Trigemino-cardiac reflex during chronic subdural haematoma removal: report of chemical initiation of dural sensitization

The trigemino-cardiac reflex is a well-known clinical phenomenon described during different craniofacial or skull base surgery as well as neuroradiological interventions and defined as the sudden onset of parasympathetic dysrhythmia, sympathetic hypotension, apnea, or gastric hyper-motility during (intraoperative) stimulation of any of the sensory branches of the trigeminal nerve. According to strict and generally accepted diagnostic criteria, the occurrence of the trigemino-cardiac reflex is considered if there is observed a 20% or more decrease in heart rate and MABP as response to an adequate stimulus. In the early 20th century, this phenomenon has gained increased clinical attention in the form of the oculocardiac reflex which represents the cardiac response associated with stimulation of the ophthalmic division of the trigeminal nerve during ocular surgeries. In 1999, Schaller et al. have, for the first time, demonstrated that a similar reflex occurs after the stimulation of the intracranial (central) portion of the trigeminal nerve during skull base surgery and has subsummarized all these trigemino-depressor responses under the term ‘TCR’. Later, Schaller’s group has also described the occurrence of the trigeminocardiac reflex during intraoperative stimulation of the peripheral portion of the trigeminal nerve and has also shaded light on the influence of trigemino-cardiac reflex on the surgical outcome. Since the late 1990s, there has been increasing interest and also discussion about the trigemino-cardiac reflex itself, its provoking factors, but also its treatment during intracranial or extracranial (neuro) surgical procedures. Several provoking factors for the intraoperative occurrence of trigemino-cardiac reflex have been described earlier and most attention is given to the mechanical stimulation of trigeminal afferents during surgical interventions. Currently, we are far away to define any specific risk profile for the intraoperative occurrence of the trigemino-cardiac reflex as there is a lack of detailed knowledge of the physiology of this reflex. The current case report presents the occurrence of trigemino-cardiac reflex during a standard neurosurgical intervention for removal of giant chronic subdural hematoma and give therefore substantial evidence that temporary exposure of perivascular fibers to chemical agents alters their sensitivity to mechanical stimuli of the dura mater.