Laryngeal Stenosis 

Laryngeal stenosis is a congenital or acquired narrowing of the airway that may affect the supraglottis, glottis, and/or subglottis. It can be defined as a partial or circumferential narrowing of the endolaryngeal airway and may be congenital or acquired. The subglottis is the most common site of involvement.

A formal endoscopic evaluation of the airway in the operating room is an essential part of evaluation. Treatment via an endoscopic or an open surgical approach is dependent on the patient’s symptoms, site of involvement, and the degree of stenosis.

Congenital Laryngeal Stenosis

Congenital laryngeal stenosis results from failure of the laryngeal lumen to recanalize. During normal development, the laryngeal lumen is obliterated to give rise to the epithelial lamina, which later recanalizes. By the 10th week of gestation, the laryngeal lumen is reestablished following recanalization. Incomplete recanalization results in various degrees of glottic and/or subglottic stenosis.

Congenital laryngeal atresia represents the most severe end of the spectrum of disease, arising from failed recanalization of the larynx and trachea during embryogenesis. Atresia can be diagnosed prenatally based on ultrasound by identifying signs of congenital high airway obstruction syndrome (CHAOS). Glottic and supraglottic atresia requires immediate tracheotomy at the time of delivery. Prenatal diagnosis of CHAOS allows for the use of the ex utero intrapartum treatment (EXIT) procedure to evaluate and secure the airway at birth. Laryngotracheal reconstruction to repair the atresia is necessary at a later stage.

Congenital laryngeal webs account for about 5% of congenital laryngeal anomalies. Seventy-five percent of these are at the glottic level. Treatment varies depending on the nature of the web and associated symptoms, ranging from division of thin membranous webs, staged dilations following incision, keel placement, open laryngotracheal reconstruction, and tracheostomy. Laryngeal webs often involve both the glottis and subglottis and may rarely involve the supraglottis. Glottic stenosis may also result from impaired vocal cord mobility or, rarely, complete fusion of the true vocal folds.

Congenital subglottic stenosis is the third most common congenital laryngeal anomaly after laryngomalacia and vocal fold paralysis. It is diagnosed where subglottic narrowing exists with no history of intubation or surgical trauma. Distinguishing congenital from acquired stenosis once a child has been intubated is difficult, but the suspected incidence is 5%. Congenital stenosis can be a contributing factor to acquired laryngeal stenosis.

Congenital subglottic stenosis may be divided into 2 types: membranous (fibrosis, submucous gland hyperplasia, granulation tissue) and cartilaginous. Membranous stenosis is more common than cartilaginous stenosis. Most commonly, membranous stenoses are circumferential and symmetric and may extend upward to include the true vocal cords. Cartilaginous stenosis is a deformity of the cricoid cartilage or tracheal ring projecting into the lumen. It may be symmetric (small but normal shaped cricoid or a nondistensible complete first tracheal ring trapped inside the cricoid) or asymmetric (elliptic or oval-shaped cricoid, isolated enlargement of either the anterior or posterior cricoid lamina, or laryngeal cleft).

Congenital subglottic stenosis is defined as a subglottic diameter of 4 mm or less in a full-term neonate (< 3.5 mm in the premature neonate). Diagnosis depends on exclusion of acquired stenosis.

Treatment is individualized. Mild cases of stenosis (grade I) are typically managed with a conservative approach consisting of regular follow-up care and aggressive medical management of upper respiratory infections.

Most patients with greater than 50% obstruction are likely to require some surgical intervention. These include both endoscopic (dilation, laser resection) and external approaches to cricoid expansion. Laser resection and dilation are rarely effective if the stenosis is cartilaginous.

Acquired Laryngeal Stenosis

Instrumentation of the airway for nonlaryngeal and nontracheal illnesses remains a primary cause for laryngeal stenoses. External trauma and infection have been supplanted by iatrogenic trauma as the most common cause of laryngotracheal stenosis in adults.

Approximately 15% of patients who are intubated for more than 10 days develop some degree of laryngeal stenosis. Ninety percent of acquired subglottic stenoses in infants and children are due to endotracheal intubation. The incidence of subglottic stenosis after intubation is reported to be 1-10%.

Extrinsic factors that contribute to the increased risk of stenosis following intubation include traumatic intubation, prolonged duration of intubation, multiple extubations and reintubations, use of an oversized endotracheal tube for intubation, motion of the patient or the tube, gastroesophageal reflux, and local infection. In the pediatric population, since the pediatric subglottis is the narrowest portion of the airway, it is predisposed to injury by intubation.

The above-mentioned extrinsic factors lead to such changes as submucosal edema and granulation tissue deposition from fibroblast proliferation. Ulceration due to pressure or trauma (ie, from endotracheal or nasogastric tube) can progress perichondritis or chondritis with associated scar formation and/or arytenoid fixation.

Acquired posterior glottic stenosis, typically resulting from trauma due to endotracheal intubation, is the most common form of glottic stenosis.

Caustic ingestion, foreign bodies, and iatrogenic causes due to surgery on the larynx may also result in laryngeal stenosis.

Supraglottic stenosis may result from tracheotomy or laryngotracheal reconstruction. This is thought to be due to disruption of the supraglottic lymphatics and/or relaxation or injury to the suspensory muscles of the hyoid bone and hyoepiglottic ligament. Such disruption may occur during laryngotracheal surgery.

So far, laryngeal stenosis has not been found to occur at a higher rate in percutaneous dilational tracheotomy compared with open tracheotomy.

The role of gastroesophageal reflux is not clearly delineated but is thought to be a complicating factor via chemical irritation.

For the diagnosis of idiopathic progressive subglottic stenosis to be considered, no history of recent intubation or trauma should exist. Sex hormones has been implicated as a possible cause due to the preponderance of females afflicted with this condition, but several reports were not able to confirm the presence of estrogen receptors in the biopsies.

Less common autoimmune disorders such as cicatricial pemphigoid, systemic lupus erythematosus, Wegener granulomatosis, sarcoidosis, rheumatoid arthritis, and relapsing polychondritis may result in laryngeal stenosis in addition to malignancy and other systemic diseases such as amyloidosis.

Congenital laryngeal atresia may be incomplete or complete. Incomplete atresia consists of a firm fibrous membrane obstructing the glottis. Emergent tracheotomy is necessary. Complete atresia may present as stillbirth.

Congenital laryngeal webs account for about 5% of congenital laryngeal anomalies. Seventy-five percent of these are at the glottic level. The rest are at the supraglottic or subglottic level. Congenital laryngeal webs are rare; one report identified 51 children with webs during a 32-year period. Few cases are significant enough to require immediate airway intervention. Laryngeal webs often involve both the glottis and subglottis.

The incidence of posterior glottic stenosis is reported to be as high as 15% in patients who are intubated for more than 10 days.^[1] Factors that contribute to the increased risk of stenosis following intubation include traumatic intubation, prolonged duration of intubation, multiple extubations and reintubations, use of an oversized endotracheal tube for intubation, motion of the patient or the tube, gastroesophageal reflux, and local infection.

Supraglottic stenosis has recently been identified as a factor in chronic upper airway obstruction following tracheotomy or laryngotracheal reconstruction.

Frequency

Approximately 15% of patients who are intubated for more than 10 days develop some degree of glottic stenosis. Ninety percent of acquired subglottic stenoses in infants and children are due to endotracheal intubation. The incidence of subglottic stenosis after intubation is reported to be 1-10%.

Congenital glottic stenosis is a rare disorder and may exist as a thin membranous stenosis, as a thick anterior or posterior web, or as a complete fusion of the vocal cords. Congenital laryngeal webs are rare; one report identified 51 children with webs during a 32-year period.

Causes of laryngeal stenosis include the following:

• Size of airway - The pediatric subglottis is predisposed to injury by intubation because it is the narrowest portion of the pediatric airway. The subglottic airway is lined with pseudostratified, ciliated, columnar epithelium, with a submucosal layer composed of loose areolar tissue.
• Submucosal edema - Caused by local trauma factors or infection, leads to luminal narrowing
• Stenosis - Develops due to granulation tissue deposition and fibroblast proliferation
• Gastroesophageal reflux - Thought to be a complicating factor, adding chemical irritation to the endotracheal tube-induced mechanical trauma
• Acquired posterior glottic stenosis - Typically begins as ulceration of the mucosa, due to pressure from the endotracheal tube, followed by secondary infection, perichondritis, chondritis, and formation of granulation tissue, which leads to scar formation and possible arytenoid fixation

As a result of technological improvements, more premature infants are surviving due to prolonged endotracheal intubation. This now is the primary cause of subglottic stenosis in children, with the percentage estimated at 1-10%.

Congenital glottic webs and subglottic stenosis result from failure of the laryngeal lumen to recanalize. During normal development, the laryngeal lumen is obliterated by continued growth of the arytenoid masses and hypobranchial eminence. By the tenth week of gestation, the laryngeal lumen is reestablished when this condensation is recanalized. Incomplete recanalization results in various degrees of glottic and/or subglottic stenosis.

Acquired glottic stenosis most commonly is due to trauma secondary to endotracheal intubation. Other causes include caustic ingestion, infections (such as croup), foreign bodies, external trauma, and iatrogenic causes due to surgery on the larynx. Long-term nasogastric intubation also may contribute to mucosal erosion and ulceration in the postcricoid region, progressing to posterior glottic stenosis.

Supraglottic stenosis or collapse is thought to be due to disruption of the supraglottic lymphatics and/or relaxation or injury to the suspensory muscles of the hyoid bone and hyoepiglottic ligament. Such disruption may occur during laryngotracheal surgery.

The clinical presentation of laryngeal stenosis is variable depending on the age, medical condition, and activity level of the patient and the extent of stenosis. Stridor is a common presenting sign in laryngeal obstruction. Supraglottic or glottic obstruction generally presents as inspiratory stridor, while narrowing between the glottis through the trachea is associated with biphasic stridor.

Other symptoms include episodes of apnea, suprasternal and subcostal retractions, tachypnea, and dyspnea. Hypoxia can result in cyanosis and anxiety. If the glottis is involved, symptoms of hoarseness or weak husky cry, aphonia, or dysphagia may be noted.

In children, failure to thrive and feeding problems are often noted. Mild-to-moderate stenosis may be asymptomatic until an upper respiratory tract infection leads to airway edema and thickened secretions which further compromise the airway. Recurrent or persistent croup is also a typical finding in children with subglottic stenosis. Also, children may be asymptomatic but difficult to intubate for anesthesia, as may be the case in children with Down syndrome. Any individual with a history of endotracheal intubation or laryngeal trauma can potentially develop subglottic stenosis. In general, congenital stenoses are less severe than acquired ones.

The history should include an assessment of dyspnea and stridor, including the characteristics of the stridor, time of onset, and relieving and aggravating factors. Voice quality should also be assessed. History should also include questions to identify possible etiological factors, such as a history of prolonged intubation, prior surgery (airway or otherwise), trauma, or caustic ingestion.

In general, while anterior glottic scarring results in dysphonia, posterior glottic scarring tends to present with dyspnea. Acquired posterior glottic stenosis usually presents as difficulty on extubation or tracheotomy dependence.

In children, supraglottic stenosis typically presents as persistent upper airway obstruction following tracheotomy or laryngotracheal reconstruction. This problem has recently been identified as a major factor in preventing decannulation following laryngotracheal reconstruction in the pediatric patient.

The primary goals of the treatment of laryngeal stenosis are the development of an adequate airway and voice quality preservation or improvement.

Treatment can be organized as follows into 4 broad categories:

• Observation
• Intralesional injections or applications
• Endolaryngeal procedures
• Open surgical procedures

Treatment depends on the overall medical condition of the patient, symptoms, and extent of stenosis.

The normal subglottic lumen diameter is 4.5-5.5 mm in the full-term neonate and about 3.5 mm in premature neonates. A subglottic diameter of 4 mm or less in a full-term baby is considered to be narrow. In children, the subglottic region (cricoid cartilage) is the narrowest portion of the airway. It is most susceptible to injury from endotracheal intubation.

The proximal subglottic airway is bounded by the thyroid cartilage anteriorly and by the posterior plate of the cricoid cartilage laterally and posteriorly. Distally, the cricoid ring circumferentially surrounds the subglottic airway. This area is lined with pseudostratified ciliated columnar epithelium.

The glottic segment of the larynx is composed of the true vocal cords, the anterior and posterior commissures, and the vocal processes of the arytenoid cartilages. The superior border of the glottis is the ventricle, which separates it from the supraglottis. The inferior border is the inferior limit of the true vocal cord. The posterior glottis consists of the posterior third of the vocal cords, the posterior commissure with the interarytenoid muscle, the cricoid lamina, the cricoarytenoid joints, the arytenoids, and the overlying mucosa. The anterior glottis is lined with squamous epithelium, and the posterior glottis shares respiratory epithelium with the subglottis.

Patients with a need for ventilatory support are generally poor surgical candidates. Pulmonary status must be maximized prior to any airway intervention. Infants and children with a history of bronchopulmonary dysplasia may need to demonstrate a season without hospitalization for severe respiratory illness before consideration for reconstruction. A tracheotomy for airway control may be necessary until pulmonary reserve is optimized.

Some authors recommend a minimum patient weight of 10 kg before laryngotracheal reconstruction, as this allows adequate growth, maturity of the immune system, and stabilization of pulmonary disease.

Control of gastroesophageal reflux and asthma is essential prior to treatment.