Unilateral vocal fold paralysis occurs following a vagus or recurrent laryngeal nerve injury due to iatrogenic, idiopathic, or other intrinsic or extrinsic causes.1 It impairs vocal fold movement resulting in a breathy voice; treatment modalities include injection laryngoplasty and laryngeal framework surgery.

Laryngeal framework surgeries for voice disorders were developed by Isshiki et al. in the 1970s.2,3 They are innovative, because the tension on and position of the vocal folds is altered only by changing the form of the framework without directly contacting the vocal folds. Especially, medialization thyroplasty (Type 1 thyroplasty: TP1) and arytenoid adduction (AA) have been widely accepted as effective surgical options for unilateral vocal fold paralysis, and various artificial materials for implants and newer techniques have been introduced.4

TP1 and AA are relatively less-invasive surgical treatment modalities, which can be performed under local anesthesia. Phonosurgeons can monitor changes in voice by encouraging the patient to phonate during the surgery, which allows delicate adjustments of glottal closure by changing the size and/or location of implanted materials and the pulling force on arytenoid cartilage.

Although one of the advantages of TP1 and AA, compared to injection thyroplasty, is their persistent effect; sometimes, adequate improvement in vocal function by initial surgery is not obtained, and revision surgery is often required. Further, atrophic changes in the vocal fold mucosa or dislocation of the implanted material can occur with time. In such cases, glottal closure is rendered incomplete, and revision framework surgery is considered.

The concept of revision framework surgery has been well accepted, however, the outcomes and indications of revision TP1 and/or AA have not been adequately documented. For better understanding of the indications for revision procedures and to help in achieving better phonetic outcomes, we performed a retrospective chart review of patients who underwent revision TP1 and/or AA for unilateral vocal fold paralyses.

In this study, we retrospectively reviewed cases treated with revision framework surgeries for unilateral vocal fold paralyses, and our results suggested that revision framework surgeries are a safe and promising option for patients exhibiting unsatisfactory results with prior framework surgeries.

Framework surgeries such as TP1 and/or AA for unilateral vocal fold paralysis have become widely accepted, and the favorable success rate of the procedure has been well-documented.7 However, according to a national survey in the United States, unchanged and worsened voice after medialization laryngoplasty were observed in 3% and 1% patients, respectively, and the revision rate accounted for 6%.7 Thus, revision framework surgeries are rare but are occasionally required.

In our case series, 15 of the 21 cases had iatrogenic causes such as thyroidectomy, aortic surgery, or neck dissection, and this finding is similar to previous studies of primary or revision framework surgeries.5,8,9 Regarding the causes for revision surgeries, endoscopic examination revealed anterior and/or posterior glottic incompetence in all patients, and no overcorrection was observed. Cohen et al. reported that the most common problem in glottal closure was undercorrection,10 and this is consistent with the results of our study.

Revision surgery was considered in early postoperative period in 11 cases, and inadequate correction in prior surgery was indicated. In fact, seven cases that underwent AA complained of hoarseness just after the prior surgeries, and revision surgeries were suggested within 6 months after the prior surgeries. AA should be considered in the prior surgery in these cases, and the initial assessment and planning are thought to be important for the better outcomes.

Regarding the prostheses, GORE-TEX or PTFE were used in 18 of 21 cases in prior surgeries. Higher prevalence of under correction with sheet-like material has been reported,11 and the type of materials might be one of the reasons for the failure in prior surgeries. Because Isshiki has recommended overcorrection in the adjustment procedure,12 we demonstrated intraoperative flexible laryngoscopy and preferred overcorrection in revision TP1 using GORE-TEX, and this might contribute to good outcomes in our case series.

During revision surgeries, post-operative scars from prior surgeries render the procedures more difficult compared to primary surgeries.13 Sometimes, it is not easy to locate the implant and thyroplasty window of prior surgery. In our case series, implants were easily identified and were removed without any severe damage to the surrounding tissues, and revision surgeries were completed without interruption or cessation of the procedures except for one case. Although two patients with prior AA were expected to have revision AA in our cases, one patient did not undergo revision AA because of severe scar formation. However, Matsushima et al. have reported successful revision AA in patients with prior AA,14 and also we have completed revision AA in one case. Thus, laryngeal framework surgery was thought to be revisable and reversible, if performed carefully.

Complications of TP1 and/or AA include postoperative bleeding, hematoma formation, laryngeal edema, laryngeal or pharyngeal fistula, and laryngeal granulation, and their incidence has been reported to be 8.5%–16% in primary surgery.15,16 During revision surgeries, vocal fold mucosa or pyriform sinus mucosa could be easily torn, because fibrous changes render the tissues stiff. Thus, rates of complications could be higher in revision surgeries. However, in our case series, only one patient presented with postoperative hematoma, and no other complications were observed. As shown in Table 5, previous retrospective studies have not demonstrated high complication rates, and this shows postoperative complications can be avoided with careful and cautious procedure performance.

Regarding vocal outcomes, significant improvements were observed in VHI10, MPT, MFR, AC/DC ratio, and PPQ, but not in APQ and NHR. In previous studies, vocal outcomes have been evaluated with varied parameters, and thus, it is difficult to compare our results with the results of other studies. Some improvements have been observed in all studies, and it was suggested that revision framework surgeries contribute to improvement in vocal functions in patients with unilateral vocal fold paralyses.5,10,13,17 Although Misono suggested that a difference of 6 in VHI-10 score represents a minimum significant difference, 3 of 12 cases demonstrated improvements of less than 6 in VHI-10 scores.18 Further, while significant improvements in acoustic parameters after primary framework surgeries have been documented, significant improvements in APQ have not been demonstrated in any previous study of revision surgeries. Alterations in the viscoelastic properties of vocal fold mucosae and muscles caused by multiple surgical procedures could limit the acoustic outcomes of framework surgeries.

One of the limitations of this study was its retrospective design. The sample size was small, and vocal outcomes were not evaluated at the same time point in all cases, and it is difficult to elucidate reasons of failure in prior surgeries or indications of revision procedures. However, at least we confirmed that revision surgeries were required because of undercorrection in all cases and initial assessment and planning were thought to be important. Also, we observed that revision framework surgery for unilateral vocal fold paralysis is safe and could contribute to improvement in vocal functions. Further prospective studies with larger sample sizes are warranted to clarify the indications and limitations of revision framework surgeries for unilateral vocal fold paralysis.

This retrospective chart review of patients who underwent revision TP1 and/or AA for unilateral vocal fold paralysis showed undercorrection in all cases, and determined the importance of the initial assessment and planning to avoid revision surgeries.

Revision framework surgeries for unilateral vocal fold paralyses were completed safely, and significant improvements in vocal outcomes were confirmed even after multiple procedures. Revision surgery is a promising option and should be considered for patients with unsatisfactory vocal functions after primary framework surgeries for unilateral vocal fold paralysis.

The authors declare no conflicts of interest.