External Branch Of The Superior Laryngeal Nerve Injury Research Articles

Utility of video-assisted method for identifying and preserving the external branch of the superior laryngeal nerve during thyroidectomy.

The EBSLN is vulnerable to damage during thyroidectomy, results in voice related complications, negatively affect patient quality of life, routine identification of the EBSLN prior to surgical manipulation is necessary for a complication-free thyroidectomy. We aimed to validate a video-assisted procedure for identifying and preserving the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy and analyze the EBSLN Cernea classification and the localization of the nerve entry point (NEP) from the insertion of the sternothyroid muscle. A prospective descriptive study was performed; 134 patients, who scheduled for lobectomy with an intraglandular tumor max diameter ≤ 4 cm and without extrathyroidal extension, were randomly divided into the video-assisted surgery (VAS) and conventional open surgery (COS) groups. We used the video-assisted surgical procedure for visually identifying the EBSLN directly, and compared the differences in the visual identification rate and total identification rate of the two groups. We also measured the localization of the NEP using the insertion of the sternothyroid muscle as a reference. There was no statistically significant difference in clinical characteristics between the two groups. The visual identification rate and total identification rate were significantly higher in the VAS group than the COS group (91.04% vs. 77.61%, 100% vs. 89.6%). The EBSLN injury rate was 0 in both groups. The mean vertical distance (VD) of the NEP from the sternal thyroid insertion was 1.18 mm (SD 1.12 mm, range, 0-5 mm), with approximately 88.97% of the results occurring within the 0-2 mm range. The mean horizontal distance (HD) was 9.33 mm (SD 5.03 mm, range, 0-30 mm), with over 92.13% of the results occurring within the 5-15 mm range. Both the visual and total identification rates of the EBSLN were significantly higher in the VAS group. This method provided a good visual exposure rate of the EBSLN, aiding in identifying and protecting the EBSLN during thyroidectomy.

Assessment of different classification systems for predicting the risk of superior laryngeal nerve injury during thyroid surgery: a prospective cohort study.

A multitude of anatomical variations have been noted in the external branch of the superior laryngeal nerve (EBSLN). In this study, intraoperative neuromonitoring (IONM) was used to assess the potential value of the different classical EBSLN classifications for predicting the risk of EBSLN injury. In total, 136 patients with thyroid nodules were included in this prospective cohort study, covering 242 nerves at risk (NAR). The EBSLN was identified by observing the cricothyroid muscle twitch and/or typical electromyography (EMG) biphasic waveform. The EBSLNs were classified by Cernea classification, Kierner classification, and Friedman classification, respectively. The EMG parameters and outcomes of vocal acoustic assessment were recorded. The distribution of Cernea, Kiernea, and Friedman subtypes were, respectively, Cernea 1 (40.9%), Cernea 2A (45.5%), Cernea 2B (10.7%), Kierner 1 (40.9%), Kierner 2 (45.5%), Kierner 3 (10.7%), Kierner 4 (2.9%) and Friedman 1 (15.7%), Friedman 2 (33.9%), Friedman 3 (50.4%). The amplitudes of EBSLN decreased significantly after superior thyroid pole operation, respectively, in Cernea 2A (193.7 vs. 226.6μV, P=0.019), Cernea 2B (185.8 vs. 221.3μV, P=0.039), Kierner 2 (193.7vs. 226.6μV, P=0.019), Kierner 3 (185.8 vs. 221.3μV, P=0.039), Kierner 4 (126.8vs. 226.0μV, P=0.015) and Friedman type 2 (184.8 vs. 221.6μV, P=0.030). There were significant differences in Fmax and Frange for Cernea 2A (P=0.001, P=0.001), 2B (P=0.001, P=0.038), Kierner 2 (P=0.001), Kierner 3 (P=0.001, P=0.038), and Friedman 2 (P=0.004, P=0.014). In the predictive efficacy of EBSLN injury, the Friedman classification showed higher accuracy (69.8% vs. 44.3% vs. 45.0%), sensitivity (19.5% vs. 11.0% vs. 14.0%), and specificity (95.6% vs. 89.9% vs. 89.9%) than the Cernea and Kierner classifications. However, the false negative rate of Friedman classification was significantly higher than other subtypes (19.5% vs. 11.0% vs. 14.0%). Cernea 2A and 2B; Kierner 2, 3, and 4; and Friedman 2 were defined as the high-risk subtypes of EBSLN. The risk prediction ability of the Friedman classification was found to be superior compared to other classifications.

Visual identification and neuromonitoring vs. no sighting the external branch of the superior laryngeal nerve in thyroid surgery: a randomized clinical trial.

To evaluate the incidence of external branch of the superior laryngeal nerve (EBSLN) injuries after thyroid surgical procedures with or without the functional and visual identification of the EBSLN before ligation at the superior thyroid pole. Patients with papillary thyroid carcinoma (PTC) enrolled from a single tertiary referral academic medical center were assigned to functional and visual identification of EBSLN group (study group) or no identification of EBSLN group (controlled group). The main outcome measures were the incidence of EBSLN injury detected by the intraoperative neuromonitoring and Voice Handicap Index-10 (VHI-10) and Impairment Index-5 (VII-5) valuation questionnaires. Postoperative complications were recorded. A total of 140 (50.4%) patients were enrolled in study group and 138 (49.6%) in controlled group. In the study group, 110 (39.3%) EBSLNs were direct visual recognized and 170 (60.7%) nerves were visually identified with the help of neuromonitoring. Three patients in the study group and two patients in the controlled group were diagnosed with vocal cord paralysis. Six (4.4%) patients in the identification group and 37 (27.2%) patients in the no identification group presented no response from the stimulation of sternothyroid-laryngeal triangle. The VII-5 scores of the study group were significantly higher than those of the controlled group at one and three months postoperatively (P = 0.024 and P = 0.034). With significant lower scores of VII-5 and VHI-10, functional and visual identification of EBSLN might be necessary during thyroid surgery to protect the structural integrity and motor activity of the nerve.

Assessment of nerve stimulation during thyroidectomy for identification of the external branch of superior laryngeal nerve

Background The external branch of the superior laryngeal nerve (EBSLN) injury is an important and not uncommon, though frequently overlooked, complication of thyroid surgery. The rate of EBSLN injury has been reported to vary from 0 to 58%, depending on different postoperative assessment methods. Injury to the EBSLN during thyroid operation can paralyze ipsilateral cricothyroid muscle, and the clinical symptoms mainly include vocal fatigue and diminished vocal frequency range, especially with respect to raising pitch, which may result in decreased quality of life, particularly for voice professionals. Patients and methods This prospective study included 22 patients with goiter. They were divided into two groups: group 1 (G1) included all cases in whom nerve stimulator was used and group 2 (G2) included all cases in whom trial of visual identification of the EBSLN was done. Results It was found that patients with short obese neck, large gland size, large gland weight, and retrosternal extension showed difficulty in EBSLN identification and had high risk of nerve injury (P Conclusion It was concluded that routine use of nerve stimulator in surgical interventions on the thyroid gland will be beneficial for more secure identification and prevention of EBSLN injury and preservation of voice quality postoperatively.

The strap intermuscular approach can significantly increase the exposure rate of the external branch of the superior laryngeal nerve during thyroid surgery

BackgroundAvoiding injury to the external branch of the superior laryngeal nerve (EBSLN) is a major challenge during thyroid surgery. EBSLN injury can have an impact on the quality of life of patients. The aim of this study was to introduce the strap intermuscular approach, to dissect the EBSLN with two different approaches in thyroid surgery, to compare the differences between these two approaches, and to describe a way for surgeons to treat the upper thyroid gland to find the EBSLN. MethodsA prospective study of hemithyroidectomy was performed. In total, 104 patients were included and randomly divided into two groups: one group used the traditional approach to expose and protect the EBSLN, and the other group used the strap intermuscular approach. We described the surgical procedure for the strap intermuscular approach and compared the differences in the rates of EBSLN exposure, injury, and classification to illustrate the advantages of the intermuscular approach in thyroid surgery. ResultsThe exposure rate of the EBSLN was higher with the strap intermuscular approach than with the traditional approach (96.15% vs. 76.92%, p = 0.01), with an odds ratio (OR) and 95% confidence interval (CI) of 0.133 (0.028–0.630). The exposure rate of EBSLNs classified as type 1 was higher in the strap intermuscular approach than in the traditional approach (30.77% vs. 13.46%, p = 0.033), with an OR and 95% CI of 0.350 (0.130–0.942). ConclusionsThe exposure rate of the EBSLN was significantly higher with the strap intermuscular approach method than with the traditional approach during thyroid surgery. This approach allows for better identification of the EBSLN during thyroidectomy.

Intraoperative Neuromonitoring in Thyroid and Parathyroid Surgery.

Background: It has been reported that the incidence of recurrent laryngeal nerve (RLN) injury is higher in an operational procedure in the thyroid and parathyroid region. Elevating voice pitch is achieved by the cricothyroid contraction, which in turn is innervated by the external branch of the superior laryngeal nerve (EBSLN). Due to the subtle nature and clinical variability of EBSLN damage, diagnosis may be difficult. The use of intraoperative neuromonitoring (IONM) as a supplement to enhance surgical identification in thyroid and parathyroid operation appeared to have collected momentum with operators. Methods: IONM clinical usage rationale, efficiency, and safety profile are discussed in this overview in thyroid and parathyroid surgery. Results: IONM usage incurred numerous skepticisms in decreasing the frequency of EBSLN or RLN injury. However, a recent article has shown the efficacy and benefits of using IONM in thyroid and parathyroid procedures. IONM facilitates the recognition of RLN and EBSLN, verifies its functional integrity, localizes the site of a nerve injury, and gives postsurgical function feedback. This technique has been successful in reducing rates of bilateral laryngeal paralysis, with the elevated safety profile for surgical patients. Conclusions: It is recommended using IONM in all thyroidectomies and in high-risk parathyroidectomies.

The evolution and progress of intraoperative monitoring of the external branch of the superior laryngeal nerve in thyroid surgery

Hypoparathyroidism and recurrent laryngeal nerve (RLN) damage are the most frequent reported morbidity in thyroid surgery whereas damage of the external branch of the superior laryngeal nerve (EBSLN) has been considered to be the most neglected sequel. EBSLN injury results in subtle changes in voice as a result of dysfunction of the cricothyroid muscle (CTM): changed basic voice frequency, deterioration of voice quality in the production of high frequency sounds and reduced voice projection. Symptoms of this dysfunction are usually more notable for professional voice users and can be difficult to diagnose. EBSLN injury can happen during dissection of the vessels of the upper thyroid pole due to proximity between the nerve and these vessels. Several maneuvers can minimize the risk of injury to the EBSLN including visual identification of the nerve before ligation of the upper thyroid pole vessels and use of either a nerve stimulator or intraoperative neuromonitoring (IONM) for neuromapping and evidence of the EBSLN identification. The EBSLN monitoring is relied on evaluation of CTM twitch (present in all patients) and electromyographic curve traced by the monitor using surface tube electrodes within the vocal folds which present in the majority but not all individuals (70–80% of patients using standard EMG tubes) or approaching to 100% of patients (using NIM TriVantage tubes). IONM has a potential to increase the rate of the EBSLNs identification, diminish prevalence of neural damage, and decrease prevalence of postoperative voice impairment which has been repeatedly supported by recently published data. It is advised that at the end of upper thyroid lobe dissection the EBSLN should be stimulated at the most cranial arc of dissection to confirm not only anatomical but what is even more important functional preservation of intact neural function.

Injury of the external branch of the superior laryngeal nerve in thyroid surgery.

The external branch of the superior laryngeal nerve (EBSLN) innervates the cricothyroid muscle (CTM) to promote lengthening and thinning of the vocal fold, thus increasing voice pitch. The close relation with the superior thyroid vessels (STV) puts the EBSLN in risk every time the superior pole of the thyroid is dissected. It travels downward to innervate the CTM, lateral to the thyroid cartilage and to the inferior pharyngeal constrictor muscle (IPCM), being eventually covered by this muscle fibers as it approaches its entry point. During its descending course, the EBSLN curves and crosses the STV posteriorly. The lower this crossing occurs in the neck, the higher the risk of surgical damage to the nerve by transection, traction, entrapment, thermal damage or disrupted blood supply. The chances of surgical trauma are also increased by size and weight of the specimen, shorter neck length and non-white ethnicity. Voice changes following thyroid surgery are common and multifactorial. The actual rate of vocal impairment due to EBSLN injury is unclear, since changes to the everyday speaking voice can be minimal and laryngeal findings are usually subtle and controversial. CTM electroneuromyography (EMG) is the most accurate tool to diagnose abnormal EBSLN conductivity, but it is technically difficult and barely applicable in routine practice. Recommended approaches to prevent injury include: (I) individual distal ligature of the STV by the thyroid capsule; (II) visual identification of the nerve and its trajectory and (III) electrostimulation with either observation of CTM twitch or intraoperative nerve monitoring (IONM) via dedicated endotracheal tube electrodes. There is accumulating evidence that a combination of visual and standardized electrophysiological EBSLN identification with meticulous division of the STV improves preservation rates. IONM bears the additional benefits of prognostication, quantification and documentation of neural function once it allows intraoperative laryngeal EMG.

External laryngeal nerve to identify or not during thyroidectomy: a single-institute experience

Background Iatrogenic injury to the external branch of the superior laryngeal nerve (ESLN) may occur during thyroidectomy because of its close proximity to the upper pole of the thyroid gland. Injury to the ESLN results in postoperative voice changes, which may be severe, especially in professional voice users. Although the main principle in neck surgery is proper dissection and identification rather than avoidance of important structures for their preservation, many surgeons do not routinely identify the ESLN during thyroidectomy because the nerve has variable anatomical courses. This encouraged us to conduct this study to evaluate the incidence of ESLN injury during thyroidectomy when superior thyroid vessels were ligated individually close to thyroid capsule without prior identification of the nerve. Patients and methods The present study included 200 patients with goiters who underwent either total or hemithyroidectomy at the Department of Surgery, Medical Research Institute Hospital, Alexandria University. In all patients, superior thyroid vessels were ligated in branches very close to thyroid capsule without prior positive search for the ESLN. Results In the present study, 185 (92.5%) patients underwent total thyroidectomy, whereas the remaining 15 (7.5%) patients underwent hemithyroidectomy. Transient ESLN injury occurred in 3% of patients, whereas 2% suffered from permanent nerve injury. Conclusion Preservation of the ESLN is necessary during thyroidectomy, especially in professional voice users. Ligation of superior thyroid vessels in branches close to thyroid capsule without prior identification of the ESLN is a safe procedure and does not increase the incidence of nerve injury.

Aerodynamic Phonatory Pattern as a New Sign of Superior Laryngeal Nerve Injury

Objectives: Reduced quality of life after thyroid surgery is multifactorial and may include the need of lifelong different treatments. About 1 in 20 patients experience voice changes, and it is very frequent that these changes may not be caused by neural lesions. The purpose of this study is to describe aerodynamic phonatory features in thyroidectomized patients in order to determine what mechanisms are involved in voice changes in these patients and what are the best rehabilitative options. Methods: We studied 58 thyroidectomized patients with neither apparent neural cause of thyroidectomy-related dysphonia nor recurrent laryngeal nerve injury nor external branch of the superior laryngeal nerve (EBSLN) injury. The patients were asked to produce sustained vowels, syllables, and sentences. Three items were recorded in upright and sitting positions. Afterward, acoustic and aerodynamic measurements were made: fundamental frequency, jitter, shimmer, intensity, harmonic/noise ratio, spectrographic analysis, subglottic pressure, mean transglottic flow, and laryngeal resistance. All measurements were made using Voice Plus from Alamed Corporation software. STATA software was used to analyze variables. Results: We describe 2 different groups of patients with different aerodynamic pattern in voice production that correlate with voice quality. In 66% of patients there was no change and in 34% the glottal pressure and laryngeal resistance decreased as a result of lower tension in the vocal fold as a consequence of an injury of the EBSLN. Conclusions: This aerodynamic phonatory pattern that may be understood by objective aerodynamic measurements could be another new sign of EBSLN injury.

Intraoperative neuromonitoring of the external branch of the superior laryngeal nerve during thyroidectomy: the need for evidence-based data and perioperative technical/technological standardization.

The external branch of the superior laryngeal nerve (EBSLN) is surgically relevant since its close anatomical proximity to the superior thyroid vessels. There is heterogeneity in the EBSLN anatomy and EBSLN damage produces changes in voice that are very heterogenous and difficult to diagnose. The reported prevalence of EBSLN injury widely ranges. EBSLN iatrogenic injury is considered the most commonly underestimated complication in endocrine surgery because vocal assessment underestimates such event and laryngoscopic postsurgical evaluation does not show standardized findings. In order to decrease the risk for EBSLN injury, multiple surgical approaches have been described so far. IONM provides multiple advantages in the EBSLN surgical approach. In this review, we discuss the current state of the art of the monitored approach to the EBSLN. In particular, we summarize, providing our additional remarks, the most relevant aspects of the standardized technique brilliantly described by the INMSG (International Neuromonitoring Study Group). In conclusion, in our opinion, there is currently the need for more prospective randomized trials investigating the electrophysiological and pathological aspects of the EBSLN for a better understanding of the role of IONM in the EBSLN surgery.

Normative Intra‐operative Electrophysiologic Waveform Analysis of Superior Laryngeal Nerve External Branch and Recurrent Laryngeal Nerve in Patients Undergoing Thyroid Surgery

Injury to the external branch of the superior laryngeal nerve (EBSLN) can occur during superior pole dissection in thyroid surgery; the EBSLN injury rate is reported as high as 28 % (Cernea et al., Head Neck 14:380-383, 1992). Injury to the EBSLN leads to variable symptoms that may be overlooked, but that can be significant, especially to professional speakers and singers. Intraoperative nerve monitoring (IONM) is employed widely to aid in nerve identification. We report on normative electroneuromyography (EMG) data on EBSLN-IONM and cricothyroid muscle (CTM) twitch response during stimulation as an aid to EBSLN identification. A prospective study of the SLN and the recurrent laryngeal nerve (RLN) IONM data in 72 consecutive thyroid surgeries was carried out. All patients underwent preoperative and postoperative laryngeal exams, and patients with abnormal preoperative laryngeal function were excluded. Normative EMG data and CTM twitch response during EBSLN stimulation were recorded and analyzed. Stimulation of the EBSLN resulted in a positive CTM twitch response in 100 %, whereas EMG response was recordable in 80 %. Electromyographic amplitude was ~1/3 of ipsilateral RLN amplitude and did not change through the case with multiple stimulations. Stimulation of the EBSLN was similar for men and women and at 1 and 2 mA stimulation levels. Intraoperative nerve monitoring of the EBSLN aids in EBSLN identification and provides electroneuromyographic information in 80 % of cases. The laryngeal head of the sternothyroid muscle is a useful landmark to locate EBSLN.

Neuromonitoring in thyroidectomy: a meta-analysis of effectiveness from randomized controlled trials

Neuromonitoring in thyroid surgery has been employed to make nerve identification easier and decrease the rates of laryngeal nerve injuries. Several individual randomized controlled trials (RCTs) have been published, which did not identify statistical differences in the rates of recurrent laryngeal nerve (RLN) or external branch of the superior laryngeal nerve (EBSLN) injuries. The objective of this report is to perform meta-analysis of the combined results of individual studies to measure the frequency of RLN and EBSLN injuries in patients who underwent thyroidectomy with routine neuromonitoring in comparison with common practice of search and identification. RCTs comparing routine neuromonitoring versus no use in patients who underwent elective partial or total thyroidectomy were evaluated. Outcomes measured were temporary and definitive palsy of the RLN and EBSLN. A systematic review and meta-analysis was done using random effects model. GRADE was used to classify quality of evidence. Six studies with 1,602 patients and 3,064 nerves at risk were identified. Methodological quality assessment showed high risk of bias in most items. Funnel plot did not reveal publication bias. The risk difference for temporary RLN palsy, definitive RLN palsy, temporary EBSLN palsy, and definitive EBSLN palsy were -2% (95% confidence interval -5.1 to 1); 0% (-1 to 1); -9% (-15 to -2) and -1% (-4 to 2), respectively. Quality was rated low or very low in most outcomes due to methodological flaws. Meta-analysis did not demonstrate a statistically significant decrease in the risk of temporary or definitive RLN injury and definitive EBSLN injury with the use of neuromonitoring. The neuromonitoring group had a statistically significant decrease in the risk of temporary EBSLN injury.

External Branch of the Superior Laryngeal Nerve: Applied Surgical Anatomy and Implications in Thyroid Surgery

The external branch of the superior laryngeal nerve (EBSLN) is the only motor supply to the cricothyroid muscle and has an important role during phonation in high frequencies. Iatrogenic injury of the EBSLN, most commonly during thyroid surgery, is associated with varying levels of alterations in phonation, which may have an impact on a patient's life, especially when his or her career depends on the full range of voice. EBSLN injury incidence after thyroid surgery ranges widely in the literature (0 to 58%). Despite this wide variation, it appears that EBSLN injury is a not uncommon, and frequently overlooked, complication of thyroid surgery. An in-depth knowledge of the surgical anatomy of the EBSLN is therefore required from the part of the operating surgeon to protect this nerve during thyroid surgery.

Prospective Electromyographic Evaluation of Functional Postthyroidectomy Voice and Swallowing Symptoms

Voice and swallowing symptoms following thyroidectomy in the absence of any demonstration of laryngeal nerves injury are usually considered a functional outcome of uncomplicated operations, mainly related to scar formation and emotional reaction. They could be related to unapparent laryngeal nerve or cricothyroid (CT) muscle injuries detectable only by laryngeal electromyography (LEMG). We correlated such symptoms with LEMG patterns. A total of 33 consenting patients undergoing total thyroidectomy (TT) were enrolled. Video-strobolaryngoscopy (VSL), acoustic voice analysis (AVA), and maximum phonation time (MPT) were performed preoperatively and 3months postoperatively. Subjective evaluation of voice (Voice Impairment Score, or VIS) and swallowing (Swallowing Impairment Score, or SIS) were obtained preoperatively and 1 and 3months postoperatively. At 1month postoperatively LEMG was performed examining thyroarytenoid (TA) and CT muscles to evaluate the inferior laryngeal nerve (ILN) and the external branch of the superior laryngeal nerve (EBSLN), respectively. One patient experienced transient vocal cord palsy and was excluded. The remaining 32 patients completed the postoperative evaluation. No significant difference was found between preoperative and postoperative AVA and MPT parameters. Mean VIS was significantly worse than preoperatively 1 and 3months after TT. No significant difference was found between preoperative and postoperative SIS. LEMG evaluation of TA muscle showed decreased voluntary activity and spontaneous fibrillation potentials in one patient. LEMG of the CT muscle did not reveal any sign of EBSLN injury. Patients frequently complain of subjective symptoms early after TT. LEMG demonstrated the absence of subclinical laryngeal nerve injury in all but one patient, confirming their functional nature.

Surgical anatomy of the external branch of the superior laryngeal nerve and its clinical significance in head and neck surgery

Injury of the external branch of the superior laryngeal nerve (EBSLN) increases the morbidity following a variety of neck procedures and can have catastrophic consequences in people who use their voice professionally. Identification and preservation of the EBSLN are thus important in thyroidectomy, parathyroidectomy, carotid endarterectomy, and anterior cervical spine procedures, where the nerve is at risk. There are large variations in the anatomical course of the EBSLN, which makes the intraoperative identification of the nerve challenging. The topographic relationship of the EBSLN to the superior thyroid artery and the upper pole of the thyroid gland are considered by many authors to be the key point for identifying the nerve during surgery of the neck. The classifications by Cernea et al. ([1992a] Head Neck 14:380-383; [1992b] Am. J. Surg. 164:634-639) and by Kierner et al. ([1998] Arch. Otolaryngol. Head Neck Surg. 124:301-303), as well as clinically important connections are discussed in detail. Along with sound anatomical knowledge, neuromonitoring is helpful in identifying the EBSLN during neck procedures. The clinical signs of EBSLN injury include hoarseness, decreased voice projection, decreased pitch range, and fatigue after extensive voice use. Videostroboscopy, electromyography, voice analysis, and electroglottography can provide crucial information on the function of the EBSLN following neck surgery.

Anatomical and surgical considerations of the external branch of the superior laryngeal nerve: a systematic review

The anatomical course of the external branch of the superior laryngeal nerve (EBSLN) is variable, and a consistent approach to its preservation during thyroid surgery is needed to reduce risk of post-operative voice impairment. Despite agreement that careful dissection in the region of the superior thyroid pole is required, there is no accepted 'best' approach, nor any universal acknowledgement that location of the EBSLN is actually necessary. The popular cernea classification of EBSLN has limitations, including its decreased reliability with increased thyroid size and its irrelevance in cases of 'buried' variants. * Recent work has identified factors such as ethnicity and stature in the prevalence of EBSLN variants. Consistent approaches to the post-operative detection of EBSLN injury are needed to build an accurate picture of the incidence of surgical nerve injury. Then a standardised approach to EBSLN preservation may emerge.

Importance of the Intraoperative Identification of the External Branch of the Superior Laryngeal Nerve During Thyroidectomy: Electromyographic Evaluation

To establish the frequency and degree of postthyroidectomy injury of the external branch of the superior laryngeal nerve (EBSLN) by means of electromyography and to assess whether intraoperative identification of the nerve and the presence of malignancy influence morbidity. Prospective, randomized, blind study. Comparison of 100 superior thyroid poles subjected to surgery because of benign and malignant disease, divided in three groups: G1, thyroidectomies, without searching for the EBSLN; G2, thyroidectomies, searching for the EBSLN; G3, Control, lobes, contralateral to the lobectomy, not surgically manipulated. The electromyographic function of the EBSLN was assessed in all cases, classifying the degree of injury and clinically assessing its function. Central tendency measures were used, as well as X (2) and multiple variance analysis. In G1, with 50 dissections of the superior pole, 25 injuries were found in 15 patients (10 bilateral and 5 unilateral). In G2, EBSLN injury was found after 13 explorations of the superior pole in 8 patients (5 bilateral and 3 unilateral). G3 patients did not present EBSLN injury. X (2) among groups and degree of injury revealed that intraoperative identification of the EBSLN decreases its injury. No evidence were found that injury frequency is increased by the presence of thyroid malignancy, extracapsular infiltration, or size of tumor. Clinical manifestations of hoarseness were present in 14% of G1 patients and 8% of G2 patients. The rate of EBSLN injury increased when not exploring and/or identifying it expressly. The presence of cancer, extracapsular extension, or size of the thyroid tumor exerted no influence on the frequency of injury; localization of the nerve was the only factor affecting injury. Hoarseness correlated with the degree of injury. EBSLN must be localized expressly to decrease the risk of injury.

Computer-assisted evoked electromyography with stimulating surgical instruments for recurrent/external laryngeal nerve identification and preservation in thyroid and parathyroid operation

Background. The reported incidence of recurrent laryngeal nerve (RLN) palsy/paralysis in thyroid and parathyroid operation ranges from 2% to 13%. Injury to the external branch of the superior laryngeal nerve (EBSLN) is less clearly documented. We hypothesized that a novel evoked electromyography system using an audio warning alarm might be beneficial for detection and preservation of the RLN and EBSLN. Methods. A total of 117 thyroid/parathyroid operations were performed using a nerve locator/monitor (Neurovision SE, RLN Systems Inc, Jefferson City, Mo). Dissection was performed using a stimulating hemostat with conduction to an endotracheal surface electrode. Results. A total of 97 thyroidectomies (50 total, 47 lobectomies) and 20 parathyroidectomies (16 directed, 4 bilateral) were performed representing 176 RLN and 152 EBSLN at risk. Of 176 RLN, 161 were correctly identified by the nerve stimulator alarm including 2 nonrecurrent nerves. The cricothyroid space and the superior pole vessels were scanned to identify the EBSLN by observing for cricothyroideus contraction or an alarm. Fourteen of 152 (8.9%) cases of type 2 anatomy were suggested where meticulous dissection of superior pole vessels prevented EBSLN injury. Conclusions. Computer-assisted evoked electromyography with stimulating surgical instruments is a useful surgical tool. This technology may be especially useful in reoperation in dense scar tissue and preserving the EBSLN in thyroid operation. (Surgery 2002;132:1100-8.)

Is the identification of the external branch of the superior laryngeal nerve mandatory in thyroid operation? Results of a prospective randomized study

Background. The aim of this study was to investigate the incidence of injury to the external branch of the superior laryngeal nerve (EBSLN) with 2 different surgical approaches. Methods. From 1998 to 2000, 289 consecutive patients undergoing thyroidectomy were randomly divided into 2 groups. In group A (137 patients [215 upper pole ligations]), the superior thyroid artery was ligated after identification of the EBSLN. In group B (152 patients [244 upper pole ligations]), the superior thyroid artery's branches were ligated separately close to the gland. In all patients, a phoniatric evaluation with videostrobolaryngoscopy and spectrographic examination was performed. Results. The 2 groups were well matched regarding age, sex, thyroid pathological findings, and type of operation. In group A, the EBSLN was not clearly identified in 11.6% of cases. Alterations of EBSLN function were absent in both groups of patients, either postoperatively or 1 and 6 months after operation. Group B showed statistically significant shorter operative time compared with that for group A. Conclusions. Even if the EBSLN often crosses the superior thyroid pedicle, especially in large goiters, this study demonstrated that accurate distal ligation of the branches of the superior thyroid artery is a safe technique to prevent EBSLN injury. (Surgery 2001;130:1055-9.)