In Reply to the Letter to the Editor Regarding “Evidences in Neurological Surgery and a Cutting Edge Classification of the Trigeminocardiac Reflex: A Systematic Review”

Territorial and Extraterritorial Trigeminocardiac Reflex: A Review for the Neurosurgeon and a Type IV Reflex Vignette

“…Heart rate and mean arterial blood pressure scores were independently altered during TCR elicitation. Of remark, these cardiovascular measures inversely correlated with each other with the clinically established reflex, which covaried with age [1,2]. TCR was triggered more often by surgical manipulation of the maxillary nerve; therefore, TCR type II was the most prevalent reflex type found when using the newly devised TCR classification.…”

“…TCR was triggered more often by surgical manipulation of the maxillary nerve; therefore, TCR type II was the most prevalent reflex type found when using the newly devised TCR classification. Importantly, this new classification method not only outlines the territorial TCR type according to the stimulated TN branch but also pinpoints the extraterritorial TN origin for the reflex such as that following spinal cord and limb stimulation [1,2].…”

“…TCR is defined as dramatic bradycardia and marked hypotension commonly preceded by sudden and unexplained high blood pressure in the context of a normal or near-normal heart rate [1,2]. Territorial TCR was defined according to TN anatomical branch distribution as type I, II, and III [1.2].…”

“…Oculo-cardiac reflex, reported in 1908 by Aschner and Dagnini, is triggered by stimulating the ophthalmic branch of the TN and anatomical areas surrounding the ocular globe [6,7]. This reflex corresponds to the TCR type I [1,2]. Nasotrigeminocardiac reflex, described by Kratschmer in 1870, occurs by stimulating the nasotrigeminal nerve, and mostly the nerve fibers located at the tip of the nose [8].…”

“…Although neurobiology of this reflex has been widely studied for centuries in animals, only recently it attracted scientific attention in human neurological surgery. As a consequence, human TCR neurobiology is still poorly understood, precluding it to identify and control this reflex in a timely manner during neurosurgical interventions [1,2].…”