The utility of the potassium titanyl phosphate laser in modulating vocal fold scar in a rat model

Predictive Factors Affecting the Outcomes Of angiolytic Laser-Assisted Glottoplasty for Sulcus Vocalis

OBJECTIVE

Glottoplasty using an angiolytic laser is an option for the surgical treatment of sulcus vocalis. In this study, we sought to evaluate the clinical outcomes of using a 532-nm diode laser in sulcus vocalis patients and to identify predictive factors of improved voice outcomes after angiolytic laser-assisted glottoplasty.

METHODS

A total of 66 patients with sulcus vocalis who underwent laser-assisted glottoplasty with a 532-nm diode laser were included in this study.

RESULTS

3 months after surgery, GRBAS scores, patient-reported outcome measures, fundamental frequency (F0), jitter percent, and noise-to-harmonic ratio decreased significantly, while cepstral peak prominence (CPP) of vowel and sentence production increased. Patients with auditory-perceptual improvements showed greater improvement in the Voice Handicap Index (VHI) scores, F0, and CPP of vowel and sentence production compared to those with no improvement. While young male patients with preoperatively high F0 were predicted to have favorable outcomes, the type of sulcus vocalis was not predictive of treatment outcomes. Patients treated with lower laser power showed better improvement in the VHI scores postoperatively than those who received higher laser power per vocal fold. Combined injection laryngoplasty with laser glottoplasty was effective in lowering the F0, especially in male patients with high F0.

CONCLUSION

A 532-nm diode laser is useful for treating sulcus vocalis. Young male patients and individuals with preoperatively high F0 showed better voice outcomes after laser glottoplasty. Laser power and combined injection laryngoplasty are considered to affect improvement in the VHI and lowering F0 after laser glottoplasty in sulcus vocalis.

Regenerative Effect of a 532-nm Diode Laser on Vocal Fold Scar in a Rabbit Model

OBJECTIVES

We evaluated the regenerative effect of a 532-nm diode laser in a rabbit model of vocal fold scarring.

METHODS

This study included 40 male New Zealand white rabbits: 20 underwent vocal fold scar surgery only (control group) and 20 underwent 532-nm diode laser glottoplasty 1 month after vocal fold scar surgery (glottoplasty group). Histological and high-speed video analyses of vocal fold vibration were performed 1 month after vocal fold scar surgery and laser glottoplasty. The maximum amplitude of vocal fold vibration and dynamic glottal gap was measured. Real-time polymerase chain reaction (PCR) was also performed to evaluate scar regeneration and wound remodeling. Transforming growth factor (TGF)-ß1, interleukin (IL)-6, procollagen-1, matrix metalloproteinase (MMP)-2, MMP-9, hyaluronan synthase (HAS)-2, and HAS-3 levels were measured.

RESULTS

The maximum difference in amplitude of vocal fold vibration and the dynamic glottal gap was significantly greater in the glottoplasty than in the control group. Real-time PCR revealed significantly higher MMP-2, MMP-9, HAS-2, and HAS-3 levels, and lower TGF-ß1, IL-6, and procollagen-1 level, in the glottoplasty than control group. The histological findings showed that the lamina propria (LP) ratio (LP pixels/total vocal fold pixels) was not significantly different between the two groups.

CONCLUSIONS

Based on the vocal fold vibration and real-time PCR results, the 532-nm diode laser improved vocal fold vibration in a rabbit model of vocal fold scarring.

5-Fluorouracil for Treatment of Vocal Fold Scar

BACKGROUND

Vocal fold (VF) scar can result from trauma, neoplasm, inflammatory processes, congenital causes, surgery and other etiologies. In general, once the vibratory margin of the VF has been scarred, it has not been possible to return VF function to normal; but often it can be improved. The drug 5-fluorouracil (5-FU) is a pyrimidine antimetabolic that has many clinical applications ranging from systemic chemotherapy to topical treatment of actinic keratosis and basal cell carcinoma of the skin. Local injection with 5-FU also has been used for hypertrophic scar and keloids. 5-FU was shown to have benefit in animal models of VF scar and subglottic stenosis.

OBJECTIVES

The present study aimed to evaluate the effect of 5-FU injection on VF vibratory function in patients with VF scar. Outcomes of 5-FU injection were compared to controls injected with dexamethasone.

METHODS

Adult voice center patients who had undergone VF injection with dexamethasone or a series of three 5-FU injections for treatment of VF scar were included in the study. Postoperative outcomes included percentage of subjects demonstrating improvement after injection, change in scar size, glottic closure, and VF stiffness, as well as digital image analysis measurements of mucosal wave. Outcomes were compared between subjects who received 5-FU and those who received dexamethasone.

RESULTS

There were 58 VFs injected with 5-FU and 58 historical controls injected with dexamethasone. Baseline subject characteristics and etiology of scar did not differ significantly between the 5-FU and dexamethasone cohorts, except that scar size was greater in the 5-FU group and mucosal wave was worse at baseline. After a series of three 5-FU injections, 61.22% improved, 8.16% demonstrated no change, and 30.61% worsened. In the dexamethasone cohort, 51.06% improved, 0.00% demonstrated no change, and 48.94% worsened. The response differed significantly between the 5-FU and dexamethasone cohorts, with a greater proportion of subjects who underwent 5-FU injection demonstrating improvement postoperatively. In the 5-FU cohort, 32.76% of subjects previously had undergone and failed dexamethasone injection for VF scar: and within that group 84.21% improved, 5.26% demonstrated no change, and 10.53% worsened following 5-FU injection. On digital image analysis, the percent improvement in postoperative mucosal wave was significantly greater in the 5-FU cohort compared to the dexamethasone group, which demonstrated a worsening of mucosal wave.

CONCLUSIONS

A series of three intralesional injections with 5-FU outperformed dexamethasone for improving mucosal wave in patients with VF scar. A prior failed trial of dexamethasone injection predicted a favorable response to 5-FU. Further research is encouraged to confirm or refute these findings.

Experimental model for controlled endoscopic subepithelial vocal fold injury in rats

Purpose:

To present a detailed, reproducible, cost-efficient surgical model for controlled subepithelial endoscopic vocal fold injury in the rat model.

Methods:

Six male Sprague Dawley rats were enrolled in the experiment. The left vocal folds were used to carry out the injury model, and the right vocal fold served as control. After deep sedation, the rats were placed on a custom operating platform. The vocal fold injury by subepithelial stripping was carried out using custom-made microsurgical instruments under endoscopic guidance. Data were analyzed for procedural time and post-procedural pain. Microcomputed tomography (micro-CT) scan and histologic images were obtained to assess the length, area, and depth of injury to the vocal fold.

Results:

The mean procedural time was 112 s. The mean control vocal fold length was 0.96 ± 0.04 mm. The mean vocal fold injury length was 0.53 ± 0.04 mm. The mean vocal fold surface was 0.18 ± 0.01 mm² with a mean lesion area of 0.05 ± 0.00 mm². Mean vocal fold injury depth was 375.4 ± 42.8 μm. The lesion length to vocal fold length ratio was 0.55 ± 0.03, as well as lesion area to vocal fold surface area was 0.29 ± 0.02.

Conclusions:

Our described experimental vocal fold injury model in rats is found to be fast, safe, cost-efficient, and reproducible with a rapid learning curve.

Use of 532 nm Potassium Titanyl Phosphate Laser on Vocal Fold Scars Under Topical Anesthesia: A Pilot Study

OBJECTIVE

This pilot study aims to evaluate the efficacy of 532 nm potassium titanyl phosphate (KTP) laser under topical anesthesia in patients with vocal fold scars.

METHODS

A series of 18 patients with vocal fold scars of varying degrees were treated. The KTP laser was used under local anesthesia in the outpatient clinic. It was set to deliver 6 W of power using a continuous output mode. Close-to-contact mode was used for laser irradiation, and contact mode was used for ablation and excision of the lesions. Some of the patients received laser scar ablation on both vocal folds; the scarred vocal fold on one side and the hypertrophic vocal fold on the other. Parameters include glottic closure, amplitude, and mucosal wave pattern were measured using laryngeal stroboscopic examination. Aerodynamic and voice evaluations were carried out using maximum phonation time (MPT), jitter, shimmer, Voice Handicap Index questionnaire (VHI-30), and GRBAS scale.

RESULTS

In total, 21 surgeries were performed on 18 patients. Glottic closure, amplitude, and mucosal wave pattern showed improvement 2 months postoperatively (P < .05). There was significant improvement in the postoperative scores for VHI-30, VHI-emotional sub-scale, VHI-physical sub-scale, and GRBAS (P < .05). There was no significant difference in the MPT and VHI-functional sub-scale before and after the operation (P > .05). Re-adhesion of the anterior commissure was observed in 2 patients with Type III scars.

CONCLUSION

The 532 nm KTP laser is an effective tool for the treatment of vocal fold scars. Further research is required to determine if serial laser applications could improve outcomes for this challenging condition.

LEVEL OF EVIDENCE

Level IV.

Pathophysiology of Fibrosis in the Vocal Fold: Current Research, Future Treatment Strategies, and Obstacles to Restoring Vocal Fold Pliability

Communication by voice depends on symmetrical vibrations within the vocal folds (VFs) and is indispensable for various occupations. VF scarring is one of the main reasons for permanent dysphonia and results from injury to the unique layered structure of the VFs. The increased collagen and decreased hyaluronic acid within VF scars lead to a loss of pliability of the VFs and significantly decreases their capacity to vibrate. As there is currently no definitive treatment for VF scarring, regenerative medicine and tissue engineering have become increasingly important research areas within otolaryngology. Several recent reviews have described the problem of VF scarring and various possible solutions, including tissue engineered cells and tissues, biomaterial implants, stem cells, growth factors, anti-inflammatory cytokines antifibrotic agents. Despite considerable research progress, these technical advances have not been established as routine clinical procedures. This review focuses on emerging techniques for restoring VF pliability using various approaches. We discuss our studies on interactions among adipose-derived stem/stromal cells, antifibrotic agents, and VF fibroblasts using an in vitro model. We also identify some obstacles to advances in research.

Office-Based 532-Nanometer Pulsed Potassium-Titanyl-Phosphate Laser Procedures in Laryngology

With fiber-based lasers that may be passed via the working channel of a flexible laryngoscope, in-office laser laryngeal surgery has become possible. The potassium-titanyl-phosphate laser has several features that make it ideal for laryngeal surgery, and it is now the laser of choice for in-office management of a variety of laryngeal lesions. Its applications have expanded significantly since its introduction, with reports of new indications continuing to appear in the literature. This article provides a comprehensive review of the indications and technical details of in-office potassium-titanyl-phosphate laser laryngeal surgery, and a summary of the existing literature regarding outcomes of these procedures.

Treatment Outcomes of Angiolytic Laser-Assisted Glottoplasty in Patients With Sulcus Vocalis

Objective:

We have been performing glottoplasty using angiolytic laser, including pulsed dye laser (PDL) or potassium titanyl phosphate (KTP) laser, for the treatment of sulcus vocalis. In this study, we retrospectively reviewed the treatment results of sulcus vocalis patients who had undergone glottoplasty using angiolytic laser and evaluated the efficacy and safety of this surgical technique.

Methods:

From January 2008 to April 2016, 79 patients with sulcus vocalis who underwent angiolytic LASER-assisted glottoplasty were enrolled in the study.

Results:

Of the 79 patients who participated in this study, 55 were male, and 24 were female. PDL was used for glottoplasty in 68 patients, and KTP was used in the remaining 11 patients. Seventy-seven patients underwent surgery for bilateral vocal cord lesions, and only 2 patients underwent surgery for unilateral vocal cord lesion. After glottoplasty using angiolytic laser, most patients showed continuous improvement of the GRBAS (grade, roughness, breathiness, asthenia, strain) score and Voice Handicap Index score until 6 months after the operation. In addition, we observed improvement of objective voice indices such as noise to harmonic ratio, jitter, shimmer, and maximal phonation time postoperatively.

Conclusions:

Based on these results, we confirmed the efficacy and safety of glottoplasty using angiolytic laser in sulcus vocalis patients. Further studies are needed to confirm appropriate laser settings such as frequency of treatments and total energy delivered to the lesion. Also, multi-institutional studies are needed to confirm the efficacy and safety of the operation.

Potassium titanyl phosphate laser-induced inflammatory response and extracellular matrix turnover in rabbit vocal fold scar

PURPOSE

The objectives of this study were to observe the regulating effect of KTP laser and Nd:YAG laser in the repair of vocal fold scars.

METHODS

All rabbits were injured in the muscular layer with a sharp instrument, and then the vocal folds were treated with a KTP laser and a Nd:YAG laser at a power of 2, 4, 6 and 8 W 1 month after the injury. One month after treatment, the rabbits were killed and the throats were removed to detect changes in histology and gene expression of the vocal fold scar after laser therapy.

RESULTS

The best efficacy of all KTP laser treatment groups was the KTP laser 6 W group. Regarding the detection of gene expression, in the KTP laser 6 W and Nd:YAG laser 6 W groups, col-3A1 was decreased compared to the scar group (P < 0.05), and col-1A1 was decreased only in the KTP laser 6 W group (P < 0.05). TGF-β1 levels in the two groups were lower than in the scar group. There were also significant differences in the levels of IL-1β, COX-2 and TNF-α in the two laser groups compared with the scar group (P < 0.05).

CONCLUSION

KTP laser and Nd:YAG laser treatments for vocal fold scars have particular therapeutic effects. The KTP laser may be better than the Nd:YAG laser for the regulation of vocal fold scars.

LEVEL OF EVIDENCE

NA.

Analysis of Potassium Titanyl Phosphate Laser Settings and Voice Outcomes in the Treatment of Reinke’s Edema

Objective:

Despite increased clinical utility of the 532-nm potassium titanyl phosphate (KTP) laser, no studies have examined outcomes for Reinke’s edema (RE) as a function of laser parameters and initial treatment effects. Variability in delivery parameters, fiber-to-tissue distance, and immediate end-tissue effects limits universal application of existing study outcomes. We examine voice outcomes using standardized treatment classification, providing justification for laser parameter selection and immediate tissue effect in clinical use.

Methods:

Retrospective review of 9 patients who underwent KTP laser treatment for RE. Demographics, RE severity, laser settings, total laser energy, and immediate tissue effects were correlated with quantified voice outcomes.

Results:

An average of 157 joules (6-640 J) was delivered over a 0.369-second exposure time (0.1-0.9 seconds). Immediate tissue effects varied from nonablative treatment (type I and type II) to ablation without tissue removal (type III). Overall, Voice Handicap Index-10 (VHI-10) decreased by 8.23; improvement was most pronounced with type II treatments (delta VHI-10 = 12). No complications were encountered.

Conclusion:

Potassium titanyl phosphate laser can be safely and effectively used to improve voice in RE patients regardless of severity. This is the first study to provide detailed information on laser settings, energy delivery, and treatment effect in RE management; these results may guide clinical use of this modality, especially for novice laser surgeons.