ORIGINAL RESEARCH |
https://doi.org/10.5005/jp-journals-10023-1259 |
Efficacy of Total Selective Reinnervation in Bilateral Vocal Cord Palsy
1,3,4Department of Laryngology, Dr Jayakumar’s Institute of Laryngology, Thiruvananthapuram, Kerala, India
2Department of ENT, Sree Mookambika Institute of Medical Sciences, Kulashekharam, Kanyakumari, Tamil Nadu, India
Corresponding Author: Ammu Sreeparvathi, Department of Laryngology, Dr Jayakumar’s Institute of Laryngology, Thiruvananthapuram, Kerala, India, Phone: +91 7559097882, e-mail: inku1988@gmail.com
Received on: 08 February 2024; Accepted on: 22 April 2024; Published on: 15 November 2024
ABSTRACT
Background: Bilateral vocal cord palsy (BVCP) continues to be a challenge for laryngologists. The cause varies from idiopathic to trauma. At present, there are many static surgical treatments available for BVCP, which improve airway at the expense of voice. More than 75% of nerve fibers goes to adductors. Bilateral adductor involvement is rare in BVCP. For improving the airway without compromising the voice a dynamic procedure is needed. Two such procedures at experimental stages are total selective reinnervation and posterior crico arytenoid (PCA) pacemaker. Here, we are analyzing our experience with eight such cases of total selective reinnervation.
Aim: To assess the efficacy of total selective reinnervation in cases of BVCP.
Objectives: (1) To assess the improvement in airway post total selective reinnervation; (2) To assess the improvement in voice post total selective reinnervation; (3) To assess the involvement of swallowing function in total selective reinnervation.
Methodology: This is a prospective study of cases of BVCP who had undergone total selective reinnervation during a period of 7 years. Among the eight cases, two cases had idiopathic BVCP and six cases were post total thyroidectomy. All patients had a minimum follow-up period of 12 months except the last case which was in 7th postoperative month. Patient selection: all cases were seen within 2 years of their complaint. Examination under anesthesia was done in all cases to rule out cricoarytenoid joint fixity. Electromyography (EMG) was not done pre-op assessment of quality of voice in each of these patients was done with dyspnea index and Voice Handicap Index (VHI). Glottic space assessment was done with endoscopy. None of the patients had swallowing dysfunction at presentation. A repeat assessment was done at 6 and 12 months post-op and the results were compared.
Results: In the immediate post-op period, the patient had worsened voice quality. However, voice improved by 4 months and by 12 months all patients had better voice and lower VHI. Regarding airway: six patients were decannulated in 2 weeks, one patient was decannulated after 4 months and the youngest one after 1 year. By 6 months all patients had improved their dyspnea index by 1. However, between 8 and 12 months four patients had worsening dyspnea index requiring static procedures. Out of the four patients who did not require static procedures, one has completed only 6 months. The immediate swallowing dysfunction following the procedure improved within a period of 2 weeks.
Conclusion: Total selective reinnervation improved the voice in all cases and it did not have any adverse effect on swallowing; however, the long-term effect in improving the airway was ambiguous. The best results were obtained in younger patients. This is in sharp contrast with nonselective reinnervation for unilateral vocal cord palsy, whose success rate is as high as 90%. This raises the question of doing such a long, tedious, financially and emotionally draining procedure for a marginal improvement in the airway, which could be attained by doing other static procedures albeit with poorer voices.
How to cite this article: Sreeparvathi A, Saralakumari SNH, Menon JR, et al. Efficacy of Total Selective Reinnervation in Bilateral Vocal Cord Palsy. Int J Phonosurg Laryngol 2024;14(2):26-32.
Source of support: Nil
Conflict of interest: None
Keywords: Bilateral vocal cord paralysis, Greater auricular nerve graft, Laryngeal endoscopy, Laryngoscopy, Recurrent laryngeal nerve injury, Total selective reinnervation, Vocal cord palsy, Vocal cord.
INTRODUCTION
Bilateral vocal cord palsy (BVCP) remains a significant challenge for specialists in laryngology. Its causes range from idiopathic origins to trauma. Currently, there exist several surgical interventions aimed at stabilizing the airway, albeit often at the cost of compromising vocal function. In BVCP, <25% of nerve fibers typically innervate the adductor muscles, making bilateral adductor involvement uncommon. To enhance airway function without sacrificing voice quality, dynamic procedures are necessary. Two experimental approaches in this regard include total selective reinnervation and posterior crico arytenoid (PCA) pacemaker. This study reviews our experience with eight cases of total selective reinnervation.
The primary reason for bilateral vocal cord paralysis is typically damage to the recurrent laryngeal nerve (RLN) during thyroid surgery, which is found in approximately 1–4.6% of patients undergoing this procedure,1 immediately after extubation or at a later stage.2 Initially, most cases are managed with intubation or tracheostomy. Surgical correction focuses on enlarging the airway at the level of the glottis.
Managing bilateral vocal fold paralysis presents a substantial challenge for laryngologists as it necessitates balancing adequate glottal volume with maintaining voice quality and ensuring the integrity of the lower airway. The goal is to maintain a patent larynx to facilitate unrestricted breathing, preserve vocal function, and prevent aspiration, which is crucial for the successful decannulation of tracheostomized patients.
Laser surgeries such as arytenoidectomy, posterior cordotomy, or lateral fixation of the vocal fold are frequently performed procedures. While these interventions effectively alleviate breathing difficulties, they are viewed as less than ideal. The preferred approach would be to restore vocal cord mobility while preserving or minimally impairing phonatory function.3
While laryngeal denervation surgery is relatively recent, its conceptual foundations’ date back to the early 19th century, and the first human surgery was conducted in 1908.4 Since then, research on laryngeal innervation has progressed significantly, starting with animal models and expanding to include experimental models and selective bilateral reinnervation in humans.
In 2014, Marie et al. documented a 92.5% decannulation rate among patients treated with bilateral superior laryngeal reinnervation (BSLR), with a 1-year follow-up on 40 patients.5 To date, the BSLR technique has only been implemented in a limited number of centers.6-8 Our group has applied this technique in a series of patients with bilateral vocal fold paralysis, and the outcomes are detailed in this report.
AIM
To assess the efficacy of total selective reinnervation in cases of BVCP.
OBJECTIVES
-
To assess the improvement in airway post total selective reinnervation.
-
To assess the improvement in voice post total selective reinnervation.
-
To assess the involvement of swallowing function in total selective reinnervation.
METHODOLOGY
This prospective study examines cases of BVCP treated with total selective reinnervation over a period of 7 years (2015–2024). Among the eight cases studied, two had idiopathic BVCP, and six occurred following total thyroidectomy. All patients were followed up for a minimum of 12 months, except for the most recent case, who is currently in the 8th postoperative month (Table 1).
| VHI | Mean ± SD | Median | Min–max |
|---|---|---|---|
| Pre-op | 15.9 ± 3.7 | 15 | 11–22 |
| 6 months | 5.8 ± 2.4 | 5 | 4–10 |
| 12 months | 4.7 ± 1.6 | 4 | 3–8 |
Pre-op vs post-op 6 months, Z# = 2.53*, p = 0.011; Pre-op vs post-op 12 months, Z# = 2.37*, p = 0.018; Post-op 6 months vs post-op 12 months, Z# = 1.41, p = 0.157; *Significant at 0.05 level; #Wilcoxon signed-rank test
Patient selection criteria included evaluation within 6 months to 2 years of symptom onset. Examination under anesthesia was conducted in all cases to assess cricoarytenoid joint mobility. Electromyography (EMG) was not performed. The absence of permanent muscle denervation was confirmed by the presence of active paradoxical movement during deep inspiration, indicating no muscle fibrosis (Table 2).
| Dyspnea index | Pre-op | 6 months | 12 months | |||
|---|---|---|---|---|---|---|
| Count | Percent | Count | Percent | Count | Percent | |
| Dyspnea on severe exertion | 0 | 0.0 | 2 | 25.0 | 2 | 28.6 |
| Dyspnea on moderate exertion | 1 | 12.5 | 4 | 50.0 | 2 | 28.6 |
| Dyspnea on minimal exertion | 4 | 50.0 | 2 | 25.0 | 3 | 42.9 |
| Dyspnea at rest | 3 | 37.5 | 0 | 0.0 | 0 | 0.0 |
| Mean ± SD | 3.3 ± 0.7 | 2 ± 0.8 | 2.1 ± 0.9 | |||
| Median | 3 | 2 | 2 | |||
| Min–max | 2–4 | 1–3 | 1–3 | |||
Pre-op vs post-op 6 months, Z# = 2.64*, p = 0.008; Pre-op vs post-op 12 months, Z# = 1.84, p = 0.066; Post-op 6 months vs post-op 12 months, Z# = 0.38, p = 0.705; *Significant at 0.05 level; #Wilcoxon signed-rank test
Prior to surgery, each patient’s voice quality was assessed using the Voice Handicap Index (VHI): 10 scores. Dyspnea was evaluated using our center’s dyspnea index score. Glottic space was assessed via endoscopy. None of the patients exhibited swallowing dysfunction at the initial evaluation. Follow-up assessments were conducted at 6 and 12 months postsurgery, and the results were subsequently compared (Table 3).
| Dyspnea index score | |
|---|---|
| 1 | Dyspnea on severe exertion |
| 2 | Dyspnea on moderate exertion |
| 3 | Dyspnea on minimal exertion |
| 4 | Dyspnea at rest |
Surgical Procedure
All surgeries were conducted under general anesthesia with ventilation through the tracheostomy tube. A 16F Ryles tube was inserted. A U-shaped neck incision (Gluck–Sorensen’s) was made approximately 1 cm below the lower edge of the cricoid cartilage, extending superolaterally to the tip of the mastoid process on both sides. Subplatysmal flap dissection was performed in layers. Bilateral accessory nerves were isolated. The great auricular nerve (GAN) was identified, and two Y-shaped free nerve grafts were harvested for subsequent use (Fig. 1).
Fig. 1: Diagram illustrating the anatomy of the nerves (highlighted in yellow) utilized in the BSLR procedure
The right phrenic nerve was dissected and traced retrogradely until its roots (C3-C5) were identified using a disposable nerve stimulator. The nerve was isolated for later use (Fig. 1). The inferior constrictor muscles were released from the posterior margins of the thyroid alae to expose the posterior cricoarytenoid (PCA) muscle and the RLN supplying it. The RLNs were followed proximally to the site of injury. Any scar tissue or neuroma at the distal stumps of the bilateral RLNs was removed. The cricothyroid joint was dislocated to provide access to the intralaryngeal branches of the RLNs. The main trunk of the RLN was isolated. The branch to the thyrohyoid, which courses medially and inferiorly from the main trunk of the hypoglossal nerve, was dissected and then transected distally on both sides (Table 4). The main trunk of the RLN was connected to the thyrohyoid branch using a cable graft from the GAN.
| Dyspnea index | ||
|---|---|---|
| Pre-op | 6 months | 12 months |
| 2 | 1 | 2 |
| 3 | 1 | 1 |
| 3 | 2 | 3 |
| 3 | 2 | 2 |
| 3 | 2 | 3 |
| 4 | 3 | 1 |
| 4 | 2 | |
| 4 | 3 | 3 |
The proximal end of the right phrenic nerve sectioned after the C3 root but before C4-C5, was anastomosed with the main trunk of the Y-shaped free nerve graft (GAN from the opposite side). Each distal branch of the Y-shaped free nerve graft was implanted into the main body of each PCA muscle. Neurorrhaphies were performed using 7/0 Prolene or PDX sutures under magnification of a surgical microscope. Figure 2 shows a schematic representation of the neurorrhaphies performed in BSLR.
Fig. 2: Diagram illustrating the neurorrhaphies conducted in BSLR: donor and recipient nerves depicted in yellow, with grafts shown in green (harvested from the superficial cervical plexus) and blue (Y-shaped GAN graft)
The wound was closed in layers. A minimal negative suction ready vac drain (no. 12) was used to avoid negative pressure on the anastomoses. A cuffed tracheal tube was placed in all patients (Table 5).
| Vocal cord mobility (right) | Pre-op | 6 months | 12 months | |||
|---|---|---|---|---|---|---|
| Count | Percent | Count | Percent | Count | Percent | |
| Adducted | 7 | 87.5 | 2 | 25.0 | 5 | 71.4 |
| Slight abduction | 1 | 12.5 | 6 | 75.0 | 2 | 28.6 |
Pre-op vs post-op months, Z# = 2.24*, p = 0.025; Pre-op vs post-op 12 months, Z# = 0.58, p = 0.564; Post-op 6 months vs post-op 12 months, Z# = 1.73, p = 0.083; *Significant at 0.05 level; #Wilcoxon signed-rank test
Postoperative Care
The patient remained in the surgical intensive care unit (ICU) for an initial postoperative period ranging from 2 to 5 days. Upon removal of the drain and urinary catheter and upon ambulation, they were transferred to a regular room. Enteral feeds were initiated on the 1st postoperative day, and intravenous fluids were gradually discontinued over 48 hours. Swallowing therapy (dry stimulation) commenced on the 4th postoperative day. Over the following 3 weeks, removal of the nasogastric tube and decannulation of the tracheostomy were performed based on serial flexible laryngeal evaluations of airway and swallowing. The patient received broad-spectrum antibiotics as prophylaxis against infection, and active chest physiotherapy was administered to aid in clearing secretions.
RESULTS
In our study, there were eight patients in total, consisting of two females and six males (Fig. 3). Among them, two were children/adolescents (under 18 years old) and six were adults (Fig. 4). In 75% of cases, bilateral vocal cord paralysis resulted from thyroidectomy, while the remaining 25% were idiopathic (Fig. 5).
Fig. 3: Percentage of distribution of sample according to sex
Fig. 4: Percentage distribution of the sample according to age
Fig. 5: Percentage of distribution of sample according to cause
The preoperative evaluation included assessing the VHI, awake endoscopy, and flexible endoscopic evaluation of swallowing (FEES). In the immediate postoperative period, patients’ VHI scores indicated worsened voice quality (high VHI 10 score). However, voice quality improved by 4, and by 12 months, all patients demonstrated better voice quality with lower VHI scores. Voice was assessed using the VHI 10 score throughout the study (Fig. 6).
Fig. 6: Effectiveness of intervention on VHI
Comparing the preoperative VHI with the VHI at 6 months postoperatively, a statistically significant improvement was observed. Similarly, there was a statistically significant improvement in VHI at 12 months compared to preoperative values. However, no statistically significant improvement was found when comparing VHI between the 6- and 12-month postoperative assessments (Fig. 6).
Regarding the airway, six patients were decannulated within 2 weeks, one patient after 4 months, and the youngest patient after 1 year. By 6 months, all patients showed improvement in the dyspnea index by 1 point. However, between 8 and 12 months, four patients experienced a worsening dyspnea index necessitating static procedures. Among the four patients who did not require static procedures, one had completed only 8 months (Table 5).
When comparing the preoperative dyspnea index with that at 6 months postoperatively, a statistically significant improvement was noted. However, comparing the preoperative dyspnea index with the index at 12 months postoperatively did not show statistically significant improvement (Table 6).
| Vocal cord mobility (left) | Pre-op | 6 months | 12 months | |||
|---|---|---|---|---|---|---|
| Count | Percent | Count | Percent | Count | Percent | |
| Adducted | 6 | 75.0 | 0 | 0.0 | 4 | 57.1 |
| Slight abduction | 2 | 25.0 | 8 | 100.0 | 3 | 42.9 |
Pre-op vs post-op 6 months, Z# = 2.45*, p = 0.014; Pre-op vs post-op 12 months, Z# = 0.58, p = 0.564; Post-op 6 months vs post-op 12 months, Z# = 2*, p = 0.046; *Significant at 0.05 level; #Wilcoxon signed-rank test
The initial swallowing dysfunction improved within 3 weeks postprocedure.
Upon evaluating vocal cord mobility preoperatively and at 6 months postoperatively, statistically significant improvement was observed, particularly in slight abduction. Recovery was notably more pronounced in the left vocal cord, though the reasons for this are unclear. However, comparing vocal cord mobility between the 6th and 12th months, as well as between preoperative and 12th-month assessments, did not show statistically significant improvement. This suggests a potential for delayed synkinesis.
Statistical Tests Used
Categorical variables were presented as frequency (percentage), while quantitative variables were expressed as mean ± SD and median, as appropriate. The Wilcoxon signed-rank test was employed to compare quantitative parameters between two-time intervals. Statistical significance was set at p < 0.05 for all analyses. Data analysis was conducted using Statistical Package for the Social Sciences (SPSS) software, version 20.0.
DISCUSSION
Until the 1920s, tracheostomy was the sole conventional treatment for symptomatic bilateral vocal fold paralysis (BVFP). In 1922, Jackson pioneered open ventriculocordectomy to restore airway function while preserving voice.9 In the 1970s, Woodman and Pennington introduced transcervical arytenoid resection, which gained widespread acceptance.10 Subsequently, the transoral approach has evolved, with transoral laser-assisted posterior cordotomy (Kashima) now preferred for its cost-effectiveness, absence of neck scarring, and quicker recovery.10 However, glottic expansion surgeries often yield incomplete airway improvements, leading to compromised speech quality and, in some cases, increased risk.4,11
Selective laryngeal innervation techniques have been refined to restore PCA muscle function and overcome limitations of static glottic expansion procedures.7,12,13 Tucker introduced the neuromuscular pedicle technique using the ansa hypoglossi and muscle strip for PCA reinnervation, achieving a success rate of 74%.14 Free nerve grafting, linking the upper phrenic nerve root to both PCAs and the thyrohyoid branch of the hypoglossal nerve to the adductor branch of the RLN, has shown promising results,4 albeit few centers have replicated the successes of Marie and Li.7
Vocal fold function is crucial for survival, especially in cases of bilateral involvement leading to dysphagia, aspiration, and airway compromise.15 Awake laryngoscopy is essential for assessing vocal fold mobility and function.
The management of bilateral vocal fold motion impairment (BVFMI) requires a multidisciplinary approach involving intensivists, laryngologists, and speech pathologists. Securing a safe airway is paramount, often necessitating tracheostomy in 19.2–74% of cases.16-19 Some case series report no need for tracheostomy,20,21 while others cite rates as high as 90–100%,22,23 highlighting treatment variability across centers.
Many centers advocate for early surgical intervention within 1 year if spontaneous recovery does not occur.21,24,25 Conversely, some recommend delaying irreversible procedures for several years to allow potential recovery.26,27
Patients unable to be extubated with persistent VFP have options to improve airway patency, categorized into static, chemical, and dynamic methods, often involving laryngeal framework surgeries.27-31 Laryngeal chemodenervation, targeting the thyroarytenoid or cricothyroid muscles with botulinum toxin type A injections, is another treatment option.32,33 Dynamic surgeries include laryngeal reinnervation and functional electrical stimulation.
Candidates suitable for bilateral selective reinnervation should exhibit a VHI score of 10 and a high demand for laryngeal function restoration. Assessment of the cricoarytenoid joint under general anesthesia via endoscopy is crucial. Failure to detect interarytenoid or cricoarytenoid joint involvement can lead to poor patient selection and suboptimal outcomes following selective reinnervation.34 In cases of joint fixation or scar tissue, an endoscopic approach (e.g., arytenoidectomy/posterior cordotomy) may be necessary.11,35
Ideally, there should be a 12–18-month window for muscle reinnervation postnerve injury before irreversible motor endplate degeneration occurs.36 Delayed diagnostics can be costly, potentially resulting in severe atrophy and irreversible fibrotic changes hindering successful axonal regeneration.4 Early neurological rehabilitation has been shown to improve functional outcomes.37
In summary, spontaneous recovery typically takes 12 months, although recent studies suggest that 6 months may suffice to mitigate pathological synkinetic movements.4 Definitive evidence of RLN injury without chance of recovery warrants prompt bilateral selective reinnervation.38
Marie et al. advocate for bilateral selective reinnervation using ansa hypoglossi for adductor anastomosis and C3 for bilateral abductor muscles, utilizing nerve grafts.4,7,11 The phrenic nerve, identified by Baldissera et al.36 as optimal for muscle innervation, yields favorable outcomes.4 Selective reinnervation of PCAs involves a Y-shaped free nerve graft harvested from the GAN attached to the phrenic nerve’s root (usually C3) and implanted into both PCAs. Orestes et al. propose reinnervating PCAs via the external branch of the superior laryngeal nerve to avoid hemidiaphragm paralysis risk,39 yet this method’s efficacy may be compromised in thyroid surgery patients lacking a superior laryngeal nerve.
According to Marie, reinnervation of adductors involves RLN trunk transection to denervate intrinsic muscles before neural anastomosis. Recent preferences favor the thyrohyoid branch over ansa hypoglossi, as this branch supports laryngeal adductors during phonation and swallowing without inspiratory reinnervation risks.4,12 This approach minimizes the need for precise abductor fiber identification within the larynx.4 RLN transection induces complete vocal cord paralysis, facilitating early tracheostomy removal due to immediate airway improvement.
Recovery and denervation course are closely linked; axonal regeneration initiates distally at the Ranvier nodes, with 50–100 sprouts maturing into growth cones guided by local neurotrophic and neurotropic factors.39 Thus, the surgery-to-recovery interval should not be shorter than 6 months, aligning with graft length for optimal axonal growth.
Abductor function recovery hinges on injury timing and graft characteristics. Li et al. advise a 1–2 cm shorter phrenic nerve graft length than thyrohyoid branch to synchronize axonal regrowth into laryngeal muscles.17 For primary nerve repair, 50% of axons regenerate successfully; this rate drops to 25% for grafts, exacerbated by chronic axotomy and muscle fibrosis.39 Consequently, outcomes may be affected by preoperative uncertainties and unanticipated neuromuscular changes.
Bilateral superior laryngeal reinnervation aims to mitigate airway compromise, preserve voice function, and prevent aspiration,4,12 necessitating an 8–10 mm glottic opening for secure airway.40
Accurate patient selection and comprehensive diagnostics are critical for treatment success. Selective reinnervation of PCAs aids vocal fold abduction during respiration, preventing atrophy and ensuring proper tension. While lung function improves and voice quality is maintained, temporary tracheostomy may be necessary, with transient aspiration a potential postprocedural issue.
CONCLUSION
Bilateral vocal fold immobility (BVFI) poses a life-threatening risk, particularly in pediatric cases. Accurate diagnosis hinges on a thorough history and comprehensive physical examination. Maintaining airway patency stands as the primary objective for the healthcare team. A multidisciplinary approach is essential for managing this condition over the long term. Balancing breathing, swallowing, and speech is critical to enhancing patients’ quality of life. Treatment strategies must be personalized to meet individual patient needs, emphasizing the expertise of the treating laryngologist.
In cases where spontaneous recovery is possible, conservative management may be initially attempted. If conservative measures prove ineffective, less vocally impairing static procedures or chemodenervation techniques may be considered. Some patients may require multiple interventions.
For cases necessitating a surgical procedure with sustained airway improvement, an evaluation is first conducted to determine suitability for bilateral selective reinnervation. If selective reinnervation or laryngeal reinnervation does not achieve desired outcomes, long-term static surgical interventions like posterior cricoid cartilage graft or Kashima’s posterior cordotomy may be recommended.
Our study showed that selective reinnervation significantly improved voice quality in all cases and had no lasting adverse effects on swallowing, except for transient issues immediately after surgery. However, long-term airway improvement outcomes were inconclusive, likely influenced by our small patient cohort. Better outcomes were observed in younger patients, particularly adolescents. This contrasts sharply with nonselective reinnervation for unilateral vocal cord palsy, where success rates can reach up to 95%.
Ongoing research and advancements strongly suggest that reinnervation and pacing techniques may represent preferred treatment options, offering potential to optimize laryngeal functions such as airway patency, swallowing, and voice quality.
ORCID
Sabari Nath Hareendranath Saralakumari https://orcid.org/0009-0000-1977-096X
Manju E Issac https://orcid.org/0009-0002-6990-8589
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