Comprehensive Insights into Recurrent Laryngeal Nerve and Cervical Plexus Block Management in Thyroid Surgery: Anatomical Considerations, Injury Prevention, And Postoperative Strategies

Recurrent laryngeal nerve (RLN) intricacies during thyroid surgery demand a meticulous approach to safeguard patient outcomes. This article delves into the multifaceted landscape of RLN, emphasizing its pivotal role in interactions and phonation. The discourse navigates through the anatomy of RLN, elucidating its intricate pathways and variations that pose challenges for surgeons. A nuanced exploration of RLN injuries, spanning from neuropraxia to neurotmesis, underscores the potential morbidities arising from thyroid and parathyroid surgeries. the significance of RLN detection becomes paramount, advocating for methods like preoperative examination improvements, anatomical dexterity, and skilled surgical performance. Cutting-edge insights into the utility of intraoperative nerve monitoring (IONM) emerge, revealing its potential to enhance RLN identification accuracy while preserving functional integrity. Incidences of vocal cord palsy post-thyroid surgery accentuate RLN's critical role, further emphasizing the medico-legal implications for surgeons. navigating the contentious terrain of RLN preservation, the article discusses the efficacy of visual identification during thyroid operations and the added benefits of IONM. Recommendations from prominent organizations endorse IONM as a standard practice in thyroid surgery, underlining its role in preventing bilateral vocal cord paralysis. The narrative extends to innovative techniques like laryngeal ultrasound for real-time observation during RLN stimulation. in the aftermath of RLN sacrifice, expeditious repair methodologies are spotlighted to mitigate post-surgery complications. Attention is drawn to potential risk factors, including hyperthermal liquids, urging the use of protective measures during surgery. Postoperative assessment methods for vocal cord mobility are discussed, advocating for fibrotic endoscopy for optimal visualization. this comprehensive exploration concludes by underlining the imperative role of IONM in minimizing RLN traction injuries and its potential as a reliable instrument for predicting post-surgery vocal cord palsy. furthermore, the intersection of anesthesiology with thyroid surgery is discussed, emphasizing the role of superficial cervical plexus blocks in pain management. The systematic review and meta-analyses by Laura Wilson et al. and D. Mayhew et al. provide evidence for the effectiveness of Bilateral Superficial Cervical Plexus Block (BSCPB) in reducing postoperative pain, opioid consumption, and hospital stay after thyroid surgery. the collaborative effort between surgeons and anesthesiologists in implementing superficial cervical plexus blocks demonstrates a patient-centered approach. Advances in anesthesiology techniques, such as BSCPB, align with the goal of comprehensive patient care, emphasizing improved surgical outcomes and enhanced patient experience in thyroid surgery. the article encapsulates a holistic approach to RLN management, amalgamating anatomical precision, cutting-edge monitoring techniques, and postoperative care strategies for optimal patient outcomes.

One of the most important nerves for interactions and phonation is the recurrent laryngeal nerve. A rich heritage of scientific investigation and research has considered the complexity of vocal cord function and surgical renovation. One of the most important points in thyroid surgery is to detect and visualize, RLN in this part we are going to talk about the pre- and post-management of the surgery. RLN is a branch of the vagus nerve that supplies most of the intrinsic muscles of the larynx. Nerve injuries can be grouped into three degrees: Neuropraxia, axonotmesis and neurotmesis. To avoid RLN injuries should use the following methods: 1) improvements in preoperative examination 2) dexterity in the anatomy and variations of RLN 3) performance of operation by professionally skilled. The avoidance of use of electric knives close to the nerves to ensure that injuries will not occur in dissecting, clamping, resecting and suturing. Recent research indicates that the utilization of intraoperative nerve monitoring (IONM) can enhance the accuracy of recurrent laryngeal nerve (RLN) identification while minimally impacting the nerve's functional integrity [1.4].

The recurrent laryngeal nerve (RLN) anatomy

Intrinsic laryngeal musculature and sensory of glottis larynx innervation is by RLN. RLN is surrounded by the fourth arch vessels. The fourth arches on the right and left sides become the subclavian artery and the aortic arch [5,6]. Axons of the RLN are grouped within the vagus nerve. This nerve travels via the jugular foramen. The left RLN loops under the aorta medially and ascends the trachea-oesophageal groove [7]. As the right vagus nerve follow the common carotid artery right RLN loops around the subclavian artery and travels along the right superior lobe pleura. RLN enters the trachea-oesophageal groove more laterally than the left side behind the common carotid artery [8]. Different variations of this artery and its position relative to the RLN makes a hard situation for surgeons because of the meagre landmark; surgeon shouldn’t close the artery before detecting the RLN [9]. This nerve has many different anatomical paths.  In traditional technique surgeons search for the distal segment just below Berry’s ligament to find RLN to prevent disruption to the blood supply to the inferior parathyroid gland [10].

Injury to the RLN

Neuropraxia is the least severe degree injury. It results in complete block of nerve transmission.  It usually recovers over a few hours to few months. The second is axonotmesis, in which the nerve sheath remains intact but the axons are divided. recovery takes several months to years. The third one is neurotmesis, which is the most severe nerve injury because the axons severed [11,12]. Recurrent laryngeal nerve (RLN) injury is a recognized risk during thyroid and parathyroid surgery and can result in significant morbidity. Injury can present as paralytic dysphonia, dysphagia, paroxysmal coughing, aspiration, limited social functioning, or acute airway obstruction and is associated with significant grief. transection, clamping, stretching, electro thermal injury, ligature entrapment or ischemia can injure RLN. recurrent laryngeal nerve palsy (RLNP) is still considered the most significant and severe complication of thyroid surgery and RLNP still occurs in some cases [13-16]. Energy-based devices can also injure the nerve but most of them such as Electro tome, Harmonic scalpel, are safe even at a distance of 2-5 mm [17,18].

The incidences of temporary and permanent vocal cord palsy after thyroid surgery were reported to range from 3.4% to 7.2% and 0.2% to 0.9%, respectively, based on the number of nerves at risk [19,20]. RLN palsy is one of the most important reasons for law suit against surgeons because of its importance and effect in excellence of the life [21]. Injury to the RLN can be caused by a variety of insults. Complications such as bleeding, hypoparathyroidism and Recurrent Laryngeal Nerve Injury (RLNI) represent nearly half of all the complications of thyroid surgery. It also depends on surgeons’ ability and experience. best way to avoid injury of RLN is to detect the nerve. Paralysis of vocal cord and related muscle to the RLN may have an overwhelming influence on the patient’s life. Recurrent laryngeal nerve dysfunction commonly causes voice impairment, a disability that can damage quality of life because of its attendant communication and work-related problem [8, 21-23].

Detects RLN 

To detect the RLN during the surgery, surgeon must the knowledge of the anatomic course of the nerve and its variations to decrease RLN injury incidence [24-26]. Because of RLN different anatomic variations, the chief controversy in thyroid surgery revolved for decades around the issue of RLN preservation through visual identification [21]. Visual identification of RLN during thyroid operations has been associated with lower rates of permanent RLN palsy [27]. a 6.9% palsy rate with nerve identification and 21% without nerve identification in the patient under surgery. [27] Lahey from Boston [19,38][28] became important supporter of routine nerve dissection and visualization during thyroidectomy. RLN integrity is preserved significantly more with routine visual identification than without routine visual identification. However, even experienced surgeons can inadvertently injure the nerve due to variability in RLN anatomy and difficulties in nerve identification that can occur under challenging conditions and even with or without using IONM [21,26,27]. 

Intraoperative nerve monitoring (IONM) can help improve RLN identification, without having much effect on the nerve’s functional honour and IONM facilitates RLN identification, and with this, almost every nerve can be identified and After RLN identification, IONM facilitates nerve mapping and allows a more secure dissection [29-31]. IONM has been theorized to reduce the risk of RLN injury in thyroid surgery patients, particularly those with a higher risk of RLN paralysis including those with aggressive or recurrent thyroid cancer, Grave’s disease, and those with substernal or large cervical goiters [32]. The use of neuromonitoring in thyroid surgery has gained increasing acceptance among endocrine and head neck surgeons because of several intraoperative advantages, and it has recently been well standardizedan. recent surveys have shown its rates of use during thyroid surgery to be as high as 95% by surgeons in the United States and internationally [33-36]. RLN should be detected definitely with IONM at the level of the ITA, and then meticulously dissected to the entry of the larynx. This is a better way to keep up all branches of the RLN. For safe thyroid operations and the development of modern thyroid surgery, intraoperative confirmation of functional and anatomical RLN integrity are suggested as standards of care. All exposed RLNs should be electromyographically documented with IONM to show functional nerve integrity, and all nerves should be photographically documented with a high-resolu-tion camera to show anatomical nerve integrity [8]. 

definite localization of RLN and Clarification of RLN anatomy during the operation and assessment of RLN function and reduction of temporary palsy rate are major goals of minimization of the danger of the thyroid surgery [37-40]. multiple organizations have recommended IONM like International Neural Monitoring Study Group, the American Academy of Otolaryngology and Head and Neck Surgery, the American Head and Neck Society, and the American Thyroid Association [41-44]. IONM may also decrease the incidence of total vocal cord paralysis (VCP) and prevent the development of bilateral VCP [45] Most of all, IONM is valued for preventing the most hazardous complication of thyroid surgery, bilateral VCP. IONM enables a change of surgical strategy in bilateral thyroid surgery, when nerve dysfunction is detected intraoperatively [41,46-48]. It is unavoidable to use I-IONM in thyroid surgery and prevent RLN traction injury. C-IONM is a better way to prevent the imminent traction injury by detecting progressive decreases in electromyographical amplitude combined with progressive latency increases. using a combination of careful operative technique, visual identification, as well as continuous RLN neuro monitoring through CIONM of the vagus nerve can reduce the incidence of intraoperative RLN injury. [49,50] IONM could be considered to be a reliable instrument to predict the post surjury vocal cord palsy. Nerve integrity could be evaluated by CIONM more accurately and facilitate intraoperative decision-making [51].

One useful new method to confirm functional integrity of the RLN at the time of surgery is using laryngeal ultrasound (LUSG) to observe vocal cord quevling while the RLN is being stimulated. it’s cheaper and has a similar detection accuracy to electromyography and can be useful when the electromyography is lost [52,53]. because of the importance of RLN we should repair this nerve when it is sacrificed during the surgery as fast as possible. surgeons usually don’t understand nerve injury during the operation in most instances even when the integrity of the RLN was assured by visual inspection of the nerve to find the injury site you can use IONM and many techniques like direct end-to-end anastomosis, free nerve graft anastomosis, ansa cervicalis to RLN anastomosis, vagus to RLN anastomosis which you can repair the nerves fast in the operation and prevent some post-surgery problems [19,21,35,54-57]. another thing we have to heed is the hyper thermal liquids smog and spray which can be the potential risk factors for RLN thermal injury. They effect on conductive ability and the shape of nerve and muscles. Surgeons can use endoscopic gauze to protect the RLN against thermal injuries [58]. after surgery mobility of the vocal cord must be assessed. it can be assessed by Macintosh laryngoscope and fibrotic endoscope which is better to use fibrotic endoscope because Macintosh laryngoscope fails to give ideal visualization and lead the patient to significant discomfort and stress [59].

Anesthesiology and Superficial Cervical Plexus Block

In the realm of thyroid surgery, the intersection with anesthesiology and the implementation of superficial cervical plexus blocks are crucial considerations. Administering appropriate anesthesia is fundamental for patient comfort and safety during the procedure. Superficial cervical plexus block, a regional anesthesia technique, holds promise in minimizing pain and discomfort postoperatively. the superficial cervical plexus encompasses sensory nerves supplying the skin of the neck and portions of the ear. By strategically blocking these nerves, this technique contributes to effective pain management and reduced opioid reliance in the postoperative phase. Anesthesiologists play a pivotal role in assessing the patient's suitability for superficial cervical plexus blocks, considering factors such as allergies, coagulation status, and potential contraindications [60]. furthermore, the integration of superficial cervical plexus blocks can contribute to a multimodal pain management strategy. This aligns with the evolving paradigm in perioperative care, aiming not only for effective pain control but also for a reduction in opioid-related side effects and complications. Laura Wilson et al. conducted a systematic review and meta-analysis to assess the effectiveness of Bilateral Superficial Cervical Plexus Block (BSCPB) in thyroid surgery for analgesia. The study, an update to a 2018 paper, included 31 studies and 2,273 patients. BSCPB demonstrated: Significant reduction in post-thyroidectomy opioid consumption (P < 0 xss=removed>

The administration of superficial cervical plexus blocks requires a nuanced understanding of the anatomy and variations of the cervical nerves. Anesthesiologists collaborate with surgeons to ensure precise and targeted blocks, considering the unique anatomical variations among individuals. This collaborative effort aims to enhance the efficacy of pain management while minimizing potential complications associated with the procedure. The systematic review by JJ Pandit investigates complication rates associated with different cervical plexus blocks in carotid endarterectomy. Examining deep and superficial/intermediate blocks, the study analyzes 69 papers comprising 7558 deep/combined blocks and 2533 superficial/intermediate blocks. Findings reveal a higher serious complication rate related to the injecting needle in deep/combined blocks (odds ratio 2.13, P = 0.006). Additionally, deep/combined blocks exhibit a greater conversion rate to general anesthesia (odds ratio 5.15, P < 0 xss=removed>

As the field of anesthesiology continues to evolve, the adoption of techniques like superficial cervical plexus blocks reflects a commitment to patient-centered care and improved surgical outcomes. The judicious use of regional anesthesia, in conjunction with other pain management modalities, contributes to a holistic approach that extends beyond the operating room. D. Mayhew et al. conducted a meta-analysis and systematic review to evaluate the analgesic efficacy of bilateral superficial cervical plexus block (BSCPB) for thyroid surgery. The study included 14 randomized controlled trials published between 2001 and 2016, comprising 1154 patients. Results indicate that BSCPB significantly reduces analgesic requirements (OR 0.30; 95% CI 0.18, 0.51; P<0 P=0.44).>

In conclusion, the intricate landscape of recurrent laryngeal nerve (RLN) management in thyroid and parathyroid surgery demands a nuanced understanding and application of various surgical strategies. The review underscores the paramount importance of detecting and visualizing the RLN, emphasizing preoperative examinations, anatomical dexterity, and professional skill to mitigate the risk of RLN injuries. The advent of intraoperative nerve monitoring (IONM) stands out as a transformative tool, enhancing RLN identification accuracy while preserving functional integrity. exploring the anatomy of the RLN and its variations provides crucial insights for surgeons, especially in navigating the challenges posed by the relationship with fourth arch vessels. Categorizing RLN injuries into neuropraxia, axonotmesis, and neurotmesis underscores the severity spectrum, with an awareness of potential morbidities arising from RLN injury during thyroid and parathyroid surgery. the narrative delves into the surgical controversy surrounding RLN preservation through visual identification, advocating for routine nerve dissection and visualization. The role of IONM in improving RLN identification, mapping, and facilitating secure dissection is highlighted, offering a valuable resource for surgeons faced with variability in RLN anatomy. recommendations from prominent organizations endorsing IONM underscore its increasing acceptance and standardized use in thyroid surgery. The significance of detecting RLN at the level of the inferior thyroid artery (ITA) and meticulous dissection to the laryngeal entry is emphasized, aligning with standards of care for safe thyroid operations. beyond identification, the narrative extends to the repair and protection of the RLN, emphasizing the need for rapid repair during surgery and detailing various techniques to address potential injuries. Protective measures against thermal risks and post-surgery vocal cord mobility assessments contribute to a comprehensive approach to RLN management. in essence, this review serves as a valuable resource for surgeons, providing a synthesis of current knowledge and recommendations for optimizing RLN outcomes in thyroid and parathyroid surgery. The integration of advanced techniques, adherence to standards of care, and a commitment to ongoing research will further refine RLN management practices, ultimately enhancing patient safety and surgical excellence, Continuous advancements in anesthesiology techniques, including superficial cervical plexus blocks, underscore the commitment to comprehensive patient care within the context of thyroid surgical interventions.