Challenges and Strategies in Achieving Laryngeal Exposure for Transoral Laser Microsurgery: A Case Report

Abstract

Endolaryngeal microsurgery is a well-established procedure, with proper laryngeal exposure is critical for success. However, there are instances where achieving complete visualization of the laryngeal inlet, particularly the anterior commissure, can be challenging, termed as difficult laryngeal exposure (DLE). The Laryngoscore, introduced in 2014, can accurately predict DLE and assist in preoperative planning. We report a case of DLE encountered during transoral laser microsurgery in a 50-year-old obese woman with bilateral vocal fold paralysis following total thyroidectomy and describe the maneuvers applied, which led to successful surgery. This case underscores the importance of the role of Laryngoscore in preoperative assessment and discusses the useful maneuvers in managing DLE.

Introduction

Endolaryngeal microsurgery utilizing a straight direct laryngoscope is a well-established procedure in clinical practice. Adequate laryngeal exposure serves as a fundamental requirement for the success of transoral microlaryngeal surgery [1, 2]. Typically, the use of a suspension laryngoscope provides satisfactory visualization of the glottis in most cases. However, there are instances where achieving complete visualization of the laryngeal inlet, particularly the anterior commissure, can be challenging, termed as difficult laryngeal exposure (DLE). When encountered, DLE can lead to unnecessary trauma, incomplete surgery, and may even necessitate the abandonment of the procedure [1–3]. Laryngoscore was introduced in 2014 and has proven to be accurate in predicting DLE. We describe a case of DLE encountered during transoral laser microsurgery in an obese patient, resulting in transient postoperative complications involving the lingual and hypoglossal nerve. We discuss the measurements to overcome DLE.

Case Report

A 50-year-old woman was diagnosed with iatrogenic bilateral vocal fold paralysis (BVFP) following a total thyroidectomy and was referred to our center due to difficulties in laryngeal exposure. She was an active smoker with a history of total thyroidectomy for multinodular goiter one year prior and presented with acute airway obstruction symptoms, necessitating emergency tracheostomy at the previous facility. Subsequent attempts of direct laryngoscopy and LASER posterior cordectomy were made but abandoned due to difficulties in laryngeal exposure. Postoperatively, the patient experienced transient hypoglossal and lingual nerve palsy. The patient was referred to our center for DLE. Upon assessment, her BMI was 30 and her laryngoscore was 10 (Fig. 1). Flexible nasopharyngolaryngeal scopy revealed BVFP with Reinke edema of the right vocal fold. She was scheduled for direct laryngoscopy, endoscopic laryngeal microsurgery, and right LASER posterior cordectomy. Intraoperatively, achieving adequate laryngeal exposure proved challenging. Various maneuvers were employed to visualize the laryngeal inlet. The patient was positioned with the tragal and sternum aligned along the same horizontal plane by placing a folded cloth over the upper shoulder, neck, and head ( Fig. 2). Cricoid pressure was applied, and the laryngoscope was introduced through the side of the patient’s mouth between the missing molars rather than the center (Fig. 3). Multiple types of laryngoscopes were utilized, including the Lindholm, anterior commissure, and Wierda laryngoscopes, before achieving visualization with the Dedo laryngoscope. The tip of Dedo laryngoscope was placed at the laryngeal surface of epiglottis and then suspended to proceed with endoscopic laryngeal microscopic surgery and right LASER posterior cordectomy. The suspension was released every 15 min for 2 min to avoid prolonged compression. Post-operatively, patient recovered well without significant neurological deficit and complication.

Fig. 1.

The patient’s laryngoscore and individual parameter scores

Fig. 2.

The patient was positioned with the tragal and sternum aligned along the same horizontal plane, also known as ‘ramped position’ by placing a folded cloth over the upper shoulder, neck, and head

Fig. 3.

The missing right upper premolar and molar tooth where the laryngoscope was introduced

Discussion

The prevalence of DLE has been reported to range from 1.5 to 24% [1, 2]. In transoral laser microsurgery, DLE poses a significant challenge as inadequate exposure can impede the accurate identification and excision of lesions, resulting in suboptimal outcomes. A study by Piazza et al. in 2017 reported a statistically significant association between laryngeal exposure and the incidence of positive surgical margins in glottic cancer treated with transoral laser microsurgery [2]. Specifically, insufficient laryngeal exposure was correlated with a higher rate of positive margins compared to cases with adequate exposure [2]. Notably, the incidence of positive margins more than doubled in cases where suboptimal exposure was encountered. These findings underscore the clinical importance of achieving adequate laryngeal exposure during transoral laser microsurgery.

In 2014, Piazza and his team developed a standardized preoperative assessment tool, the laryngoscore [1]. This assessment is designed to predict the likelihood of encountering difficult laryngeal exposure during endoscopic laryngeal microsurgeries. Laryngoscore consists of 11 parameters, including interincisor gap, thyro-mental distance, upper jaw dental status, trismus, mandibular prognathism, macroglossia, micrognathia, degree of neck flexion-extension, history of prior open-neck and/or radiotherapy, modified Mallampati’s score, and body mass index. A cumulative score of 17 is calculated, with a threshold of 6 or higher indicating an increased likelihood of encountering challenging laryngeal exposure during surgery. In our case, the patient’s laryngoscore was determined to be 10, and indeed, challenging laryngeal exposure was encountered intraoperatively. This highlights the reliability and accuracy of laryngoscore as a preoperative assessment tool, enabling surgeons to anticipate the potential for difficult laryngeal exposure. Consequently, proactive preoperative counseling with the patient and discussion with the anesthesia team could be initiated, allowing for thorough preparation and tailored management strategies to address potential challenges during surgery.

In phonosurgery, achieving optimal visualization of the vocal folds relies on several factors including patient positioning, external laryngeal counter-pressure, and internal laryngeal distension. Three postures are applicable in direct laryngoscopy which are flexion-flexion position, flexion-extension position commonly known as sniffing position, and extension-extension position [4]. The sniffing position is conventionally considered optimal for direct laryngoscopic examination of the vocal folds, as it aligns the oral, pharyngeal, and laryngeal axes, maximizing glottis visualization. This posture facilitates alignment of the oral, pharyngeal, and laryngeal axes, maximizing visualization of the glottis. Although the flexion-flexion position provides excellent exposure of the anterior glottis, its upward orientation toward the ceiling may not be conducive to endolaryngeal microsurgery, as noted in the study by Hochman et al. [5]. In a study by Ohno et al., the extension-extension position was used in patients with DLE, but it resulted in limited surgical view and working space [4]. In our case, we adopted a specific positioning technique by elevating the head, neck, and upper body using a folded blanket until the tragus and sternum aligned in the same horizontal line. This positioning method, also known as ‘ramped position’ in the study by Collin et al. [6], was found to be superior to the traditional sniffing position for improving laryngeal visualization during laryngoscopy, particularly in morbidly obese patients. Furthermore, a study by Greenland et al. utilized magnetic resonance imaging as an evaluation tool and demonstrated that achieving horizontal alignment of the external auditory meatus with the sternum serves as a reliable endpoint for ensuring proper positioning in the sniffing position [7].

We employed cricoid pressure as an external counterpressure technique to achieve optimal visualization of the larynx. Zeitels et al. have highlighted the efficacy of external counterpressure, particularly in cases involving lesions near the anterior commissure [8]. The study demonstrated that despite the constraint imposed by the endotracheal tube, applying external counterpressure can posteriorly displace the anterior commissure by up to 6 mm, significantly improving exposure of the anterior glottal region during surgical management. Table 1 outlines the various techniques implemented in our case DLE during transoral laser microsurgery. Previous literature has documented alternative surgical approaches to effectively manage DLE, such as employing angled rigid endoscopes alongside malleable endoscopic instruments, as well as utilizing flexible fiberscopes with a video system [3, 9]. However, in our case, these methods were considered impractical since transoral laser microsurgery required direct access to the vocal fold lesion through the rigid direct laryngoscope.

Table 1.

Maneuvers for difficult laryngeal exposure

Strategies for managing difficult laryngeal exposure
Align tragus and sternum
Sideway insertion of laryngoscope
Application of cricoid pressure
Preparation of various types and sizes of laryngoscopes
Placement of sandbag over the upper thorax, neck and head

In previous literature, lingual and hypoglossal nerve injuries have been documented as complications, mirroring our case where the patient experienced lingual nerve injury and hypoglossal nerve palsy during her first surgery, both of which spontaneously resolved. The incidence of lingual nerve injury in direct laryngoscopy ranges from 2.6 to 18% [10], while for hypoglossal nerve injury, it varies from 0.36 to 2.7% [11]. Several hypotheses have been proposed in the literatures to elucidate the mechanisms underlying these nerve injuries during direct laryngoscopy. Primarily, these injuries are attributed to the proximity of the nerves to the hyoid bone and tongue, rendering them vulnerable to compressive or stretching injuries during manipulation of the direct laryngoscope [10].

Conclusion

Performing the laryngoscore assessment for all patients undergoing transoral laryngeal microsurgery is recommended, as it offers a simple and cost-effective preoperative evaluation tool to alert the surgeon to potential instances of difficult laryngeal exposure. Despite the challenges associated with difficult laryngeal exposure, performing transoral laser microsurgery in such patients is feasible with appropriate manoeuvring and preparation. Patient scheduled for direct laryngoscopy procedures should be informed about the potential risks of lingual and hypoglossal nerve injuries.

Author Contributions

WJ, MA, NM conceived the original idea. This was also discussed with MB. Eventually, all the authors discussed and agreed with the focus and ideas of this paper. The main text of the paper was written by WJ and edited and supervised by MA, NM, MB. All authors revised the manuscript and contributed equally.

Funding

No funding is involved in this paper.

Data Availability

No applicable.

Declarations

Ethics Approval and Consent to Participate

Not applicable.

Consent for Publication

Written consent was obtained from the patient for the publication of this case report.

Competing Interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.