Subglottic stenosis (SGS) is a medical condition defined by the abnormal narrowing of the airway located just below the vocal cords. This restriction causes an obstruction that limits the amount of air moving into the lungs, making it a serious respiratory disorder. Because this narrowing affects the main breathing passage, the condition can range from causing mild difficulty breathing to a life-threatening airway blockage.
Understanding the Subglottis and Stenosis
The subglottis is the segment of the windpipe situated immediately beneath the vocal cords and extending downward to the first tracheal ring. It forms the transition zone between the voice box (larynx) and the trachea. This region is structurally unique because it is encased by the cricoid cartilage, which is the only complete ring of cartilage in the entire airway.
This anatomical feature makes the subglottis particularly susceptible to damage and subsequent narrowing. When inflammation or injury occurs, the cricoid ring prevents the tissue from swelling outward. This forces resulting scar tissue to grow inward, decreasing the airway’s diameter and physically obstructing airflow. For children, this area is the narrowest point of the entire airway, meaning even minor inflammation can significantly impair breathing.
Primary Causes of Subglottic Stenosis
Subglottic stenosis is categorized based on its origin, falling into two primary types: congenital and acquired. Congenital SGS is present at birth, often due to an irregularity in the formation of the cricoid cartilage ring during fetal development. This developmental issue results in an airway that is too small, though the exact cause of this anomaly is often unknown.
Acquired SGS is the more common form in adults and is frequently a consequence of medical intervention or trauma. The most significant cause is prolonged endotracheal intubation. Pressure from the tube against the delicate inner lining of the subglottis can cause tissue damage, ulceration, and a subsequent inflammatory response.
This inflammation triggers the formation of granulation tissue, ultimately leading to the development of dense scar tissue that constricts the airway. The risk of this injury increases significantly after approximately seven to ten days of intubation, though damage can occur much sooner. Other acquired causes include external trauma to the neck, autoimmune conditions like Granulomatosis with Polyangiitis, and persistent irritation from severe gastroesophageal reflux.
Recognizing the Signs and Diagnostic Methods
The symptoms of subglottic stenosis are directly related to the degree of airway narrowing and often become more noticeable during physical exertion or a respiratory infection. The most recognizable symptom is stridor, a high-pitched, harsh, and noisy breathing sound heard as the patient inhales. Patients may also experience shortness of breath, persistent hoarseness, or recurring croup-like illnesses that do not respond to standard treatments.
In infants and children, additional signs include respiratory distress, such as the skin pulling in between the ribs with each breath, and difficulty feeding or poor weight gain. Because SGS symptoms can be mistaken for asthma or chronic bronchitis, a specialized evaluation is necessary for an accurate diagnosis. The diagnostic process begins with a detailed medical history and a physical examination to assess breathing quality.
Imaging studies, such as a Computed Tomography (CT) scan, can provide cross-sectional pictures of the airway to visualize the narrowing. The definitive diagnosis and assessment of severity are achieved through an endoscopic procedure, such as a laryngoscopy and bronchoscopy, performed under general anesthesia. During this procedure, the obstruction is precisely graded using the Myer-Cotton classification system. This system divides the stenosis into four grades based on the percentage of the airway lumen that is obstructed, ranging from Grade I (0–50% obstruction) to Grade IV (100% obstruction).
Current Approaches to Treatment
The management of subglottic stenosis is determined by the specific cause, the length of the narrowed section, and the severity grade. For mild cases, particularly Grade I, the condition may only require observation with monitoring. Minimally invasive, endoscopic techniques are often the first line of treatment for less severe strictures.
These procedures may involve using a specialized laser to remove scar tissue or employing a balloon to dilate and stretch the constricted area. Steroids may also be injected directly into the scar tissue to reduce inflammation and prevent further scarring. For more advanced stenosis that is unresponsive to endoscopic methods, open surgical reconstruction is necessary to expand the airway’s diameter.
The two main open procedures are Laryngotracheal Reconstruction (LTR) and Partial Cricotracheal Resection (PCTR). LTR involves surgically widening the airway by inserting a graft, often cartilage taken from the rib, to keep the passage open. PCTR is a more extensive procedure where the surgeon removes the scarred, narrowed section of the cricoid cartilage and then reconnects the healthy segments of the airway.