CO₂ laser in benign vocal fold lesions: an observational study

Abstract

Background

To evaluate the clinical and functional outcome of patients having benign vocal fold lesions who were treated with carbon dioxide laser.

Methods

For this Study a total of 41 Patients who had hoarseness of voice and satisfied the inclusion criteria were included. A detailed medical history and a thorough ENT examination was performed. Voice evaluation was done using (G)rade, (R)oughness, (B)reathiness, (A)sthenia….weakness (S)train (GRBAS), voice handicap index (VHI), and maximum phonation time scores.

Results

All 41 patients reported hoarseness of voice as their primary complaint, and most of them developed their symptoms gradually. The following causes seem to have contributed to the presence of hoarseness of voice: LPR in 8 patients, smoking in 25 patients, voice abuse in 14 patients, and irritation exposure in 6 patients. The most frequent lesion in 25 (60.97 percent) of the subjects was a vocal polyp. This study showed majority of patients 35 (85.4%) had posterior phonatory gap and six (14.6%) had anterior gap preoperatively. All patients had incomplete glottic closure preoperatively, whereas glottic closure was complete at first follow-up postoperatively. The mean preoperative GRBAS score in study subjects was 10.972 with an SD (standard deviation) of 2.1724 and a median of 10.000. The mean postoperative GRBAS score at six months was 0.268 with an SD of 0.4486, median 0.000, Z score − 5.618, and p value < 0.001 which is statistically significant.

Conclusion

Precision, hemostasis, and minimal postoperative edema are benefits of using carbon dioxide laser. This research therefore supports the idea that benign vocal fold lesions might be successfully treated with the super-pulsed microspot carbon dioxide laser, which offers good voice outcomes.

Background

The true vocal folds have a multilayered anatomy, which is the basis of Hirano’s cover-body hypothesis of phonation, first forwarded in 1974 (Hirano 1974). Squamous epithelium, three layers of lamina propria, and the vocalis muscle [thyroarytenoid] make up the vocal folds’ five histological layers. During vibration, these five layers function as three mechanical layers that are progressively stiffer. Stratified squamous epithelium covers the front vibratory part of the larynx, while pseudo-stratified ciliated epithelium covers the posterior glottis. The mid-membranous vocal fold, also known as the “striking zone,” has the greatest amount of contact with the true vocal folds during phonation, and it is at this location that the majority of phono-traumatic lesions are discovered (Hochman et al. 1999).

Vocal polyps, vocal nodules, vocal cysts, pseudocysts, vocal fold sulcus, contact granuloma, mucosal bridge, and/or Reinke’s edema are all referred to as benign ‘vocal fold lesions in general. The most of the lesions on the vocal folds are benign. Although many different circumstances might contribute to the formation of these lesions, the majority of them are linked to vibratory damage to the vocal cords. The most frequent risk factors include talkative extroverts and jobs that need a lot of voice. Additionally, smoking, acid reflux, untreated allergies, and infections may exacerbate vibratory harm (Smit et al. 2013). The most prevalent sign of a benign vocal fold lesion is a change in voice quality, which may range in severity from mild to severe.

The voice may be compromised when speaking, singing, or both. Hoarseness is often accompanied by greater effort while speaking, which leads to fatigue or voice fatigue over time. A history of how the voice issue first showed itself and an assessment of speaking and speech patterns are crucial elements in the diagnosis of benign vocal fold lesions. A thorough examination of the vocal folds is necessary to diagnose a benign vocal fold lesion. A stiff or flexible laryngoscope and a stroboscopic light source are commonly used for examination. Videostroboscopy is the most common method of visualizing vocal fold vibration and is an essential tool for voice assessment. Videostroboscopy can also be used to monitor disease processes as well as asses pre- and postoperative outcomes. It uses a synchronized, flashing light passed through a flexible or rigid telescope. The flashes of light from the stroboscope are synchronized to the vocal fold vibration at a slightly slower speed, allowing the examiner to observe vocal fold vibration during sound production which appears to be slow motion. Stroboscopic examination includes glottic closure pattern, mucosal wave, description of lesion, vocal fold opening pattern, supraglottic appearance, and symmetry of arytenoids (Kendall 2009).

Regardless of the kind, benign vocal fold lesions prevent the vocal folds from closing and vibrating, which results in hoarseness. It is crucial to identify the kind of vocal fold lesion(s) since some might be treated successfully with voice therapy alone, while others would need to be surgically removed.

The goal of all therapies is to help patients regain their voice’s functionality. Singing voice therapy, speaking voice therapy, phono-microsurgery (surgery on the vocal folds), medicine, and voice rest are often used as treatments. When conducted with precision phono-microsurgical methods followed by specialized postoperative voice treatment, surgery for benign vocal fold lesion(s) may be very beneficial. A multitude of disorders that affect the vocal cords, such as benign nodules, vocal cord dysplasia, laryngeal papilloma, polyps, and various laryngeal malignancies, may be removed and treated with laser vocal cord surgery, an endoscopic technique.

A device that generates light using an optical amplification procedure on the basis of the stimulated emission of electromagnetic radiation is known as a laser (“Light Amplification by Stimulated Emission Of Radiation”). Since the 1960’s CO₂ lasers have developed into a significant technical advancement and a crucial tool for laryngeal surgeons. With promising results, surgeons have employed lasers to treat both benign and malignant larynx lesions. The potential heat dispersion to the deeper layers of the lamina propria has decreased with the introduction of microspot CO₂ lasers with a spot size of less than 250 μm. It has been proposed that the microspot CO₂ laser is a suitable technique for the excision of superficial benign lesions of the vocal fold and may be used as a suitable alternative to microdissection (Metson 1996). The light produced by CO₂ lasers has a wavelength of 10.6 μm, which is in the center of the infrared spectrum. Water is quite effective at absorbing this energy. Water absorbs the majority of the energy; therefore, there is little penetration into the tissues. Human tissue contains between 70 and 90 percent water, hence CO₂ lasers mainly vaporize tissue to induce death (Benninger 2000). The CO2 laser’s capacity to absorb water also makes it a useful tool for treating laryngeal diseases since the laryngeal tissue is mostly composed of water with just small amounts of melanin or hemoglobin.

Subjective and objective assessments of voice are critical to the analysis of outcome of surgical intervention as well as comparison between pre- and postoperative voice in patients with dysphonia. The GRBAS scale was perhaps the first widely utilized measure, and is still in use today. This includes five components: G(rade)—overall grade of hoarseness, R(oughness), B(reathiness), A(esthenia)—weakness, and S(train). Each component is rated on an integer four point scale, in which 0 is normal, 1 slight, 2 moderate, and 3 severe. This scale has been well-received because it is brief and user-friendly, making it practical for application in a clinical setting (Nemr et al. 2012). Self–assessment measures like voice handicap index (VHI) provide us with the information on the impact of dysphonia on the quality of life (Rosen et al. 2004). A simple test of glottic efficiency is maximum phonation time (MPT). MPT is the maximum time (in seconds) for which a person can sustain a vowel sound when produced on one deep breath at a relatively comfortable pitch and loudness. For maximum phonation time (MPT), the maximum length of time a patient can vocalize after taking a deep breath is measured. In general, 10 s or less is abnormal, and 5 s or less interferes with daily living (Sawaya et al. 2022).

The study was done with the aim to evaluate the clinical and functional outcomes of patients having benign vocal fold lesions who were treated with carbon dioxide laser.

Methods

This prospective observational study was conducted in the postgraduate “Department of Otorhinolaryngology, Head and Neck Surgery, Government Medical College, Srinagar” from November 2018 to April 2020 in OPD attending patients aged 16 years and above. In this study, a total of 41 individuals who had hoarseness of voice and fullfilled the inclusion criteria were included. All patients provided their written, fully informed consent. A detailed history was obtained, and a full ENT examination was performed, including anterior rhinoscopy, oral cavity examination, and an indirect laryngoscopy. Telelaryngoscopy using 70-degree rigid endoscopy and Stroboscopic examination was done preoperatively and at 1 week, 1 month and 6 months postoperatively to study the glottic closure and mucosal wave. Voice evaluation was done using GRBAS, VHI, and MPT scores.

All 41 patients underwent trans-oral laser excision (TOLE) under general anesthesia with the smallest possible endotracheal tube. The surgeon put himself in most comfortable position using a chair with articulated arm support which provided the surgeon with arms and feet supported and shoulders in an unraised neutral position. Patient was put in sniffing position to enable the use of largest luminal laryngoscope. Proper anesthetic laser-resistant tubes were used during anesthesia and wet cottonoids were kept in subglottis, over the face and eyes to prevent thermal damage, and the whole staff was made to use proper protection. Laser settings used were as 4 to 8 W, intermittent mode (0.1 s “on” and 0.5 s “off”), and patients were examined at regular intervals up to six months (one week / one month / six months after surgery).

Statistical analysis

In a Microsoft Excel spreadsheet, data were entered. Frequency and percentage were utilized to sum up categorical variables. The mean and SD were utilized to sum up continuous variables. GRABS, MPT, and VHI-10 were summarized as median and range. Paired samples “t” test was utilized to test the pre- and post-CO₂ laser differences in continuous measurements. Pre- and post-CO₂ laser GRABS and VHI-10 scores were compared using the Wilcoxon signed ranks test. Statistics were reported using two-sided p values, and a p value of 0.05 or below was deemed to be statistically significant.

Results

Forty-one patients who were found to have benign vocal cord lesions were included in the study. There were 14 (34.1%) female and 27 (65.9%) male patients respectively. Most of the patients in this study were aged between 31 and 50 years with mean age being 41.78 years. Eight (19.51%) of the study subjects were housewives and seven (17.07%) were government employees by profession. All (41) of the patients presented with complaint of hoarseness of voice, and the majority of them had a slow development of symptoms. The following factors seem to have contributed to the presence of hoarseness of voice: LPR in eight patients, smoking in 25 patients, voice abuse in 14 patients, and exposure to irritants in 6 patients. The most frequent lesion seen in 25 (60.97%) of the research participants was a vocal polyp. This study showed majority of patients 35 (85.4%) had posterior phonatory gap and six (14.6%) had anterior gap preoperatively. All patients had incomplete glottic closure preoperatively, whereas glottic closure was complete at first follow-up postoperatively (Table 1).

Table 1 Distribution of participants as per age, profession, and lesion

The mean preoperative GRBAS score in study subjects was 10.972 with a SD of 2.1724 and a median of 10.000. The mean postoperative GRBAS score at six months was 0.268 with an SD of 0.4486, median 0.000, Z score − 5.618, and p value < 0.001 which is statistically significant. Aerodynamics maximum phonation time (MPT) preoperatively had a mean value of 12.854, with a SD of 2.8685 and a median of 13.00. Aerodynamics MPT at third postoperative follow-up had a mean value of 21.683, SD of 3.1340, median value of 22.000, Z score − 5.589, and p value < 0.01. The mean preoperative voice handicap index 10 was 23.073, standard deviation 5.8025, and median 22.000. Voice Handicap Index 10 at third postoperative follow-up had a mean value of 0.585, stand and deviation 0.5906, median 1.000, Z score − 5.582, and P value < 0.001. (Table 2).

Table 2 Comparison of GARBAS score preop and postoperative first, second, third by using Wilcoxson signed scale | Improvement in maximum phonation time after surgery | Voice handicap index preoperative and postoperative first, second, and third

Stroboscopy was done for all of the study subjects. Two parameters, glottis closure and mucosal wave, were examined and recorded. Glottic closure was incomplete in all of these patients preoperatively which was complete postoperatively for all 41 (100%) patients. (Table 3).

Table 3 Glottic closure comparison preoperative and postoperative

Mucosal wave amplitude was reduced in 39 out of 41 patients preoperatively. At first follow-up 35 out of 39 patients had normal mucosal wave amplitude, and at second follow-up (1 month), all the 39 patients had normal mucosal wave amplitude (Table 4).

Table 4 Mucosal wave amplitude preop and postoperative first, second, and third

Discussion

The main concern for both the patient and the surgeon after micro-laryngeal surgery is the outcome of the voice. The usage of carbon dioxide laser in such surgeries has grown since it was first utilized in laryngeal procedures. We conducted this research to assess the voice quality and the vocal fold function after benign vocal fold lesions were removed using a carbon dioxide laser.

There were 41 patients in the study 27 men and 14 women with a male-to-female ratio of 1.92. With a minimum age of 20 and a highest age of 66, the study patients’ average age at presentation was 41.78 years. The majority of patients, i.e., 13 (31.7%) in our study were in the fourth decade of their life followed by 11 (26.8%) patients in the fifth decade of their life, three (7.3%) patients were between 16 and 20 years, five (12.2%) patients between 21 and 30 years, one (2.5%) patient between 51 and 60 years, and eight (19%) patients above 60 years of age. Studies conducted by Pal et al. (2014) and Baitha et al. (2002) have shown similar pattern of age distribution of the subjects.

In this study, eight (19.51%) were housewives followed by seven (17.07%) government employees five (12.19%) laborers, four (9.75%) teachers, four (9.75%) preachers/imams, four (9.75%) drivers, three (7.31%) students, and three (7.31%) shopkeepers. In the studies by Gosh et al. (2001) and Banjara et al. (2014), majority of patients were housewives.

Vocal fold polyp was the most common lesion present in 25 (60.97%) patients followed by vocal fold nodules in 14 (34.1%), and cysts in two (4.87%) patients (Figs. 1, 2 and 3). Uphaday et.al (2019) show the vocal cord polyps in 10%, vocal cord nodules in 13%, and vocal cord cysts in 14% patients.

Fig. 1

Preoperative and postoperative images of left vocal cord nodule

Fig. 2

Preoperative and postoperative images of right vocal cord cyst

Fig. 3

Preoperative and postoperative image of left vocal cord polyp

Pre- and postoperative voice assessment was done in the form of auditory perceptual rating GRBAS (Grade, Roughness, Asthenia, Breathiness, Strain), Aerodynamic measure [MPT (Maximum Phonatory Time) in seconds], and patient self-reporting instrument voice handicap index 10 (VHI-10). There are several scoring methods for perceptual analysis of voice. GRBAS offers a simplified grading system for estimating the extent of voice modification. The mean preoperative GRBAS score of the patients in the current research was 10.972, with an SD of 2.1724 and a median of 10.000. All postoperative periods had continuous increases in GRBAS scores, and the mean GRBAS score at 6 months showed a major improvement with a 0.001 p value. Divakaran et al. (2015) in their study of Voice Outcome Following CO₂ laser-assisted microlaryngeal surgery found improvement in GRBAS scores with preoperative median GRBAS score 9 and post op median GRBAS score was 2 after 3 months.

Maximum phonation time was statistically significantly improved in our patients after surgery. The mean preoperative MPT (Maximum phonation time) was 12.854, with a standard deviation of 2. 8685 and a median of 13.000. In the third postoperative follow-up mean MPT was 21.683, standard deviation of 3.1340, median of 22.00, Z score − 5.519, and p value < 0.01, which was statistically significant.

Analyzing the outcomes of patients with dysphonia requires both subjective and objective evaluations of voice. We can learn about the effects of dysphonia on quality of life using self-assessment tools like VHI. In our research, we employed the voice handicap index 10 to examine patients both subjectively and objectively. In the present study, the mean preoperative VHI-10 was 23.073 with a standard deviation of 5.8025 and a median of 22.00. Voice handicap index 10 on third postoperative follow-up had a mean value of 0.585, SD of 0.5906, median 1.00, Z score − 5.582, and p value of 0.01. Significant improvement in voice handicap index and MPT has been found in patients treated with carbon dioxide laser in studies done by MARC Remacle et al. (1999) and Kumar et al. (2019).

Stroboscopy was used to examine the pre- and postoperative vocal cord morphology in all patients. Mucosal wave and glottic closure pattern were chosen as parameters since they are two significant aspects that affect voice quality. In our study of 41 patients preoperative glottic closure was incomplete in all patients (100%) with an anterior gap in six (14.6%) patients and posterior gap in 35 (85.4%) patients. We also found reduced mucosal wave amplitude in 39 (95%) patients, while mucosal wave amplitude was normal in two (4.9%) patients. Postoperatively, there was complete glottic closure in all patients at first follow-up. At their first postoperative checkup, 35 patients had normal mucosal waves, and at their second postoperative checkup, every patient had normal mucosal waves. Complete glottic closure may be described by enhanced vocal fold contact after lesion removal. As a consequence of the enhanced contact between the vocal folds and the improved creation of sub-glottic pressure, the mucosal wave also tends to become regular and normal following surgery. Divakaran et al. (2015) confirmed that after surgery, most of the patients achieve complete glottic closure and normal mucosal wave (98% each). In another study by Mobarsa et al. (2019), normal mucosal wave amplitude was present in 56.67%, and complete glottic closure was present in 80% patients at the end of tenth postop week.

The recuperation period is shortened, and the patient has less discomfort after laser procedures. There is minimal chance of significant bleeding, infection, or other consequences. With laser surgery, there is also a very low chance of scarring, which is crucial when the larynx is involved since scar tissue is thicker than normal tissue and does not vibrate as readily. In the present study, none of our patients had any complications.

Conclusions

Earlier concerns about the safety of CO₂ lasers have been allayed with the implementation of stringent laser safety measures, and scanner micromanipulators and super- and ultra-pulsed CO₂ laser advancements have made it possible to make accurate and controlled incisions of any desired form, size, or depth. Two techniques may be used to gauge voice quality and make comparisons: acoustic analysis and perceptual voice analysis. Stroboscopy, perceptual, and acoustic analyses were used to determine that the voice result in our research was outstanding.

Precision, hemostasis, and little postoperative edema are benefits of using a CO₂ laser. This research therefore supports the idea that benign vocal fold lesions may be successfully treated with the super-pulsed microspot carbon dioxide laser, which offers good voice outcomes.

Voice analysis indicated a tendency in the direction of normality, though the results did not reach statistical significance. The overall and subscale scores for the voice handicap index decreased.

Acoustic analysis, videostroboscopy, and the voice handicap index are helpful methods for evaluating the efficiency of therapy in individuals with benign vocal cord lesions from both an objective and subjective perspective. It is advised to use them often in a voice clinic.