Subglottic stenosis (SGS) is a respiratory condition marked by the narrowing of the airway just below the vocal cords. This restriction makes breathing difficult by physically constraining the passage for air moving into the lungs. While the severity of this narrowing can vary widely, the condition always presents a challenge to normal breathing. Medical and surgical interventions have advanced significantly, offering effective solutions for a stable, functional airway.
Defining Subglottic Stenosis
The subglottis is the portion of the larynx, or voice box, situated immediately beneath the glottis, which contains the vocal cords. Anatomically, this region extends downward about one centimeter from the vocal cords to the inferior border of the cricoid cartilage. This cartilage is distinctive because it forms a complete, non-expandable ring encircling the airway, making the subglottis the narrowest part of the upper respiratory tract, especially in children.
Stenosis occurs when scar tissue forms or the cartilage ring is malformed, constricting the airway lumen. This scar tissue, or fibrosis, develops from trauma or chronic inflammation in the subglottic lining. The rigid cricoid cartilage prevents the airway from expanding to compensate for the reduction caused by internal scarring.
The degree of narrowing determines the symptoms and guides treatment decisions. Severity is often measured using the Cotton-Myer grading system, which classifies the condition based on the percentage of airway obstruction. This system ranges from Grade 1 (less than 50% occlusion) up to Grade 4 (complete obstruction with no detectable lumen).
Causes and Risk Factors
Subglottic stenosis is broadly categorized into two types: congenital and acquired, each with distinct origins. Congenital SGS is present at birth and is generally considered a rare birth defect. This type results from an abnormal development of the cricoid cartilage during gestation, leading to an inherently smaller or abnormally shaped airway ring.
Acquired SGS is more common and develops later in life due to injury or inflammation. The most frequent cause, particularly in children, is prolonged or traumatic endotracheal intubation. Pressure from the breathing tube damages the subglottic lining, which heals by forming restrictive scar tissue. Historically, over 90% of acquired cases in children were secondary to intubation, especially in premature infants requiring critical care.
Other factors can increase the risk of developing acquired SGS. Chronic inflammation from conditions like gastroesophageal reflux disease (GERD) can irritate the subglottic mucosa, contributing to scarring. Systemic or autoimmune diseases, such as Granulomatosis with Polyangiitis (a form of vasculitis) or Sarcoidosis, can also cause inflammation and the build-up of scar tissue in the airway. In some instances, the cause remains unknown, and the condition is termed idiopathic subglottic stenosis.
Recognizing the Signs and Symptoms
The primary and most characteristic symptom is stridor, a high-pitched, harsh, or musical breathing sound. This noise is generated as air is forced turbulently through the narrowed airway segment.
Stridor is often inspiratory, meaning it is most noticeable when breathing in, though it can also be biphasic (heard on both inhalation and exhalation). Patients also experience dyspnea, or difficulty breathing, ranging from noticeable only during exertion to being present at rest in severe cases. These symptoms are frequently misdiagnosed as asthma or recurrent croup due to shared respiratory distress characteristics.
For infants, signs can include loud breathing, poor feeding, and a failure to gain weight properly. Recurrent episodes of croup-like cough, which involves a brassy, barking sound, are also common indicators of an underlying airway issue. Symptoms are often progressive and tend to worsen significantly with an upper respiratory infection, which causes even mild swelling to further compromise the already narrowed airway.
Treatment Approaches
Management of subglottic stenosis is tailored to the individual patient based on the severity of narrowing and symptoms. For very mild cases, particularly in infants with congenital SGS, conservative management involving careful observation may be appropriate. The airway may naturally enlarge as the child grows, potentially resolving the condition without intervention.
For moderate cases, or when symptoms begin to interfere with daily life, minimally invasive endoscopic procedures are often the first line of treatment. These procedures are performed through the mouth and involve techniques like balloon dilation, where a small balloon is inflated to stretch the scar tissue. Surgeons may also use a carbon dioxide (CO2) laser or a microdebrider to precisely remove scar tissue, sometimes followed by the application of anti-scarring medications like corticosteroids to prevent recurrence.
In severe cases, or when endoscopic methods fail to provide a lasting solution, open surgical reconstruction is necessary to create a stable, wider airway. The two main open surgeries are Laryngotracheal Reconstruction (LTR) and Cricotracheal Resection (CTR). LTR involves expanding the narrowed cricoid ring by surgically inserting cartilage grafts, often taken from the patient’s rib or ear, to permanently widen the airway. CTR is a more complex procedure that involves removing the scarred, narrowed section of the windpipe and then reconnecting the healthy segments, aiming to achieve a definitive repair.