Utility of Injection Laryngoplasty in the Management of Post-Thyroidectomy Vocal Cord Paralysis

Abstract

Background:

This prospective study investigated the efficacy of injection laryn-goplasty in the management of postthyroidectomy vocal cord paralysis (VCP).

Methods:

From March 2005 to December 2008, 174 consecutive injection laryngoplasties were performed in patients with unilateral glottic insufficiency. This included 34 patients with post-thyroidectomy VCP: 15 with temporary VCP and 19 with permanent VCP. Percutaneous injection was performed under local anesthesia into the vocalis muscle, using disposable 25G-long needles through the cricothyroid membrane or directly through the thyroid cartilage. Patients completed the acoustic, aerodynamic, perceptual, stroboscopic, and voice handicap index evaluations before and at 3 and 6 months after the injection.

Results:

All injection laryngoplasty could be performed under local anesthesia without morbidity. Acoustic and perceptual parameters (overall grade of hoarseness, roughness, breathiness, asthenia, and strain), maximum phonation time, jitter, and shimmer, voice handicap index, and grades of mucosal waves and glottic closure were significantly improved after the injection and they remained stable over 6 months in both the temporary VCP and permanent groups (p < 0.05).

Conclusions:

Based on these preliminary results, injection laryngoplasty improved the voice, and voice-related quality of life in patients with post-thyroidectomy VCP. It is a simple, safe, and useful method for rehabilitating post-thyroidectomy VCP patients.

Introduction

I atrogenic recurrent laryngeal nerve (RLN) injury is one of the most serious complications of thyroid surgery (1 –4). Unilateral vocal cord paralysis (VCP) is frequently well tolerated, but can be life threatening in some patients, because of aspiration pneumonia, especially in older patients or patients with impaired pulmonary function preoperatively (2). Postoperative dysphonia is a serious problem, especially for professional voice users (5). Currently, medialization thyroplasty with or without arytenoid adduction is the standard treatment of post-thyroidectomy VCP. However, medialization thyroplasty is an open framework surgery that requires an external skin incision. Additionally, it is very stressful psychologically and physically. In recent years, injection laryngoplasty techniques have regained popularity as means to manage unilateral VCP (6). It is easier and less invasive than conventional medialization thyroplasty and may provide equally durable and effective results (7,8). However, no prospective study has examined the utility of injection laryngoplasty in the management of post-thyroidectomy VCP. Thus, this prospective study determined the efficacy of injection laryngoplasty in the management of postthyroidectomy VCP.

Materials and Methods

Patients

Of 174 consecutive patients with unilateral VCP, 34 patients had post-thyroidectomy VCP (Table 1). They underwent injection laryngoplasty between March 2005 and February 2008, at the Department of Otolaryngology-Head and Neck Surgery, Soonchunhyang University Bucheon Hospital.

Table 1.

Causes of Unilateral Vocal Cord Paralysis (n = 34)

Thyroidectomy related	16 (47.1%)
Thyroid cancer invasion	13 (38.2%)
Mediastinal dissection	3 (8.8%)
Endoscopic thyroidectomy	1 (2.9%)
Parathyroidectomy	1 (2.9%)

Temporary VCP included patients who developed VCP following thyroidectomy, although the RLN was preserved during thyroidectomy. This was designated the temporary VCP (TVCP) group and included patients who underwent injection laryngoplasty because of severe aspiration problem or a great voice demand, such as in professional voice users.

Permanent VCP included patients in whom the RLN was sacrificed at thyroidectomy, because of evident thyroid cancer invasion or in whom the RLN was resected iatrogenically during thyroidectomy. They constituted the permanent VCP (PVCP) group. Such patients with a mild-to-moderate posterior glottic gap underwent injection laryngoplasty. But in patients with a severe posterior glottic gap exceeding 3 mm during phonation, we preferred a traditional medialization thyroplasty. As the biocompatible filler for injection, we used a polyacrylamide hydrogel (Aquamid^® Ferrosan AS) for permanent purposes and a hyaluronic acid derivative (Rofilan^® Rofil Medical International) for temporary purposes. We prefer the cricothyroid approach as the primary approach for injection laryngoplasty. However, when external anatomical landmarks were unclear, especially in patients who were obese, had short necks, or had previously undergone other neck treatments, we used the transcartilaginous approach.

Ultimately, the study included 15 TVCP patients and 19 PVCP patients. Overall, their mean age was 54.6 ± 19.4 (range, 15–88) years. Demographic information and patient characteristics are shown in Table 2. The study design was approved by the institutional review board (SCHBC IRB 09 09). All patients gave their informed consent for injection laryngoplasty procedures.

Table 2.

Patient Demographics (n = 34)

TVCP vs. PVCP	15 vs. 19 patients
Technique	18 CT app: 16 TC app
Mean age	54.6 ± 19.4 years
Mean volume injected	0.76 ± 0.2 mL
Material injected
PAAG (Aquamid^®)	20 patients (19 PVCP, 1 TVCP)
Hyaluronic acid (Rofilan^®)	14 patients (14 TVCP)

CT app, injection laryngoplasty through the cricothyroid membrane; TC app, injection laryngoplasty directly through the thyroid cartilage; TVCP, temporary vocal cord paralysis following thyroidectomy; PVCP, permanent vocal cord paralysis following thyroidectomy; PAAG, polyacrylamide gel.

Objective voice evaluation

Acoustic and aerodynamic analyses were conducted prospectively, before injection, and at 3 and 6 months after the injection by a single speech language pathologist. For the acoustic analyses, each patient sat in a quiet room wearing a microphone (C410; AKG) at a constant 3 cm distance from the mouth. Sustained 3-s /Ah/-like phonations were recorded, and jitter and shimmer were analyzed using the Dr. Speech 4.0 software (Tiger DRS). For aerodynamic analyses, the maximum phonation time was calculated. Each patient sustained /a/ vowel phonations for as long as possible over three trials.

Subjective voice evaluation

Perceptual voice evaluations were conducted using the overall grade of hoarseness, roughness, breathiness, asthenia, and strain (GRBAS) rating scale. Speech language pathologists evaluated voice quality, using the GRBAS scale, focusing on the overall sum for each scale (0 = normal; 1 = slight disturbance; 2 = moderate disturbance; and 3 = severe disturbance). The patients used a 10-point visual analog scale (VAS) to self-rate their voice function and the degree of aspiration independently (0 = normal voice/no aspiration problems; 10 = worst voice/maximum aspiration problems), to evaluate subjective voice improvement and aspiration status. In the stroboscopic evaluation (Rhinolaryngeal stroboscope 9100; KAY), mucosal waves and the posterior glottic gap were analyzed. For practical purposes, we rated the mucosal wave of vocal fold vibration and the posterior glottic gap independently using a four-point scale (0 = no wave, severe glottic gap; 1 = marked decreased mucosal wave, moderate glottic gap; 2 = slightly decreased mucosal wave, mild glottic gap; and 3 = full wave, no glottic gap). At each follow-up visit, the patients also completed the voice handicap index (VHI), a patient-based survey, divided into three subscales that measure the functional, physical, and emotional aspects the handicap has on the voice-related quality of life.

Injection procedures

All injection laryngoplasties were performed percutaneously under local anesthesia by the same surgeon. Before the procedure, each patient inhaled a 4% lidocaine nebulizer for 10 min. An extra nozzle was used to spray additional 4% lidocaine onto the pharynx, larynx, and nose. The cricothyroid approach was performed through the cricothyroid membrane, directly into the vocalis muscle, using a disposable 25G-long needle under transnasal flexible fiberscopic monitoring (Olympus laryngobronchoscope type triiodothyronine). For the transcartilaginous approach, direct puncture was performed through the thyroid cartilage, just inferior to the halfway point of the cartilage, 0.5–1 cm lateral to the midline. The appropriate needle location was confirmed through the flexible fiberscope before injection. The tip of the needle could be seen submucosally and was then withdrawn slightly for injections. Injection was started slowly into the vocalis muscle in front of the vocal process and continued until slight overcorrection was achieved.

Statistical analyses

Statistical analyses were performed using Wilcoxon's signed-rank test (SPSS 12.0 for Windows). p-Values less than 0.05 were deemed to be statistically significant.

Results

Objective parameters

Table 3 presents the subjective voice analysis data of the TVCP and PVCP groups. For the TVCP group, statistically significant increases were observed in the maximum phonation time (p < 0.01), and significant decreases were observed in jitter and shimmer at 3 months postoperatively and they remained stable at 6 months significant (p < 0.05). For the PVCP group, the average maximum phonation time increased significantly (p < 0.01), and the average percentage of shimmer decreased significantly at 3 months postoperatively and remained stable at 6 months (p < 0.05). The average percentage of jitter decreased during the follow-up period, although this was not statistically significant (p > 0.05).

Table 3.

Objective Analysis of the Temporary Vocal Cord Paralysis and Permanent Vocal Cord Paralysis Groups

	TVCP group				PVCP group
	Pre	Post 3M	Post 6M	p-Value	Pre	Post 3M	Post 6M	p-Value
MPT (seconds)	7.8 ± 4.9	10.5 ± 3.2	12.1 ± 4.4	p < 0.01	4.3 ± 1.9	8.1 ± 3.5	8.2 ± 3.6	p < 0.01
Jitter (%)	3.8. ± 1.0	1.9 ± .05	1.3 ± 0.3	p < 0.05	3.6 ± 2.6	2.2 ± 0.7	2.7 ± 0.8	p > 0.05
Simmer (%)	7.8 ± 2.1	4.9 ± .0.7	3.8 ± 0.6	p < 0.05	7.8 ± 1.2	4.5 ± 0.7	5.4 ± 0.7	p < 0.05

MPT, maximum phonation time (seconds); jitter (%), percentage of jitter; shimmer (%), percentage of shimmer; pre, preinjection; post 3M, 3 months after injection laryngoplasty; post 6M, 6 months after injection laryngoplasty.

Subjective parameters

Table 4 presents the objective voice analysis data of the TVCP and PVCP groups. The patients' overall ratings of their voice, VHI, GRBAS scale, and stroboscopic analyses revealed significant improvements at 6 months postoperatively over baseline for both the TVCP and PVCP groups.

Table 4.

Subjective Analysis of the Temporary Vocal Cord Paralysis and Permanent Vocal Cord Paralysis Groups

	TVCP group				PVCP group
	Pre	Post 3M	Post 6M	p-Value	Pre	Post 3M	Post 6M	p-Value
GRBAS	4.7 ± 1.6	1.3 ± 1.2	0.8 ± 1.2	p < 0.01	4.9 ± 1.1	1.5 ± 1.0	1.3 ± 1.3	p < 0.01
VHI	71.6 ± 19.9	40.7 ± 17.5	33.4 ± 12.8	p < 0.01	83.3 ± 23.5	59.4 ± 28.8	47.2 ± 26.3	p < 0.01
Hoarseness VAS	6.3 ± 2.6	3.5 ± 2.6	3.4 ± 2.1	p < 0.01	6.8 ± 2.8	5.1 ± 2.3	3.9 ± 2.4	p < 0.05
Aspiration VAS	5.1 ± 2.4	1.9 ± 1.7	1.6 ± 1.5	p < 0.01	4.8 ± 1.9	3.5 ± 1.7	2.5 ± 2.1	p < 0.05
Mucosal wave	0.5 ± 0.2	2.6 ± 0.2	2.9 ± 0.4	p < 0.01	0.8 ± 0.2	2.5 ± 0.6	2.3 ± 0.8	p < 0.01
Glottic gap	1.0 ± 0.7	2.6 ± 0.2	2.9 ± 0.3	p < 0.01	1.1 ± 0.5	2.7 ± 0.8	2.7 ± 0.8	p < 0.01

GRBAS, overall sum for grade of hoarseness, roughness, breathiness, asthenia, and strain; VHI, voice handicap index; Hoarseness VAS, visual analog scale of the patients' symptomatic rating of hoarseness; Aspiration VAS, visual analog scale of the patients' symptomatic rating of aspiration; Mucosal wave, grade of the mucosal wave; Glottic gap, grade of the glottic gap.

For the TVCP group, the overall sum of the GRBAS scale, VHI, and average scores for hoarseness and aspiration on the VAS improved statistically at 3 months postoperatively and remained stable at 6 months (p < 0.01). The stroboscopic analyses also revealed that the average grade of the mucosal wave and the glottic gap improved significantly at 3 and 6 months postoperatively (p < 0.01).

For the PVCP group, the overall sum of the GRBAS scale, VHI, and average scores for hoarseness and aspiration on the VAS improved statistically at 3 months postoperatively and remained stable at 6 months (p < 0.05). Stroboscopic analyses also revealed that the average grade of the mucosal wave and glottic gap improved significantly at 3 and 6 months postoperatively (p < 0.01).

Spontaneous recovery of VCP in the TVCP group

Most of the patients in the TVCP group who underwent injection laryngoplasty recovered vocal fold mobility during the follow-up period. Eleven patients (11/15) showed spontaneous vocal fold recovery within 5 months following thyroidectomy. Mucosal wave analysis in stroboscopy, GRBAS, and VHI did not differ statistically between 3 and 6 months postoperatively. This means that the material injected in the vocal fold did not worsen the patient's voice quality or affect the mucosal vibration of the vocal fold.

Voice analyses after long-term follow-up

Table 5 presents the voice analysis data after long-term follow-up of the PVCP group. In these patients, maximum phonation time, percentage of shimmer, overall sum of the GRBAS scale, VHI, and grade of the mucosal wave improved statistically at 12 months postoperatively and remained stable for 24 months (p < 0.05). However, the percentage of jitter and grade of the posterior glottic gap did not improve significantly during the 2-year follow-up. Eight patients in the PVCP group who were followed for more than 2 years showed that the therapeutic effect of injection laryngoplasty continued for 2 years. Of these, six patients had an acceptable voice for 2 years with no any additional procedure, whereas two patients needed an additional booster injection laryngoplasty, because of material resorption and voice deterioration.

Table 5.

Voice Analysis of Long-Term Follow-up Patients

	Pre	Post 12M	Post 24M	p-Value
MPT	4.7 ± 2.9	8.8 ± 4.5	7.8 ± 5.4	p < 0.05
Jitter	2.9 ± 1.1	3.0 ± 2.7	2.2 ± 0.6	p > 0.05
Shimmer	7.8 ± 1.8	2.4 ± 0.5	4.4 ± 0.7	p < 0.05
GRBAS	5.6 ± 1.3	1.0 ± 0.9	1.4 ± 0.4	p < 0.05
VHI	81.5 ± 22.1	36.5 ± 11.8	41.0 ± 10.5	p < 0.05
Mucosal wave	0.9 ± 0.3	2.7 ± 0.2	2.1 ± 0.4	p < 0.05
Glottic gap	1.1 ± 0.2	2.7 ± 0.2	2.0 ± 0.5	p > 0.05

Post 12M, 12 months after injection laryngoplasty; post 24M, 24 months after injection laryngoplasty.

Postoperative complications

No serious adverse effect, such as airway obstruction, material migration, or granuloma formation, was observed in any patient during the follow-up period. One patient demonstrated failure to augment the paralyzed vocal fold, because the polyacrylamide hydrogel leaked after puncturing the vocal fold mucosa during the injection. We treated this patient using booster injection laryngoplasty at 1 month postoperatively.

Discussion

Unilateral VCP is a well-known complication of thyroid surgery. Even for experienced surgeons, a number of patients will develop temporary VCP, especially those with extensive local disease, with paratracheal nodal disease, or at a repeat operation (9). The current standard treatment algorithm for TVCP is waiting for spontaneous vocal fold recovery for about 1 year (10). During this period, however, patients suffer from hoarseness and aspiration problems. These result in worsening of the quality of life and can have a negative influence on the doctor-patient relationship, especially in the patients who suffer from severe aspiration following thyroidectomy or those with a great demand on their voices, such as professional voice users (6). In our study, injection laryngoplasty using absorbable material improved the voice and voice-related quality of life while awaiting spontaneous recovery in the TVCP group. These results are supported by the aerodynamic, perceptual, stroboscopic, VHI, and VAS results.

With permanent RLN paralysis, persistent hoarseness and the increased vocal effort adversely affect the patient's quality of life. There are several surgical techniques to improve and eliminate aspiration, including medialization thyroplasty, arytenoid adduction, reinnervation procedures, and injection laryngoplasty. The main goal of all of these surgical methods should be to achieve optimum glottic closure, to improve the quality of voice (10). The quality of the voice can improve considerably after either medialization thyroplasty or injection laryngoplasty. Both procedures have indications, limitations, and complications. Compared with conventional medialization thyroplasty, injection laryngoplasty has several advantages: it can be performed under local anesthesia without morbidity in the office setting. However, it also has some drawbacks: it cannot correct a large posterior glottic gap, it is less precise than the medialization procedure, and the injected materials can be absorbed (11). However, as surgeons accumulate experience in injection laryngoplasty, these can be overcome, to some degree.

Currently, medialization thyroplasty with or without arytenoid adduction is the gold standard for treating unilateral VCP. However, medialization thyroplasty is an open procedure that requires another external skin incision with sedation. This is very stressful to the patients. Because the newer transcutaneous injection laryngoplasty technique does not require general anesthesia, it is an appealing option for the TVCP group.

This study revealed that injection laryngoplasty confers statistically significant improvements in voice and aspiration, and that the therapeutic efficacy continues for at least 6 months for both the TVCP and PVCP groups. These results are supported by the aerodynamic, perceptual, stroboscopic, VHI, and VAS results. The vibratory activity of the vocal fold and the posterior glottic gap also improved, and these results were confirmed by stroboscopic follow-up.

For some patients in the PVCP group in whom permanent injection material was used, the effectiveness persisted for 2 years, although two patients needed repeat injections. These promising results show a new future in the management of post-thyroidectomy VCP. With advances in biotechnology, numerous biocompatible fillers have been introduced (6). Thus, the future of injection laryngoplasty appears bright. Although our results are promising, further study is needed on a larger sample size and for a longer follow-up period to determine the viability of injection laryngoplasty in the management of post-thyroidectomy VCP.

We recommend that for TVCP patients who suffer aspiration problems or who have an occupation that places great demands on their voice, injection laryngoplasty with absorbable material is a good treatment option. In post-thyroidectomy PVCP patients with a small to moderate posterior glottic gap, injection laryngoplasty using permanent material can be a good treatment option. Injection laryngoplasty using permanent material under local anesthesia in the office setting can improve the quality of life of patients.

Patients with a symptomatic larger posterior glottic likely require medialization thyroplasty, although this is not an absolute criterion. Patients with a large glottic gap who were in poor general condition and underwent injection laryngoplasty showed some voice and aspiration problem improvement. Based on this trial, we believe that injection laryngoplasty is a good option for treating temporary and permanent post-thyroidectomy VCP using an appropriate injection material in selected patients.

Conclusions

On the basis of the results of this clinical trial, injection laryngoplasty is a convenient, safe method for the rehabilitation of post-thyroidectomy VCP patients. It can improve the voice and voice-related quality of life in patients with postthyroidectomy VCP.

Disclosure Statement

The authors have no conflict of interest to declare and received no financial support for the research reported in this article.

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