Trigeminocardiac reflex during skull base surgery: mechanism and management

The Influence of Trigeminocardiac Reflex on Postoperative Cardiac Adverse Events in Patients Undergoing Cerebellopontine Angle Tumor Resections: A Case-Control Study

OBJECTIVE

To assess the potential impact of the trigeminocardiac reflex (TCR) on postoperative adverse cardiac events and to identify predictors of the TCR in cerebellopontine angle surgery.

METHODS

Patients undergoing elective cerebellopontine angle surgery from October 1, 2015, to September 30, 2020, were recruited consecutively for this retrospective case-control study. The TCR was evaluated by reviewing electronic anesthesia records and defined as a drop in heart rate was >20%. Controls were identified from the same retrospective cohort and matched by age, sex, and similar (±5 days) surgery date in the ratio of 1:2.

RESULTS

Of 2446 patients, 68 (2.78%) experienced TCR episodes. A total of 97 TCR episodes occurred among the 68 patients. In 2 TCR episodes, severe cardiac complications developed after surgery-myocardial injury in one case and cardiac arrest in the other case. The prevalence of adverse cardiovascular events was higher in the TCR group (60.3% vs. 36.0%, P = 0.001) than in the control group. The independent risk factor for the TCR in the multivariate condition logistic regression was tumor compression of the brainstem (odds ratio = 2.36, 95% confidence interval 1.40-3.95; P = 0.001).

CONCLUSIONS

Intraoperative TCR episodes seemed to be associated with postoperative adverse cardiac events in patients undergoing cerebellopontine angle surgery. Moreover, tumor compression of the brainstem might be a risk factor for TCR episodes.

The endoscopic-assisted approach versus the microscopic only approach in resection of cerebellopontine angle epidermoids: a 5-year retrospective study

Background

The endoscopic-assisted technique has been utilized with various intracranial lesions with many approaches. In the cerebellopontine angle (CPA), the technique has been used to combine the benefits of the operating microscope and the endoscope. In this study, we highlight the use of the endoscopic-assisted technique in resection of CPA epidermoid tumors to ensure a total resection, decrease complications and protect the neurovascular tangles.

Results

In the endoscopic-assisted group, only 18.8% of the patients had post-operative residual in the post-operative MRI. However, in the microscopic only group 56.3% of the patients had post-operative residual. Consequently, there is a statistically significant difference regarding the post-operative residual between the two groups.

Conclusions

The endoscopic-assisted approach is superior to the microscopic only approach in the excision of CPA epidermoids and minimizing the post-operative residual and the recurrence.

Trigeminal Nerve Repair: Is the Trigeminocardiac Reflex a Concern?

PURPOSE

Our hypothesis is that direct manipulation of the third and second divisions of the trigeminal nerve during microneurosurgery does not affect the incidence of trigeminocardiac reflex (TCR). The purpose of this paper was to analyze the incidence of TCR events during microneurosurgery involving the second and third divisions of the trigeminal nerve.

MATERIALS AND METHODS

This was a retrospective cohort study of 94 patients who underwent nerve repair of the second and third divisions of the trigeminal nerve, between July 2014 and February 2021 by a single surgeon (J. Z.). The independent variables were the trigeminal nerve branch injured, the laterality of the trigeminal nerve injury, the Sunderland classification, the ASA classification, the intraoperative narcotic(s) used, and the depth of anesthesia. The dependent variables included the occurrence of intraoperative hypercapnia, hypoxia, and TCR event. Since the data was retrospective and categorical in nature, χ² analysis was performed initially.

RESULTS

None of the patients in this retrospective cohort demonstrated intraoperative hypercapnia, hypoxia or TCR events. Initial χ² calculation was performed for the dependent variables with the trigeminal nerve groups (IAN, LN, and ION). The χ² calculation [χ² (1, n = 101)] was 0.2235. The P-value was .6364. Since there was no statistical significance found, there was no further analysis of surgical and anesthesia independent variables in the data collection.

CONCLUSIONS

The zero incidence of TCR in a large number of patients provides strong evidence supporting the rejection of the hypothesis that TCR can occur during the surgical repair of peripheral trigeminal nerves.

The trigeminal system: The meningovascular complex- A review

Supratentorial sensory perception, including pain, is subserved by the trigeminal nerve, in particular, by the branches of its ophthalmic division, which provide an extensive innervation of the dura mater and of the major brain blood vessels. In addition, contrary to previous assumptions, studies on awake patients during surgery have demonstrated that the mechanical stimulation of the pia mater and small cerebral vessels can also produce pain. The trigeminovascular system, located at the interface between the nervous and vascular systems, is therefore perfectly positioned to detect sensory inputs and influence blood flow regulation. Despite the fact that it remains only partially understood, the trigeminovascular system is most probably involved in several pathologies, including very frequent ones such as migraine, or other severe conditions, such as subarachnoid haemorrhage. The incomplete knowledge about the exact roles of the trigeminal system in headache, blood flow regulation, blood barrier permeability and trigemino-cardiac reflex warrants for an increased investigation of the anatomy and physiology of the trigeminal system. This translational review aims at presenting comprehensive information about the dural and brain afferents of the trigeminovascular system, in order to improve the understanding of trigeminal cranial sensory perception and to spark a new field of exploration for headache and other brain diseases.

Trigeminocardiac Reflex Induced by Maxillary Nerve Stimulation during Sphenopalatine Ganglion Implantation: A Case Series

BACKGROUND

The trigeminocardiac reflex (TCR) is a brainstem reflex following stimulation of the trigeminal nerve, resulting in bradycardia, asystole and hypotension. It has been described in maxillofacial and craniofacial surgeries. This case series highlights TCR events occurring during sphenopalatine ganglion (SPJ) neurostimulator implantation as part of the Pathway CH-2 clinical trial "Sphenopalatine ganglion Stimulation for Treatment of Chronic Cluster Headache".

METHODS

This is a case series discussing sphenopalatine ganglion neurostimulator implantation in the pterygopalatine fossa as treatment for intractable cluster headaches. Eight cases are discussed with three demonstrating TCR events. All cases received remifentanil and desflurane for anesthetic maintenance.

RESULTS

Each patient with a TCR event experienced severe bradycardia. In two cases, TCR resolved with removal of the introducer, while the third case's TCR event resolved with both anticholinergic treatment and surgical stimulation cessation.

CONCLUSION

Each TCR event occurred before stimulation of the fixed introducer device, suggesting the cause for the TCR events was mechanical in origin. Due to heightened concern for further TCR events, all subsequent cases had pre-anesthesia external pacing pads placed. Resolution can occur with cessation of surgical manipulation and/or anticholinergic treatment. Management of TCR events requires communication between surgical teams and anesthesia providers, especially during sphenopalatine ganglion implantation when maxillary nerve stimulation is possible.

Sudden arrhythmia followed by bradycardia during sagittal split ramus osteotomy: trigeminocardiac reflex

Trigeminocardiac reflex (TCR) is a brainstem reflex triggered by the stimulation of any branch of the fifth cranial nerve along its course, presenting as a reduction in heart rate and blood pressure. Oculocardiac reflex is a well-known subtype of TCR. In the case reported here, remarkable arrhythmia followed by bradycardia occurred suddenly in a healthy patient undergoing orthognathic surgery. The heart rhythm recovered when the surgical manipulation ceased, but bradycardia was reproduced when the surgery resumed. This case of TCR is unique in that remarkable arrhythmia first appeared and led to bradycardia; accordingly, intravenous lidocaine and an anticholinergic agent were administered simultaneously instead of anticholinergic agents alone, and were protective. Although TCR rarely occurs during orthognathic surgery, clinicians should be aware of its possibility and able to judge and manage it promptly.

Potential Neuroendoscopic Complications: An Anesthesiologist's Perspective

Endoscopic techniques are being used extensively used in the current times for the diagnosis and treatment of numerous intracranial pathologies. Although the morbidity associated with these procedures is lower as compared to other conventional surgical modalities, neuroendoscopic techniques have its own fair share of distinct complications such as bleeding, cerebrospinal fluid leakage, and subdural hematoma. However, certain specific complication fall within the purview of the attending anesthesiologist who should remain vigilant, anticipating these problems to occur and should be well equipped to deal with such contingencies. This review attempts to sensitize the anesthesiologists regarding the well-known as well as rare complications of intracranial neuroendoscopic procedures and to familiarize them with their diverse presentations, preventive strategies, and management protocols.

Sinus arrest with prolonged asystole due to the trigeminocardiac reflex during application of local anaesthetic in the nasal mucosa

The trigeminocardiac reflex (TCR) is defined as a sudden onset of parasympathetic dysrhythmias during stimulation of the trigeminal nerve. We describe a peripheral variation of TCR during manipulation of the nasal mucosa. A 42-year-old patient suffering from severe obstructive sleep apnoea was scheduled for surgical treatment. After inducted anaesthesia, the surgeon infiltrated the nasal mucosa with a local anaesthetic. The patient immediately showed an asystole and was treated with ephedrine and five chest compressions, despite spontaneous sinus rhythm return after ceasing of manipulation. Treatment with atropine established this TCR episode and ensured an event-free surgery.The authors present here, for the first time, a prolonged asystole caused by the TCR, triggered by minimal manipulation of the nasal mucosa. This severe manifestation of peripheral TCR demonstrates its importance in daily clinical business. This case was treated according to a modified treatment algorithm for all subtypes of TCR which is presented here.

The clinical surrogate definition of the trigeminocardiac reflex: Development of an optimized model according to a PRISMA-compliant systematic review

BACKGROUND

The trigeminocardiac reflex (TCR) is defined as sudden onset of parasympathetic dysrhythmias including hemodynamic irregularities, apnea, and gastric hypermotility during stimulation of sensory branches of the trigeminal nerve. Since the first description of the TCR 1999, there is an ongoing discussion about a more flexible than the existing clinical definition. Aim of this work was to create a clinical surrogate definition through a systematic review of the literature.

METHODS

In this meta-analysis study, literature about TCR occurrences was, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement, systematically identified through various search engines including PubMed (Medline), Embase (Ovid SP), and ISI Web of Sciences databases from January 2005 to August 2015. TCR was defined as a drop of heart rate (HR) below 60 bpm or 20% to the baseline. We extracted detailed data about hemodynamic changes and searched for connections between arterial blood pressure (BP) and HR changes during such episodes.

RESULTS

Overall 45 studies harboring 57 patients were included in the study but only 32 patients showed sufficient data for final analyze. HR showed a nonlinear behavior with a "tipping point" phenomena that differs in variance from the central/peripheral (20-30% drop) to ganglion (40-49% drop). BP showed a linear behavior with a "central limit" phenomena not differing in variance in the whole subgroup (30-39% drop). An analyzation of the correlation between BP and HR showed a trend to a linear correlation.

CONCLUSIONS

We can show for the first time that HR is the dominant variable in the TCR and present a new surrogate definition model. This model and the role of BP must be better investigated in further studies.

The Trigeminocardiac Reflex During the Anterior Transpetrosal Approach

OBJECTIVE

The anterior transpetrosal approach (ATPA), during which the trigeminal nerve (TN) is manipulated, has a risk of eliciting the trigeminocardiac reflex (TCR). The aim of this study was to assess the risk of TCR during ATPA.

METHODS

Surgical records of 92 patients who had surgical treatment via ATPA at the Keio University Hospital between December 2005 and June 2015 were retrospectively analyzed. Patients were divided into 2 groups on the basis of the occurrence of TCR during surgery, and clinical and tumor characteristics were compared. Tumor characteristics were evaluated based on preoperative images and intraoperative findings and included the side of the lesion, size of the lesion, tumor size in Meckel cave, pathology of the disease, cavernous sinus invasion, extension into Meckel cave, and adhesion of lesion to TN.

RESULTS

TCR was observed in 14 of 92 patients (15.2%). TCR occurrence was significantly related to Meckel cave tumor size (P = 0.0264) and adhesion of the lesion to TN (P = 0.0002).

CONCLUSIONS

This study suggests that TCR is related to Meckel cave tumor size and tumor adhesion to TN in ATPA. To our knowledge, this is the first report describing TCR during ATPA.

Oculocardiac reflex elicited by orbital floor fracture and inferior globe displacement

Purpose

To review the physiology, presentation and management of the oculocardiac reflex (OCR) by describing a case of the OCR associated with an orbital foreign body and complete ocular prolapse through a large orbital floor fracture in a 40-year-old male following a motor vehicle accident.

Observations

The patient demonstrated marked bradycardia and hypotension necessitating intubation and medical therapy for autonomic shock. A computed tomography (CT) showed a total blow out floor fracture and complete dislocation of a radiographically intact globe with uninterrupted rectus muscle attachments into the left maxillary sinus. He was taken to the operating room for urgent repair resulting in subsequent termination of severe OCR.

Conclusions and importance

The oculocardiac reflex can precipitate marked bradycardia and hypotension in the setting of trauma with significant orbital and maxillofacial injury. Prompt identification and management with vagolytic agents or definitive surgical intervention may prevent morbidity or mortality.

Functional Outcome Changes in Surgery for Pituitary Adenomas After Intraoperative Occurrence of the Trigeminocardiac Reflex: First Description in a Retrospective Observational Study

Trigeminocardiac reflex (TCR) represents now a nearly ubiquitary phenomenon in skull base surgery. Functional relevance of the intrainterventional TCR occurrence is hitherto only proven for vestibular schwannoma. In a retrospective observational study, 19 out of 338 (8%) enrolled adult patients demonstrated a TCR during transsphenoidal/transcranial surgery for pituitary adenomas. The 2 subgroups (TCR vs non-TCR) had similar patient's characteristics, risk factors, and histology. Preoperatively, there was a similar distribution of normal pituitary function in the TCR and non-TCR subgroups. In this TCR subgroup, there was a significant decrease of that normal pituitary function after operation (37%) compared to the non-TCR group (60%) (P < 0.03). The TCR subgroup therefore demonstrated a 3.15 times (95%CI 1.15-8.68) higher risk for non-normalizing of postoperative pituitary function compared with the non-TCR subgroup (P < 0.03). It is presented, for the first time, an impact of TCR on the functional hormonal outcome after pituitary surgery and strongly underline again the importance of the TCR in clinical daily practice. As a consequence, TCR should be considered as a negative prognostic factor of hormonal normalization after surgery for pituitary adenomas that should be included into routine practice.

Trigeminocardiac reflex during cerebellopontine angle surgery: anatomical location as a new risk factor

ABSTRACT 

Aim: Trigeminocardicac reflex (TCR), a brainstem reflex, can be manifested in almost all types of surgery in the head and neck region. Patients & methods: Retrospective review of 125 patients operated on cerebellopontine angle (CPA) tumors according to strict inclusion/exclusion criteria. Results: A total of 14 out of 125 patients showed TCR during CPA tumor operation. In total, 29% of those patients presented with a meningioma located exclusively premeatal, but not retromeatal in the CPA. There was significant relationship between meningiomas subgroups and TCR (Barnard test; p < 0.05). Conclusion: Anatomical location may represent an important, but not yet described risk factor for the TCR having therefore an important role in the understanding of the TCR.

Incidence and ramifications of the oculocardiac reflex during the orbitozygomatic approach: a prospective assessment

OBJECTIVE

The oculocardiac reflex (OCR) is a sudden decrease in heart rate resulting from mechanical manipulation of the orbit, especially due to traction on the orbital contents. The purpose of this study was to determine the incidence and clinical ramifications of OCR elicitation by the orbitozygomatic (OZ) approach.

METHODS

Electrocardiographic strips were collected prospectively from 104 patients undergoing OZ approaches. Recording was started at the commencement of the craniotomy cuts and was stopped after completion of the OZ osteotomy. Each recording was divided into stage 1, which encompassed the time between the start of the craniotomy cuts to the commencement of the osteotomy cuts, and stage 2, which encompassed the time from commencement of osteotomy cuts until completion of all bone work and dural tacking Orbital manipulation occurred exclusively during stage 2. A decrease in heart rate of 10 bpm or more between stage 1 and stage 2 was recorded as an OCR event.

RESULTS

In our 104 patients we detected OCR events 31.7% of the time. There was no significant difference in rate of OCR occurrence found in analysis of the covariates of hypertension, hyperlidemia, diabetes mellitus, hypothyroidism/hyperthyroidism, β-blocker use, calcium channel blocker use, or tobacco use. In each case, transient cessation of orbital manipulation was sufficient to normalize heart rate. No patients required anticholinergic intervention as a result of OCR, and there were no postoperative ramifications of the OCR.

CONCLUSIONS

OCR occurs in nearly one-third of patients who undergo the OZ approach. However, simple cessation of orbital manipulation is sufficient to normalize the patient's heart rate. Rarely is medical management required or does there appear to be any significant postoperative ramifications.

A unique case of asystole secondary to facial injury

Bradycardia has been reported during intraoperative settings of craniofacial, cerebropontine angle and trigeminal ganglion surgeries (Schaller et al. (2009, 1999); Parbhakar et al. (2009); Koerbel et al. (2005); Roberts et al. (1999)). It is also commonly seen in children undergoing orbital and maxillary fractures repair. This mechanism has been described as the trigeminocardiac reflex (TCR) (Schaller et al. (2009, 2004); Kim et al. (2000); Lang et al. (1991); Van Brocklin et al. (1982)). We report an unusual case of posttraumatic bradycardia and recurrent asystole in a previously healthy adult patient from possible TCR in the absence of any surgical intervention to the head and orbital area.

Sudden asystole due to trigeminocardiac reflex during transsphenoidal surgery for pituitary tumor

BACKGROUND

A sudden attack of an asystolic phenomenon is an extremely rare event during transsphenoidal surgery (TSS). It may be caused by an extreme type of trigeminocardiac reflex (TCR) during the manipulation of the trigeminal nerve or its innervated structures.

CASE DESCRIPTION

We report two cases of sudden asystole and a case of severe bradycardia due to TCR during TSS. All patients were managed successfully by cessation of the surgical manipulation or with the injection of an anticholinergic agent.

CONCLUSIONS

Although TCR occurs rarely and usually is self-limiting, surgeons should be cautious of its occurrence, especially when manipulating the cavernous sinus during TSS. This allows the early detection and appropriate treatment of this manifestation. Stopping the surgical procedure as soon as TCR occurs is likely to normalize the vital parameters. In addition, if further manipulations are inevitable, the administration of anticholinergic medication should be considered cautiously to improve surgical outcomes.

Trigeminocardiac reflex in a child during pre-Onyx DMSO injection for juvenile nasopharyngeal angiofibroma embolization. A case report

We describe the occurrence of the trigeminocardiac reflex (TCR) during DMSO pre-flushing of the microcatheter in preparation for Onyx embolization via the internal maxillary artery. TCR has not been previously associated with embolization of extradural entities. Familiarity with this clinical reflex and its proper management may help in planning neurointerventional procedures involving DMSO injection in the trigeminal territory.

Intraoperative brainstem auditory evoked potential observations after trigeminocardiac reflex during cerebellopontine angle surgery

BACKGROUND

The occurrence of trigeminocardiac reflex (TCR) is known to be a negative prognostic factor for hearing preservation in cerebellopontine angle tumor surgery. Our study was conducted to investigate brainstem auditory evoked potential (BAEP) changes after this reflex in cerebellopontine angle tumor surgery and to evaluate their impact on postoperative hearing function.

METHODS

Five of 102 consecutive patients had an intraoperative TCR (4.9%) and were retrospectively evaluated for the intraoperative BAEP changes after TCR and postoperative auditory function (7 to 10 d after surgery). One of the 5 patients was preoperatively deaf and therefore excluded from this analysis.

RESULTS

Four patients with preoperative functional hearing developed one or more episodes of TCR. Intraoperative BAEP was maintained in 1 patient, whereas in 3 cases an acute intraoperative BAEP deterioration occurred within 2:04 to 3:27 minutes (mean 2:44 min) after TCR with increased wave latency, decreased wave amplitude, and even wave loss. Two patients had deteriorated BAEP waves until the surgical completion and were postoperatively deaf.

CONCLUSIONS

Although no direct cause-effect relationship has yet been shown, we suggest TCR as an additional event that may cause BAEP changes. The observed BAEP alterations occurred minutes rather than seconds after the TCR incident leading to both temporary and permanent wave deterioration. This association of BAEP deterioration and TCR occurrence, however, remains yet to be proven justifying further study in the field.

The role of the trigeminocardiac reflex in postoperative hearing function in non-vestibular schwannoma cerebellopontine angle tumors

The trigeminocardiac reflex (TCR) is a common event during skull base surgery that can lead to intraoperative arterial hypotension and bradycardia. Arterial hypotension associated with TCR can be a negative prognostic factor for postoperative auditory function and ipsilateral tinnitus in patients undergoing surgery for vestibular schwannoma (VS). In this study, the contribution of TCR to postoperative auditory function in non-VS cerebellopontine angle (CPA) tumor surgery was investigated. From a consecutive series of 102 patients with CPA tumors, we studied the occurrence of TCR and its influence on postoperative auditory function in patients with non-VS tumors. Pre- and postoperative auditory function, pre- and intraoperative mean arterial blood pressure, as well as preoperative medication, tumor size, and occurrence of TCR were evaluated. Of the 35 patients evaluated, four developed intraoperative TCR, of whom one was preoperatively deaf. Preoperative functional hearing was detected in 30/35 patients (85.7%): preoperative deafness was documented in one patient in the TCR group and in four patients in the non-TCR group. Of the 30 patients with preoperative functional hearing, 1/3 (33.3%) patients in the TCR group and 23/27 (85.2%) patients in the non-TCR group had functional hearing postoperatively. When patients with large tumors and functional, hearing were considered, only 33.3% of patients in the TCR group and 77.8% of patients in the non-TCR group remained within the same hearing classes following surgical treatment (p=0.1573). TCR may be a negative prognostic factor for postoperative auditory function in patients with large, non-VS CPA tumors.

A new predisposing factor for trigemino-cardiac reflex during subdural empyema drainage: a case report

INTRODUCTION

The trigemino-cardiac reflex 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, trigemino-cardiac reflex has been reported to occur during neurosurgical skull-base surgery. Apart from the few clinical reports, the physiological function of this brainstem reflex has not yet been fully explored. Little is known regarding any predisposing factors related to the intraoperative occurrence of this reflex.

CASE PRESENTATION

We report the case of a 70-year-old Caucasian man who demonstrated a clearly expressed form of trigemino-cardiac reflex with severe bradycardia requiring intervention that was recorded during surgical removal of a large subdural empyema.

CONCLUSION

To the best of our knowledge, this is the first report of an intracranial infection leading to perioperative trigemino-cardiac reflex. We therefore add a new predisposing factor for trigemino-cardiac reflex to the existing literature. Possible mechanisms are discussed in the light of the relevant literature.

Trigeminocardiac reflex during Le Fort I osteotomy: a case-crossover study

OBJECTIVE

The present study aimed to assess the occurrence of trigeminocardiac reflex (TCR) during Le Fort I osteotomies.

STUDY DESIGN

This case-crossover study included 25 Le Fort I osteotomy candidates without systemically compromising conditions. Mean arterial blood pressure and pulse rate values were recorded before downfracture (DF) (MABP1, PR1), during DF (MABP2, PR2), and after DF (MABP3, PR3). The data were analyzed using repeated measure ANOVA tests (alpha = 0.05).

RESULTS

PR1 and PR3 were significantly higher than PR2 (P < .001). MABP2 value was significantly lower compared with MABP1 and MABP3 values (P < .001). PR2 and MABP2 showed a mean decrease of 6.5% and 9.7% compared with PR1 and MABP1, respectively.

CONCLUSION

Different values have been suggested for TCR. Considering the limitations, the present study may suggest a revision of the values or descriptions for TCR, at least in maxillofacial Le Fort I osteotomy.

The incidence of trigeminocardiac reflex in endovascular treatment of dural arteriovenous fistula with onyx

This paper reports the incidence of tri-geminocardiac reflex (TCR) in endovascular treatment of dural arteriovenous fistulas (DAVFs) with Onyx. The consecutive case histories of 45 patients with DAVFs, treated with Onyx transarterially and transvenously, from February 2005 to February 2008 at Beijing Tiantan Hospital, China, were retrospectively reviewed. The time period was limited as the anesthetic and intravascular procedure was performed under the same standardized anesthetic protocol and by the same team. The TCR rate was subsequently calculated. Of the 45 patients, five showed evidence of TCR during transarterial Onyx injection and transvenous DMSO injection. Their HR fell 50% during intravascular procedures compared with levels immediately before the stimulus. However, blood pressure values were stable in all cases. The TCR rate for all patients was 11.1% (95% CI, 4 to 24%), 7.7% (95% CI, 2 to 21%) in patients treated intraarterially and 33.3% (4 to 78%) in patients treated intravenously. Once HR has fallen, intravenous atropine is indicated to block the depressor response and prevention further TCR episodes. TCR may occur due to chemical stimulus of DMSO and Onyx cast formation under a standardized anesthetic protocol and should be blunted by atropine.

The trigemino-cardiac reflex: an update of the current knowledge

The trigemino-cardiac reflex (TCR) is clinically defined as the sudden onset of parasympathetic activity, sympathetic hypotension, apnea, or gastric hypermotility during central or peripheral stimulation of any of the sensory branches of the trigeminal nerve. Clinically, the TCR has been reported to occur during craniofacial surgery, manipulation of the trigeminal nerve/ganglion and during surgery for lesion in the cerebellopontine angle, cavernous sinus, and the pituitary fossa. Apart from the few clinical reports, the physiologic function of this brainstem reflex has not yet been fully explored. The manifestation of the TCR can vary from bradycardia and hypotension to asystole. From the experimental findings, the TCR represents an expression of a central reflex leading to rapid cerebrovascular vasodilatation generated from excitation of oxygen-sensitive neurons in the rostral ventro-lateral medulla oblongata. By this physiologic response, the systemic and cerebral circulations may be adjusted in a way that augments cerebral perfusion. This review summarizes the current state of knowledge about TCR.

Avoidance and management of trigeminocardiac reflex complicating awake-craniotomy

The trigeminocardiac reflex occurs from manipulation or stimulation of peripheral branches or the central component of the trigeminal nerve and consists of bradycardia, hypotension, apnea, and increased gastric motility. The efferent limb of the response is mediated by the vagus nerve. This 65-year-old Caucasian male suffered an episode of bradycardia progressing to transient asystole during the course of an awake-craniotomy procedure for tumor resection. The cardiac rhythm changes resolved with administration of intravenous atropine, removal of the precipitating stimulus, and application of topical anesthetic on the dura of the middle cranial fossa. The trigeminocardiac response may complicate the course of a craniotomy and may place an awake, unintubated patient at increased risk for morbidity. The reflex may be prevented by anesthetizing the dura innervated by the trigeminal nerve via injection or topical application of local anesthetic. If encountered, removal of the stimulus, airway protection, and administration of vagolytic medications are measures that need to be considered.

[Trigeminocardiac reflex in pituitary surgery. A prospective pilot study]

BACKGROUND

The trigeminocardiac reflex (TCR) is a relatively recently described brainstem reflex in the fields of neurosurgery which leads to a simultaneous drop in mean arterial pressure (MAP) and heart rate of at least 20% from baseline levels after stimulation of a sensible branch of the trigeminal nerve.

PATIENTS AND METHODS

The purpose of this study was to register prospectively for the first time the rate of TCR during trans-sphenoidal surgery and to describe possible predispositional factors. This was examined by determining selected biomarkers thought to correlate with possible intraoperative ischemic events after occurrence of TCR and furthermore with neuroprotective mechanisms ("ischemic tolerance").

RESULTS

Three of the 40 patients included (7.5%) demonstrated intraoperative occurrence of TCR after exposure of the cavernous sinus. One (2.5%) demonstrated a TCR during preparation of the nasal mucosa. Permanent cardiovascular damage or unfavorable postoperative outcome through the appearance of TCR was not found. There was a trend to lower C-reactive protein levels after occurrence of TCR (32 mg/dl vs 14 mg/dl) following normal values before operations in all cases. Considering that no clinical clue of ischemia was detected, this could mean that some neuroprotective cascades are initiated. There was a correlation between tumor necrosis factor A and noradrenalin levels with the size (invasivity) of the pituitary adenoma. The administration of atropine was necessary in only one patient with intraoperative occurrence of TCR.

CONCLUSION

On the basis of this study, it cannot be said to what extent neuroprotective mechanisms after TCR are activated, but a trend is still apparent. Considering the adverse effects and the reflex arc, prophylactic or therapeutic treatment with atropine is not justified.

Trigemino-cardiac reflex during transsphenoidal surgery for pituitary adenomas: Methodological description of a prospective skull base study protocol

A systematic clinical neuroscience protocol is described for the use to examine the trigemino-cardiac reflex (TCR) response in humans. Target neurosurgical conditions are operations that require manipulations around the peripheral and central part of the trigeminal nerve and its branches, e.g. the cerebellopontine angle or the sellar region. To assess the hemodynamic and cardiac responses of patients after TCR initiation, anesthetic monitoring has been applied. The TCR is defined as a drop of more than 20% of the heart rate and the mean arterial blood pressure compared with the baseline values before the stimulus and coinciding with the surgical manipulation at or around any branches of the trigeminal nerve. By help of illustrative cases, we present for the first time preliminary results regarding the differentiation of the TCR in a central and a peripheral induction during transsphenoidal surgery of pituitary adenomas. Based on these results, we can conclude that we have developed a battery of preoperative examination procedures based on event-related diagnostics that was useful to differentiate different subgroups of TCR during transsphenoidal surgery. The presented protocol can be performed directly pre-, intra- and postoperatively and applied for assessment of TCR even in patients with known risk factors.