Evaluation of laryngeal function after implantation of the vagus nerve stimulation device.

OBJECTIVES: The vagus nerve stimulation device (VNS) is used for the management of seizures. This study evaluated what effect the diameter of the vagus nerve helical electrode might have on true vocal cord (TVC) mobility. The study was prompted after 2 cases of TVC immobility. Electrode nerve compression was suspect. METHODS: Eighteen patients underwent intraoperative vagus nerve measurement and electrode placement with subsequent voice and TVC evaluation. Electrode selection was based on vagus nerve measurements. RESULTS: Seven patients had vagus nerves measuring less than 2 mm diameter and received the 2-mm inner diameter electrode. Eleven patients had vagus nerves measuring more than 2 mm in diameter and received the 3-mm inner diameter electrode. No patients experienced transient or permanent hoarseness or paresis/paralysis. CONCLUSION: Precise vagus nerve measurements and electrode selection appear to decrease the incidence of nerve compression injury and TVC immobility.     

Revision and removal of stimulating electrodes following long-term therapy with the vagus nerve stimulator

BACKGROUND

A significant concern about vagus nerve stimulation therapy has been the disposition of the spiral stimulating electrodes once treatment is considered ineffective or is no longer desired. Because the electrodes are wrapped around the vagus nerve, there is the potential for nerve injury during their removal.

METHODS

We attempted removal of the spiral stimulating electrodes from 10 patients who received long-term vagus nerve stimulation therapy for drug-resistant epilepsy. In some patients, replacement with electrodes was also performed for poorly functioning leads.

RESULTS

The mean duration of electrode implantation was 3.7 ± 2.2 years (range 1.1–7.3 years). In seven patients, the old electrodes were removed completely from the nerve. No adverse events occurred intraoperatively or postoperatively.

CONCLUSIONS

Our results indicate that the spiral electrodes may be safely removed from the vagus nerve, even after the electrodes have been implanted for several years. The reversibility of lead implantation may enhance the attractiveness of vagus nerve stimulation therapy for patients with medically-intractable epilepsy.     

The use of vein grafts in upper extremity nerve surgery

Vein grafts have been used to cope with several problems in peripheral nerve surgery, including vein wrapping of scarred nerves involved in chronic pain syndromes, vein caps for recurrent end-stump neuromas, vein conduits for nerve gaps after resection of neuromas-in-continuity, and following trauma. From 1993–1997, 30 vein grafts were performed in 28 patients. Five chronic peripheral nerve pain syndromes were treated by vein wrapping for two ulnar, two median and one radial sensory nerve, with significant pain resolution in all cases. Two recurrent digital neuromas were treated with vein caps, with pain resolution in each case. Nine patients with neuromas-in-continuity underwent neuroma resection and nerve repair with vein conduits. Twelve patients (14 nerves) underwent primary or delayed repair with vein conduits for nerve gaps following trauma. Sensory return measured by two point discrimination after repair of nerve gaps, following either neuroma-in-continuity resections or trauma, was 5–10 mm in 17 digital or common digital nerve injuries, and greater than 10 mm in three radial sensory nerve injuries. Received: 15 July 1998 / Accepted: 8 December 1998     

Cervico-mediastinal schwannoma of the vagus nerve: resection with intraoperative nerve monitoring

Schwannomas are usually benign, single, encapsulated, slow-growing tumours originating from cranial or spinal nerve sheaths. The vagus nerve involvement at the mediastinal inlet is very uncommon. For anatomical reasons, the resection of cervical and mediastinal schwannoma of the vagus nerve has a high risk of vocal fold paralysis. We describe the case of a 67-year-old female with a cervico-mediastinal schwannoma of the vagus nerve that we removed using the intraoperative neuromonitoring technique. The patient presented with mild hoarseness and complained of discomfort behind the jugular notch. Neck and chest computerized tomography described a 35 × 30 mm solid lesion behind the left clavi-sternal junction; preoperative fine needle aspiration cytology revealed schwannoma. Resection of the mass was performed with a cervical approach and the vagus nerve tumour was completely removed under continuous neuromonitoring (NIM-3^® System), preserving the vagus and the recurrent laryngeal nerve function. Pathology on the resected mass documented A-type schwannoma with “ancient schwannoma” areas. The intraoperative neurostimulation and neuromonitoring approach for the resection of vagus schwannoma are recommended because it may reduce the risk of injury to the vagus and to the recurrent laryngeal nerve.     

Revision of vagal nerve stimulator electrodes: technical approach

Summary Background. As the number of implanted vagal nerve stimulators grows, the need for removal or revision of the devices will become more frequent. Our purpose was to demonstrate the feasibility of complete removal of the vagal nerve stimulator electrode using microsurgical technique.Methods. Operative databases at the University of Utah (1995 through 2002), Westchester Medical Center (1995 through 2001), and University of Arizona Health Sciences Center (1995 through 1999) were retrospectively reviewed. Patients who had undergone removal or revision of a previously placed vagal nerve stimulator electrode were identified. Patients who had a vagal nerve stimulator device removed but had the lead trimmed and incompletely removed were excluded.Findings. Seven patients underwent complete removal of the lead. Microsurgical dissection allowed removal of the helical electrode from the vagus nerve without apparent physiological consequences. Four patients had a new electrode placed just proximal to the original lead site. The operative procedure required an additional 30 minutes to complete compared with initial device placement. The four patients who underwent replacement of the electrode demonstrated normal device function and lead resistance at the time of postoperative follow-up. Each experienced a return to prior stimulation response and seizure control.Conclusions. This series suggests that the electrode can be removed from the vagus nerve and repositioned without significant consequence in most cases.     

Endotracheal tube electrodes to map and monitor activities of the vagus nerve intraoperatively. Technical note

Difficulty swallowing due to damage of the vagus nerve is one of the most devastating complications of surgery in and around the medulla oblongata; therefore, intraoperative anatomical and functional evaluation of this nerve is crucial. The authors applied endotracheal tube surface electrodes to record electromyography (EMG) activity from vocal cords innervated by the vagus nerve. The vagal nucleus or rootlet was electrically stimulated during surgery and vocalis muscle EMG activities were displayed by auditory and visual signals. This technique was used successfully to identify the vagus motor nerve and evaluate its integrity during surgery. The advantages of this method compared with the use of needle electrodes include safe simple electrode placement and stable recording during surgery. In cases involving a pontine cavernoma pressing the nucleus or a jugular foramen tumor encircling the rootlet, this method would be particularly valuable. Additional studies with a larger number of patients are needed to estimate the significance of this method as a means of functional monitoring to predict clinical function.     

Modified Radical Neck Dissection Is Better Than Partial Dissection of Lymph Nodes

Background  For papillary thyroid cancer, lymph node excision may be less important for smaller tumors and rather limited node excision might be sufficient to prevent recurrence. Methods  We compared patients who had undergone modified radical neck dissection with patients who had undergone limited node basin excision. Between 1967 and 1996, 4966 patients at our institution had resection of pure papillary carcinoma tumors larger than 11 mm. Results  In patients whose tumors were larger than 25 mm without local adhesion, modified radical neck dissection had a significantly better prognosis compared to that of more limited node excision. For patients with a primary tumor larger than 11 mm, modified radical had a better prognosis than partial node excision only if there was adhesion or invasion to the recurrent nerve, jugular vein, common carotid artery, vagus nerve, or trachea. Conclusion  The size of papillary cancer of the thyroid directly affects prognosis and the role of nodal dissection.     

Controlled intermittent asystole cardiac therapy induced by pharmacologically potentiated vagus nerve stimulation in normal and hibernating myocardium

BACKGROUND: Pharmacologically potentiated electrical stimulation of the right vagus nerve achieves controlled intermittent asystole cardiac therapy. The present study examined pathophysiologic consequences of repetitive intermittent asystoles on contractile function, myocardial blood flow, and vagus nerve function and morphology. METHODS: Open-chest anesthetized canines, with either normal left anterior descending (LAD) coronary arteries (n = 8) or severely stenotic LADs (n = 8), received pharmacologic pretreatment with pyridostigmine (0.5 mg/kg), propranolol (80 microg/kg), and verapamil (50 microg/kg) before vagus nerve stimulation. Time-matched control animals with normal (n = 4) or severely stenotic LADs (n = 6) received drugs but no vagus nerve stimulation. The vagus nerve was stimulated for 12 seconds ("on") and rested for 15 seconds ("off"). This algorithm was repeated for 15 on-off cycles, simulating using controlled intermittent asystole during the placement of 15 sutures in a distal coronary anastomosis. This 15-cycle sequence was repeated twice more, simulating a three-vessel bypass. RESULTS: Normal coronary arteries: Ninety minutes after three sets of controlled intermittent asystole, LAD blood flow was unchanged from base line (36.6 +/- 4.5 versus 33.0 +/- 4.2 mL/min, p = 0.4), and global left ventricular performance (impedance catheter, end-systolic pressure-volume relations) was similar to baseline (7.4 +/- 1.2 versus 7.2 +/- 1.0 mm Hg/mL, p = 0.1). Left anterior descending coronary artery stenosis model: Ninety minutes after CIA, there were no significant differences versus control animals in regional LAD blood flow (27 +/- 4 versus 29 +/- 5 mL/min, p = 0.4) or fractional shortening of LAD myocardium (sonomicrometry; 6.2% +/- 1.8% versus 5.4% +/- 1.2%, p = 0.1). Vagus nerve conduction and morphology were unchanged from baseline. CONCLUSIONS: Repetitive controlled intermittent asystole does not impair poststimulation coronary blood flow, cardiac contractile function, or vagus nerve function. Controlled intermittent asystole may be useful to facilitate off-pump or endoscopic coronary artery bypass grafting.     

Performance of bipolar forceps during coagulation and its dependence on the tip material: a quantitative experimental assay. Technical note

The aim of this study was to measure objectively the adherence of burned tissue to bipolar forceps to evaluate the coagulation performance of forceps made of different types of metals. Coagulation performance of bipolar forceps made of gold, titanium, and stainless steel was determined by comparing the amount of protein in the adhered coagulum on the tips. The amount of adhered coagulum was significantly less on the gold-plated bipolar forceps than on those made of the other two materials. The ease with which coagulum could be removed was compared using the cleaning cycle of an ultrasonic rinsing device. This ease of removal was also significant with the gold-plated forceps. Electron microscopy observations of the surface of the forceps tips revealed a significant difference in roughness among these materials, and there were also significant differences in wetting tensions. Measuring adherence based on three different types of roughness and wetting tensions of forceps made from the same metal (titanium) also demonstrated a significant difference in the cleaning cycle. Histological examination of an artery coagulated with the gold-plated bipolar forceps showed that the structure had been completely collapsed without destruction of the layers, whereas arteries coagulated with the other materials revealed severely damaged structures. Adherence to bipolar forceps was dependent on both the material in the tips and the roughness of this material. The gold-plated bipolar forceps demonstrated the best performance.     

完整迷走神经刺激对大鼠全身炎性反应的影响

目的 了解完整迷走神经刺激(IVNS)对大鼠全身炎性反应的影响. 方法以内毒素血症为全身炎性反应模型.将100只SD大鼠随机分为A组[静脉注射内毒素/脂多糖(LPS)]、B组(切断迷走神经、注射LPS后对其远端行电刺激)、C组(注射LPS后行迷走神经干电刺激)、D组(除注射等量等渗盐水外,同C组处理)、E组(仅注射等量等渗盐水).于注射前及注射后2、4、6 h,观察血清肿瘤坏死因子α(TNF-α)、白细胞介素10(IL-10)水平变化.每组取5只大鼠测定平均动脉压(MAP). 结果注射后10 min,前3组大鼠MAP值显著升高(P<0.05),以A组最明显[(134.4±7.3)mm Hg,1 mm Hg=0.133 kPa,P<0.05];注射后30 min,前3组MAP值明显下降(P<0.05);注射后10 min～6 h,A组MAP值均明显低于B、c组(P<0.05).注射后2、4、6 h,B、C组血清TNF-α水平均明显低于A组(P<0.05).注射后4、6 h,C组大鼠IL-10水平显著高于A、B组(P<0.05).结论 IVNS能稳定全身炎性反应时的血流动力学指征,并具有抗炎效应.     

Substance P and somatostatin content and transport in vagus and sciatic nerves of the streptozocin-induced diabetic rat

Substance P (SP) and somatostatin (SS) are two widely distributed neuropeptides that within the vagus and sciatic nerves are localized predominantly in sensory fibers. The effect of diabetes mellitus on their content or transport in sensory nerves is unknown. With the nerve ligation technique, the peripheral orthograde 24-h transport of both peptides was quantified in the vagus nerve 3 days or 1 mo after induction of streptozocin (STZ) diabetes and in both the vagus and sciatic nerves after diabetes of 3 mo duration. In acute (3-day) diabetics, neuropeptide transport in the vagus was unaltered. After 1 mo, SP transport was significantly increased; content in unligated contralateral nerve was unaltered. Transport of SS was unchanged, and content in contralateral nerve was too low to reliably quantitate. After diabetes of 3-mo duration, transport of both peptides in the vagus nerve was increased in STZ-induced diabetic (STZ-D) rats versus both weight- and age-matched controls: SP 474 +/- 17 (N = 10) vs. 358 +/- 32 (N = 13) pg/24 h, STZ-D rats vs. controls, mean +/- SE, P less than .03; SS 29 +/- 4 vs. 20 +/- 3 pg/24 h, STZ-D rats vs. controls, P less than .02. In the sciatic nerve, SP transport and content were unaltered. SS content was significantly reduced: 17 +/- 3 vs. 30 +/- 3 pg/3-mm nerve segment, STZ-D rats vs. controls, P less than .01. SS transport in the sciatic nerve of diabetic rats was variably reduced (P less than .07), and transport rates were increased (1.41 +/- 0.13 vs. 0.96 +/- 0.10 mm/h.(ABSTRACT TRUNCATED AT 250 WORDS)     

The use of Heanley bone-cutting forceps to reduce the thickened and broad bony dorsum in rhinoplasty

Heanley bone-cutting forceps can be used in a modified rhinoplasty technique for patients with nasal bones that are broad and thickened by callus as a result of several previous nasal fractures. In these patients, the conventional technique of dehumping followed by medial and lateral osteotomies may leave a roof of thickened nasal bones due to callus formation that prevents the pyramid from being narrowed. In this situation, Heanley forceps may be used instead of medial osteotomies to resect paramedian segments of the remaining thickness of the nasal bones so that the nasal bones can be medialized. If no dehumping is required and the bones are just splayed and thickened by callus, Heanley forceps can be used before infracturing and lateral osteotomies. Several points are important for the success of this technique, including introducing the beaks of the forceps submucosally in the correct plane on each side of the nasal bones, advancing the tips of the forceps as far as the nasion, and mobilizing the bony segments before performing lateral osteotomies.     

周围神经小间隙动脉桥接后的组织学观察

目的探讨动脉套管内神经间隙缝合后神经再生的机理。方法在ＳＤ大鼠腓总神经切断后，行外膜直接缝合及用２ｍｍ间隙自体动脉套接作比较。术后７、１４、２１、２８天取两组样本，采用多种染色法染色后，在光镜及电镜下观察神经的再生过程。结果动脉桥接组神经再生时间比直接缝合组慢２周，但再生速度基本相同。动脉套管内神经纤维向远端生长的有效率较直接缝合组大。结论神经缝合段留出供神经自然随机选择及化学特异选择的空隙，有益于混合神经修复后的有效再生     

Comparison of a new automatically controlled electrocoagulator (Valleylab NS 2000-INSTANT RESPONSE technology) with a high-frequency coagulator.

Bipolar electrocoagulation is one of the most important procedures in modern neurosurgery. However, there are still many practical problems, especially tissue adherence to the tips of the coagulating forceps and the difficulty removing carbonized clots from the tips. Both make the process less accurate and more time-consuming. To prevent formation of coagulum, recently, irrigation with a saline solution and coating of the forceps tips with a special metal have been tried. In this work, we compare a new bipolar electrocoagulator with automatic output control in relation to tissue impedance (Auto Suture - Valleylab NS 2000 with INSTANT RESPONSE technology) with a high-frequency coagulator (Erbotom ICC 350, Erbe). The femoral arteries and nerves of Wistar rats, weighing on average 360 g, were prepared and coagulation was carried out with variable power settings during a constant time (3 seconds). Sections were stained with haematoxylin-eosin, van Gieson and Luxol-Fast-Blue for histological examination. Coagulation with Erbotom ICC 350 resulted in tissue sticking to the tips of the forceps in all cases, regardless of the power chosen. With the new electrocoagulator, tissue adherence to the forceps tips was not seen. With the new system, effective coagulation was also achieved at comparably lower power settings.     

Intraoperative nerve stimulation: a simple, effective, and inexpensive alternative to standard devices

Many surgical procedures require intraoperative stimulation of peripheral nerves. Using a pair of conventional bipolar forceps and an anesthetic impulse generator (Stimlocator, Model SL3, B. Braun Australia Pty Ltd, Australia), we have developed a simple, effective, and inexpensive alternative to standard nerve stimulation devices that enables the accurate localization of motor fascicles intraoperatively. Bipolar forceps provide better control than a monopolar electrode, as the current generated across the nerve fibers generates an action potential that is then propagated down the axon. This inexpensive and reusable device is routinely used at Royal Children's Hospital, Melbourne, and its efficacy and ease of use has been demonstrated over a long period.     

Controlled-tension suture-tying forceps.

Suture-tying forceps have been designed to enable surgeons to tie consecutive sutures to the same tension to create an evenly compressed wound. The tensioning effect of the forceps was tested by tying a suture to the end of a cantilever beam strain-gauge device. Three sutures were used: 10/0 nylon, 8/0 polyglactin (Vicryl) and 8/0 virgin silk. The tests were repeated, coating the tips with citrated blood, sodium hyaluronate and saline. Adjustment of the forceps altered the suture tension in 0.015-N steps. Sterilization of the forceps by ethylene oxide or by an autoclave caused no obvious regression in the forceps performance. When the suture and surface lubricant remain constant, there is a linear relationship between forceps setting and the tension induced in the suture.     

An advanced system for electrocoagulation in neurosurgery

The authors present a new, advanced system for electrocoagulation. In order to solve the problems connected with standard and bipolar EC machines available to date (i.e.: uneven and incostant coagulation; adhesion of tissue to the tips of the forceps, etc.), the Authors realized bipolar screened forceps with a well balanced current flow to avoid any heat dissipation. This new type of forceps are fed by a peculiar, two-step heating pattern, time dependent, that coagulates only the core of the clamped tissue.     

Management of vagus nerve stimulation therapy in the peri-operative period

Vagus nerve stimulation is a well-established treatment option for patients with drug-resistant epilepsy and has an expanding range of other clinical indications. Side effects of vagus nerve stimulation therapy include: cough; voice changes; vocal cord adduction; rarely, obstructive sleep apnoea; and arrhythmia. Patients with implanted vagus nerve stimulation devices may present for unrelated surgery and critical care to clinicians who are unfamiliar with their function and safe management. These guidelines have been formulated by multidisciplinary consensus based on case reports, case series and expert opinion to support clinicians in the management of patients with these devices. The aim is to provide specific guidance on the management of vagus nerve stimulation devices in the following scenarios: the peri-operative period; peripartum period; during critical illness; and in the MRI suite. Patients should be aware of the importance of carrying their personal vagus nerve stimulation device magnet with them at all times to facilitate urgent device deactivation if necessary. We advise that it is generally safer to formally deactivate vagus nerve stimulation devices before general and spinal anaesthesia. During periods of critical illness associated with haemodynamic instability, we also advise cessation of vagus nerve stimulation and early consultation with neurology services.     

Modification of the Surgical Strategy for the Dissection of the Recurrent Laryngeal Nerve Using Continuous Intraoperative Nerve Monitoring

Background

The aim of this study was to describe first experiences and changes in management using continuous intraoperative neuromonitoring (C-IONM) in thyroid and parathyroid surgery.

Method

Retrospective analysis of patients who underwent surgery with C-IONM since 2012. Surgical maneuvers were modified when electrophysiologic events occurred. Patients with persistent loss of signal (LOS) underwent postoperative laryngoscopy.

Results

One hundred and one patients (of 1586 neck surgeries) were included and 19 had events: In 13 these were temporary (resolved before end of surgery) and led to intraoperative modifications in surgical approach; in all cases traction was released, and in 8, recurrent laryngeal nerve (RLN) approach was changed [superior approach (2), inferior approach (2), both (4)]. Six patients had persistent LOS (5.9%, present at end of procedure), with RLN palsy (RLNP) on postoperative day 1: In three, LOS occurred at electrode placement on the vagus nerve, leading to distal placement of the electrode allowing ipsilateral dissection under continuous monitoring; all three had complete recovery at 6 months. In the three other patients, LOS occurred on the RLN: one probable thermal, one traction lesion and one accidental section of the anterior RLN branch. The RLN recovered within 6 months in two patients, and in the third, RLNP persisted after 6 months (1/101 = 1%).

Conclusion

C-IONM provides real-time evaluation of the RLN function, allowing for adaptation of surgical maneuvers to prevent RLNP. It seems particularly useful in difficult cases like redo neck surgery, invasive thyroid cancer and intrathoracic or large goiter. Care should be given at electrode placement on the vagus nerve.

     

A technique of end-to-side anastomosis of a prosthetic graft to the ascending aorta: reinforcement of the anastomosis with wrapping of the ascending aorta

In temporary, permanent or extra-anatomic bypass grafting to the side of the ascending aorta, a technique of prosthetic fabric wrapping of the ascending aorta associated with reinforcement of the anastomosis is devised as a simple and useful method for aortic surgery. With this technique, dislodgement of the vascular forceps can be prevented completely, and the ascending aortic wall may be protected from injuries owing to the vascular forceps.