A Study on Comparison of Conventional Micro Laryngeal Micro Dissection Surgery with Carbon Dioxide Laser in Management of Benign Lesions of Larynx

Abstract

Dysphonia is a common symptom in benign and pre malignant lesions of larynx affecting vocal cords. Surgical excision is the main stay of treatment. Only a limited number of studies have compared the efficacy of microdissection versus CO₂ laser surgery in the larynx. In the present study we have compared conventional micro-laryngeal surgery and carbon dioxide laser assisted microsurgical technique in the management of these lesions. A randomized prospective study was conducted in 88 cases of benign and pre malignant lesions affecting vocal cords were divided randomly to undergo surgery either by conventional micro dissection or CO₂ laser assisted techniques in a tertiary care hospital. The groups were assessed through vocal cord morphological observation by videostroboscopy and subjective voice assessment parameters GRBAS score and VHI10 index preoperatively and 2 weeks and 3 months postoperatively by a panel of blinded viewers and listeners. Surgical and recovery times were compared between the two groups. Intraoperative blood loss was compared by gauze visual analogue. Patients recovered remarkably well following both the techniques as denoted by the voice parameters. Peroperative bleeding was observed to be significantly reduced in the laser excision group; operating time was significantly increased in this group. Duration of hospital stay was similar in both groups. No differences in clinical outcomes are identified when comparing microdissection with laser excision of benign lesions.

Electronic supplementary material

The online version of this article (10.1007/s12070-020-01923-9) contains supplementary material, which is available to authorized users.

Introduction

The incidence of vocal cord disorders has been increasing owing to vocal abuse. Minimally invasive dissection procedures are employed to treat these vocal cord disorders for an effective outcome. Two types of microsurgical techniques were developed gradually and practiced namely, the conventional laryngeal microsurgery, which involves the use of cold instruments and the laryngeal laser micro-surgery. Only a limited number of studies have compared the efficacy of microdissection versus microspot CO₂ laser surgery in the larynx [1, 2]. Recent advancements have been made in both techniques to improve surgical outcomes in treatment of vocal cord lesions. With the advent of micro dissection and micro flap techniques, micro surgery of vocal cord has become more precise. In the present study, both micro surgical techniques by cold steel and laser have been compared in the management of benign and precancerous lesions of vocal cord. The groups were assessed through vocal cord morphological observation by videostroboscopy and by comparative analysis of subjective voice assessment parameters using GRBAS and VHI index scores.

Materials and Methods

A randomized prospective study was conducted at the Department of ENT and Head and Neck Surgery, at a tertiary care centre between May 2014 and May 2019. One hundred cases of vocal cord lesions as confirmed by fibreoptic laryngoscopy were included in the study. Cases which could not be followed up for 3 months postoperatively were excluded from the study. Patients who initially enrolled in the study and were found at time of surgery to have an unexpected pathological condition were excluded from the study. After excluding such cases, a total of 88 cases were evaluated and studied on the following parameters:

1. Visual analysis on fibreoptic laryngoscopy/stroboscopy

2. Voice analysis –VHI 10 and GRBAS indices

3. Time of surgery analysis

4. Peroperative bleeding

Written and informed consent was taken prior to surgery for each patient.

Exclusion criteria.

1. age below 17 years

2. Professional singers and actors

3. patient unfit for general anaesthesia

4. Pregnant women and mentally impaired persons

All patients were encouraged to have a trial of conservative medical and rehabilitative therapy before consideration of surgery. This included voice therapy; general voice hygiene efforts such as voice moderation, hydration, mucolytics, and humidification; smoking cessation; and anti- reflux diet with or without anti-reflux medications. Patients were generally taken up for surgery on persistence of symptoms on failure of medical treatment for at least 6 weeks. However in some patients who did not elect for conservative treatment;surgery was offered.

Patients were then assigned to the following two groups by the total consecutive sampling method:

1. Microdissection group

2. Laser excision group

All the patients underwent surgery under general anaesthesia. Laser safe endotracheal tubes were used for intubation in patients of the laser excision group. Operating microscope at 400-mm focal length through a suspension laryngoscope was used for all surgeries.

In the cold steel group either microdissection or excision was used for excision of smaller lesions. For larger lesions the microflap technique was employed. In all cases effort was made to preserve the underlying middle and deep layers of the lamina propria and muscles.

In laser excision group, institutional laser precautions and safety procedures were strictly followed. Laser microsurgery was performed using microspot CO₂ surgical laser. Firstly, hydrodissection was done with normal saline and then lesions excised by acuspot or acublade. The laser beam was focused to smallest spot size 1 mm acuspot 10 W for excision and set at repeat superpulse mode after holding the lesion with laryngeal forceps.

Postoperative care patients were advised voice rest, speech therapy for 6 weeks and given antireflux medication for 6 weeks.

Postoperative assessment of patients by videostroboscopy after 2 weeks and after 3 months.

The results were analysed using Statistical Package for Social Sciences (SPSS) version 20. Fischer Exact test was used to find the significance of study parameters for the categorical data and the Student t test was used for the data variables in the continuous scale. The Student unpaired t test was use to compare the data between the two groups and the Student paired t test for comparison between the preoperative and postoperative results within the same group. In all the tests the level of significance was taken as p ≤ 0.05.

Results

A total of 88 cases underwent surgery for benign and precancerous lesions of vocal cord, out of which 53 (60.23%) were male and 35 (39.77%) were female. The patients were between the age range of 20–60 years and mean age was 40.64 ± 10.18 years. Mean age in the Microdissection group was 39.16 years and mean age in the laser group was 42.64 years. Overall pathological distribution of benign and precancerous lesions of vocal cord is illustrated in Table 1. The distribution of patients in microdissection group according to pathology was vocal cord polyp (28%), vocal cord nodule (30%), vocal cord cyst (14%), and vocal cord growth (26%).The distribution of patients in the laser group according to pathology was nodule (23%), vocal cord cyst (15%), vocal cord growth (28%) and vocal cord polyp (32%) (Table 1).

Table 1.

Pathological distribution of microdissection and laser excision group

Pathological distribution	Microdissection group	Laser excision group
Vocal cord polyp	12	15
Vocal cord nodules	13	11
Vocal cord cyst	06	07
Vocal cord growth	11	13

Assessment of all patients was also done by subjective methods of voice assessment (GRBAS score, VHI 10 index) after 3 months for comparative analysis.

Voice Outcomes

In our series, patients recovered remarkably well subjectively in both the groups (Table 2).

Table 2.

Postoperative voice outcomes of microdissection and laser excision group

Voice outcomes	Microdissection group	Laser excision group	P value (between the two groups)
VHI 10 indices
Preoperative VHI 10 index	8.32 ± 0.74	8.16 ± 0.88	–
Postoperative VHI 10 index at 3 months	2.82 ± 0.72	2.94 ± 0.76	–
p value	p value of 0.0001 (between pre and post op observations)	p value of 0.0001 (between pre and post op observations)	0.0001
GRBAS score
Mean GRBAS score	Preoperative-15.98	Preoperative-16.34	0.0001
	Postoperative (3 months)-7.68	Postoperative (3 months)-7.42	–
p value	0.0001	0.0001	–
Videostroboscopy
Incomplete glottic closure	Preoperative-42	Preoperative-46	0.0001
	Postoperative (3 months)-2	Postoperative (3 months)- 3	–
Amplitude	Preoperative-33	Preoperative-38	–
	Postoperative (3 months)-1	Postoperative (3 months)-2	–
Mucosal wave asymmetry	Preoperative-36	Preoperative-42	–
	Postoperative (3 months)-3	Postoperative (3 months)-4	–
Absent mucosal wave	Preoperative-37	Preoperative-39	–
	Postoperative (3 months)-4	Postoperative (3 months)-3	–
p value	0.0001 (between pre and post op observations)	0.0001 (between pre and post op observations)	–

Microdissection Group

Mean GRBAS score (15.98 preop. to 7.68 postop.)

Mean VHI 10 score (8.32 preop. to 2.82 postop.)

Laser Excision Group

Mean GRBAS score (16.34 preop. to 7.42 postop.)

Mean VHI 10 score (8.16 preop. to 2.94 postop.)

Videostroboscopic Analysis

Glottic closure patterns and mucosal wave studies was done in all the patients. Videostroboscopic evaluations of vocal fold edge and mucosal wave showed significant improvements from the preoperative period to 2 week postoperative phase and from 2 week postoperative period to 3 month postoperative period in both treatment groups. Incomplete glottis closure pattern was noted on videostroboscopy. At 3 months post-operative period, 2 out of 42 (35%) was noted in Microdissection group and 3 out of 46 (32%) was noted in Laser excision group. Mucosal wave amplitude at 3 months post-operative period was slightly higher in Laser excision group with 1 out of 33 (42%) over Microdissection group with 2 out of 38 (40%). Mucosal wave asymmetry at 3 month post-operative period was slightly lower for Laser excision group 4 out of 42 (46%) compared to Microdissection group 3 out of 36 (44%). There was no significant difference in mucosal wave absence between two groups. There was no statistical significant difference between two groups (p value 0.0001). In all of these parameters, there were no statistical differences between the microdissection and laser excision groups. These results show that expected improvements occur following surgery over time, but not between the two treatment arms as assessed by videostroboscopy.

Time Analysis

The total intubation time in the microdissection group was 71.35 min while in the laser excision group it was 78.06 min. The total hospital stay in the microdissection group was 46.84 h and in the laser excision group was 47.76 h. In our study, operating time was significantly increased in the laser excision group (p value < 0.05). No difference was, however, observed in duration of hospital stay.

Peroperative Bleeding

In our study, mean peroperative bleeding was 3.88 mL for microdissection group and 3.04 mL for laser excision group. Peroperative bleeding was significantly reduced in the laser excision group (p value of 0. 0015 was obtained).

Discussion

Benign and precancerous lesions of vocal cord may be classified depending upon the layer of vocal cord involvement such as changes in epithelium (vocal nodules, leukoplakia, hyperkeratosis, acanthosis, dysplasia, etc.), exudative changes in the Reinke’s space (vocalcord polyps, Reinke’s edema) and subepithelial lesions such as cysts [3–6].

The changes in vocal cord structure related to vocal trauma to the laryngeal mucosa occur by means such as excessive talking or coughing, use of inappropriate pitch and throat clearing. Vocal edema and nodules are induced due to vibration-induced elevations in capillary pressure [7].

Management of benign and precancerous lesions of vocal cord is primarily surgical excision. With the advent of newer and refined cold steel surgical instrumentation, microsurgical techniques such as microdissection and mucosal flap have evolved over time. This growing recognition of the unique ultrastructure of the vocal fold has resulted in greater concern for maintaining the integrity of the deep layers of the lamina propria during microsurgery for benign lesions of the larynx. Newer microlaryngeal instruments have been developed and popularized which allow precise microscopic excision of vocal fold lesions with preservation of the deep layer of the lamina propria and muscle. Development of the videostroboscope [8, 9] has allowed surgeons to assess the impact of their surgery on the subtle features of vocal fold vibration. Stroboscopy provides excellent real time mucosal wave movement endoscopically and helps in evaluating pattern of mucosal fold vibration, Regrowth of normal mucosa and subsequent normal waveforms was seen on videostroboscopy following microlaryngeal excision of benign lesions [8, 10]. In a study by Bennett et al. [11] microdissection resulted in a more rapid return of vocal function when compared with standard CO₂ laser excision or vocal fold stripping, probably because of the less traumatic technique which promoted more rapid healing.

Strong et al. [12] described their early clinical experience with a continuous CO₂ laser in the larynx. They suggested that laser stripping of the vocal folds was more precise than mechanical stripping, with less scar formation for the former method. Early laryngeal carcinoma is better treated by carbon dioxide (CO₂) laser [13]. Shapshay [13] believed that CO₂ laser treatment induces thermal damage causing deepened surgical trauma and affecting the healing of wounds. Benninger et al. [14] suggested that use of proper CO₂ laser mode and duration slightly influences early wound healing during the treatment of vocal cord benign diseases.

With the advent of the microspot CO₂ laser the potential heat distribution to the deeper layers of the lamina propria has been reduced. The thermal damage to tissues by CO₂ laser is reduced by microspot size and use of superpulse mode. The superpulse or UltraPulse microspot CO₂ lasers have brought distinct advantages to microscopic laryngeal surgery. The small spot decreases the contact to the normal surrounding tissue, restricting the laser energy to the mucosa and the superficial layer of the lamina propria, thus avoiding injury to the deep layer of the lamina propria and muscle. Injury to these levels of the vocal fold could result in stiffness, change of mucosal wave, and changes in voice. The superpulse action allows for the delivery of high levels of energy with time intervals between pulses for thermal relaxation and tissue cooling. Greater depths of penetration provided by the higher energy levels can result in tissue cutting without carbonization or necrosis. The spot size can be adjusted so that the laser could be used for cutting (small spot size) or coagulation of small vessels (larger spot size).

Preference for microlaryngeal laser excision is due to the properties of lasers which makes it beneficial in surgery are its monochromaticity (only one wavelength), coherence (wave travels in phase and in one direction) and concentrated direction of the beam [15]. The disadvantage for laser excision is that they cause thermal tissue damage which may cause excessive scarring.

In our study, both microdissection and laser excision group showed excellent results. Voice assessment by the VHI 10 score and GRBAS score in both groups showed improvement in post-operative results. There was no statistical difference in the results in voice assessment after surgery in both groups. In our study, operating time was significantly increased in the laser assisted group as compared to the microdissection technique (p value of < 0.05). The postoperative recovery and morbidity in both groups was not statistically significant. No difference was hence observed in duration of postoperative hospital stay. Benninger et al. [12] in their study found that there were no differences in intubation (surgical) time, recovery room time, or total time of stay. In our study we incorporated laser precautions and there were no complications associated with laser use.

Mizuta et al. [16] showed that use of CO₂ laser was particularly indicated for vascular lesions of the vocal cords as it helped to achieve better haemostasis. Peroperative bleeding was significantly higher in the microdissection group as compared to the laser assisted group (p value of 0. 0015).

The efficacies of CO₂ laser and conventional laryngeal microsurgery for vocal cord benign (vocal cord polyp) and precancerous (vocal cord leukoplakia) lesions in 90 cases were compared in a study by Zhang et al. [1]. The subjective and objective data of the two groups pre-and post-surgery showed that the voice recovery of the laser group was significantly better than that of the conventional group (P < 0.05). CO₂ laser laryngeal microsurgery for vocal cord polyp and leukoplakia can improve significantly the vocal cord morphology and pronunciation quality. There was no statistical difference between conventional treatment and CO₂ laser treatment seen in forty-four patients with benign lesions of the vocal fold [2]. Laser excision of benign and precancerous lesions of vocal cord is preferred over microdissection due to fewer complications, side effects and better postoperative care [17].

There was no statistical difference between microdissection and CO₂ laser treatment seen in in our study of benign lesions of the vocal cord.

Conclusion

Benign and precancerous lesions of vocal cord are primarily managed by surgical excision. Surgical excision is done by either microdissection by cold microsurgical instruments or laser excision. No differences in clinical outcomes are identified when comparing microdissection with laser excision of nodules, polyps, and mucous retention cysts of the vocal folds.

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Funding

None.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical Approval

Permission taken from institutional ethical committee for doing this study.