Trigemino-Cardiac Reflex and Trigeminal Neuralgia

Abstract

Depressor response on heart due to stimulation of sensory branches of trigeminal nerve have been known since a long time. However, a formal interest in trigemino-cardiac reflex (TCR) grew after its introduction to neurosurgery in 1999 [1]. TCR is one of the strongest autonomic response and shows the complex relationship between brain and heart. There is no formal definition for the reflex; the widely accepted definition suggests TCR as a sudden fall in heart rate and mean blood pressure (BP) by 20% or more during surgical manipulation of structures innervated by the trigeminal nerve [2]. A definition to encompass other clinical manifestation of efferent vagal nerve suggests that trigemino-vagal reflex is an autonomic manifestation (e.g. change in breathing pattern and gastrointestinal motility) with or without change in heart rate or BP, coinciding with the stimulation of trigeminal nerve. Because bradycardia can be observed during operative procedures due to several reasons, a cause-effect relationship must be established to label a bradycardic episode as TCR. The cause–effect relationship can be established if TCR appears promptly on application of stimulus within 5 s (plausibility); stimulus cessation brings back the cardiovascular changes to baseline (reversibility); reapplication of similar stimulus leads to same hemodynamic changes (repetition); and trigeminal nerve block or use of anticholinergics or lower intensity stimulus does not lead to a repeat response (prevention) [2].