Trigeminal Cardiac Reflex

Hi, my name is Dr Ross Hauser. Many of us in the healthcare field have heard the term vasovagal (drop in blood pressure). It is a common occurrence when medical procedures are being done or if someone has severe pain. These people suddenly don’t feel good, feel like vomiting, turn pale and the skin may get clammy. It can be a dangerous situation if the blood pressure gets too low. This video will discuss trigeminal cardiac reflex or TCR. This is also a sudden or prolonged drop in blood pressure caused by stimulation of the trigeminal nerve.

Upper Cervical Influence on the trigeminal nerve. Where do symptoms come from?

In the caption of this image, the trigeminal nerve/spinal cord tracts can reach the C3 level. This indicates that upper cervical spine instability can manifest as symptoms related to trigeminal nerve dysfunction, this would include the problems of a drop in blood pressure.

The trigeminal cervical nucleus, the nerve tract for the trigeminal nerve in the spinal cord, because it can descend to the C3 level, means that upper cervical instability, the wandering, and instability of the cervical vertebrae, can rub, compress, impinge, and irritate the nerve tract for C1, C2, and then those can irritate the trigeminal nerve and you can get trigeminal symptoms including trigeminal cardiac reflex.

Focus on the trigeminal cardiac reflex producing a wide array of cardiorespiratory manifestations

A lead researcher in trigeminal cardiac reflex is Dr. Tumul Chowdhury, MD, most recently of University Health Network, Toronto Western Hospital. In a 2017 paper in the Frontiers in Neurology (1), he along with co-authors wrote: “Trigeminal (nerve) innervated areas in the face, nasolacrimal (tear drainage system), and nasal mucosa (soft tissue of nasal cavity) can produce a wide array of cardiorespiratory manifestations that include apnea, bradypnea (abnormally slow breathing), bradycardia (abnormally slow heart rate), hypotension (low blood pressure), and arrhythmias. This reflex is a well-known entity called “trigemino-cardiac reflex” (TCR). The role of trigeminal cardiac reflex is investigated in various pathophysiological conditions especially in neurosurgical, but also skull base surgery procedures.”

We will be citing Dr. Chowdhury’s further work below. Indeed, much of the research surrounding trigeminal cardiac reflex relates to complications during or following surgery. In fact, in 2015 Dr. Chowdhury and co-authors wrote in the Journal of neurosurgical anesthesiology: “Clinically, the trigeminal cardiac reflex has been reported in all the surgical procedures in which a structure innervated by the trigeminal nerve is involved. “(2)

A sudden drop in blood pressure from dental procedures

In July 2017 an observational study (3) looked at one hundred and thirty-five patients (69 males and 66 females) who had dental implant surgery. Heart rate and blood pressure were monitored during the procedure. The researchers found significant decreases in heart rate and blood pressure during the implant procedure and after the procedure. Patients who had implants in the maxilla (upper jaw) had greater risks for blood pressure drop than those receiving implants in the mandible. The researchers concluded: “A significant heart rate and blood pressure reduction possibly due to trigeminal cardiac reflex can occur during dental implant surgery. Therefore, dentists should monitor the hemodynamic changes during dental implant surgery to prevent the possible occurrence of medical risks related to trigeminal cardiac reflex.”

The same researchers also reported in June 2018 (4) that root canal procedures may cause trigeminal cardiac reflex by stimulation of the trigeminal nerve during the initial removal of the dental pulp.

A May 2022 paper describes two extractions in two patients. (5)

The first patient was a 44-year-old female patient with severe decay in the upper right back maxillary right third molar. During a routine extraction, suddenly and to the great surprise of the attending dentist who is the author of this case, the patient became unconscious and stopped responding. Her pulse rate fluctuated between 33 and 42 beats per minute, her respiration rate was 8–9 cycles per min, and her blood pressure was recorded to be 90/70. After approximately 30–40 min, her heart rate started restoring up to 60–65 beats per minute, her respiration rate was 12–14 cycles per minute, and the blood pressure recorded was 100/80 mmHg. The patient was stable, conscious, oriented, and responding well to the commands and was discharged in a fair condition after a few hours.

The second patient was a 29-year-old female who came to the dentist to also have an upper right back maxillary right third molar removed. After administering 2% lignocaine with adrenaline, the tooth was extracted and the patient was quite happy. The dentist reported that suddenly she went unconscious trying to get up from the dental chair and stopped responding. The dentist started managing the patient expecting it to be a vasovagal syncope, her pulse was not recordable and no respiration was noticed, medical assistance was summoned; however, to the next surprise, the patient suddenly started responding after a gasp of deep respiration. Within 15–20 min, her heart rate and respiration rate were recorded to be within normal limits and her blood pressure was 110/70.

The dentist/authors of these two cases wrote: “Monitoring of vitals such as heart rate and blood pressure during simple oral procedures such as teeth extraction is deemed necessary to identify any alterations which can be attributed to the onset of trigeminal cardiac reflex or trigeminal cardiac reflex-mediated syncope. In case of encountering this sudden reflex, cessation of the procedure leading to the withdrawal of stimulus usually reverses the phenomenon, but the need for further management should be anticipated well in time to avoid catastrophic complications.”

A sudden drop in blood pressure from jaw surgery

A patient’s story was present in the BMJ (British Medical Journal) case reports. (6) This case centers on a 23-year-old man who was having surgery to correct mandibular prognathism (his lower jaw was bulging out past the upper jaw). The patient had previous shoulder surgery was no adverse events, nor did he have a history of cardiovascular disease. During his jaw surgery, everything was normal when suddenly his heart rate dropped sharply to 25–30 beats/min. The surgical procedure was interrupted, and the heart rate recovered to 70–75 beats/min with sinus rhythm.  Eventually, the surgery was complete when intravenous lidocaine and an anticholinergic agent (to block the parasympathetic nervous system receptors – the system to reduce heart rate and blood pressure) were administered simultaneously.

The doctors suggested: “Although TCR rarely occurs during orthognathic surgery (1 – 2%), remarkable arrhythmia and bradycardia may occur during the manipulation of the mandible, and both surgeons and anaesthesiologists should be aware of its possibility and able to judge and manage it promptly.” When manipulating the mandible overstimulation of the trigeminal nerve may occur.

Trigeminal cardiac reflex –  sudden drop in heart rate and blood pressure without a surgical cause

I wanted to read some texts I received from a local cardiologist. These texts will explain how many patients who have bradycardia (pulse rate under 60) and may experience syncope, dizziness, or fainting are looked at by the cardiologist. The cardiologist’s job is to see if there is some problem with the heart so they’ll normally order an echocardiogram. If the echocardiogram does not find an intrinsic heart problem, if there is not, then the thinking is to explore the electrical input to the heart or the electrical circuits within the heart.

The vagus nerve.

The function and dysfunction of the cardiovascular system in relation to the vagus nerve are explained at great length throughout this website. Links are provided below to these articles. Here is a summary discussion.

What are we seeing in this image? This image describes the impact of compression of the vagus nerve and the glossopharyngeal nerve on heart rate and blood pressure

This image describes the impact of compression of the vagus nerve and the glossopharyngeal nerve on heart rate and blood pressure

A brief understanding of the autonomic nervous system (ANS) and Dysautonomia

The autonomic nervous system (ANS) controls our bodies’ automatic functions. It is the system that helps regulate heart rate, blood pressure, and other vital functions.

  • Dysautonomia is a dysfunction of the nerves that regulate the involuntary functions of the body such as heart rate, and blood pressure.

Vagus nerve malfunction and dysfunction.

The vagus nerve is the longest and most widely extended of the nerves of the body. There are two, a left side and a right side vagus nerve. Many of the vagus nerve sensory fibers that regulate blood pressure are in the carotid artery and the glossopharyngeal nerve fibers. The nerves are part of a network that carries impulses to the brain that tells the brain what is going on with heart rate and blood pressure from moment to moment. For example, if your blood pressure is going too low you need this network to alert the adrenaline system or the sympathetic nervous system to upregulate your blood pressure. If the communication network that carries these messages is off, so is the regulation of your blood pressure. The communication center is within the vagus nerve network. Cervical spine instability can lead to compression or impingement of the nerve and an alteration of the nervous system’s ability to convey proper messaging.

  • Vagus nerve degeneration can be very serious. Widespread arterial vasospasm (closure of the artery through spasms) in the body can occur.
  • The most common symptoms of vagus nerve dysfunction (Cervicovagopathy – vagus nerve degeneration and/or the interruption and distortion of vagal nerve impulses, dysautonomia) include chronic pain, fatigue, dizziness, lightheadedness, spinning or pulling sensation (in a particular direction), weight loss, poor focusing, exercise intolerance, emotional lability, inflammation, heartburn, bloating, diarrhea, tinnitus, headache, anxiety, depression, brain fog, swallowing difficulty, vision changes, and inability to handle stress well.


The cardiologist says there’s nothing wrong with your heart

Vasovagal or a drop in blood pressure bradycardia is a very common problem. Many times cardiologists cannot find a cause and will suggest to patients “There’s nothing wrong with your heart, something else is going on, I’ll go send you to the neurologist.” Sometimes the cardiologist will recognize that this may be a problem of the vagus nerve and that the patients are describing symptoms that may be coming from neck pain and neck instability, such as other common neurologic-like, digestive-like and cardiovascular-like symptoms. Then a recommendation may include a doctor who can look at the structural problems of the neck as a possible cause of cardiovascular-like symptoms.

Correspondence between a cardiologist and Dr. Hauser:

At this point in the video, Dr. Hauser discusses a patient case with the cardiologist.

Cardiologist: Saw a (younger) patient with vasovagal syncope (fainting spells), fairly recurrent despite normal treatment. She also has hyperhidrosis or excessive sweating and upper hand cold extremities.  I think she has an imbalance in her sympathetic nervous system. Please see our article: Determining the Cause(s) of Dysautonomia, Vagopathy, and Autonomic Nervous System Imbalances.  I am ruling out any cardiac issues. I think she has autonomic dysfunction, the patient should come and see you to see if she has cervical instability.

The Trigeminal cardiac reflex is a neurologic response to stimulation of the trigeminal nerve. Typical symptoms are a drop in blood pressure and heart rate. Stimulation of the trigeminal nerve can be sudden and life-threatening.

The slide above is adapted from Meuwly C, Chowdhury T, Sandu N, Golanov E, Erne P, Rosemann T, Schaller B. Definition and Diagnosis of the Trigeminocardiac Reflex: A Grounded Theory Approach for an Update. Front Neurol. 2017 Oct 9;8:533. (7)

  • Sudden onset of bradycardia and hypotension, can be life-threatening when trigeminal sensory branches are stimulated.
  • Caused by parasympathetic dysrhythmias (the parasympathetic nervous system, lead by the vagus nerve, is slowing the heart rate too much) and is associated with other potential symptoms including gastric hypermotility and apnea.
  • Possible cause of sudden adult death syndrome and other serious life-threatening cardiac conditions.

Reflex arc:  sensory stimulation of trigeminal nerve through the gasserian ganglion (provides sensation to head and face and chewing muscles – see below for a connection between teeth grinding and abnormally slow heart rate) to the sensory nucleus of the trigeminal nerve (fourth ventricle) these then connect to the nucleus ambiguous (responsible for swallowing and speaking) and dorsal motor nucleus (which sends signals to heart and lungs) of vagus which then activates the cardioinhibitory parasympathetic vagal neurons (slows the heart rate) which leads to the clinical symptoms (among them low blood pressure, dizziness, and fainting.)

Autonomic innervation of the heart

In the image above, we see the vagus nerve and the cardioinhibitory center (the slow-the-heart down center) in the medulla that goes to the heart to slow the heart rate down. If this connection is altered, symptoms develop. Sometimes they are mystery symptoms because the connection between the nervous system and the heart has not been diagnosed. Hauser’s Law is when you have a symptom or you’ve been diagnosed with a certain condition that no one knows the cause of, a “mystery condition,” if you follow the neurology, the nerve path, you will find cervical spine instability at the end of the path.

Bradycardia which involves the heart rate is managed by the vagus nerve. If you follow the path of the vagus nerve, all the way from the brain stem, you will see that it runs on the front of the cervical vertebrae. If you suffer from severe bradycardia, it may be caused by the loss of cervical lordosis or natural neck curve causing stretching and pull on the vagus nerve, causing damage and dysfunction.

Trigeminal Cardiac Reflex Triggers

The trigeminal nerve provides sensation to the face, tongue, and swallowing muscles. We have seen patients where:

  • The patient would report that when they touched their nose, they would suddenly get tinnitus in one ear. That is because of stimulation of the trigeminal nerve.
  • The patient would report that when they blew their nose, it would create heart and digestive problems. This is a trigger of the trigeminal cardiac reflex.
  • The patient would report that when they had hot tea, they would get dizzy.
  • A patient who wore contact lenses would get dizzy because they are stimulating the eye surface which in turn stimulates the trigeminal nerve.

In the image below – the trigeminal network is shown. This interconnection of function shows how stimulation of the nose, or skin, or the act of chewing can trigger Trigeminal Cardiac Reflex. Triggers

Teeth grinding, the Trigeminal Cardiac Reflex, and the need for a pacemaker

Let’s look at a 2018 case reported by doctors at the Mayo Clinic and published in the journal Heart Rhythm case reports. (8) It is the case of a 27-year-old woman with symptoms of palpitations and syncope. She told the doctors that for three years she had developed and suffered from nocturnal and early morning nausea and vomiting that would often wake her from sleep. The doctors also noted that she had a long-standing history of severe bruxism. This persisted despite the use of a retainer and bite block.

The doctors discussed her treatment: “With her constellation of symptoms—severe bruxism, AV nodal block (interruption of impulse transmission from the atria to the ventricles) with cardiac pauses (that were predominantly nocturnal), and gastrointestinal symptoms—we diagnosed her with hypervagotonia (sinus node dysfunction) from stimulation of the powerful Trigeminal Cardiac Reflex from severe bruxism. Out of concern for the risk of cardiac death from these pauses without a stable ventricular escape, we elected to place a dual-chamber pacemaker for bradycardic prevention.”

How did all these symptoms start?

For some people, problems of blood pressure and heart rate started with a head trauma or a neck injury. The image below shows neck hyperextension, hyperflexion, hyper-compression, and the various injuries caused to the cervical ligaments. Sometimes, prolonged computer or electronic use can pull on the ligaments causing cervical spine instability.

People who have bradycardia or fainting episodes may display evidence of cervical spine instability stability such as clicking, popping, and grinding sounds and sensations in the neck.

What are we seeing in this image?

This is a simple diagram of a complex upper cervical vertebra – the vagus nerve – baroreceptor connection. The vagus, along with the glossopharyngeal nerve, runs just in front of the upper cervical vertebrae (atlas and axis) and branches out to innervate (sends and receives nerve signals) the receptors in the carotid sinus and aortic arch that control blood pressure. When atlanto-axial instability is present, blood pressure issues (along with heart rate and rhythm problems) can occur because of impairment in the vagus and glossopharyngeal nerve function.

Summary and contact us. Can we help you? How do I know if I’m a good candidate?

If you are like many of the patients we see, you have been chasing a diagnosis and treatment that works for years. For you, who had coexisting coronary artery disease ruled out, maybe wearing cervical neck collars, getting cervical traction, physical therapy, nonsteroidal anti-inflammatory drugs, and muscle relaxants, and perhaps waiting for surgery, you are probably exploring another way. This may be where Prolotherapy may be of benefit.

In our three decades of helping patients with problems related to the cervical spine, we have seen these symptoms and treatment failures many times. In our own peer-reviewed published studies we have been able to document cervical neck ligament damage as a possible cause of many symptoms including a group of symptoms thought cardiovascular in nature.

We hope you found this article informative and that it helped answer many of the questions you may have surrounding Trigeminal Cardiac Reflex. Just like you, we want to make sure you are a good fit for our clinic prior to accepting your case. While our mission is to help as many people with chronic pain as we can, sadly, we cannot accept all cases. We have a multi-step process so our team can really get to know you and your case to ensure that it sounds like you are a good fit for the unique testing and treatments that we offer here.

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1 Chowdhury T, Bindu B, Singh GP, Schaller B. Sleep disorders: is the trigemino-cardiac reflex a missing link?. Frontiers in neurology. 2017 Feb 27;8:63. [Google Scholar]
2 Chowdhury T, Mendelowith D, Golanov E, Spiriev T, Arasho B, Sandu N, Sadr-Eshkevari P, Meuwly C, Schaller B, Trigemino-Cardiac Reflex Examination Group (TCREG. Trigeminocardiac reflex: the current clinical and physiological knowledge. Journal of neurosurgical anesthesiology. 2015 Apr 1;27(2):136-47. [Google Scholar]
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8 Sugrue A, DeSimone CV, Gaba P, El-Harasis MA, Deshmukh AJ, Asviravtham SJ. Grinding to a halt: Stimulation of the trigeminal cardiac reflex from severe bruxism. HeartRhythm Case Reports. 2018 Aug 1;4(8):329-31. [Google Scholar]





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