Trigeminocardiac reflex: the current clinical and physiological knowledge

The trigeminocardiac reflex (TCR) is defined as the sudden onset of parasympathetic dysrhythmia, sympathetic hypotension, apnea, or gastric hypermotility during stimulation of any of the sensory branches of the trigeminal nerve. Clinically, the TCR has been reported in all the surgical procedures in which a structure innervated by the trigeminal nerve is involved. Although, there is an abundant literature with reports of incidences and risk factors of the TCR; the physiological significance and function of this brainstem reflex has not yet been fully elucidated. In addition, there are complexities within the TCR that requires examination and clarification. There is also a growing need to discuss its cellular mechanism and functional consequences. Therefore, the current review provides an updated examination of the TCR with a particular focus on the mechanisms and diverse nature of the TCR.