eMedicine Specialties > Pediatrics: Surgery > Otolaryngology

Subglottic Stenosis

Author: John E McClay, MD, Assistant Professor, Department of Otolaryngology, Division of Pediatric Otolaryngology, Children's Medical Center, University of Texas Southwestern Medical School
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Updated: Oct 24, 2008

Introduction

Background

Subglottic stenosis (SGS) is a narrowing of the subglottic airway (see Media file 1), which is housed in the cricoid cartilage. The subglottic airway is the narrowest area of the airway because it is a complete, nonexpandable, and nonpliable ring, unlike the trachea, which has a posterior membranous section, and the larynx, which has a posterior muscular section. The term SGS implies a narrowing that is created or acquired, although the term is applied to both congenital lesions of the cricoid ring (see Media files 3-5) and acquired SGS (see Media file 2, Media files 6-10, Media files 12-16, and Media file 30).

Acquired SGS is the most common acquired anomaly of the larynx in children and the most common abnormality requiring tracheotomy in children younger than 1 year. Correction of this abnormality requires expanding the lumen of the cricoid area to increase airflow and decrease obstructive breathing. Surgical correction of SGS has been performed with various techniques over the years.

Early in the 20th century, acquired SGS was usually related to trauma or infection from syphilis, tuberculosis, typhoid fever, or diphtheria. Also, children often had tracheotomies placed that caused laryngeal stenosis. In this era, attempted laryngeal dilation failed as a treatment for SGS.

Acquired SGS increasingly occurred in the late 1960s through the 1970s, after McDonald and Stocks introduced long-term intubation as a treatment method for neonates in need of prolonged ventilation for airway support.¹ The increased incidence of SGS focused new attention on the pediatric larynx, and airway reconstruction and expansion techniques were developed.

Surgery without cartilage expansion

In 1971, Rethi and Rhan described a procedure for vertical division of the posterior lamina of the cricoid cartilage with Aboulker stent placement. A metal tracheotomy tube was attached to the Aboulker stent with wires, and the anterior cartilaginous incision was closed. In 1974, Evanston and Todd described success with a castellated incision of the anterior cricoid cartilage and upper trachea, which was sewn open, and a stent made of a rolled silicone sheet was placed in it for 6 weeks. In 1980, Cotton and Seid described a procedure in which tracheotomy is avoided called the anterior cricoid split (ACS).² The procedure was designed for use in neonates (usually, those born prematurely) with anterior SGS or SGS who had airway distress after extubation. The cricoid ring was divided anteriorly and a laryngofissure was created in an attempt to expand the airway without a tracheotomy. Holinger et al also described success with this procedure in 1987.³

Surgery with cartilage-grafting reconstruction

In 1974, Fearon and Cotton described the successful use of cartilage grafts to enlarge the subglottic lumen in African green monkeys and in children with severe laryngotracheal stenosis.⁴ All augmentation materials were evaluated, including thyroid cartilage, septal cartilage, auricular cartilage, costal cartilage, hyoid bone, and sternocleidomastoid myocutaneous flaps. After significant work, it appeared that costal cartilage grafts had the highest success rate.

In the 1980s, Cotton reported his experience with laryngeal expansion with cartilage grafting.^5,6,7,2 His success rates depended on degree of stenosis. More severe forms of stenosis required multiple surgical procedures. Cotton used the Aboulker stent.

In 1991, Seid et al described a form of single-stage laryngotracheal reconstruction in which cartilage was placed anteriorly to expand the subglottis and upper trachea to avoid a tracheotomy.⁸

In 1992, Cotton et al described a 4-quadrant cricoid split, along with anterior and posterior grafting.⁹  In 1993, Zalzal reported 90% decannulation with any degree of SGS with his first surgical procedure.¹⁰ Zalzal customized the reconstruction on an individual basis, and most patients received Aboulker stents for stabilization.

Cricotracheal resection

In 1993, Monnier described partial cricotracheal resection with primary anastomoses for severe SGS because grade III and grade IV SGS (ie, severe SGS) often requires multiple (3-4) surgical augmentations for decannulation.¹¹ In 1997, Stern described his experience with the procedure, reporting a decannulation rate higher than 90% for primary and rescue cricotracheal resection.¹²

Pathophysiology

The pathophysiology of congenital SGS is a malformed cricoid cartilage in utero. The cause of congenital SGS is in utero malformation of the cricoid cartilage.

The etiology of acquired SGS is related to trauma of the subglottic mucosa. Injury can be caused by infection or mechanical trauma, usually from endotracheal intubation but also from blunt, penetrating, or other trauma. Historically, acquired SGS has been related to infections such as tuberculosis and diphtheria. Over the past 40 years, the condition has typically been related to mechanical trauma.

Factors implicated in the development of SGS include the size of the endotracheal tube relative to the child's larynx, the duration of intubation, the motion of the tube, and repeated intubations. Additional factors that affect wound healing include systemic illness, malnutrition, anemia, and hypoxia.

Local bacterial infection may play an important role in the development of SGS. Gastroesophageal reflux (GER) may play an adjuvant role in the development of SGS because it causes the subglottis to be continually bathed in acid, which irritates and inflames the area and prevents it from correctly healing. A systemic or GI allergy may cause the airway to be more reactive, creating a greater chance of developing stenosis.

Acquired SGS is often caused by endotracheal intubation. Mechanical trauma from an endotracheal tube, as it passes through or remains for long periods in the narrowed neonatal and subglottic airway, can lead to mucosal edema and hyperemia. These conditions then can progress to pressure necrosis of the mucosa. These changes have been observed within a few hours of intubation and may progress to expose the perichondrium of the cricoid cartilage. Infection of the perichondrium can result in a subglottic scar.

This series of events can be hastened if an oversized endotracheal tube is used. Always check for an air leak after placing an endotracheal tube because of the risk of necrosis of the mucosa, even in short surgical procedures. This practice is common among anesthesiologists. Usually, the pressure of the air leak should be less than 20 cm of water, so that no additional pressure necrosis occurs in the mucosa of the subglottis.

Frequency

United States

No known frequency has been reported for congenital SGS; the incidence of acquired SGS has greatly decreased over the past 40 years.

• In the late 1960s, when endotracheal intubation and long-term ventilation for premature infants began, the incidence of acquired SGS was as high as 24% in patients who required such care.
• In the 1970s and 1980s, estimates of the incidence of SGS were 1-8%.
• In 2000, Choi reported that the incidence of SGS had remained constant at the Children's National Medical Center in Washington DC, accounting for approximately 1-2% of the children who had graduated from the neonatal ICU (NICU).¹³
• Walner reported that, among 504 neonates who were admitted to the level III NICU at the University of Chicago in 1997, 281 were intubated for an average of 11 days; over a 3-year period, no patients developed SGS.¹⁴
• In 1996, a report from France also described no incidence of SGS in the neonatal population who were intubated with very small endotracheal tubes (2.5 mm internal diameter) in attempts to prevent trauma to the airway.

International

International frequency is the same as that of the United States.

Mortality/Morbidity

Patients can die if they have significant SGS that is left untreated. Difficulty breathing and exercise intolerance can occur with mild, moderate, or severe SGS.

Race

No racial predilection is noted.

Sex

Equal sex distribution is noted.

Age

SGS is observed more often in premature infants because they may require mechanical ventilation for other system or pulmonary problems secondary to their prematurity. The mechanical ventilation can result in airway trauma and, potentially, SGS.

Clinical

History

Children with subglottic stenosis (SGS) have an airway obstruction that may manifest in several ways.

• In neonates, SGS may manifest as stridor and obstructive breathing after extubation that requires reintubation. At birth, intubation in most full-term neonates should be performed with a 3.5-mm pediatric endotracheal tube. If a smaller-than-appropriate endotracheal tube must be used, narrowing of the airway may be present, which could suggest SGS.
• The stridor in SGS is usually biphasic. Biphasic stridor can be associated with glottic, subglottic, and upper tracheal lesions. Inspiratory stridor is usually associated with supraglottic lesions; expiratory stridor is usually associated with tracheal, bronchial, or pulmonary lesions.
• The level of airway obstruction varies depending on the type or degree of SGS. In mild SGS, only exercise-induced stridor or obstruction may be present. In severe SGS, complete airway obstruction may be present and may require immediate surgical intervention.
• Depending on the severity, SGS can cause patients to have decreased subglottic pressure and a hoarse or a weak voice. Hoarseness or vocal weakness can also be associated with glottic stenosis and vocal cord paresis or paralysis.
• Always assess the history of gastroesophageal reflux disease (GERD). If present, always evaluate GERD prior to surgical intervention. A child who eventually has a diagnosis of SGS often has a history of either laryngotracheal trauma or intubation and ventilation. Frequently, these patients were born prematurely, have bronchopulmonary dysplasia, and may require oxygen administration. The degree of pulmonary disease and the amount of oxygen the child requires may affect the ability to perform decannulation. Prior to surgical intervention, the child should not require a substantial oxygen supplementation.

Physical

A child's physical examination varies depending on the degree of SGS present.

• Perform a complete head and neck evaluation.
• Evaluate the child's initial overall appearance, including the following:
  • Comfort level
  • Presence of increased breathing difficulty, especially during periods of heightened emotion
  • Presence of suprasternal, substernal, or intracostal retractions
  • Presence of any nasal flaring
• Evaluate the child's voice.
  • Presence and nature of stridor
  • Abnormal or normal speaking voice
• Evaluate the child's neurological status.
• In the presence of tracheotomy, evaluate the patient's breathing while tracheotomy is occluded.
• Auscultate the child's lung field and neck to elicit any airway obstructive symptoms and to evaluate the status of their pulmonary function.
• Identify associated facial abnormalities such as cleft palate, choanal atresia, retrognathia, and facial deformities.

Causes

The cause of congenital SGS is in utero malformation of the cricoid cartilage.

The etiology of acquired SGS is related to trauma of the subglottic mucosa. Injury can be caused by infection or mechanical trauma, usually from endotracheal intubation but also from blunt, penetrating, or other trauma. Historically, acquired SGS has been related to infections such as tuberculosis and diphtheria. Over the past 40 years, the condition has typically been related to mechanical trauma.

Factors implicated in the development of SGS include the size of the endotracheal tube relative to the child's larynx, the duration of intubation, the motion of the tube, and repeated intubations. Additional factors that affect wound healing include systemic illness, malnutrition, anemia, and hypoxia.

Local bacterial infection may play an important roll in the development of SGS. GER may play an adjuvant role in the development of SGS because it causes the subglottis to be continually bathed in acid, which irritates and inflames the area and prevents it from correctly healing. A systemic or GI allergy may cause the airway to be more reactive, creating a greater chance of developing stenosis.

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