The triad of non-recurrent laryngeal nerve; three associated predicting variants in the era of nerve monitoring: A case report.

INTRODUCTION AND IMPORTANCE: The prediction and early identification of non-recurrent laryngeal nerve (RLN) may minimize risk of injury. It could be associated with other coincident variants that predict non-RLN, leading to its proper identification. CASE PRESENTATION: A patient with multinodular goiter underwent total thyroidectomy under intraoperative neuromonitoring (IONM) guidance. Preoperative thoracic computerized tomography (CT) scan/angiography revealed aberrant right subclavian artery (ARSA). During thyroid surgery, the vagus nerve (VN) was identified in the neurovascular bundle. An anatomic variation of the VN was observed, as it was medially placed in relation to the common carotid artery (CCA). Pre-dissection electrophysiological stimulus of the VN (V1) was negative. Thus, a right non-RLN was identified with careful surgical dissection. The branching point of the non-RLN on the VN was identified, and non-RLN was fully exposed until the laryngeal entry. IONM revealed that V1 signal was negative if derived distal to the non-RLN separation, and positive if derived proximal to the non-RLN separation. CLINICAL DISCUSSION: ARSA detected by preoperative CT scan is associated with non-RLN. The medial course of the VN in relation to the CCA was found as a coincident anatomic variant with the non-RLN. Absence of pre-dissection V1 signal by IONM was an electrophysiological variant associated with the non-RLN. CONCLUSION: ARSA is a reliable variant for predicting the non-RLN. VN medial to the CCA and absence of electrophysiological V1 signal could precisely predict the non-RLN. Therefore, the coincidence of three anatomical and electrophysiological variants with non-RLN could lead to the prediction of non-RLN.

Anatomy and motor function of extra-laryngeal branching patterns of the recurrent laryngeal nerve; an electrophysiological study of 1001 nerves at risk.

INTRODUCTION: Safe thyroid surgery depends on a deep knowledge of human neck anatomy, including the recurrent laryngeal nerve (RLN). Anatomic variations such as extra-laryngeal terminal branching (ETB) are common. PATIENTS AND METHODS: We studied the ETB pattern of 1001 RLNs at risk in 596 patients. We identified and exposed the location of division points on the cervical part of bifid RLN. The function of nerve branches was assessed through intraoperative nerve monitoring (IONM). RESULTS: Bifid RLNs was identified in 39.6% of patients. The nerve-based prevalence of ETB was 28.5%. The prevalence of ETB for the right and left RLN was 21.8% and 35.5%, respectively (p < 0.001). The location of the division point was found in the middle, distal, and proximal segments in 48.8%, 33.3%, and 18% of bifid RLNs, respectively. Electrophysiological monitoring revealed motor functions in all anterior and in 7% of posterior branches. The rate of injury was 0.4%, and 1.1% in single trunk and bifid nerves, respectively (p = 0.360), and 3.9% in nerves with proximal branching (p = 0.084). CONCLUSIONS: The ETB prevalence is high and showing division points in different cervical segments of the RLN. All anterior branches and some posterior branches contain motor fibers. Knowledge and awareness of these anatomic and functional variations are mandatory for every thyroid surgeon to avoid misidentification and misinterpretation of human RLN anatomy.

Intraoperative Monitoring and Preservation of Anatomic Integrity of Palsied Recurrent Laryngeal Nerve is Extremely Meaningful During Redo Thyroid Surgery.

Redo thyroid surgery on patients with unilateral recurrent laryngeal nerve (RLN) palsy certainly poses a great surgical challenge. We present a case of a patient with unilateral vocal cord (VC) palsy who underwent redo thyroid surgery under intraoperative neuromonitoring. The patient's normal speaking voice was maintained after the primary surgery, even though preoperative laryngoscopy showed an immobile right VC with a normal structure. During reoperation, surgical exploration revealed the anatomical integrity of palsied RLN with extralaryngeal terminal bifurcation. The electrophysiological stimulation of the vagus nerve and palsied RLN generated wave amplitudes (V1: 242, R1: 347, R2: 352 and V2: 152 µV). Despite positive amplitudes, postoperative laryngoscopy confirmed RLN palsy and corresponding VC paralysis but preserved the structure of the immobile VC. Even palsied RLN should be monitored during redo surgery. A positive signal delineates at least partial neural transmission despite VC palsy. The preservation of anatomical integrity of palsied RLN for eventual partial conductivity may be vital in preserving the normal structure of VC and maintaining the patient's voice despite its immobility. Key Words: Surgery, Redo thyroidectomy, Recurrent laryngeal nerve injury, Vocal cord palsy.

Anatomical and functional identification of the external branch of the superior laryngeal nerve: classification based on morphology and electrophysiological monitoring.

BACKGROUND: Motor function of the external branch of superior laryngeal nerve (EBSLN) is vital for voice quality. We studied the rate of EBSLN identification and integrity in the era of intraoperative neuromonitoring (IONM). METHODS: Anatomic and functional identification of 515 EBSLNs-at-risk was performed under the guidance of IONM that motor integrity was electrophysiologically checked. The functional integrity was assessed with crico-thyroid muscle (CTM) twitches and/or recordable waveform amplitude. We tried to establish the systematic classification of EBSLN identification and integrity. RESULTS: Visual, electrophysiological and total identification rates were 64.3%, 31.6% and 95.9%, respectively. We could identify 4.1% of EBSLNs neither anatomically nor electrophysiologically. We recorded CTM twitches alone or both CTM twitches and wave amplitude in 203(39.4%) and 291(56.5%) branches respectively. Identification features of EBSLNs were systematically classified under three main types: Visualized-monitored (1), non-visualized-monitored (2), unidentified (3), and electrophysiological integrity of EBSLNs under two subtypes: CTM twitches alone (a) and CTM twitches and wave amplitude (b). CONCLUSION: Dedicated thyroid surgeon could visually identify EBSLNs. IONM contribution significantly increases the identification rate. Systematic classification of identification and electrophysiological integrity of EBSLNs may increase comprehensive knowledge about its motor function that is crucial for complication-free thyroidectomy.

Targeted axillary biopsy and sentinel lymph node biopsy for axillary restaging after neoadjuvant chemotherapy.

PURPOSE: Accurate restaging of the axilla after neoadjuvant chemotherapy (NAC) is an important issue to ensure deescalating axillary surgery in patients with initial metastatic nodes. We aimed to present our results of targeted axillary biopsy (TAB) combined with sentinel lymph node biopsy (SLNB) for axillary restaging after NAC. METHODS: In 64 breast cancer patients who underwent NAC, biopsy-proven positive nodes were marked with clips before NAC, and ultrasound-guided wire localization of clip-marked nodes was performed after NAC. Patients underwent TAB and SLNB for post-NAC axilla restaging. RESULTS: Identification rates of post-NAC TAB and SLNB were 98.4% and 87.5%, respectively (P = 0.033). Histopathology revealed a nodal pathologic complete response (pCR) rate of 47% in which axillary lymph node dissection (ALND) was avoided. TAB alone and SLNB alone detected residual disease in 29 (85.3%) and 20 (58.8%) patients (P = 0.029), respectively. Whereas rates of up to 97% had been achieved with a combination of TAB and SLNB. The pCR rates after NAC were 64.3% for human epidermal growth factor receptor 2 positive and triple-negative tumors and 13.6% in luminal tumors (P = 0.0002). CONCLUSION: Pathologic analysis following TAB combined with SLNB revealed the pCR rates to NAC in a considerable number of patients that provided de-escalation of axillary surgery. A combination of SLNB and TAB was found to be an accurate procedure in establishing residual nodal disease. This combined procedure in patients with initially positive nodes was a reliable method for post-NAC axillary restaging.

Separate thyrothymic thyroid remnant; clinically crucial anatomic variation.

PURPOSE: The anatomical variations of the thyroid gland including separate thyroidal remnant at the thyrothymic area are of significance during thyroid surgery for "total" thyroidectomy, and for recurrent goitre. In the present study, we aimed to detect the separate rests of thyroidal tissue in the thyrothymic region. METHODS: The thyrothymic region was explored for identification, dissection, and excision of separate thyroidal remnants in 134 patients who underwent primary thyroid surgery. In this series, we studied the incidence and anatomical features of the thyrothymic remnant and its relation with other embryologic remnants. RESULTS: Overall, 222 sides of the thyroid were explored in this study. An entirely separate thyrothymic remnant of the thyroid was identified and excised in 8 of 134 patients (6%). Mean size of removed remnants was 36.4 mm (range, 29-45 mm) in diameter. The incidences of pyramidal lobe (PL) and Zuckerkandl's tubercle (ZT) were 71.6% and 59.7%, respectively. The thyrothymic remnant coexisted with PLs in 4 patients. Four patients had all 3 embryologic remnants: thyrothymic remnant, PLs, and ZTs. CONCLUSION: An entirely separate thyroidal remnant at the thyrothymic area is not a rare variation. The considerably large size of a remnant may threaten the completeness of thyroidectomy and may result in recurrence if it is left behind after thyroid surgery. Awareness, identification, and excision of the separate remnant at the thyrothymic area and the other embryologic remnants are critical for ensuring completeness of thyroidectomy and preventing recurrences.

Video-endoscopic Tension-free Groin Hernia Repair via Total Extraperitoneal Approach.

Introduction Tension-free repair of groin hernias with synthetic material by video-endoscopic surgery is a widely accepted method that is performed by various approaches. We aim to present our results of video-endoscopic tension-free repair of groin hernias via the total extraperitoneal (TEP) approach. Methods Between September 2016 and December 2018, 124 patients with groin hernias underwent tension-free repair using prolene mesh by video-endoscopic surgery via the TEP approach. This is a retrospective analysis of 110 (88.7%) male and 14 (11.3%) female patients with a mean age of 48.1 years. Groin hernia types, locations of hernias, intraoperative and postoperative complications, results of the mean 24-month follow-up, and recurrence rate were reported. Results A total of 134 hernias were repaired in 124 patients who had 53 (42.7%) right, 61 (49.2%) left, and 10 (8.1%) bilateral groin hernias. The most common hernia type was an indirect inguinal hernia in 83/134 (62%) groin hernias. A total of 119 (88.8%) and 15 (11.2%) hernias were primary and recurrent, respectively. Seroma was detected in two (1.6%) patients in the early postoperative period. The mean duration of hospital stay was 1.4 (1-3) days. During the follow-up period, hernia recurrence was determined in three (2.4%) patients. Hernia recurrence was detected among patients who were operated on during the first half of the study. Conclusion Tension-free repair of groin hernias by video-endoscopic technique via the TEP approach can be performed with very low complication and recurrence rates. The success of the TEP approach increases parallel to increasing surgical experience. The results of hernia repair via the TEP approach are highly satisfactory and encouraging, especially when attention is paid to proper patient selection during the learning curve period.

Inverse 'D' incision technique in treatment of pilonidal sinus disease; excision with minimal tissue loss, closure without tension and lateral location of the suture line.

PURPOSE: Surgical excision is the preferred treatment modality for sacrococcygeal pilonidal sinus (PS). Notably, the desirable features of an ideal surgical intervention are excision with minimal tissue loss, closure without tension, and a lateral suture line. The present study aimed to investigate early outcomes of surgical excision through the inverse D (ᗡ) incision based on tissue loss, wound tension, and suture line location. METHODS: This prospective study was comprised of 80 patients with PS in whom excision of PS was performed through the 'ᗡ' incision to minimize tissue loss with a tensionless primary surgical wound closure. The suture line was located laterally in all patients. Early and late postoperative complications, duration of hospital stay, return to work, and recurrence rates were investigated. The mean duration of the follow-up period was 36 months. RESULTS: Sixty-three patients (78.8%) were male. PS in all patients was surgically removed by subcutaneous excision through a 'ᗡ' incision. Laterally placed surgical wounds were closed primarily with interrupted vertical mattress sutures. No general complications were encountered. Five patients (6.3%) experienced early postoperative surgical site complications. On average, the duration of hospital stay and return to work were 2.4 days and 3.8 days, respectively. Recurrence was seen in 1 case (1.3%) during the follow-up period. Satisfaction score was high in 83.8% of patients. CONCLUSION: The method of sinus excision using the 'ᗡ' incision with a primary suture facilitates excision with minimal tissue loss and closure without tension with an off-midline suture. It is both a simple and effective surgical technique for the treatment of sacrococcygeal PS.

Recurrent Goiter Presented with Marine-Lenhart Syndrome 27 Years After Initial Surgery.

Marine-Lenhart syndrome (MLS), a rare form of hyperthyroidism, is the coexistence of Graves' disease (GD) and autonomously functioning thyroid nodule(s). Herein, we report a case of recurrent goiter presented with MLS. A 52-year-old man presented at our department with recurrent goiter, exophthalmia, and symptoms of hyperthyroidism. In addition to clinical signs and thyroid eye disease, suppressed thyroid-stimulating hormone (TSH) and high free thyroxine (FT4) and autoantibody levels lead to the diagnosis of GD. Thyroid ultrasound and nuclear scan showed the presence of a large, solid, and functioning "hot" nodule in the right lobe. Thus, in recurrent goiter cases, the diagnosis was MLS, wherein autoimmune hyperthyroidism was associated with the functioning nodule. Following medical control with methimazole, the patient underwent total excision of recurrent goiter. Levothyroxine (LT4) therapy was prescribed to maintain normal serum hormone levels. At follow-up, the gradual decrease in serum levels of autoantibody was detected. This patient is a very rare example of MLS that occurs in recurrent goiter case. Clinical signs, serum hormone and autoantibody levels, thyroid ultrasound, and nuclear scan establish the correct diagnosis of this specific and rare disorder. Thyroid surgery and total removal of glandular tissue provides definitive control of hyperthyroidism and obviates autoimmune reaction.

Visual and electrophysiological identification of the external branch of superior laryngeal nerve in redo thyroid surgery compared with primary thyroid surgery.

PURPOSE: Thyroid reoperations are surgically challenging because of significant anatomical variance. Visual and functional identification of the external branch of the superior laryngeal nerve (EBSLN) were studied in 2 groups of patients who underwent primary and redo thyroid surgery. METHODS: This study was conducted on 200 patients: 100 patients with redo and 100 patients with primary thyroid surgery. In addition to visual identification, nerve branches were functionally identified by intraoperative nerve monitoring (IONM). Visual, functional, and total identification rates of the EBSLN in both primary and redo surgery were determined and compared between the 2 groups. RESULTS: We attempted to identify 138 and 170 EBSLNs at risk in redo and primary surgery, respectively. Visual identification rates were 65.3% and 30.4% (P < 0.001) in primary and redo surgery groups, respectively. In total, 164 (96.5%) and 97 EBSLNs (70.3%) were identified in primary and redo surgery, respectively (P < 0.001), including the use of IONM. In primary surgery group, 53 nonvisualized EBSLNs of 164 identified nerves (32.3%) were determined by IONM alone. In redo surgery group, 55 of 97 identified nerves (56.7%) were determined by IONM alone (P < 0.001). CONCLUSION: Both visual and total identification rates of the EBSLN are significantly decreased in reoperative thyroidectomy. IONM increases the total identification rate of the EBSLN in primary and redo thyroid surgery. Electrophysiological monitoring makes a substantial contribution to the identification of the EBSLN both in primary and especially in redo thyroid surgery.

Nonrecurrent Laryngeal Nerve: Precise Detection by Electrophysiological Nerve Monitoring.

Complication-free thyroid surgery is mainly based on the motor integrity of the recurrent laryngeal nerve (RLN). The nonrecurrent laryngeal nerve (non-RLN) is a rare anatomical variation that may increase the risk of vocal cord palsy. Early identification and exposure of the non-RLN may minimize injury risk. This case report presents functional detection of the non-RLN by intraoperative neuromonitoring (IONM). Total thyroidectomy was performed under the guidance of IONM on a patient with bulky multinodular goiter. The first step of IONM is pre-dissection stimulation (V1) of the right vagus nerve (VN). V1 at a standard distal point was negative as indicated by the absence of both a sound signal and wave amplitude. The right VN was then followed proximally and dissected under the guidance of IONM. This dissection established a proximal point creating a positive signal that led us to determine the separation point of the non-RLN. The right non-RLN arising from the proximal VN was identified and fully exposed until laryngeal entry. Its motor integrity was confirmed with post-dissection signals. The left RLN was identified at the usual anatomical position that was fully exposed and preserved during thyroid surgery. Total thyroidectomy was then accomplished without complication. The postoperative period was uneventful. Postoperative laryngoscopy confirmed normal vocal cord function. The non-RLN is accurately identified by IONM during the early part of the thyroid surgery. The absence of a distal VN signal is predictive of the non-RLN. IONM-guided proximal dissection of the right VN leads to the identification of the non-RLN. The prediction of the non-RLN by the absence of a VN signal during an early stage of surgery may prevent or minimize the risk of nerve injury.

Motor Interconnections Between Superior and Inferior Laryngeal Nerves.

Introduction Anatomical studies on human cadavers have established anastomoses between laryngeal nerves. However, we need to functionally identify motor communication via these anastomoses between the recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (EBSLN) in living bodies. We aim to establish motor interconnections using intraoperative nerve monitoring (IONM). Methods IONM of 112 EBSLNs and RLNs in 62 thyroidectomy cases was used to establish motor functions of laryngeal nerves. Electrophysiological parameters were recorded, and cricothyroid muscle (CTM) contraction was observed after stimulation of laryngeal nerves. Results Eighty (71.4%) EBSLNs were visually identified, and 109 (97.3%) EBSLNs were functionally identified with CTM contraction. Stimulation of 74 (67.9%) EBSLNs induced contraction of laryngeal muscles and generated wave amplitude from intrinsic laryngeal musculature. The stimulation of the RLN induced CTM contraction in 65 (58%) of the 112 muscles. The mean conductivity powers of the EBSLN and of the RLN to intrinsic laryngeal musculature were calculated as 231.3 µV and 1354.5 µV, respectively. Conclusion Recordable waveform amplitude with EBSLN stimulation yielded motor relations between laryngeal nerves. CTM contraction after stimulation of the RLN confirmed these relations. These results of IONM established motor interconnections between superior and inferior laryngeal nerves in the majority of patients. The EBSLN may have an effect on motor innervations for intrinsic laryngeal muscles via motor interconnections.

Displacement of the Recurrent Laryngeal Nerve in Patients with Recurrent Goiter Undergoing Redo Thyroid Surgery.

Thyroid reoperations are surgically challenging because of scarring and disturbances in the anatomy of the recurrent laryngeal nerve (RLN). This study was conducted on 49 patients who underwent redo surgery. 61 RLNs were identified and completely exposed. Their functional integrity was evaluated using intraoperative nerve monitoring (IONM). Indications for secondary surgery, anatomical changes secondary to recurrent goiter mass and prior surgery, and results of IONM were studied. Frequent indications for redo surgery were multinodular goiter (MNG) in 19 (38.8%) and results of cytology in 14 (28.5%) patients. The mean time interval between primary and redo thyroid surgery was 23.4 years. We laterally approached 41 (67.2%) thyroid lobes between the sternocleidomastoid and sternohyoid muscles. 16 (26.2%) RLNs were found to be adherent to the lateral surface of the corresponding thyroid lobe. The functional integrity of all RLNs was confirmed by IONM. The remnant thyroid tissue can then lead to goiter recurrence requiring secondary surgery after a long period of time. The indications for redo surgery were similar to primary cases. Lateral displacement of the RLN which is adherent to the lateral surface of recurrent goiter mass is common anatomic variation. Thyroid reoperations based on awareness of anatomical disturbances can be performed safely by an experienced surgeon with support of ancillary electrophysiological technology.

Intraoperative Monitoring of External Branch of the Superior Laryngeal Nerve: Functional Identification, Motor Integrity, and its Role on Vocal Cord Function.

PURPOSE: Beside recurrent laryngeal nerve (RLN), protection of the external branch of the superior laryngeal nerve (EBSLN) is required for complication-free thyroid surgery. This study investigates the contribution of intraoperative neuromonitoring (IONM) to identification and motor integrity of the EBSLN. METHODS: This prospective study was performed on 245 EBSLNs in 147 patients with thyroid surgery. The rate of visual identification, contribution of IONM to functional localization, the rate and levels of recordable waveform amplitude from vocal cord (VC) movement were determined during surgery. RESULTS: 164 (66.9%) EBSLNs were visually identified and additional 74 branches were functionally identified by IONM. Additional identification rate of IONM was 30.2%. Seven (2.9%) EBSLNs could not be identified during surgery. Cricothyroid muscle (CTM) twitch established functional integrity in 97.1% of EBSLNs. Electrophysiological stimulation of 151 (63.4%) EBSLNs created waveform amplitude >100 µV that mean amplitude level was calculated as 186 µV, and an amplitude >300 µV was recorded in 19 of 151 (12.6%) EBSLNs. CONCLUSIONS: In addition to visual identification, surgeons can functionally localize the EBSLN with the assistance of IONM that CTM twitch is a reliable evience for functional integrity of the EBSLN. In the majority of patients, stimulation of the EBSLN creates recordable waveform amplitude thus the EBSLN appears to be a second source of motor innervations for intrinsic laryngeal muscles.

Toxic Adenoma in a Patient with Thyroid Hemiagenesis.

Thyroid hemiagenesis (TH) is a rare congenital anomaly that is usually asymptomatic. Functional disorders of the thyroid make the patient symptomatic. TH is usually and incidentally established during evaluation of patients with symptomatic thyroid pathology. We report the case of a patient of TH who became symptomatic with hyperactivity of the gland. The patient presented with signs and symptoms of thyrotoxicosis. Physical examination revealed asymmetric nodular goiter at the right lobe. Biochemical analysis established the diagnosis of hyperthyroidism. Ultrasound of the thyroid gland revealed the absence of the left lobe and a large, solitary hypoechoic solid nodule in the right lobe. Nuclear scan showed the absence of the left lobe and revealed a large, autonomous solitary nodule in the right lobe. The diagnosis was a toxic adenoma. After medical control of hyperthyroidism, the patient was surgically treated with hemithyroidectomy. We prescribed postoperative replacement medication with L-thyroxin. Hyperthyroidism makes TH cases symptomatic. Thyroid ultrasound and scintigraphy incidentally discover agenesis of one lobe during evaluation of thyrotoxicosis. Hemithyroidectomy, including the autonomous nodule, is the procedure of choice for patients with toxic adenoma. Hemithyroidectomy in TH cases technically becomes a total thyroidectomy with a need for postoperative thyroid replacement therapy.

Effects of Erdosteine on Experimental Acute Pancreatitis Model.

OBJECTIVE: To create acute pancreatitis condition experimentally in rats using cerulein, and to reveal histopathological effects in pancreatic tissue with erdosteine. STUDY DESIGN: An experimental study. PLACE AND DURATION OF STUDY: Department of General Surgery, Duzce University, Turkey, from June to October 2014. METHODOLOGY: Thirty male Wistar albino rats were divided into three groups. No procedures were applied to Group 1. The rats in Group 2 and Group 3 were injected cerulein, to establish an experimental pancreatitis model and the blood amylase and lipase values were examined. The rats in Group 3 were given 10 mg/kg erdosteine. This treatment was continued for another 2 days and the rats were sacrificed. The pancreatic tissues were examined histopathologically for edema, inflammation, acinar necrosis, fat necrosis, and vacuolization. RESULTS: The lipase and amylase values and the histopathological examination of pancreatic tissues evidenced that the experimental acute pancreatitis model was established and edema, inflammation, acinar necrosis, fat necrosis, and vacuolization were observed in the pancreatic tissues. The statistical results suggest that erdosteine can decrease the edema, inflammation, acinar necrosis, fat necrosis and vacuolization scores in the tissues. CONCLUSION: The severity of acute pancreatitis, induced by cerulein in rats, is reduced with the use of erdosteine.

Coexistence of Right Nonrecurrent Nerve and Bifurcated Recurrent Laryngeal Nerve Pointed by Zuckerkandl's Tubercle.

The recurrent laryngeal nerve (RLN) has many anatomical variations and various relations with adjacent structures. Identification and total exposure of the cervical part of the RLN was performed during operations on the thyroid gland. An extremely rare anatomical variation of the nerve was encountered during the surgical procedure. Coexistence of both right RLN and non-RLN was observed in one patient surgically treated with total thyroidectomy. We first exposed the right RLN with an extralaryngeal terminal bifurcation at its usual position. Thereafter, we also identified an ipsilateral non-RLN joining the anterior branch of the RLN just before laryngeal entry. A Zuckerkandl's tubercle has pointed out the junction of the two nerves. In this period, the incidence of coexistence of non-RLN and RLN was 0.2% in our series. A non-recurrent course is a rare anatomical variation of the inferior laryngeal nerve. The coexistence of both non-RLN and RLN is an extremely rare anatomical finding which should be taken into account during thyroid surgery.

Nonrecurrent Laryngeal Nerve in the Era of Intraoperative Nerve Monitoring.

Nonrecurrent laryngeal nerve (non-RLN) is an anatomical variation increasing the risk of vocal cord palsy. Prediction and early identification of non-RLN may minimize such a risk of injury. This study assessed the effect of intraoperative neuromonitoring (IONM) on the detection of non-RLN. A total of 462 (236 right) nerves in 272 patients were identified and totally exposed, and all intraoperative steps of IONM were sequentially applied on the vagus nerve (VN) and RLN. Right predissection VN stimulation at a distal point did not create a sound signal in three cases (3/236; 1.27%). Proximal dissection of the right VN under IONM guidance established a proximal point, creating a positive signal. The separation point of non-RLN from VN was discovered in all three patients. Non-RLNs were exposed from separation to laryngeal entry. Positive IONM signals were obtained after resection of thyroid lobes, and postoperative period was uneventful in patients with non-RLN. Absence of distal VN signal is a precise predictor of the non-RLN. IONM-guided proximal dissection of the right VN leads to identification of the non-RLN. The prediction of non-RLN by the absence of the VN signal at an early stage of surgery may prevent or minimize the risk of nerve injury.

Morphology and Functional Anatomy of the Recurrent Laryngeal Nerve with Extralaryngeal Terminal Bifurcation.

Anatomical variations of the recurrent laryngeal nerve (RLN), such as an extralaryngeal terminal bifurcation (ETB), threaten the safety of thyroid surgery. Besides the morphology of the nerve branches, intraoperative evaluation of their functional anatomy may be useful to preserve motor activity. We exposed 67 RLNs in 36 patients. The main trunk, bifurcation point, and terminal branches of bifid nerves were macroscopically determined and exposed during thyroid surgery. The functional anatomy of the nerve branches was evaluated by intraoperative nerve monitoring (IONM). Forty-six RLNs with an ETB were intraoperatively exposed. The bifurcation point was located along the prearterial, arterial, and postarterial segments in 11%, 39%, and 50% of bifid RLNs, respectively. Motor activity was determined in all anterior branches. The functional anatomy of terminal branches detected motor activity in 4 (8.7%) posterior branches of 46 bifid RLNs. The motor activity in posterior branches created a wave amplitude at 25-69% of that in the corresponding anterior branches. The functional anatomy of bifid RLNs demonstrated that anterior branches always contained motor fibres while posterior branches seldom contained motor fibres. The motor activity of the posterior branch was weaker than that of the anterior branch. IONM may help to differentiate between motor and sensory functions of nerve branches. The morphology and functional anatomy of all nerve branches must be preserved to ensure a safer surgery.