Laryngotracheal Stenosis

Etiology

Several etiologies have links to the development of laryngotracheal stenosis (LTS).[1] Recognized causes of laryngeal stenosis include: iatrogenic (ex. complication of endotracheal intubation), autoimmune, infectious, neoplastic, traumatic, and idiopathic. Autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, vasculitis, sarcoidosis, and scleroderma, among others, can cause laryngotracheal stenosis. Infectious causes include bacterial tracheitis, viral papillomatosis, and tuberculosis. Neoplasm at the level of the larynx or trachea can also cause narrowing of the airway, with squamous cell carcinoma and adenoma being the most common malignancies in this setting.[2] Direct injury to the trachea by trauma, inhalation burns, or radiation are a few causes of traumatic laryngotracheal stenosis.[3]

Acute laryngeal injury has been described as a potential component of post-intensive care syndrome.[4]  Common post-intubation complications include transient dysphonia, dysphagia, and sore throat for patients undergoing surgery. However, these complications present more markedly in critically ill patients. Endotracheal tubes (ETT) can lead to laryngeal injury by direct compression injury of ETT to the posterior glottis mucosa, which may eventually progress to fibrosis and scar, leading to stenosis.

Epidemiology

There is no clear data regarding the epidemiology of laryngotracheal stenosis, as it is difficult to see this disorder as a single entity given the range of different causes. Tracheal stenosis may occur in up 30% of patients with tracheostomies, though there are many factors that can contribute to this, dependent upon the comorbidities of the patient and the indication for, and duration of, the tracheotomy [5].

Pathophysiology

The most narrow part of the adult airway is at the subglottic space at the level of the cricoid cartilage, which extends from the inferior part of the vocal cords to the lower part of the cricoid cartilage.[3] This area is only a few centimeters in length but can be commonly injured during endotracheal intubation, as the endotracheal tube makes contact with the posterior aspect of the subglottic space during intubation. Prolonged intubation can also cause laryngotracheal stenosis when the cuff pressure exceeds the mucosal capillary perfusion pressure (approximately 35 mmHg), which can lead to ischemia, ulceration of the posterior mucosa, and subsequent fibrotic strictures.[6] In terms of patients with underlying autoimmune diseases, granulomatosis with polyangiitis (formerly known as Wegener granulomatosis) is the most commonly associated with laryngotracheal stenosis, as seen by the necrotizing granulomatous inflammation that is seen in the upper airways with vasculitis perpetuating fibrotic changes and stenosis.[7]

History and Physical

Evaluating a patient with suspected laryngotracheal stenosis includes a detailed history and physical examination. History should include any previous endotracheal intubations and their duration, history of infection, autoimmune disease, vasculitis, trauma, surgery, as well as current symptoms. The most common symptoms of LTS from any etiology include dyspnea, stridor, hoarseness, and cough. In the acute emergent setting, a physician may not have enough time to obtain such detailed information, in which case the physical examination becomes crucial. One must be able to identify inspiratory stridor, which is most common in the neck associated with cough and dyspnea. If the patient has extrathoracic stenosis, they may present with hoarseness, inspiratory wheezing, stridor, and nonproductive cough. Intrathoracic stenosis is evident with difficulty in expiration and laying in the recumbent position. There may be decreased ability in clearing secretions, as well as wheezing mimicking asthma without response to bronchodilators.[8] Localization of the stenosis is difficult on clinical grounds alone. 

Evaluation

Laryngotracheal stenosis can be evaluated by laryngoscopy or bronchoscopy. The clinician may obtain computed tomography (CT) scan of the neck in severe cases in which the obstruction does not allow for direct laryngoscopy or patients who have a traumatic injury to the trachea and in planning for surgical treatment. CT scan may demonstrate artificial extra-tracheal stenosis, such as in a massive goiter, owing to the dependent position of the trachea when obtaining such scans.[2] Performing spirometry on these patients helps establish a baseline and monitor their status over time.[9]

There are three classification systems based on anatomic characteristics that are derived from intraoperative findings. The Cotton-Myer classification is based on percent stenosis (I = < 50% obstruction;  II = 51% to 70% obstruction; III = 71% to 99% obstruction; IV = Complete obstruction). The Lano classification is based on subsite involvement (I = one subsite involvement; II = two subsite involvement; III = three subsite involvement, with the subsite meaning the glottis, subglottis, and trachea). The McCaffrey classification is based on the length of stenosis (I = subglottis or trachea < 1 cm; II = subglottis > 1cm; III = subglottis and trachea >1 cm;  IV = any lesion involving glottis). The percent stenosis is important in regards to prognosis, individualized treatment planning, and risk stratification of tracheostomy dependence. Patients with grade III and IV stenosis in the Cotton-Myer classification were found to be tracheostomy dependent compared to patients with grade I and II. Per the Lano classification, larger subsite involvement was associated with a higher risk of tracheostomy dependence, as well as higher stages in the McCaffrey classification. In adult LTS, the Lano and McCaffrey classifications are more precise than the Cotton-Myer scale.[1]

Treatment / Management

Overview

The management of laryngotracheal stenosis is complex, as it may entail multiple procedures with the possibility of restenosis in certain cases. Treatment goals are to maintain airway patency, reduce the number of procedures required, and decannulation in patients with tracheostomy. Unfortunately, there is no standard guideline for the approach and management of LTS as of yet. Most of the treatment modalities have been described from various studies from the medical literature across different specialties. 

Treatment options for LTS include endoscopic dilatation, surgery, stent placement, laser therapy, or immunosuppression to restore airway patency, depending on the underlying etiology as well as degree and complexity of stenosis.[10]

Bronchoscopic Approach

Bronchoscopy may be used for mechanical dilation, laser therapy, and stenting to treat laryngotracheal stenosis. These treatment modalities may have limited use in subglottic stenosis due to anatomical challenges. Dilation or laser treatments are options for strictures or granulomas; however, they are at risk of recurrence. Stent placement can migrate and cause a larger airway injury. A laser is used cautiously for subglottic stenosis due to the risk of damaging the cricoid cartilage, which is where the laryngeal nerves pass and have a role in vocal cord function. Several studies have shown that laser and stenting reach less than 20% success rates.[3] Bronchoscopic therapy has been used in cases where the patient is not a surgical candidate to palliate symptoms. 

Endoscopic Mechanical Dilation 

Endoscopically-guided dilation is performed using several devices, including gum-tipped bougies, endotracheal tubes, or balloon catheters. It could be performed in the outpatient setting for a selected group of patients. This route has more favorable outcomes in regards to voice preservation compared with patients who have stenosis less than 2 cm from the vocal folds, or those who have stenosis in several levels. Endoscopic dilation should be the first-line treatment for simple stenosis, whereas more complex stenoses require an interprofessional approach and possible surgical evaluation. The average patient may be able to go for approximately one year without requiring subsequent dilations.[11]

Tracheal Stenting

Tracheal stenting is a palliative option for patients with advanced and unresectable cancer-causing airway obstruction. As stated above, stenting is a challenging and risky approach that requires a risk-benefit conversation with the patient. Higher performance status before surgery correlates with better patient outcomes. A Japanese study by Matsuo et al. aimed to clarify indications for stent placement, which include: 1) severe central airway obstruction with dyspnea and flow limitation on a flow-volume curve, 2) prognosis will be prolonged by stent placement, and 3) peripheral airways and lungs are intact.[12]

Preoperative Assessment

Several preoperative assessments may help with prognostication and choosing a suitable treatment modality. The patient should be screened for methicillin-resistant staphylococcus aureus (MRSA) colonization at least two to three weeks prior to possible surgery as infection may lead to more postoperative complications. If patients test positive for MRSA, they should be treated prophylactically with a three-day course of double strength trimethoprim-sulfamethoxazole orally and mupirocin intranasally, as well as fourteen days of intravenous vancomycin postoperatively until all drains have been removed. Before pursuing further treatment, patients should also undergo a swallowing evaluation by way of fiberoptic endoscopic evaluation of swallowing (FEES) or modified barium swallow study (MBS) to determine the ideal mode of delivery postoperative nutrition. FEES also assesses mobility of the vocal folds and extent of the stricture.[13]

Open Surgery

Open surgery is offered in patients with Myer-Cotton grade III or IV, loss of cartilage, or stenosis longer than 1 cm. Open surgery is an option in cases with hard tissue and scar tissue greater than 1cm in length. Surgical cases have had more success rates, whereas endoscopic procedures end up requiring more repeat interventions. Open surgery may divide into 1) laryngotracheal resection with reanastomosis or 2) laryngotracheoplasty using native and tissue grafting. [13]

Laryngotracheal resection with reanastomosis 

A systematic review by Lewis et al. found that laryngotracheal resection with anastomosis was associated with a decreased need for additional surgeries and an increased rate of decannulation when compared to endoscopic procedures. They also found that patients with idiopathic stenosis required less additional surgery compared to patients with laryngotracheal stenosis due to trauma or intubation.[14](A1)

Laryngotracheoplasty

Laryngotracheoplasty encompasses different surgical techniques that involve a single-stage or multistage approach to use different types of luminal grafts or tracheal stenting.[15] Outcomes are typically favorable, with a high percentage of decannulation rates. They also have low postoperative complications, which include granulation tissue and glottic edema. They may be treated with a short course of dexamethasone for 24 to 48 hours,  as well as diuresis and elevating head of the bed.[16][17](B2)

Montgomery T-Tube 

The Montgomery T-tube is placed through the trachea’s anterior wall distal to the anastomosis. It provides a stable airway for prolonged periods (at least six months) until the consideration of decannulation, or permanently in inoperable cases.[2][9][18](B3)

Adjunctive Treatments

Several adjunctive treatment options are currently used for the treatment of LTS. A review of the literature suggests the use of adjunctive treatments such as mitomycin C, steroids, and proton pump inhibitors. 

Mitomycin C

Mitomycin C is a chemotherapeutic agent that is applied topically for four minutes after making an incision. It works as an alkylating agent that inhibits cell division, protein synthesis, and fibroblast proliferation, ultimately decreasing the formation of scar tissue. It has been reported that this may be a therapeutic option for thinner stenoses; however, restenosis may occur at similar rates at five years with or without reapplication.[19]  (B2)

Steroids

For patients undergoing dilation, corticosteroids injected locally or systemically in oral form have favorable evidence in current data, with greater success noted in stenoses that are greater than 1 cm thick.[20][21]

Differential Diagnosis

Some differential diagnoses that must be considered in the evaluation of laryngotracheal stenosis include the following:[22]  

• Angioedema
• Asthma
• Epiglottitis
• Esophageal tumor
• Foreign body aspiration
• Gastroesophageal reflux disease
• Mediastinal mass
• Retrosternal goiter
• Subglottic web
• Tracheomalacia
• Vocal cord dysfunction

Prognosis

Overall prognosis is excellent for patients with idiopathic LTS who undergo definitive surgery. Prognosis in other etiologies relates to the clinical course of the underlying disease causing LTS.

Complications

Acute LTS (for example, in post-extubation LTS) may result in respiratory arrest if not correctly identified in a timely manner. In idiopathic LTS, complications include changes in voice, tracheostomy dependence without the ability to decannulate, and the requirement for multiple procedures.

Tracheostomy decannulation is a target goal of open surgery. Approximately 63 to 95% of patients who undergo open surgery are successfully decannulated. However, patients with grade III or IV stenosis (Myer-Cotton scale), diabetes, gastroesophageal reflux disease, diabetes, and/or body mass index (BMI) greater than 30 may have higher tracheostomy dependence rates. 

Additionally, open surgery may be complicated by dysphagia due to injury to the recurrent laryngeal nerves or the use of a stent to maintain airway patency.[9] 

A prospective study by Bibas et al. in the Journal of Thoracic Disease found that quality of life in patients with tracheal stenosis from a benign origin (such as endotracheal intubation, not amenable for surgical treatment) is severely impaired.[23] Health-related quality of life entails the physical and mental welfare of the patient and their family. This study included patients with Montgomery T-tubes, endotracheal silicone stents or tracheostomy, and the ability to fill out a questionnaire. They excluded patients with chronic comorbidities, such as chronic obstructive pulmonary disease, advanced heart failure, and renal failure.