The Trigeminal Cardiac Reflex and Sleep-Related Bruxism

The Trigeminal Cardiac Reflex (TCR):

The TCR is well known to ENT surgeons and many oral surgeons. Considered to be the most powerful cranial reflex,  the trigeminal nerve and cardiovascular system are involved. When one of the branches of the trigeminal nerve is stimulated by touch, temperature, chemical stimulation, or pressure, the reflex may be activated. Once stimulated, the signal passes via the trigeminal nerve through the Gasserion ganglion, to the trigeminal sensory nucleus in the pons, then to the dorsal motor nucleus of the Vagus nerve and is carried down the vagus nerve to the heart, diaphragm,, and to the gut. To date, there have been six major regions with some sub-regions identified to activate the TCR.

 

The Occlo-Cardiac reflex: Parasympathetic

The Effect: bradycardia, hypotension, hypopnea, increased gastric stimulation.

Figure 5: The Occulo-Cardiac Reflex

The occulo-cardiac reflex is a subset of the TCR that is stimulated around the region of the eyes. For example, pressing inward on the eyeball may trigger this reflex. Surgical procedures around or behind the eye may trigger this.

 

The Photic Sneeze (Subset of the Occulo-Cardiac Reflex): Parasympathetic

The Effect: bradycardia, hypotension.

This is a subset of the occulo-cardiac reflex. It was recently discovered that when some people look at a bright light, it is accompanied by a drop in heart rate and blood pressure. It is considered a subset of the occulo-cardiac reflex and has the same parasympathetic effect and affects the heart similarly. This reflex is called the photic reflex.

 

The Naso-Cardiac Reflex: Parasympathetic

The Effect: bradycardia, hypotension, hypopnea, increased gastric stimulation.

Figure 6: The Naso-Cardiac Reflex

This variant of the TCR is stimulated when the nose or inside of the nose is stimulated. An example is if a local anesthetic is placed with an applicator into the nose. Surgery in and around the nose may trigger the TCR as well

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 The Maxillofacial-Mandibular reflex: Parasympathetic

The Effect: bradycardia, hypotension, hypopnea, increased gastric stimulation.

Figure 7: The Maxillo-Mandibular Cardiac Reflex

 

This variant of the TCR may be stimulated with surgery involving the maxilla or mandible, twisting of the mandible. The effect is classical parasympathetic stimulation. There are reported cases of this reflex being stimulated when extracting teeth.

 

The Bicuspid-Cuspid (Dento-) Cardiac Reflex: Parasympathetic

The Effect: bradycardia, hypotension, hypopnea, increased gastric stimulation.

Figure 8: The Bicuspid-Cuspid  Reflex

Considered a subset of the maxillo-mandibular reflex, conventional endodontic procedures involving only the 1st bicuspids and cuspids may activate the TCR parasympathetically resulting in classical bradycardia, hypotension, etc.

It should be noted here that the Luco Hybrid device utilizes this reflex to regulate the sympathetic stimulation of the TCR caused by SRB.

 

The Gasserion-Ganglion reflex: Sympathetic

The Effect: Tachycardia, hypertension, hyperpnea, increased gastric stimulation.

Figure 9: The Gasserion Ganglion Reflex

This subset of the TCR is the only subset that results in the sympathetic stimulation of the TCR and is associated with an increase in heart rate and blood pressure. It is the opposite effect of all other subtypes of the TCR. Restless leg syndrome also stimulates the TCR sympathetically, and both are considered a risk factor for heart disease

 

 

The Central reflex: Parasympathetic

The Effect: bradycardia, hypotension, hypopnea, increased gastric stimulation.

Figure 10: The Central Reflex

This subset of the TCR may be stimulated by neuro-surgical procedures involving the brain stem producing the classical effect.

 

The Brainstem reflex

The Effect: bradycardia, hypotension, hypopnea, increased gastric stimulation.

Figure 11: The Brainstem Reflex

This subset of the TCR may be stimulated by surgery of the brain stem below the level of the pons and produces the classical parasympathetic response.

 

How does Sleep-Related Bruxism Affect the TCR?

SRB is known to affect the TCR at the level of the Gasserion ganglion (Figure 12). This is the only subset of the TCR that results in sympathetic stimulation of the TCR and resulting tachycardia, hypertension, and hyperpnea.

Figure 12: Sleep-Related Bruxism and the TCR: This sleep tracing demonstrates the sympathetic stimulation of the TCR by SRB. The bruxism events are associated with erratic but uninterrupted breathing and heart rate increase.

In figure 12, the sleep tracing is of a patient with SRB, the SRB events correspond with erratic breathing (though not uninterrupted) as well as a heart rate increase from 62 to 95 bpm, an increase of 53%. It is medically accepted that there must be a change of 20% or greater for a diagnosis of TCR activation. Sleep bruxism far exceeds this, as in the above example of 53%, and results in significant stimulation of the TCR. The ramifications of this in cardiovascular disease are not currently known.

Of significance, it is medically accepted that there must be a change of greater than 20% in heart rate before it may be stated that the TCR has been activated. Sleep-related bruxism stimulates heart rate 75% or higher and hyper-stimulates the TCR.