Subglottic Stenosis

Claudia Fernandez, MD

Introduction/Etiology/Epidemiology

•Subglottic stenosis refers to a narrowing of the subglottic space that extends from just under the true vocal cords to the lower margin of the cricoid cartilage.

•The cricoid cartilage is a complete ring, as opposed to the trachea, where a posterior membrane allows for expansion of the lumen. The narrowest portion of the infant airway is the inferior cricoid ring.

•The normal subglottic area diameter in the term infant is 4–7 mm; in the preterm infant, it is 3.5–4.5 mm.

•A 1-mm circumferential reduction of diameter will reduce the cross-sectional area by 60% and markedly increase airway resistance.

•Subglottic stenosis is classified as either congenital or acquired.

—Congenital

▪Congenital subglottic stenosis constitutes 5%–15% of all airway malformations.

▪It is the third most common laryngeal anomaly (after laryngomalacia and vocal cord paralysis).

▪It is one of the most common causes of stridor in neonates. The true frequency is unknown, since there is a high risk for fetal death or development of postintubation acquired stenosis due to respiratory distress at birth.

▪It is often associated with other congenital head and neck lesions.

▪There is increased prevalence in children with trisomy 21.

—Acquired

▪The most common etiologic origin is scarring secondary to endotracheal intubation.

▪It is the third most common indication for tracheostomy in children.

Pathophysiology

•Congenital subglottic stenosis (CSS)

—Failure of the laryngeal lumen to canalize during embryogenesis

—Can be categorized into the following 2 types:

▪Membranous CSS (more common): There is fibrosis, submucosal gland hyperplasia, and granulation tissue formation in the subglottic area. Endoscopy demonstrates a circumferential and symmetrical shape.

▪Cartilaginous CSS: This refers to abnormal development of the cricoid cartilage. Endoscopy might show (a) a symmetrical lumen if the cricoid cartilage is small or (b) an asymmetrical lumen when the cricoid cartilage has an elliptical shape or when the submucosal cleft is associated with CSS.

—Laryngeal atresia is the most severe form

—Trisomy 21 is associated with a higher incidence of CSS

•Acquired subglottic stenosis

—The most common mechanism is mechanical trauma that leads to edema with subsequent infection. The pathophysiology after chemical trauma is similar. Sometimes CSS and acquired subglottic stenosis occur concurrently.

—Risk factors include long-term intubation, recurrent intubation, inappropriately large endotracheal tube, prematurity, trauma, eosinophilic esophagitis, gastroesophageal reflux, bacterial laryngotracheitis, and trisomy 21.

—A tracheostomy placed higher in the trachea may also lead to scarring in the subglottic area and cause acquired subglottic stenosis.

Clinical Features

•Biphasic stridor with or without respiratory distress is the most common presentation

•Brassy or barky cough

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