Real-Time Light-Guided Vocal Fold Injection: An In Vivo Feasibility Study in a Canine Model

Superior Laryngeal Nerve Block in Transcutaneous Vocal Fold Injection: A Pilot Study

OBJECTIVES

Topical lidocaine remains the mainstay for anesthesia in transcutaneous vocal fold injection (VFI). While using topical lidocaine, laryngologists sometimes encounter uncontrolled reflexes or poor compliance. Superior laryngeal nerve block (SLNB) provides deep and rapid anesthesia on the larynx above the vocal folds and abolishes the glottic closure reflex. Herein, we present a pilot study to evaluate the feasibility and safety of SLNB for transcutaneous VFI and explored its usefulness.

METHODS

Fifty-nine patients were prospectively anesthetized with SLNB during transcutaneous VFI for unilateral vocal fold paralysis. In the SLNB group, 0.5 to 1 mL of 2% lidocaine was infiltrated on bilateral SLNs through the thyrohyoid membrane. As the control group, we included previous 47 patients who underwent VFI with topical lidocaine. In the control group, 10% lidocaine spray was applied to the laryngopharyngeal mucosa. Demographic data, laryngeal exposure, patient compliance, procedural interruption, and complications were investigated. Patient compliance was evaluated based on the frequency of cough and swallowing during VFI procedures.

RESULTS

SLNB enabled endoscopic contact on the epiglottis and pharyngeal wall without gag reflex and provided good exposure of the procedure field on the vocal folds. In the SLNB group, the laryngeal exposure is significantly better than in the control (P = 0.005). The frequency of cough and swallowing was significantly lower in the SLNB group than in the control (P < 0.001). The number of procedural interruptions was lower in the SLNB group than in the control (P < 0.001). There was no acute or delayed complication related to SLNB such as bleeding, hematoma, delayed sensory/swallowing problems, or unscheduled hospital visits.

CONCLUSIONS

SLNB might be safe and effective for anesthesia in transcutaneous VFI. SLNB could be a good anesthetic option for patients with poor compliance despite the sufficient application of topical lidocaine.

LEVEL OF EVIDENCE: 4

Real-time Light-guided Vocal Fold Injection via Cricothyroid Membrane in Unilateral Vocal Fold Paralysis: A Human Pilot Study

Objectives.

Vocal fold injection (VFI) via the cricothyroid (CT) membrane is used to treat various diseases affecting the vocal folds. The technical challenges of this technique are mainly related to the invisibility of the needle. Real-time light-guided VFI (RL-VFI) was recently developed for injection under simultaneous light guidance in the CT approach. Herein, we present the first clinical trial of RL-VFI, in which we investigated the feasibility and safety of this new technique in unilateral vocal fold paralysis (VFP).

Methods.

This prospective pilot study enrolled 40 patients, who were treated with RL-VFI for unilateral VFP between September 2020 and August 2021. Adverse events were monitored during the procedure and for 4 weeks postoperatively. The Voice Handicap Index-10, the GRBAS (grade, roughness, breathiness, asthenia, and strain) scale, aerodynamic studies, and acoustic analyses were evaluated to compare the voice improvement after 4 weeks with the baseline values.

Results.

The needle tip was intuitively identified by the red light. The mean procedure time was 95.6±40.6 seconds for the initial injection, while the additional injection required 79.2±70.5 seconds. The injection was performed under light guidance without additional manipulation after the needle reached the intended point. No acute or delayed adverse events were reported. Among the 40 patients, 36 completed voice analyses after 4 weeks. Subjective and objective voice parameters, including the Voice Handicap Index-10, GRBAS scale, maximum phonation time, mean expiratory airflow, fundamental frequency, jitter, shimmer, and noise-to-harmonics ratio improved significantly after RL-VFI (P<0.05), while the expiratory volume was maintained.

Conclusion.

RL-VFI is feasible and safe for treating patients with unilateral VFP. This technique is anticipated to improve the precision and safety of the CT approach in the treatment of unilateral VFP. This study provides a rationale for further structured clinical studies.