The Trigeminal Nerve and the Heart

Abstract

Trigeminal nerve stimulation initiates complex autonomic responses which profoundly alter cardiovascular function. Protective stimuli such as the diving and the nasopharyngeal reflex trigger a sympathetic-parasympathetic co-activation inducing bradycardia, hypertension and apnea. Conversely, adaptive stimuli observed in neurosurgical procedures trigger the trigeminocardial reflex, in which the reciprocal activation of both divisions of the autonomic system induces bradycardia, hypotension, apnea and gastric hypermotility. Trigeminal reflexes tend to be powerful airway protectors and by its cardio-respiratory modifications adopt the characteristics of true oxygen-conserving reflexes. However, its association with several cardiac complications has been demonstrated. Increase in parasympathetic outflow and changes in the sympathetic outflow may disturb the autonomic- cardiac balance and inducing arrhythmias and also sometimes severe coronary complications.