Vagal Nerve Monitoring during Parapharyngeal Space Tumor Removal

The vagus nerve innervates the intrinsic and extrinsic laryngeal musculature as well as the complex pharyngeal plexus. Acute paralysis of this nerve results in dysfunctional speech, deglutition, and airway protection. These untoward effects, which lead to additional infectious and aerodigestive complications, may arise following manipulation of the vagus nerve during the surgical removal of a variety of neoplasms found in the parapharyngeal space.The vagal nerve has been intraoperatively monitored in an effort to maintain its anatomic and functional integrity. Bipolar hook-wire electrodes are introduced transcutaneously through the cricothyroid membrane and are guided into the vocalis muscle by an assistant performing direct laryngoscopy. Continuous, real-time monitoring of the vagal nerve is provided by audio and visual feedback to the operating surgeon. Potentially injurious stretching, heating, and compression of the nerve are easily detected, and monopolar stimulation of the nerve is used to map the nerve's course through the tumor bed.This presentation outlines our technique for vagal nerve monitoring in patients with tumors of the parapharyngeal space and intact preoperative vocal cord mobility. Selected cases are presented and illustrated through intraoperative and postoperative videotapes.     

Recurrent Laryngeal Nerve Monitoring during Thyroid Surgery: Normative Vagal and Recurrent Laryngeal Nerve Electrophysiological Data

Objective Injury to the recurrent laryngeal nerve (RLN) remains a significant cause of morbidity during thyroid surgery. Intraoperative nerve monitoring (IONM) is being applied in many centers to facilitate nerve identification. The aim of this study was to elucidate normative human vagal and recurrent laryngeal nerve electromyograhic (EMG) parameters during standard IONM application. Study Design A prospective IONM study conducted over an 8-month period. Internal review board (IRB) approval was obtained. Settings Department of Otolaryngology, Division of Thyroid and Parathyroid Surgery, Massachusetts Eye and Ear Infirmary, Boston. Subjects and Methods All patients who were scheduled for routine thyroid, parathyroid, or neck exploration surgery were invited to participate. All patients had a preoperative and postoperative laryngeal examination to assess vocal cord function. Any patient with an abnormal preoperative laryngeal examination was excluded. Results Fifty-eight patients participated in this study. The right and left RLN latencies were similar. The left vagus latency was greater than the right vagus but was not significant. The RLN latency was significantly less than the vagus nerve. The right vagus nerve amplitude was significantly greater than the left. There was no difference between male and female amplitudes for either the RLN or vagus nerve. Conclusion This study highlights the electrophysiological/EMG differences and similarities between the RLN and vagus nerve. Normative amplitude measurements for bilateral RLN and vagus nerve stimulation are presented. There are limited data available in the literature on normal RLN and vagal EMG signals generated during thyroid surgery.     

Intraoperative Transcranial Motor-Evoked Potential Monitoring of the Facial Nerve during Cerebellopontine Angle Tumor Resection

Objective To determine whether transcranial motor-evoked potential (TCMEP) monitoring of the facial nerve (FN) during cerebellopontine angle (CPA) tumor resection can predict both immediate and long-term postoperative FN function.Design Retrospective review.Setting Tertiary referral center.Main Outcome Measures DeltaTCMEP (final-initial) and immediate and long-term facial nerve function using House Brackmann (HB) rating scale.Results Intraoperative TCMEP data and immediate and follow-up FN outcome are reported for 52 patients undergoing CPA tumor resection. Patients with unsatisfactory facial outcome (HB >2) at follow-up had an average deltaTCMEP of 57 V, whereas those with HB I or II had a mean deltaTCMEP of 0.04 V (t = -2.6, p < 0.05.) Intraoperative deltaTCMEP did not differ significantly between groups with satisfactory (HB I, II) and unsatisfactory (HB > 2) facial function in the immediate postoperative period.Conclusion Intraoperative TCMEP of the facial nerve can be a valuable adjunct to conventional facial nerve electromyography during resection of tumors at the CPA. Intraoperative deltaTCMEP >57 V may be worrisome for long-term recovery of satisfactory facial nerve function.     

Phrenic and Vagal Nerve Activities during Spontaneous Respiration and Positive-Pressure Ventilation

Afferent vagal nerve activity from stretch-receptors in the lung and efferent phrenic nerve activity were recorded during spontaneous respiration and during positive-pressure ventilation with three different types of ventilators. During spontaneous respiration the efferent phrenic nerve activity slightly preceded the afferent vagal nerve activity. Volume-controlled ventilation did not alter the phrenic nerve activity when the ventilation was set at a rate equal to that during spontaneous respiration, but afferent vagal volleys increased in duration. At higher frequencies of insufflation spontaneous inspiration was inhibited.
An increase in afferent vagal nerve activity and a concomitant slight decrease in efferent phrenic nerve activity were obtained during animal triggered pressure-controlled ventilation.
High-frequency positive-pressure ventilation (HFPPV) gave rise to basal, non-grouped activity in vagal afferents, causing inhibition of inspiration. During HFPPV, spontaneous respiration can take place on activation of other afferents to the respiratory centre.
Clinical aspects of respirator treatment from a neurophysiological standpoint are discussed.     

Recurrent Laryngeal Nerve Monitoring during Thoracoscopic Esophagectomy

Introduction

There have been several reports on the feasibility and curability of thoracoscopic esophagectomy, which may reduce injury to the thoracic cage and decrease the invasiveness of surgery. Although the recurrent laryngeal nerve (RLN) is identified and kept intact during operations, RLN palsy sometimes occurs. Currently, surgical aides, including intraoperative neurological monitoring, are being utilized to avoid RLN injury during thyroid surgery. This system is utilized during thoracoscopic esophagectomy in the prone position.

Patients and methods

Seven consecutive patients (six men, one woman; age range 62–74 years; mean 68 years) were included. Patients underwent general anesthesia and were intubated using the NIM TriVantage? electromyography (EMG) tube. One-lung ventilation was performed with an endobronchial blocker. Thoracoscopic esophagectomy was performed in the prone position. The nerve stimulator was calibrated to 0.5 mA, and after the RLN was visually identified it was subsequently stimulated, which also confirmed normal machine functioning. In some situations, in the absence of a response, stimuli were increased to 1.0 mA and then 2.0 mA.

Results

Intraoperatively, all seven patients had their nerve signals monitored. In one case, a nerve signal disappeared after complete lymph node dissection along the left RLN. This system could identify the site of injury, and the thoracoscopic magnified view allowed the disrupted point to be located precisely. When we checked VTR after surgery, the source of injury was one point tension of the nerve pulled by fiber during lymph node dissection.

Conclusions

Intraoperative RLN monitoring during thoracoscopic esophagectomy in the prone position, with one-lung ventilation performed using the TriVantage? EMG tube and a bronchial blocker, is technically feasible, easy, and reliable.     

Vagal Nerve Function in Obesity: Therapeutic Implications

The primal need for nutrients is satisfied by mechanisms for sensing internal stores and detecting food; ATP is the most primitive signal. With increasing density of sensory neurons and glia (the primordial brain) and the emergence of autonomic neural activity throughout the endoderm, transmitters and other signaling molecules enable alimentation before the appearance of innate storage functions. Memory and, ultimately, cognition are prerequisites for processing and producing food to facilitate assimilation and safeguard the supply of nutrients. The gut–brain–gut axis via the vagus nerve is the autonomic neurohumoral pathway integrating these elements of energy homeostasis. Humans uniquely override obligate nutrient needs, eating in the absence of deprivation, resulting in pathological chronic overnutrition arising from dysautonomia. Obesity surgery circumvents powerful redundant mechanisms of alimentation and reduces excess stores of body fat from chronic overnutrition while preventing re-accumulation of fat. All bariatric operations, whether purely restrictive, maldigestive and malabsorptive, or combinations, rely on regulatory mechanisms related to autonomic nervous system function and the brain–gut axis. We review the functional anatomy and the importance of the vagus nerve for maintaining maladaptive chronic overnutrition and describe interventions to abrogate its effects. In aggregate, the preponderance of evidence supported by laboratory and clinical mechanistic studies interrupting abdominal bi-directional vagal transmission demonstrates that the majority of patients report less “hunger” and lose weight.     

Schwannoma of Parapharyngeal Space: a Case Report

The incidence of schwannoma in the head and neck region is between 25 and 45 %. The vestibular nerve is involved in most cases followed by the parapharyngeal space. Schwannoma, also known as neurilemmoma, is a benign neoplasm that originates from the Schwann cells. These cells form the myelin sheath around myelinated peripheral axons. Here, we report a case of parapharyngeal space schwannoma in a 27-year-old female.     

Giant Parapharyngeal Space Lipoma: Case Report and Surgical Approach

Large parapharyngeal space tumors near critical neurovascular structures pose challenging management problems. Only eight cases of a lipoma in the parapharyngeal space have been reported. We present a surgical approach that permits safe resection of such unusual tumors.A 49-year-old man had a 2-year history of progressive pain in the left neck radiating from the shoulder to the occiput. Contrast-enhanced computed tomography (CT) of the neck demonstrated a fat-attenuation mass located in the poststyloid parapharyngeal space. The mass extended into the foramen transversarium at the level of the second cervical vertebra and encased the vertebral artery. The tumor was removed through an extended transcervical approach that included transection of the attachments of the sternocleidomastoid, trapezius, splenius capitus, and the longissimus capitus muscles. The approach provided access to the first cervical vertebra, allowing dissection of the tumor from the vertebral artery in the foramen transversarium. An extended transcervical approach provides exposure from the carotid artery to the vertebral artery and facilitates the complete excision of large parapharyngeal space masses.     

Continuous Positive Airway Pressure Increases Vagal and Phrenic Nerve Activity in Cats

To investigate how continuous positive airway pressure (CPAP) changes the vagal nerve activity and whether CPAP alters the efferent phrenic nerve activity or the breathing pattern similarly before and after vagotomy, a study was made of vagal and phrenic nerve activity in chloralose-anaesthetized cats. In the vagal nerve, CPAP increased the mean impulse frequency during expiratory rest. The breath-related impulse frequency also increased with CPAP. With higher CPAP (greater than or equal to 0.5 kPa), the peak of breath-induced activity in the vagal nerve lasted longer than inspiration. In the phrenic nerve, the impulse frequency in the bursts increased almost linearly with CPAP irrespective of whether the vagal nerves were intact or not. The duration of the phrenic nerve bursts decreased with increasing CPAP when the vagal nerves were intact. When the vagal nerves were cut, the burst duration did not change. The rate of breathing was almost unchanged by CPAP regardless of whether the vagal nerves were cut or not. The inspiration/expiration ratio decreased with increasing CPAP when the vagal nerves were intact, but not when they were cut.     

Cutaneous Malignant Peripheral Nerve Sheath Tumor

Cutaneous malignant peripheral nerve sheath tumors (MPNSTs) are rare sarcomas of neuroectodermal origin arising in the dermis and/or subcutis. In contrast with their deep soft tissue and visceral counterparts, cutaneous MPNSTs are rarely associated with neurofibromatosis type 1. Two main subtypes of cutaneous MPNST can be distinguished histologically: conventional (ie, spindle cell) and epithelioid MPNST. The 2 subtypes also differ in predilection for deep versus superficial locations, association with preexistent benign peripheral nerve sheath tumors and S100 immunohistochemistry. Herein, we review current knowledge of cutaneous MPNST and discuss its differential diagnosis.     

Intraoperative Vagus Nerve Monitoring: A Transnasal Technique during Skull Base Surgery

Objectives Intraoperative vagus nerve monitoring during skull base surgery has been reported with the use of an oral nerve monitoring endotracheal tube. However, the intraoral presence of an endotracheal tube can limit exposure by its location in the operative field during transfacial approaches and by limiting superior mobilization of the mandible during transcervical approaches. We describe a transnasal vagus nerve monitoring technique. Design and Participants Ten patients underwent open skull base surgery. Surgical approaches included transcervical (five), transfacial/maxillary swing (three), and double mandibular osteotomy (two). The vagus nerve was identified, stimulated, and monitored in all cases. Main Outcome Measures Intraoperative nerve stimulation, pre- and postoperative vagus nerve function through the use of flexible laryngoscopy in conjunction with assessment of subjective symptoms of hoarseness, voice change, and swallowing difficulty. Results Three patients had extensive involvement of the nerve by tumor with complete postoperative nerve deficit, one patient had a transient deficit following dissection of tumor off of nerve with resolution, and the remaining patients had nerve preservation. One patient experienced minor epistaxis during monitor tube placement that was managed conservatively. Conclusions Transnasal vagal nerve monitoring is a simple method that allows for intraoperative monitoring during nerve preservation surgery without limiting surgical exposure.     

Vagal and sympathetic activity during spinal analgesia

Indices of vagal and sympathetic activity were studied in 30 elderly males, to elucidate their possible roles in causing hypotension during spinal analgesia. The technique of spinal analgesia and the regimen of intravenous fluids were standardised. An index of vagal activity was derived from the degree of heart rate variation (successive RR interval change) on ECG recordings. Sympathetic activity was evaluated by changes in the skin conductance (SCR) of 15 patients. Analgesia to pinprick reached a median dermatome level of T5-6 (range T2-T10) by 15 min. Hypotension was correlated with the level of analgesia, and was more likely when spinal analgesia was higher than T5. There was no correlation between vagal activity and the degree of hypotension. The depression of skin conductance responses was not correlated with the degree of hypotension nor with vagal activity. Vagal efferent activity, measured at the heart, does not seem to play a causative role in hypotension occurring during spinal analgesia.     

Vagal Nerve Stimulation May Be a Potentially Beneficial Treatment for Acute Myocardial Ischemia

Myocardial ischcmia reperfusion injury is an inflammatory process which is characterized with augmenting production and release of proinflammatory cytokines. Although ischemia pre-and postconditioniug can protect myocardium against iscbemia reperfusion injury, existence of some limitations restricts their clinical application widely. Vagus nerve stimulation has been identified with ability to inhibit release of proinflammatory cytokines and to provide other benefits to myocardial ischemia reperfusion injury. Moreover, vagus nerve stimulation has been already used clinically in patients with neuropsychiatric disorders and chronic advanced heart failure. Thus we consider that vagus nerve stimulation may be an effective adjunct treatment attenuating myocardial ischemia reperfusion injury prior to hospital arrival or percutaneous coronary intervention.     

Malignant Peripheral Nerve Sheath Tumor Arising in Association With the Sural Nerve

Malignant peripheral nerve sheath tumor is a rare sarcoma of peripheral nerves found most often in deep soft tissue. This aggressive tumor is difficult to diagnose clinically and must be surgically excised for therapy. An incisional biopsy will allow for testing and in most cases, diagnosis. The authors present a case of a 39-year-old African American woman with malignant peripheral nerve sheath tumor in association with the sural nerve. The tumor was surgically removed and sent for pathologic studies. The patient reported to her first postoperative appointment and was referred to an oncologist for follow-up. Despite multiple attempts at contacting the patient and explaining the prognosis of the diagnosis, the patient refused further follow-up care including referral to an oncologist.     

下颌骨外旋入路咽旁间隙肿瘤切除术的护理配合

目的 探讨下颌骨外旋入路咽旁间隙肿瘤切除术的最佳护理配合,以便更好地在术中进行医护合作.方法 对26例咽旁间隙肿瘤患者实施下颌骨外旋入路咽旁间隙肿物切除手术.结果 26例患者均完整切除肿瘤,手术顺利完成.结论 了解手术方式,做好手术用物的准备,熟练的手术配合,能缩短手术时间,提高手术成功率.     

Facial Nerve Monitoring under Neuromuscular Blockade

The characteristics of facial nerve electromyography at various levels of neuromuscular blockade are unclear. Partial blockade is well known to facilitate anesthetic safety and management. However, the use of neuromuscular blockage in many skull base procedures is avoided to allow intraoperative facial nerve monitoring.We studied the influence of various levels of neuromuscular blockade on facial nerve stimulation in the New Zealand white rabbit. The facial nerve was exposed in the middle ear of six rabbits. Using electromyographic-type facial nerve monitor, we recorded the facial electromyography signals in these rabbits at increasing levels of vecuronium-induced neuromuscular blockade. All animals demonstrated reliable facial electromyography response at all levels of partial neuromuscular blockade (P < .02). Five of the six animals could be monitored throughout complete blockade. These results clearly demonstrate that rabbit facial electromyography monitoring is possible under neuromuscular blockade. The effect of neuromuscular blockers on facial electromyography monitoring deserves further study, as partial blockade would greatly facilitate the management of anesthesia in otologic, neurotologic, and skull base surgery.