The trigeminal cardiac reflex (TCR), best known as the ‘diver’s reflex” occurs in all mammals. An example is whales, when diving deep into colder water, experience a significant drop in heart rate and blood pressure, conserving oxygen allowing them to stay underwater longer. This is due to the activation of the TCR. Humans, diving into cold water, can experience the same reaction. It was also found that sudden death syndrome in babies is likely due to an immature TCR reflex that stops their heart and breathing in response to an external stimulus.
In recent years it was found that the TCR is actually made up of a number of similar reflexes that are stimulated by different regions of the head and trigeminal nerve. The figure below shows the extent of the trigeminal nerve.
The Trigeminal Nerve
The trigeminal nerve is the largest of the 12 cranial nerves. The others include vision, hearing, balance, taste, etc. The trigeminal is cranial nerve 5 and has the greatest density of fibers of the 12. It supplies the eye region and top of the head, the temples and upper jaw, and the ear, mastoid, lower jaw, and tongue and has three major branches. It should be noted that some people appear to be much more sensitive to TCR activation than others however this is a relatively new field of research and this has not been fully explored to date.
The TCR may be activated by mechanical stimulation, chemical stimulation or by thermal stimulation. It is subdivided into the following reflexes:
The Occulo-Cardiac Reflex:
Type: Parasympathetic
Effect: bradycardia, apnea, hypotension
This reflex is stimulated by pressure on the eyeball resulting in classical stimulation of the TCR.
The Occulo-Cardiac Reflex
The result of this reflex is a lowering of heart rate (greater than 20% is the medical criteria), a significant drop in blood pressure, a significant reduction or disruption in breathing. and increased gastric acid production (GERD). This is considered a parasympathetic stimulation of the TCR as it decreases activity.
Anyone who sneezes when they look at bright lights is experiencing the occulo-cardiac reflex as this has been shown to be a stimulus for this cranial reflex.
The Naso-Cardiac Reflex (bradycardia, apnea, hypotension)
Type: Parasympathetic
Effect: bradycardia, apnea, hypotension
This reflex is stimulated by irritation in the nose. It has been reported when physicians place a cue tip with local anesthetic in the nose, this reflex may occur.
The Naso-Cardiac Reflex
The result of this reflex is a lowering of heart rate (greater than 20% is the medical criteria), a significant drop in blood pressure, a significant reduction or disruption in breathing. and increased gastric acid production (GERD). This is considered a parasympathetic stimulation of the TCR as it decreases activity.
The Maxillo-Mandibular Reflex (bradycardia, apnea, hypotension)
Type: Parasympathetic
Effect: bradycardia, apnea, hypotension
This reflex is stimulated by direct stimulation of the maxillary nerve in the upper jaw and mandibular nerve of the lower jaw. This can be externally on the skin or internally through the teeth, tongue or throat regions. Surgery or trauma to the mid-face may trigger this reflex.
The Maxillo-Mandibular Reflex
The result of this reflex is a lowering of heart rate (greater than 20% is the medical criteria), a significant drop in blood pressure, a significant reduction or disruption in breathing. and increased gastric acid production (GERD). This is considered a parasympathetic stimulation of the TCR as it decreases activity.
The Gasserion Ganglion Reflex (tachycardia, hyperpnea, hypertension )
Type: Sympathetic
Effect: tachycardia, hyperpnea, hypertension
This reflex is stimulated by direct stimulation of the Gasserion or trigeminal ganglion, which is located just in front of the brainstem. This can be stimulated by surgery in the region, or mechanoreceptors located in the teeth and periodontal ligament that surrounds the teeth.
The Gasserion Ganglion Reflex
The result of this reflex is a significant increase in heart rate (greater than 20% is the medical criteria), a significant increase in blood pressure, a significant increase and disruption in breathing. and increased gastric acid production (GERD). This is considered a sympathetic stimulation of the TCR as it increases activity.
Restless leg syndrome(RLS) also activates the TCR at this level resulting in the sympathetic effects discussed. As RLS has been mech better researched, it is known that RLD is a risk factor for heart disease. Sleep-related bruxism stimulates the TCR more than RLS and has also been shown to he a risk factor for heart disease.
The Brainstem Reflex (bradycardia, apnea, hypotension)
Type: Parasympathetic
Effect: bradycardia, apnea, hypotension
This reflex is stimulated by direct stimulation of the brainstem, below the pons. This is usually only seen when surgery is performed in this region.
The Brain Stem Reflex
The result of this reflex is a lowering of heart rate (greater than 20% is the medical criteria), a significant drop in blood pressure, a significant reduction or disruption in breathing. and increased gastric acid production (GERD).
The Central Reflex (bradycardia, apnea, hypotension)
Type: Parasympathetic
Effect: bradycardia, apnea, hypotension
This reflex is stimulated by surgery in the region or severe neck trauma.
The Central Reflex
The result of this reflex is a lowering of heart rate (greater than 20% is the medical criteria), a significant drop in blood pressure, a significant reduction or disruption in breathing. and increased gastric acid production (GERD). This is considered a parasympathetic stimulation of the TCR as it decreases activity.
The Bicuspid Reflex
Type: Parasympathetic
Effect: bradycardia, apnea, hypotension
The latest reflex of the TCR discovered. Stimulation occurs when root canal therapy is performed on the upper cuspid or 1st bicuspids.
The Bicuspid Reflex
The result of this reflex is a lowering of heart rate (greater than 20% is the medical criteria), a significant drop in blood pressure, a significant reduction or disruption in breathing. and increased gastric acid production (GERD). This is considered a parasympathetic stimulation of the TCR as it decreases activity.
The Luco Hybrid OSA Appliance and the TCR:
Both the Gasserion ganglion reflex and the Bicuspid reflex are addressed by the Luco hybrid OSA Appliance design. Please click here for more information.
