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|LETTERS TO EDITOR
|Year : 2018 | Volume
| Issue : 6 | Page : 1822-1824
Glossopharyngeal vagal reflex: A matter of concern during neurosurgery
Gaurav Singh Tomar, Rajeeb K Mishra, Arvind Chaturvedi
Department of Neuroanaesthesiology and Critical Care, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||28-Nov-2018|
Dr. Gaurav Singh Tomar
Department of Neuroanaesthesiology and Critical Care, 7th Floor, Neuroscience Centre, All India Institute of Medical Sciences, New Delhi - 110 029,
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Tomar GS, Mishra RK, Chaturvedi A. Glossopharyngeal vagal reflex: A matter of concern during neurosurgery. Neurol India 2018;66:1822-4
Intraoperative cardiac arrhythmias are not uncommon during neurosurgery. Various causes have been attributed to it, especially while operating close to the brainstem. Operating in the vicinity of the brainstem can stimulate various cranial nerve nuclei, namely, the trigeminal, glossopharyngeal, and vagus nerves, which have the potential to cause severe bradycardia leading to cardiac asystole. In literature, facts regarding the glossopharyngeal-vagal reflex (GVR) have rarely been reported. We report two such cases of GVR while operating near the brainstem during surgery for a vestibular schwannoma.
A 40-year old female patient, weighing 45 kg, was admitted with complaints of headache, decreased hearing in the right ear, and decreased vision in both the eyes for 1 year. She was diagnosed with a right vestibular schwannoma and a retromastoid suboccipital craniotomy, and excision of the tumor was planned in lateral position. During the dissection of tumor adjacent to the glossopharyngeal nerve, an episode of bradycardia occurred, which led to asystole for less than 5s with a concomitant drop in the mean arterial blood pressure. The neurosurgeon was informed, and as soon as the stimulus was withdrawn, the heart rate and mean arterial pressure (MAP) returned to the baseline without any pharmacological treatment.
A 35-year old male patient, weighing 80 kg, presented with a history of headache and vomiting for the past 7 months; the patient was diagnosed with a right-sided vestibular schwannoma and planned for a right retromastoid suboccipital craniotomy. During the intraoperative course, there was a sudden drop in heart rate and the mean arterial pressure (MAP) from the baseline value of 95/min and 88 mmHg to 55/min and 65 mmHg, respectively. The operating surgeon was notified in time to remove the surgical stimulus and it was found that the inciting stimulus was near the glossopharyngeal nerve. As soon as the stimulus was withdrawn, there was instantaneous improvement in the heart rate and MAP.
Neurogenic bradycardia is a well-recognized complication during neurosurgery and rarely manifests as a fatal event. These reactions may be elicited by activation of the GVR due to direct stimulation of the glossopharyngeal nerve near the operative area. The impulses from the glossopharyngeal nerve travel through the tractus solitarius of the midbrain, and then to the solitary nucleus. From the solitary nucleus, excitatory neurotransmission to the dorsal (motor) nuclei of vagus results in parasympathetic outflow increase to the heart, leading to reflex bradycardia and sometimes asystole, forming the GVR arc [Figure 1]. Furthermore, it also sends inhibitory signals to the intermediolateral cell column in the spinal cord through the rostral ventrolateral medulla, causing reduced sympathetic outflow to the blood vessels that manifest as hypotension after vasodilation., Another plausible cause is the overflow of responses from the ninth cranial nerve into the vagal motor nucleus during the handling of cerebellopontine angle [Figure 2] or posterior fossa tumors. This kind of reflex can be potentially prevented by using lidocaine-soaked cotton pledgets over the operative area of interest in the vicinity of glossopharyngeal nucleus. Prophylactically, atropine injection can also be administered before handling the specific area of the brainstem. However, the authors do not favour the pharmacological intervention to treat bradycardia as this may mask the signs of brainstem handling and may permanently damage the cranial nerve nuclei. Transcutaneous pacing is also a reserved method, especially in high-risk cases. The authors reiterate the priority of proper vigilance and adequate knowledge over therapeutic measures to deal promptly with the situation in such a clinical scenario for the patient's benefit. Thus, the problem should be anticipated in time and a rapid intervention initiated.
|Figure 2: T1-weighted axial postcontrast image of the brain at the level of medulla showing a homogeneously enhancing extra-axial lesion in the right cerebellomedullary space with mass effect over the medulla|
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Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
The authors are grateful to Dr. Parthiban, Senior Resident, Department of Neuroradiology, All India Institute of Medical Sciences, New Delhi, for his efforts in illustrating the image.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]