Thyroid surgery is one of the primary methods for treating benign and malignant thyroid diseases, including thyroid nodules, hyperthyroidism, and thyroid cancer (1). With continuous advancements in ultrasound technology, anesthesia management, and microsurgical techniques, the safety of thyroid surgery has significantly improved (2). However, recurrent laryngeal nerve injury (RLNI) remains one of the most common and clinically significant complications in thyroid surgery. The recurrent laryngeal nerve controls the movement of most intrinsic laryngeal muscles, serving as a vital structure for maintaining vocal cord function and respiratory capacity (3). Its injury can cause symptoms such as hoarseness, dysphonia, dysphagia, and coughing. In severe cases, respiratory distress may occur, necessitating tracheotomy to preserve airway patency (4). This complication not only impacts patients' quality of life and social interactions but also imposes long-term effects on postoperative recovery and mental health (5). Recurrent laryngeal nerve injury is typically classified as temporary or permanent. Literature reports indicate that the incidence of temporary RLNI ranges from approximately 1% to 10%, while permanent injury occurs in about 0.5% to 2% of cases (6). However, in patients with malignant thyroid tumors, giant goiters, or those undergoing repeat surgery, this proportion can reach 5% or higher (7). The mechanism of RLNI is complex, involving not only direct transection but also intraoperative traction, thermal injury, compression, or compromised neural blood supply. Additionally, anatomical variations of the recurrent laryngeal nerve constitute another significant cause of injury (8). Some patients exhibit atypical nerve courses or branch variations, particularly in the right lower pole region or in cases of non-recurrent laryngeal nerves. Failure to accurately identify these structures during surgery can easily lead to inadvertent injury (9, 10).

To reduce RLNI incidence, various protective measures have been proposed in recent years, including the application of intraoperative nerve monitoring, precise microsurgical dissection, and accumulating surgeon experience (11). Despite technological advancements, RLNI remains unavoidable. Some studies suggest that reoperation, malignant lesions, and central zone dissection significantly increase the risk of nerve injury, while others find no significant correlation (12, 13). Limited sample sizes in individual studies, substantial differences in study designs, and inadequate control of confounding factors restrict the reliability and consistency of results (14). Against this backdrop, it is necessary to systematically integrate and quantitatively analyze existing literature through systematic reviews and meta-analyses to identify independent risk factors for recurrent laryngeal nerve injury after thyroid surgery. Systematic reviews and meta-analyses can synthesize findings from multiple studies, reduce random error, enhance statistical power, and provide higher-quality evidence-based guidance for clinical practice. By identifying high-risk factors, clinicians can thoroughly assess patient risk preoperatively and develop individualized surgical strategies. During surgery, emphasis on nerve anatomy identification and protection, supplemented by nerve monitoring technology, when necessary, can effectively reduce the incidence of recurrent laryngeal nerve injury, thereby improving surgical safety and patient outcomes.

This systematic evaluation and meta-analysis will strictly follow the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines (15). And it is registered in Prospero with registration number CRD420251106124.

A systematic search was conducted in PubMed, Embase, Web of Science, and the Cochrane Library databases from their inception to October 1, 2025, to identify literature related to risk factors for recurrent laryngeal nerve injury following thyroid surgery. The search strategy combined Medical Subject Headings (MeSH) terms and free-text keywords, with primary search terms including: “thyroid surgery,” “thyroidectomy,” “recurrent laryngeal nerve injury,” “nerve damage,” “risk factor,” “predictor,” and “complication”. The detailed search strategy is provided in Supplementary Table S1. To minimize omissions, reference lists of included studies and citations from relevant reviews were manually searched.

This study comprehensively explored and quantitatively analyzed the primary risk factors for RLNI following thyroid surgery. Our findings indicate that multiple factors are significantly associated with the occurrence of RLNI, including age, gender, surgical type, recurrent goiter, and the absence of intraoperative nerve monitoring.

In this study, older age was identified as an independent risk factor for RLNI. This finding indicates that the risk of RLNI increases significantly with advancing age. Older patients typically experience physiological decline, including reduced muscle elasticity, stiffened vascular walls, and diminished tissue immune responses (37). These changes may impair soft tissue recovery during surgery, thereby increasing the risk of nerve injury.

Additionally, the anatomical structure of the thyroid gland often changes in elderly patients, particularly exhibiting increased volume, harder texture, and even calcification, which complicates surgical manipulation (38). Among thyroid cancer patients, the elderly group faces an especially heightened risk of nerve injury, likely due to the cancer's inherent invasiveness and extensive surrounding tissue adhesions. Postoperative recovery is slower in elderly patients, and the likelihood of nerve recovery after injury is lower, potentially increasing the persistence and severity of RLNI (39). Therefore, for elderly patients, especially those requiring complex procedures, consideration should be given to employing intraoperative nerve monitoring techniques and utilizing minimally invasive surgical approaches to reduce the incidence of nerve injury.

Our research indicates that women face a higher risk of RLNI following thyroid surgery compared to men. This gender difference may stem from female thyroid anatomy and hormonal levels. Studies show that women's thyroids are generally larger and softer than men's, potentially leading to greater deformation during surgery or more frequent contact with the recurrent laryngeal nerve (40). Additionally, female thyroids exhibit richer vascularity, increasing susceptibility to hematoma or edema formation, which further elevates nerve injury risk. Hormonal levels, particularly estrogen, may also influence nerve repair capacity to some extent (41). Some studies suggest estrogen offers protective effects for nerves; however, during surgical trauma, this protective action may paradoxically hinder adaptive nerve recovery. This could be one reason for poorer postoperative nerve injury recovery in female patients.

Extensive thyroid resection is a significant risk factor for RLNI. This surgical approach typically requires a larger resection margin and greater exposure of tissues and structures during the procedure, increasing the risk of recurrent laryngeal nerve injury. In extended surgeries, the anatomical structures surrounding the thyroid gland are more complex, making adjacent nerves and vessels susceptible to traction, compression, or thermal injury (10). Furthermore, extended thyroidectomy is associated with longer operative times and higher intraoperative blood flow, which also heightens the risk of nerve injury (42). Particularly in thyroid cancer cases, tumors may have invaded or formed tight adhesions with the recurrent laryngeal nerve and its blood supply, making nerve injury more likely during resection. Consequently, intraoperative nerve monitoring is critical for such complex procedures, enabling real-time assessment of nerve function to prevent unnecessary damage.

Our findings indicate that lymph node dissection is a factor closely associated with the occurrence of RLNI. Lymph node dissection procedures typically involve larger resection areas and more complex anatomical structures, increasing exposure to and manipulation difficulty of the recurrent laryngeal nerve (43). Lymph node dissection, particularly when performed in the central region, often requires careful identification and avoidance of critical neural structures. Another potential mechanism for lymph node dissection-related RLNI may be related to the duration of intraoperative manipulation. Prolonged surgical time and sustained anatomical dissection may lead to hypoxia or insufficient blood supply to neural tissue, thereby increasing the risk of nerve injury (44). For patients undergoing lymph node dissection, the use of intraoperative nerve monitoring technology allows real-time assessment of recurrent laryngeal nerve function, helping to avoid unnecessary injury.

The risk of RLNI is markedly elevated in patients undergoing reoperation. These patients often present with existing postoperative scar tissue and adhesions, making nerves more vulnerable to injury. In such cases, altered anatomical landmarks and residual surgical traces complicate nerve exposure (45). Particularly for patients with prior thyroidectomy, re-excision may necessitate complex surgical maneuvers, potentially leading to unavoidable nerve traction or transection. Furthermore, recurrent disease may exacerbate the risk of nerve injury, with malignant tumors posing a particularly high risk (46). For such patients, detailed preoperative assessment is essential to thoroughly understand the anatomical structures and extent of the lesion within the surgical field. Minimally invasive techniques should be prioritized whenever feasible to minimize the probability of nerve injury.

Retrosternal goiter is considered a significant risk factor for RLNI. Due to its deep location and proximity to the recurrent laryngeal nerve and its blood supply, resection of retrosternal goiter necessitates a larger surgical incision and more complex manipulation, increasing the risk of both direct and indirect injury to the recurrent laryngeal nerve (47). Furthermore, retrosternal goiters often present with prolonged compressive symptoms, potentially leading to diminished nerve function (48). This renders the nerves more vulnerable and susceptible to injury during surgery.

The absence of intraoperative nerve monitoring has been established as an independent risk factor for RLNI. Intraoperative nerve monitoring technology enables real-time assessment of recurrent laryngeal nerve function, allowing early detection of nerve injury signs and guiding surgeons to avoid unnecessary damage (49). Without nerve monitoring, surgeons often rely solely on surgical experience and anatomical knowledge, which may lead to missed or misdiagnosed nerve injuries, particularly in complex procedures or cases with significant anatomical variations. Therefore, promoting the use of intraoperative nerve monitoring technology is crucial for reducing the incidence of RLNI.

The primary strength of this study lies in its application of systematic review and meta-analysis methodologies, integrating data from multiple high-quality studies to achieve robust statistical power and a high level of evidence. By synthesizing findings across numerous investigations, this research accurately identifies key risk factors for recurrent laryngeal nerve injury following thyroid surgery and quantifies their effect sizes. Furthermore, stringent inclusion criteria were employed to ensure the quality and consistency of all included studies. Sensitivity analyses and subgroup analyses further validated the robustness of the findings, mitigating the potential influence of individual studies on overall results. This enables us to draw more reliable and broadly applicable conclusions, providing valuable evidence-based support for risk assessment and management in clinical practice.

Although this study offers a systematic analysis of risk factors for recurrent laryngeal nerve injury following thyroid surgery, several limitations exist. First, the majority of included studies were retrospective, potentially introducing selection bias and incomplete data, which limits the generalizability of conclusions. Second, although sensitivity analyses addressed sources of heterogeneity, differences in surgical techniques, patient characteristics, and diagnostic criteria for nerve injury across studies may still affect the consistency and reliability of results. Finally, this study did not include all potential risk factors, such as surgeon experience and specific patient pathological conditions, which may also influence nerve injury occurrence. Therefore, future research should further explore and validate these factors to enhance the accuracy of risk assessment.

This study identified multiple risk factors associated with RLNI following thyroid surgery, including older age, female gender, extended thyroidectomy, and lymph node dissection. These findings assist clinicians in conducting preoperative risk assessments and implementing personalized surgical strategies. Particularly for high-risk patients, such as the elderly or those requiring complex procedures, the use of intraoperative nerve monitoring technology can effectively reduce the incidence of RLNI, thereby enhancing surgical safety and improving the quality of postoperative recovery. Therefore, understanding these risk factors and appropriately utilizing nerve monitoring are crucial for improving the prognosis of thyroid surgery.

This study indicates that older age, female gender, extended thyroidectomy, lymph node dissection, reoperation, retrosternal goiter, and absence of nerve monitoring mya be independent risk factors for recurrent laryngeal nerve injury following thyroid surgery. Clinicians should assess these risk factors based on individual patient circumstances and implement nerve-sparing techniques during surgery whenever feasible. Particularly in complex procedures, the use of intraoperative nerve monitoring may significantly reduce the incidence of recurrent laryngeal nerve injury.