Indirect laryngeal surgery of vocal fold polyps: A dying or evolving art?| ACTA Otorhinolaryngologica Italica

Abstract

Objective. Vocal fold polyps (VFPs) are the most common benign laryngeal lesions that require surgery and are routinely managed by microlaryngoscopy (MLS) under general anaesthesia. Prior to introduction of MLS, VFPs were removed using indirect laryngoscopic surgery (ILS) in local anaesthesia, a procedure that required substantial surgical skill to operate with an unmagnified mirror view of the larynx. With the adoption of wireless endoscopy equipment and personal computers, we tried to simplify this technique so that it can be easily performed in the office. This study aimed to assess the effectiveness of ILS by comparing voice outcomes with MLS.
Materials and methods. ILS and MLS were performed in six patients each. Treatment outcomes were measured using a voice self-assessment and objective acoustic analysis. The total cost of both procedures was calculated.
Results. Both techniques allowed successful removal of VFPs in all patients, without significant intergroup differences in voice outcomes. The cost of ILS was significantly lower.
Conclusions. Despite the pilot nature of the study and the small sample size, our data indicate the potential value of this technique which, considering its simplicity and economic value could be used as an alternative to MLS in carefully selected patients.

Introduction

Benign vocal fold lesions are the most common organic cause of long-standing hoarseness, with approximately 50% of dysphonic patients showing some form of this pathology. In clinical practice, vocal fold polyps (VFP) are the most frequently encountered form of these lesions and usually require surgical treatment ¹. The concept of indirect laryngeal surgery (ILS) using the transoral route in an awake patient was established in Berlin in 1861 when Victor von Bruns performed VFP removal in his brother using mirror laryngoscopy with a specially designed curved instrument ². The exposure of the larynx in ILS was greatly improved by magnifying the laryngeal mirror view with the operating microscope ³. However, transoral manipulation with a long, curved laryngeal forceps under mirror vision and without directly visualising the tip of the instrument required a certain degree of manual dexterity. This was initially ameliorated by substituting the laryngeal mirror with a rigid telelaryngoscope connected to a video camera and transferring the laryngoscopic image on the TV monitor, and subsequently to a high definition (HD) camera and endoscopy tower ^4,5. Regardless of these improvements, ILS has never gained wider acceptance and has been considered something of a lost art, and recent literature on this technique is lacking. Suspension microlaryngoscopy (MLS) under general anaesthesia has gradually established itself as a standard approach for the removal of VFPs since its introduction in the 1960s ⁶.

The recent emergence of wireless endoscopy cameras and light sources has enabled easy transmission and recording of indirect laryngoscopic findings on computer monitors. Therefore, the aim of this article is to present our modification of the indirect laryngoscopic technique for the excision of VFPs that uses wireless components and a personal computer to monitor the procedure. Although ILS with a rigid telelaryngoscope has already been described, to our knowledge this is the first study to address the outcomes of performing the technique using wireless technology and to compare the results to those obtained using MLS as a practice standard.

Materials and methods

All patients who underwent surgery for VFPs using our modified ILS technique at a tertiary referral centre from June to October 2020 were included in this prospective study. To assess the effectiveness of the modified ILS, we compared voice outcomes in patients who underwent the modified ILS with those in patients who underwent suspension MLS under general anaesthesia, the standard practice at the institution, during the same period. Randomisation was based on the patients’ tolerance of the mirror laryngoscopy/laryngovideostroboscopic examination on the initial visit. Patients with good compliance were offered to undergo either ILS or MLS based on their preference. The patients with severe gagging were automatically transferred to the MLS group. Patients with more extensive or submucosal vocal fold pathology, which required delicate bimanual dissection under an operating microscope, or with lesions clinically suspicious for malignancy, were not included in the study.

Surgery

The ILS was performed using Brunnings curved cup forceps for indirect laryngeal operations (Karl Storz 777910, 775100, and 775600; Tuttlingen, Germany) under the visual guidance provided by a rigid 70° telelaryngoscope (Fig. 1A). For additional magnification and documentation purposes, a wireless camera (Firefly DE1250; Firefly Global, Belmont, MA) was attached to the telelaryngoscope eyepiece, projecting the telescopic image onto a personal laptop screen (MacBook Pro; Apple Inc., Cupertino, CA). A handheld light source with a rechargeable light-emitting diode (LED) battery was used instead of a conventional cabled white light source (Fig. 1B). In all indirect procedures, 10% lidocaine was applied topically by spraying the oropharynx, epiglottis with laryngeal inlet, and vocal folds (1 puff equaled 10 mg of lidocaine, with a maximum safe dose of approximately 300 mg for an average 70 kg adult). After application of the local anaesthetic, the telelaryngoscope and curved cup forceps held in the non-dominant and dominant hand, respectively, were simultaneously introduced into the patient’s oropharynx. The closed tip of the forceps was visually identified on the computer screen and advanced over the tongue base, epiglottis, and through the laryngeal inlet toward the vocal fold lesion. The lesion was gently grasped and removed in a single anterior-to-posterior motion parallel to the free edge of the vocal fold with respect to its histological structure (Figs. 2, 3). On the other hand, MLS was performed by applying medial traction to the polyp and excising it with microscissors. Dedicated instruments and directoscopes by Kleinsasser (Karl Storz, Tuttlingen, Germany) were used in all microlaryngoscopic procedures.

Outcome comparison and voice analysis

To compare the effectiveness of the surgical techniques, objective acoustic analysis and voice self-assessments were performed before and four weeks after surgery in both the ILS and MLS groups. Voice samples for the objective acoustic analysis were collected using a TASCAM DR 680 digital recorder (Teac Corporation, Santa Fe Springs, CA) and a Rode NT1-A unidirectional condenser microphone (Rode microphones, Sydney, Australia) placed in front of the patient’s face. The patients were instructed to phonate the sustained vowel /a/ at a comfortable pitch and loudness for at least 3 s in a soundproof room. All recorded samples were analysed for harmonicity (harmonics-to-noise ratio [HNR]) and perturbation (jitter and shimmer) using PRAAT software (ver. 6.1.08; Institute for Phonetics, University of Amsterdam, Amsterdam, Netherlands). The Voice Handicap Index 30 (VHI-30) was used for voice self-assessment. The mean treatment cost was calculated for each surgical group.

Statistical analysis

Data normality was tested using the Shapiro–Wilk test. Student’s t-test for independent samples was used to explore the differences in the values of the clinical parameters between the two patient groups. A p value less than ≤ 0.05 was considered statistically significant. The results in the figures are presented as the mean and standard deviation. Statistical analysis and figure plotting were performed in JupyterLab (v3.2.1, ) using Python (v3.8.12, Python) with the SciPy (v1.9.3, ) and Seaborn packages (v0.12.1, ).

Results

A total of 12 patients (nine males and three females) were included in the present study, of whom six underwent the modified ILS (experimental group) and six underwent classical MLS (control group). Both ILS and MLS allowed successful removal of VFPs without complications in all patients. The mean age of patients in the ILS group was 54.5 ± 11.8 years, while that in the MLS group was 49.8 ± 10.2 years. The size of the lesion removed varied from 2 to 10 mm, but the two groups showed no significant difference in lesion size, although the average size of the lesion was higher in the MLS group (ILS vs MLS: 4.17 ± 2.04 vs 5.83 ± 2.71; t = 1.202, p > 0.05).

Analysis and comparison of different clinical voice parameters, including the VHI-30 score, jitter, shimmer, and harmonics-to-noise ratio (HNR), before and after surgery showed voice improvement without significant intergroup differences (Fig. 4). The two groups showed no significant differences in the mean values of pre-operative VHI-30 score (t = 0.209, p > 0.05), post-operative VHI-30 score (t = 0.728, p > 0.05), pre-operative jitter (t = 1.224, p > 0.05), post-operative jitter (t = 0.34, p > 0.05), pre-operative shimmer (t = 1.710, p > 0.05), post-operative shimmer (t = 1.248, p > 0.05), pre-operative HNR (t = 0.297, p > 0.05), and post-operative HNR (t = 1.569, p > 0.05). As expected, the average cost of the surgical intervention was significantly higher in patients who underwent MLS (450.44 ± 45.52 EUR) than in those who underwent the modified ILS (44.84 ± 12.69 EUR; t = 21.02, p < 0.001).

Discussion

Despite technological advancements, suspension MLS under general anaesthesia remains the standard practice in the management of VFPs. This method offers the distinct advantage of allowing operations with both hands on a stable operative field under microscopic magnification without a specific time limit. However, the surgical field is partially obstructed by the endotracheal tube, and occasionally, the glottic plane may be difficult to expose, especially in the anterior third of the vocal folds. The suboptimal visualisation of this particular area, where the majority of VFPs occur, can result in misdiagnosis, incomplete excision, abortion of the procedure, and patient dissatisfaction ⁷. ILS allows the surgeon to observe the awake patient’s larynx in a physiologic position undistorted by the endotracheal tube. The rigid 70° telelaryngoscope in our technique provided an excellent view of the anterior commissure on the computer screen and therefore could be used to treat patients in regions with previously inadequate direct laryngoscopic exposure. The whole system consisting of the telelaryngoscope connected to the wireless camera and LED battery weighs 480 g and can be comfortably held with a nondominant hand throughout the entire ILS procedure. As a result of miniaturisation and technical revolution, our system was less than half the size of video camera from the videolaryngoscopic setup originally described in the late 1980s, which weighed 1.1 kg ^10,11. ILS typically lasts about 10 minutes, including anaesthesia application and control laryngoscopy after removal of the lesion, which is considerably shorter than other endoscopic procedures, such as endoscopic sinus surgery. The fully charged wireless camera in our setup can record up to 3.5 hours and is therefore sufficient for an average ILS. Moreover, the wireless instruments enabled better ergonomics for the surgeon, especially easier handling of the endoscope than in wired indirect laryngoscopic procedures.

While MLS requires a set of instruments with an operating microscope, hospitalisation, and an additional team of healthcare professionals (anaesthesiologist, nurse anesthetist, and scrub nurse), the ILS technique described above can be readily performed by a single surgeon with only one surgical instrument in the office and is substantially less expensive. The development of flexible nasopharyngolaryngoscopes with working channels have allowed the treatment of various laryngeal conditions in the office, including the removal of selected benign vocal fold lesions ⁸. Although patients will better tolerate the flexible endoscope passed through the nasal cavity than the two instruments in the oropharynx (as in ILS), this technique ultimately requires two physicians to perform the procedure.

More than half of patients undergoing MLS are estimated to experience some minor post-operative complaints, including sore throat, tongue numbness, or taste abnormalities ⁹. These patients also show the potential for iatrogenic trauma of the adjacent anatomic structures during laryngoscope placement, specifically to the teeth, lips, or pharyngeal mucosa. Although mucosal injury may occur with opened laryngeal forceps, this form of inadvertent trauma in ILS is avoided by introducing the tip of the forceps tightly closed and opening it just in the immediate proximity of the lesion to be removed. This procedure also eliminates possible adverse cardiorespiratory events related to general anaesthesia and is therefore convenient for high-risk patients with significant comorbidities.

The ILS procedure described above has several limitations. This technique requires a cooperative patient to remain still during the procedure. Therefore, children or patients suffering from dyskinesia or severe tremor and those with intractable gagging despite local anaesthesia are not suitable candidates for ILS. The operative field for ILS can be less stable than that for MLS owing to occasional swallowing or discrete movements of the vocal folds during respiration in an awake patient. Another factor is the 20-min time limit for lidocaine anesthetisation, which represents the time for which the patient can tolerate the procedure before experiencing discomfort and gagging. Therefore, the surgeon should perform the procedure in a rapid and decisive manner, preferably on the first attempt. Submucosal or large lesions that cannot be grasped with Brunnings forceps are better dissected bimanually in MLS under general anesthesia.

The camera delivers a 720 x 480 video resolution, which provides adequate detail for observing the ILS on a 13-inch computer display placed 70 cm from the surgeon’s face. The image quality is similar to that of the standard definition analogue video camera and television monitor well described in ILS, but unfortunately not on par with more expensive HD wired setups ^4,12. Although the wireless HD camera would be preferable for ILS, these new systems have so far been used only in small patient series in laparoscopic surgery and require larger scale clinical validation ¹³.

Finally, the number of cases in this study was small, and all indirect operations were performed by the first author at a single centre.

Conclusions

Despite the modest number of patients, our data showed similar voice outcomes for the modified ILS and suspension MLS, indicating the clinical value of the technique. Due to its technical simplicity, cost effectiveness and patient comfort, we believe that ILS should remain a viable surgical option for carefully selected patients with VFP and that technological evolution could rejuvenate this often forgotten technique, rather than allowing it to fall into oblivion. The outcomes of ILS at different centres and performed by multiple surgeons would add further value to our findings.

Conflict of interest statement

The authors declare no conflicts of interest.

Author contributions

OC wrote the manuscript, contributed to the study design, and collected the data; DR interpreted data for the study and revised the manuscript; NA and MJ contributed to the study design, interpreted the data for the study, and critically revised the manuscript; ZM co-wrote the manuscript, contributed to the study design, and critically revised the manuscript. All authors approved the final version of the manuscript to be published, and agree to be accountable for all aspects of the work related to its accuracy and integrity.

Ethical consideration

The study was approved by the Institutional Ethics Board of the Clinical Hospital Center Zemun on March 19, 2020 (reference number: 109/1).

The research was conducted ethically, with all study procedures being performed in accordance with the requirements of the World Medical Association’s Declaration of Helsinki.

Written informed consent was obtained from each patient for study participation and data publication.

Figures and tables

Figure 1.Principal instrumentation for the indirect laryngoscopic procedure (A) consisting of a pair of Brunnings curved cup forceps and a rigid 70° telelaryngoscope. (B) A wireless endoscopy camera and handheld light-emitting diode battery light source attached to the telelaryngoscope.

Figure 2.Schematic depiction of the procedure. The vocal fold polyp (*) is grasped and avulsed in anterior-to-posterior direction parallel to the free edge of the vocal fold. This approach is used to create a linear and smallest possible mucosal defect. Note the spindle-shaped epithelial cells that are also oriented parallel to the free edge of the vocal fold (**).

Figure 3.Polyp of the right vocal fold and the tip of the curved forceps in the endolarynx (A). Immediate appearance of the vocal folds after polyp removal, during respiration (B) and phonation (C). Results obtained one month post-operatively (D).

Figure 4.Comparison of different pre-operative and post-operative clinical parameters between the two patients groups. Pre-operative and post-operative values for the VHI-30 score, HNR, jitter, and shimmer were compared between groups of patients who underwent ILS and MLS interventions. The two groups showed no significant differences for any of the parameters assessed between the groups. Results are presented as mean ± standard deviation. VHI-30, voice handicap index 30; HNR, harmonics-to-noise ratio; ILS, indirect laryngoscopic surgery; MLS, microlaryngoscopy.

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