Recurrent laryngeal nerve. Identification during thyroid and parathyroid surgery

Intraoperative identification of the recurrent laryngeal nerve (RLN) is mandatory in surgery of the thyroid and parathyroid glands to avoid surgical damage. Several methods have been proposed for identifying and localizing the RLN based on vocal cord motion produced by electrical stimulation of the nerve. Most of them require complex instrumentation, while others are in contradiction with anatomical basis. We present a safe and simple method for identifying the RLN during thyroid and parathyroid gland surgery, which requires no additional surgical instruments and can be performed as a routine procedure. Nonetheless, thorough knowledge of cervical anatomy still remains the most important point in this surgery.     

Recurrent laryngeal nerve monitoring in thyroid and parathyroid surgery: the University of Michigan experience

OBJECTIVES/HYPOTHESIS: Intraoperative monitoring of the recurrent laryngeal nerve (RLN) is finding increasing acceptance during thyroidectomy. Recently, a laryngeal surface electrode was introduced to enable another form of noninvasive monitoring of the RLN. The present report examines the University of Michigan experience with RLN monitoring using the postcricoid surface electrode. STUDY DESIGN: All patients undergoing partial or total thyroidectomy or parathyroidectomy from January 1999 to July 2001 were considered candidates for the study. Audiologists trained in intraoperative electrophysiological techniques performed all of the monitoring. METHODS: Data collected on each patient included 1) stimulation threshold for a laryngeal compound muscle action potential on initial RLN identification, 2) stimulation threshold of the laryngeal compound muscle action potential on completion of the procedure, and 3) flexible fiberoptic evaluation of the larynx at the initial postoperative visit and at the 3-month follow-up visit. The average duration of follow-up was 9.8 months with a range of 3 to 60 months. RESULTS: The average minimum current required for stimulation on first identification of all nerves was 0.57 mA (+/-0.48 mA). After completion of the procedure a mean threshold level of 0.42 mA (+/-0.55 mA) was obtained during direct RLN stimulation. Post-dissection stimulation of the RLN on the side of tumor dissection was 0.92 mA (+/-0.65 mA) compared with a stimulation threshold of 0.76 mA (+/-0.57 mA) for the nontumor side. CONCLUSIONS: Electromyographic monitoring of the RLN using a postcricoid surface electrode provides a safe, simple, and effective method for intraoperative monitoring during thyroid or parathyroid surgery. Further, evoked electromyography confirms RLN integrity at the conclusion of surgery.     

Intraoperative parathyroid hormone levels in thyroid and parathyroid surgery

OBJECTIVE: To determine the utility of intraoperative parathyroid hormone measurement in predicting postoperative hypocalcemia after thyroid and parathyroid surgeries that places total parathyroid function at risk. STUDY DESIGN: Retrospective case review. METHODS: The case records of 23 patients undergoing total or completion thyroidectomy and 30 patients undergoing parathyroid exploration were reviewed. All patients had intraoperative parathyroid hormone levels measured. Samples were taken before dissection and 10 minutes after the resection was completed. Serial ionized calcium levels were measured in the postoperative period. Percentages of reduction in PTH levels from preoperative to postresection levels were calculated. Percentages of reduction in PTH level and the absolute value of the intraoperative PTH values were compared with postoperative ionized calcium levels. RESULTS: In the 23 patients who underwent thyroid surgery, the average preoperative and postoperative PTH values were 50 pg/mL (range, 17-87 pg/mL) and 34 pg/mL (range, 4-93 pg/mL), respectively. The average decrease in PTH was 39% (range, 39%-90%). The incidence of hypocalcemia was significantly higher in patients with intraoperative PTH levels less than 15 pg/mL relative to patients with PTH levels greater than 15 pg/mL in this setting ( P=.006). In the 30 patients who underwent parathyroid exploration, average preoperative and postoperative PTH levels were 291 pg/mL (range, 65-1675 pg/mL) and 113.8 pg/mL (range, 6.5-1263 pg/mL) respectively. The intraoperative PTH level did not correlate with postoperative calcium levels in the parathyroid group. Percentages of decrease in PTH levels greater than 60% was statistically associated with surgical cure in this population. CONCLUSIONS: The study demonstrates that intraoperative PTH levels greater than 15 pg/mL after total or completion thyroidectomy indicate a low risk of postoperative hypocalcemia and that these patients may be candidates for outpatient surgery. In the parathyroid group, intraoperative PTH levels do not correlate well with postoperative calcium levels.     

Electrophysiologic recurrent laryngeal nerve monitoring during thyroid and parathyroid surgery: international standards guideline statement

Intraoperative neural monitoring (IONM) during thyroid and parathyroid surgery has gained widespread acceptance as an adjunct to the gold standard of visual nerve identification. Despite the increasing use of IONM, review of the literature and clinical experience confirms there is little uniformity in application of and results from nerve monitoring across different centers. We provide a review of the literature and cumulative experience of the multidisciplinary International Neural Monitoring Study Group with IONM spanning nearly 15 years. The study group focused its initial work on formulation of standards in IONM as it relates to important areas: 1) standards of equipment setup/endotracheal tube placement and 2) standards of loss of signal evaluation/intraoperative problem-solving algorithm. The use of standardized methods and reporting will provide greater uniformity in application of IONM. In addition, this report clarifies the limitations of IONM and helps identify areas where additional research is necessary. This guideline is, at its forefront, quality driven; it is intended to improve the quality of neural monitoring, to translate the best available evidence into clinical practice to promote best practices. We hope this work will minimize inappropriate variations in monitoring rather than to dictate practice options.     

Complications of thyroid and parathyroid surgery

Today most complications of thyroid and parathyroid surgery are related to either metabolic derangements or injury to the recurrent laryngeal nerves. Other complications include superior laryngeal nerve injury, infection, airway compromise, and bleeding. Although the principal goal of thyroid and parathyroid surgery is the prevention of these complications, prompt recognition and intervention will minimize morbidity and provide the patient with the best chance of a satisfactory outcome.     

Perioperative parathyroid hormone levels in thyroid surgery

OBJECTIVE: Perioperative hypocalcemia from temporary parathyroid gland dysfunction is common after thyroid surgery. No reliable cutoff values for parathyroid hormone (PTH) and the subsequent possibility of developing hypocalcemia exist. The purpose of this study is to determine a criterion for predicting hypocalcemia based on different PTH levels as cutoff values. STUDY DESIGN: Retrospective chart review. METHODS: A centralized database of intraoperative PTH levels was analyzed. PTH values approximately 10 minutes after excision of the thyroid gland and in the recovery room were obtained; serial ionized calcium levels were also analyzed. PTH values were then compared using chi-square analysis with significance defined as P < .05. A receiver operator characteristic (ROC) curve was also constructed to define sensitivities and specificities of different PTH levels as potential cutoff values. RESULTS: Eighty patients were identified meeting the study criteria between January 1999 and February 2005. Fourteen of the 80 (17.5%) patients became hypocalcemic during the hospital stay; none experienced permanent hypocalcemia. Patients who became hypocalcemic during their hospitalization were more likely to have a PTH level below 15 pg/mL (P < .01). Patients with a PTH level less than 15 pg/mL were more likely to develop hypocalcemia (P < .01). Finally, an ROC curve was constructed, allowing the surgeon to determine acceptable sensitivities and specificities and various PTH cutoff values. CONCLUSION: Low perioperative PTH levels significantly correlate with the presence of postoperative hypocalcemia but cannot be used to predict it. Using the ROC curve allows different chosen cutoff values to predict hypocalcemia with varying sensitivity and specificity.     

Surgical considerations and controversies in thyroid and parathyroid surgery

The techniques of thyroid surgery have been fully elucidated in several surgical texts and atlases. This article discuss surgical pearls of thyroid and parathyroid surgery. We discuss preoperative, intraoperative, and postoperative considerations and controversies for both procedures.     

Perioperative parathyroid hormone levels in thyroid surgery: preliminary report

OBJECTIVES/HYPOTHESIS: An immediate method of accurately predicting postoperative hypocalcemia after total thyroidectomy would allow for selective early discharge of patients at low risk. The objective of the study was to determine the utility of perioperative parathyroid hormone measurement in predicting postoperative hypocalcemia after a thyroid surgery that places total parathyroid function at risk. STUDY DESIGN: Prospective case series. METHODS: Twenty-seven patients undergoing total or completion thyroidectomy had three blood samples drawn for parathyroid hormone measurement before dissection, 10 minutes after specimen removal, and in the recovery room. Serial ionized calcium levels were measured in the postoperative period. Preoperative, postresection, and recovery room levels were compared with postoperative ionized calcium levels. RESULTS: The average values before resection, after resection, and in the recovery room were 69.3 (range, 13-163), 42.3 (range, 0-120), and 37.4 (range 7-79) pg/mL, respectively. The incidence of hypocalcemia was 11% (3 of 27 patients). The rate of hypocalcemia was significantly higher (50%) in patients with recovery room parathyroid hormone values of 10 pg/mL or less relative to patients with recovery room parathyroid hormone values greater than 10 pg/mL (4%) in this setting (P =.01). Among patients with a parathyroid hormone value of less than 15 pg/mL in the recovery room, an increasing parathyroid hormone level in the recovery room relative to the level after resection predicted normocalcemia without calcium supplementation on chi analysis (P =.01). CONCLUSION: The study demonstrated that perioperative parathyroid hormone values can help predict patients who are at highest risk for postoperative hypocalcemia after thyroid surgery.     

Nonrecurrent laryngeal nerves: anatomic considerations during thyroid and parathyroid surgery

PURPOSE: In head and neck surgery, damage to the recurrent laryngeal nerve (RLN) during thyroid surgery is the most common iatrogenic cause of vocal cord paralysis. Identification of the RLNs and meticulous surgical technique can significantly decrease the incidence of this complication. Nonrecurrent RLNs (NRRLNs) are exceedingly rare. Surgeons need to be aware of their position to avoid damage to them. MATERIALS AND METHODS: A retrospective review of 513 RLN exposures over a 7-year period was performed. RESULTS: Two NRRLNs were encountered, for an incidence of 0.39%. CONCLUSION: NRRLNs are rare. Awareness of their existence will prevent the surgeon from accidentally severing one if it is encountered during routine thyroid or parathyroid surgery.     

Intraoperative neuromonitoring by vagus nerve stimulation in thyroid surgery: Clinical assessment of recurrent and superior laryngeal nerves

Intraoperative neuromonitoring of the laryngeal nerves during thyroidectomy is a reliable method to assess nerve function. After identification of the cricothyroid ligament, a bipolar electrode is selectively inserted through the ligament into the thyroarytenoid muscle (TAM) and cricothyroid muscle (CTM). Vagus nerve stimulation then allows precise monitoring of the recurrent laryngeal nerve and the external branch of the superior laryngeal nerve (EBSLN) in the TAM and CTM, respectively. A significant muscle response (greater than 100 μV) is 100% predictive of preserved laryngeal mobility, while the absence of a muscle response is 70% predictive of vocal fold paralysis with 100% sensitivity and 98% specificity. A significant thyroarytenoid muscle response is only recorded ipsilateral to the stimulation with a shorter latency on the right side. A concomitant TAM and CTM response to vagus nerve stimulation or EBSLN stimulation is observed in more than 70% of cases.     

The use of drains following thyroid and parathyroid surgery: a meta-analysis

The use of suction drains following thyroid and parathyroid surgery is controversial. Although there have been several prospective and retrospective studies carried out on this subject, no paper had sufficient power to provide a suitable answer to whether or not drains should be used routinely. We present the first formal meta-analysis of the data from eight randomized controlled trials on this subject. The result of the meta-analysis showed that there is no difference in complication rates between patients in whom drains have been used routinely and those in whom they have not.     

Evaluation and treatment of complications of thyroid and parathyroid surgery

The major complications of thyroid and parathyroid surgery include hemorrhage, respiratory obstruction, hyperthyroid storm, hypoparathyroidism, and laryngeal nerve injury. In this article, the incidence, diagnosis, and treatment of various complications are reviewed, with emphasis on hypoparathyroidism and vocal cord paralysis, either bilateral or unilateral. Thyroplastic phonosurgery and carbon dioxide laser arytenoidectomy, two recent surgical additions to the rehabilitation of vocal cord paralysis, are described in depth.     

甲状腺及甲状旁腺术中神经监测的研究现状

喉返神经及喉上神经的保护一直是甲状腺及甲状旁腺手术中的重点和难点,传统方式通常为视觉暴露或区域保护,但是颈部手术空间狭小,上述方法具有一定局限性.现阶段多借助于神经监测,该技术的使用有助于降低手术难度,缩短手术时间.甲状腺术中神经监测是神经电生理在临床中的良好应用,有助于更好地保护喉返神经及喉上神经.本文通过结合近年最...     

Vagus nerve stimulator implantation in children

BACKGROUND: Vagus nerve stimulation was approved in 1997 as an adjunctive treatment of partial-onset seizures refractory to medical therapy. Subsequent to the initial clinical trials, few studies have been published specifically addressing perioperative management issues. OBJECTIVES: To review the operative technique and perioperative management of patients undergoing vagus nerve stimulator implantation and to analyze complications and their management. DESIGN: Retrospective medical record review and survey of patients who underwent implantation. SETTING: A tertiary care pediatric hospital in Kansas City, Mo. PATIENTS: One hundred two patients aged 21 months to 40 years. INTERVENTION: Vagus nerve stimulator implantation and lead placement. MAIN OUTCOME MEASURES: The surgical technique of vagus nerve stimulator implantation is presented in detail. Perioperative complications are enumerated, and strategies for their management are described. A subjective patient survey addresses some quality-of-life issues and the effect on swallowing and voice. RESULTS: One hundred two patients successfully underwent vagus nerve stimulator implantation. Three patients experienced infection of the chest wound holding the generator and required explantation. These 3 patients underwent reimplantation within 2 months after the infection had cleared. Most patients experience some degree of hoarseness when the generator is activated, but this symptom usually does not significantly affect the ability to communicate. Responses to questions regarding quality of life are positive. CONCLUSIONS: Vagus nerve stimulator implantation has a low incidence of serious complications. Quality of life seems to be improved for most patients. Modifications to the surgical procedure must be considered when performing the implantation on a young patient.