What is Neurocardiogenic Syncope?
Neurocardiogenic (Vasovagal) Syncope
Neurocardiogenic syncope, also called vasovagal syncope, is when you faint because your body overreacts to a trigger, such as the sight of blood or intense emotional stress (1).
Fainting should always be checked by a medical provider, because it can sometimes be caused by a serious heart problem. Call 911 or get emergency care if fainting happens during exercise, comes with chest pain, a racing or pounding heartbeat or shortness of breath, causes an injury, or happens in someone with heart disease or a family history of sudden death.
How Common Is Neurocardiogenic Syncope?
Syncope, or fainting, is common. It is a symptom, not a disease, and it is grouped by its cause. Fainting can be caused by neurological, metabolic, psychiatric or heart problems.
Neurocardiogenic syncope is the most common type of fainting, and it is usually not dangerous on its own. About 3% of men and 3.5% of women experience it at some point in their lives. Fainting becomes more common with age, affecting up to 6% of people over 75. Vasovagal syncope can happen at any age, in people with or without other health problems (2). It is often grouped with other forms of dysautonomia, which are problems with the autonomic nervous system.
What Causes Vasovagal Syncope?
Vasovagal syncope happens when the autonomic nervous system overreacts to a trigger. This sudden, exaggerated response lowers blood flow to the brain and causes fainting (3).
What Is the Autonomic Nervous System?
The autonomic nervous system controls the body’s automatic functions, such as blood pressure, heart rate, digestion, breathing and sexual function. It has two branches: the sympathetic and parasympathetic systems.
The sympathetic system is part of the stress response. It raises heart rate and blood pressure and sends blood to the muscles and away from the skin. It’s often called the “fight or flight” system.
The parasympathetic system does the opposite. It lowers heart rate and supports digestion. It’s often called the “rest and digest” system.
These two systems constantly work together to keep your heart rate, blood pressure, stress response and many other functions in balance.
When you sit or stand up, gravity pulls blood toward your feet. A healthy autonomic nervous system quickly adjusts blood pressure, heart rate and muscle tone to keep blood flowing to your brain (4).
What Happens in Neurocardiogenic Syncope?
In neurocardiogenic syncope, a trigger leads to an inappropriate response from the autonomic nervous system. Sympathetic activity suddenly drops, so blood vessels widen. Less blood returns to the heart, and blood pressure falls. At the same time, parasympathetic activity through the vagus nerve slows the heart. Together, these reduce blood flow to the brain, and the person faints (5).
What Are the Symptoms of Vasovagal Syncope?
Before fainting, people may notice pale skin, lightheadedness, nausea, tunnel vision, feeling hot or cold, clammy sweating and blurred vision. During the episode, others may notice brief jerking movements, a slow or weak pulse and dilated pupils.
Recovery usually starts in less than a minute. But standing up too soon, within about 15 to 30 minutes, can lead to fainting again (1).
What Happens in the Nervous System With Vasovagal Syncope?
Neurocardiogenic syncope involves a sudden, excessive response from part of the lower brainstem called the medulla. The medulla contains centers that can rapidly lower blood pressure and heart rate, in part by acting through the vagus nerve.
A reflex from the heart is also thought to be involved. The heart contains sensory nerves called cardiac C fibers that act like a brake to keep the heart from beating too fast or too forcefully. When they’re stimulated, they signal the medulla, which slows the heart and lowers blood pressure.
These brainstem centers receive input from many parts of the brain and body. That’s why reflex fainting can happen in several different ways, collectively called neurally mediated reflex syncope.
What Are the Different Types of Reflex Syncope?
Neurocardiogenic (vasovagal) syncope. One theory is that a trigger such as a sudden fright, pain, panic or the period after exercise causes a surge in sympathetic activity, making the heart beat faster and harder. This stimulates the cardiac C fibers, which trigger an exaggerated response from the brainstem and a sudden drop in heart rate and blood pressure.
Carotid sinus syncope. Pressure sensors in the carotid arteries of the neck, called baroreceptors, are stimulated by things like turning the head, shaving, a tight collar or pressure on the front of the neck. The brainstem overreacts, causing fainting.
Situational syncope. Everyday actions such as coughing, sneezing, swallowing, urinating or having a bowel movement stimulate sensors in the lungs, heart, bladder or digestive tract. These signals travel through the vagus nerve to the brainstem, which overreacts.
Glossopharyngeal and trigeminal neuralgia syncope. Throat or face pain stimulates nerves that signal the brainstem, which overreacts and causes fainting (6).
Vestibular syncope. Vertigo or a false sense of motion from the inner ear and brain sets off the reflex, causing fainting (7). You can read more about this below.
How Does Vasovagal Syncope Affect Your Life?
Fainting itself is usually harmless, but it can be frightening and embarrassing, and sudden falls can cause injuries. Some people with vasovagal syncope suffer concussions from falls. Concussions can affect the brainstem, which may make fainting episodes more likely (8).
The Inner Ear’s Role in Blood Pressure
Your inner ear does more than help you balance. Through a reflex called the vestibulosympathetic reflex, signals from your inner ear reach blood pressure control centers in the brainstem and help adjust blood pressure and heart rate when you change position. This reflex responds to head movement before blood pressure has a chance to fall, while the baroreceptor reflex, which senses blood pressure in the large arteries, takes a second or two to catch up. That head start matters when you stand up quickly (9).
To use inner ear signals well, the brain has to clean them up. The inner ear’s motion sensors, the semicircular canals, give an imperfect signal, and its gravity sensors, the otoliths, can’t tell the difference between tilting your head and moving in a straight line. The brainstem and cerebellum solve these problems with a process called velocity storage, which combines and smooths these signals to estimate how your head is really moving and which way is down (9).
A 2022 study in the Annals of Clinical and Translational Neurology looked at 53 people with vestibular syncope, meaning fainting triggered by vertigo (7). More than a third had repeated episodes, and about 13% had potentially life-threatening injuries from falls. Abnormal inner ear tests were common, including abnormal head impulse tests in 31%, and about 1 in 5 also had orthostatic hypotension. The researchers proposed that when velocity storage produces a false sense of motion, the brain may adjust blood pressure for a position change that never happened. The baroreceptor reflex can then overcorrect, slowing the heart and dropping blood pressure, which can lead to fainting (7, 10).
Vestibular syncope works through the same reflex fainting pathway as neurocardiogenic syncope, but the trigger is a faulty motion signal from the inner ear and brain. The researchers concluded that vestibular syncope can occur with many different inner ear disorders, and that careful evaluation is needed to help prevent repeated falls and serious injuries. This research is a core part of how we approach fainting disorders.
That’s why we measure these systems so carefully. Videonystagmography (VNG) records eye movements that reflect how the brainstem and cerebellum are processing inner ear signals, including velocity storage. The video head impulse test (vHIT) measures how well each semicircular canal is working. CAPS computerized posturography shows how well your brain uses inner ear, visual and body-position information to stay upright.
How Is Vasovagal Syncope Diagnosed and Treated?
Testing usually starts with a heart evaluation to rule out structural heart disease and abnormal heart rhythms. After that, a tilt table test may be done, in which you lie on a motorized table that tilts you upright. People with neurocardiogenic syncope often show a sudden drop in heart rate, blood pressure or both when tilted upright (11).
Vasovagal syncope is often managed with education. People learn to lie down and raise their legs when they feel an episode coming, to recognize and avoid their triggers, and to use other strategies their provider recommends (12).
Medications can help some people. Options include midodrine, which tightens blood vessels, fludrocortisone, which increases blood volume, and in some cases SSRI antidepressants. Your medical provider can help weigh the benefits and side effects.
How the NeuroRescue Program Can Help
Our care is designed to work alongside your cardiologist, physician and other providers, never in place of them. Please make sure heart causes of fainting have been ruled out, and don’t change or stop any medication without talking with your prescriber.
Our care focuses on the nervous system reflexes involved in neurocardiogenic syncope. We use detailed testing to evaluate the brainstem, brain, cerebellum and balance systems that may be involved in your episodes, and we use what we learn to design a personal program of exercises and therapies, with the goal of helping you gain more control over your symptoms and get back to the things you love.
One of the brain’s most important jobs is figuring out where you are in the world. It uses your inner ear to sense where your head is in relation to gravity and how it’s moving, your muscles and joints to sense where your body is and what it’s doing, and your eyes to sense where you are in relation to everything around you. Your brain combines all of this into a picture of where you are, so you can respond to the world around you.
Your brain organizes this information as a set of maps: a vestibular map from your inner ear, a body map from your muscles and joints, a visual map from your eyes, and others. These maps need to agree with each other about where you are.
In some people with neurocardiogenic syncope, these maps may not match. Your eyes, inner ear and body may be sending different messages about where your head is in relation to gravity. Your inner ear also helps your body adjust blood pressure when you change position (9). When you go from lying down to sitting or standing, mismatched signals may make it harder for your brain to adjust blood flow to your head. Eye movement exercises can activate brain and brainstem areas involved in the autonomic nervous system (13).
Our approach is to first work on improving how your visual, vestibular and body-position systems function on their own. Then we gradually train them together in different positions relative to gravity, with the goal of helping your nervous system respond more appropriately when you change position.
Depending on your needs and test results, your program may include specific eye exercises (14), vestibular therapy (15), electrical stimulation (16), light therapy, also called photobiomodulation (17), and exercises in a virtual reality environment (18). The therapies we recommend are always chosen based on your testing and exam findings.
How the NeuroRescue Program Works
Your NeuroRescue Program begins with your Discovery Day. We start with a detailed history of your condition and your life on a timeline. This helps us understand the factors that may have contributed to where you are now, and identify related conditions that may be making it harder to move forward.
We measure how your visual, vestibular and balance systems are working through computerized analysis of your eye movements, inner ear reflexes and balance under different conditions. Our testing includes videonystagmography and saccadometry to measure several types of eye movements, the video head impulse test to measure inner ear reflexes, and CAPS computerized posturography to assess your balance under different sensory conditions. We also use NeuroSensoryMotor Integration testing to evaluate hand-eye coordination and cognition, and Virtualis testing to assess dynamic eye tracking and your perception of vertical in a virtual reality environment.
We combine this with a thorough physical and neurological exam of your sensory, motor, autonomic and cognitive systems. We also review any relevant lab work, imaging and prior testing, and integrate it with our findings.
Together, this helps us understand which parts of your nervous system are working well, which are struggling, and how quickly they tire. We use that information to design your personal NeuroRescue Program, aimed at improving function in the systems that need support and helping them work together. Our testing also helps us decide when to push and when to let you rest.
Our goal is to help you feel steadier and more confident when you stand, move and go about your day.
Your Next Step
Living with vasovagal syncope can make you afraid to go about your day, but you don’t have to keep living on edge. To find out if the NeuroRescue Program is right for you, contact one of our patient care coordinators to schedule your Discovery Day.
It’s never too late to take the next step.
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