nerve is an extremely long nerve that goes to many organs, including the heart.

If something overstimulates the vagal nerve, it can become overactive. It then causes the heart to become very, very slow. This causes decreased blood flow to the brain and leads to loss of consciousness.

It is easy to identify the precipitant that caused the vagus nerve overactivity. The following is a list of such precipitants. Only the first one is common:

  • Intense Emotion or Pain: Being startled, the sight of blood, intense fear etc
  • Choking on something. Rarely swallowing very cold or hot food can cause Syncope.
  • Massaging the neck or wearing a very tight collar (which leads to stimulation of sensors called carotid bodies which are connected to the vagus nerve)
  • Passing urine (Micturition Syncope)
  • Rarely: Laughing hard and Orgasms

What can cause a sudden drop in Blood Pressure on standing (Orthostatic Hypotension)?

Meaning of Orthostatic Hypotension
Ortho = Straight,  Statikos = to stand
Hypo = Low, Tension = Pressure

Meaning: Low Pressure on Standing Straight

A drop in blood pressure may cause unconciousness (syncope)

When we stand up suddenly, blood tends to pool in our legs, and our brain tends to get less blood. To prevent this, the blood vessels in our legs contract and our heart beats faster. If these things don’t happen, our heart pumps less blood, and our blood pressure drops. This may cause us to lose consciousness.

When some people stand up suddenly, their brain does not get enough blood. This is alled Postural or orthostatic hypotension.

A sudden and large drop in our Blood Pressure on getting up suddenly is called “Orthostatic Hypotension”.

During your office visit, the doctor may check your BP when you are lying down and then ask you to get up suddenly. While you are standing, he/she will check your BP two more times. If your upper (systolic) BP drops by more than 20 units, or your lower (diastolic) BP drops by more than 10 units, its likely that your events are due to Orthostatic Hypotension.

In some cases, an advanced test called a “Tilt Table Test” confirm the diagnosis.

A tilt table test is used to diagnose postural hypotension.

What can cause this drop in BP? There are many causes! It is difficult to remember all of these causes, but I list them here so that you can understand the monumental task facing your doctor and are patient while he goes through a series of tests to find the exact cause of your orthostatic hypotension:

Causes of Orthostatic Hypotension


Brain Problems– Parkinson’s disease and its sisters like MSA

– As part of normal ageing

Nerve problems (Neuropathy)Damage to nerves controlling the heart & blood vessels due to:

– Alcoholism

– Diabetes

– B12 deficiency


– Many others…

Heart Problems– Cardiac failure

– Valve problems



Not enough fluid in the body due to:

– Drinking very little water

– Diarrhoea or vomiting

Hormonal Problems– Low functioning of the Adrenals (Addison’s)

– Low thyroid levels

– Pheochromocytoma

MedicationsMany, many medications including:

– Blood pressure medications

– Antidepressants

– Anti-parkinson’s medications

Click here for a: [longer list]

The best treatment of Orthostatic Syncope is the treatment of the underlying problem, e.g. replacing the problematic medication. In some cases, medications such a Fludrocortisone, Midodrine or Pyridostigmine may be useful.


What problems with blood vessels can cause Syncope?

Usually problems with blood vessels going to the brain present with a stroke, with weakness on one side of the body. Blood vessel problems presenting only with episodes of unconsciousness and being confused with seizures are rare. Therefore, these are only briefly described below:

  1. If the blood vessels going to the brain – especially the carotid arteries described above – become narrow (e.g. due to accumulation of cholesterol) then the person may have episodes of sudden unconsciousness.
    Rarely, if an artery going to the brain is narrow or is misconnected to the arm vessels, you may have repeated episodes of unconciousness (syncope).
  2. Occasionally when blood that is going to head is shunted away to the arm, the person may get episodes of unconsciousness whenever he/she uses that arm. This condition is called Subclavian Steal syndrome.


Caution: This information is not a substitute for professional care. Do not change your medications/treatment without your doctor's permission.
Dr. Siddharth Kharkar

Dr. Siddharth Kharkar

Dr. Siddharth Kharkar has been recognized as one of the best neurologists in Mumbai by Outlook India magazine and India today Magazine. He is a board certified (American Board of Psychiatry & Neurology certified) Neurologist.

Dr. Siddharth Kharkar is a Epilepsy specialist in Mumbai & Parkinson's specialist in Mumbai, Maharashtra, India.

He has trained in the best institutions in India, US and UK including KEM hospital in Mumbai, Johns Hopkins University in Baltimore, University of California at San Francisco (UCSF), USA & Kings College in London.

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NeuroPlus Epilepsy & Parkinson's Clinic - Dr. Kharkar IconNeuroPlus Epilepsy & Parkinson's Clinic - Dr. Kharkar

near LIC, Dr Balabhai Nanavati hospital, near LIC, Swami Vivekananda Road, LIC Colony, Vile Parle

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  • Avatar Paras Prabhu ★★★★★ 6 months ago
    Out patient is epileptic from about 10 years and her seizure gotten worse during the past year with the frequency of about 3-4 times a week.So we consulted … More Dr. Kharkar. He tried a few medicines, and within 1.5-2 months now the patient is feeling very well now. There are no seizures for 14 days currently.Dr. tried to keep medicines as minimum as possible. He also tried to keep the cost of the treatment minimum.When some of the medicines started showing side-effects, he was quick to switch the medicines to the better options.Overall I think we are getting a best of the available treatments. We thank you very much Dr. Kharkar.
  • Avatar Dr Shobha Sankhe ★★★★★ a month ago
    Dr Kharkar is gem of a doctor with tremendous patience, empathy, genuine concern for his patients .He guides them very methodically & scientifically … More for their neurological ill healthOur epilepsy patient is extremely happy with his treatment , Patient feels better by just visiting him too!May his selfless service to humanity flourish to reach all the needy patients!!
  • Avatar shrruti khanna ★★★★★ a month ago
    I consulted Dr Sidharth for my sister who has become very hyper and aggressive and we could not understand the issue. Keeping in mind she is someone with … More special needs Dr Sidharth was extremely understanding of the situation and did not put her through unnecessary investigation and avoided a very long stay at the hospital. He was infact more keen on her returning home to her natural environment. We highly appreciate Dr Sidharth for his effort and for looking into the matter with utmost care. It was a very difficult decision for my family to get my sister admitted but we are glad we did it under his care.Thankyou Doc.
  • Avatar Prashant Purohit ★★★★★ a month ago
    my name is prashant purohit. I m become completely bed ridden from last 9 months and was unable to walk. I couldnt find out the cause even after visiting … More many doctors and many hospital in Ahmedabad nd jodhpur.started losing hope. A good friend of mine suggested to visit a neurologist. After searching a lot, I came to know about Dr. Siddharth Kharkar and took his appointment in Nanavati Hospital. He examined and said that he suffered from \u201cPKD(PAROXYSMAL KNESIGENIC DYSKNESIA\u201c. He assured us to reverse this in 5 days time. And indeed this happened. I started recovering miraculously. today I am fully well fit I m walking as normal . Many Many thanks to Dr. Siddharth Kharkhar sir for giving me a new life.
  • Avatar Sanjay Pradhan ★★★★★ 7 months ago
    Dr. Kharkar is truly exceptional. He is extremely knowledgeable. But simultaneously, he is extremely patient and kind - taking the time and care to respond … More to all the questions. It is rare to come across a doctor who is not in a hurry to get on to the next patient, but instead, focuses on the one in front with full attention, expertise and compassion. A great experience.
  • Avatar N N ★★★★★ 11 months ago
    We visited Dr. Kharkhar for treatment regarding my mum - who is a multi-stroke patient and has aphasia. Certain medications were creating complications … More with her condition and Dr. Kharkhar was able to help mitigate the issue. We found him and his approach to be incredibly compassionate, considerate, individualized and patient-friendly. He advice is astute, up-to-date and empathetic. His treatment always comes from a deeply human place and is about seeing how to help the patient and their caregivers feel more at ease. Something that is quite rare and refreshing within the medical community.We feel that he genuinely cares about the patients that he is treating and is always kind and respectful in his communication. Moreover, his admin team is very efficient and prompt and it's a pleasure to deal with them.Would highly recommend Dr Kharkhar himself - though we must say our experience with Nanavati hospital itself has been less than ideal.Hope this helps.
  • Avatar Manish Ranjan ★★★★★ a year ago
    I have been visiting Dr Kharkar for treatment of my father. He is a very friendly doctor. He listens to our concerns with lot of patience. He also explains … More the issue in much greater details. He has really been of great help. My father is much better now.
  • Avatar Pinakin Shah ★★★★★ 9 months ago
    One of the best Dr. Gives complete attention and time to listen to patient's history, issues. Explains various options of treatment with pros and … More cons.
  • Avatar Lawrence Castellino ★★★★★ 11 months ago
    Exceptional experience with an expert,Dr. Kharkar is a knowledge house. It is rare nowadays to find doctors with patience, knowledge, and a flair for … More handling patient’s questions, besides Dr. Kharkar’s bedside manners are exemplary. I am privileged to be treated by such an amazing soul. I have told him and will repeat it here that “I am advancing my move back to India although I am a US Citizen, because I know I am in good hands and will be well taken care of. Thanks Dr. Kharkar for your selfless service!
  • Avatar Hemant Kansara ★★★★★ a year ago
    Great doctor!! Really appreciate.The doctor diagnosed to my sister correctly and start treatment, she has good improvement after taking medicine prescribed … More by doctor as no epilepsy attake. We have good experience with the doctor. Thank you

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