Idiopathic Airway or Subglottic Stenosis: Symptoms and Treatment

Introduction

Idiopathic airway stenosis is the obstruction of the airway in one of the sections of the larynx called the subglottis. When narrowing occurs in this subglottis, the airway is obstructed, and this condition is called subglottic stenosis. This condition is often accompanied by inflammation and the formation of scar tissue, leading to restricted airflow. The term idiopathic subglottic stenosis (iSGS) is used when the underlying cause of the condition remains unknown to medical professionals. This article will delve into detail into the idiopathic type of airway or subglottic stenosis called idiopathic subglottic stenosis.

What Is Idiopathic Subglottic Stenosis?

Idiopathic subglottic stenosis refers to a condition that is characterized by the narrowing of the airway in the throat that causes obstruction in the airway. The term idiopathic subglottic stenosis itself mentions what it stands for. Idiopathic means unknown cause; subglottic is the lowest part of the larynx (voice box); and stenosis means narrowing. Therefore, idiopathic subglottic stenosis simply means a condition in which the subglottis becomes narrow, and the cause remains unknown. The larynx is made up of three parts, supraglottis, glottis, and subglottis, and it helps in breathing, talking, and swallowing. If any of its parts get damaged, its functions will also be affected, and this is what happens in idiopathic subglottic stenosis.

How Rare Is Idiopathic Subglottic Stenosis?

Idiopathic subglottic stenosis is more common in women than in men. In women, the ages between 30 and 50 are the most common ages at which this disease occurs. However, there is evidence that idiopathic subglottic stenosis is reported in women younger than 30 years of age too. Among the other types of subglottic stenosis (congenital and acquired), idiopathic subglottic stenosis accounts for only 15 percent. Because of its low percentage, it is considered rare. Furthermore, the exact percentage of incidence and prevalence is not known because there are many cases of idiopathic subglottic stenosis that are not reported because they are either misdiagnosed or undiagnosed.

What Are Idiopathic Subglottic Stenosis Symptoms?

The symptoms of idiopathic subglottic stenosis are listed below:

• Asthma-Like Symptoms: It resembles asthma in symptoms. For example, the affected individual will have shortness of breath during activities. If the patients’ asthmatic-like symptoms do not improve with asthma treatment, they should be screened for idiopathic subglottic stenosis. It could also be misdiagnosed as other respiratory diseases, such as recurrent bronchitis or chronic pulmonary obstructive disease.

• Sound With the Breathing: As the larynx, or voice box, got obstructed in this disease, breathing became associated with a high pitch musical sound called stridor. Hence, during each breath of the affected individual, the stridor will be heard.

• Change in Voice: The affected person’s voice will either change or there will be a vocal roughness.

How Is Idiopathic Epiglottis Stenosis Diagnosed?

The diagnostic methods are explained below.

1. History and Physical Examination: A thorough patient history and physical examination are important initial steps in assessing the symptoms and identifying potential risk factors. In the case of iSGS, patients are typically Caucasian women aged 30 to 60 years. Common symptoms include shortness of breath, stridor, chronic cough, and wheezing, which may be present for several months to years before diagnosis.

2. Serologic Testing: Certain markers, such as antineutrophil cytoplasmic antibodies (ANCA) and angiotensin-converting enzyme (ACE) levels, can be checked with serologic testing. These tests help evaluate for possible underlying autoimmune or inflammatory conditions associated with subglottic stenosis.

3. Pulmonary Function Tests: Pulmonary function tests can provide valuable information about lung function and the presence of airway obstruction. In the case of iSGS, the flow-volume loop may reveal fixed upper airway obstruction, even in the presence of preserved muscle strength and patient effort. A reduction in maximal voluntary ventilation may also be observed.

4. Imaging Studies:

a. Chest X-ray: While limited in diagnosing iSGS, a chest X-ray may be performed to rule out other potential respiratory diseases.

b. Chest and Neck CT: High-resolution CT (computed tomography) with 3D reconstruction or virtual bronchoscopy (VB) is regarded as being extremely helpful and crucial in diagnosing and managing iSGS. This imaging technique allows for detailed visualization of the airway, including the characteristics and type of stenosis (concentric, complex, hourglass, etc.).

c. Dynamic Expiratory CT: In some cases, dynamic expiratory CT may be used to identify airway collapse due to associated tracheomalacia.

5. Endoscopic Evaluation: Endoscopic examination, either laryngoscopy or bronchoscopy, is considered the gold standard for diagnosing iSGS and planning appropriate management strategies. Flexible endoscopic evaluation aids in identifying the location, scope, and complexity of the stenosis, among other fundamental characteristics. It classifies strictures as simple if they are concentric and web-like, measuring less than one cm in length without cartilage involvement, and complex if they are associated with structural defects.

6. Grading Systems: Two commonly used grading systems, the Myer-Cotton system, and the McCaffrey system, are employed to classify the severity and location of central airway stenosis. This grading system aids in prognosis prediction and treatment planning.

7. Additional Procedures: Sometimes, radial probe endobronchial ultrasound with a balloon is used to measure the thickness of the tracheal mucosa's lamina propria, find out how big and complicated the stenosis is, and look at the structure of cartilaginous rings. This can help differentiate iSGS from other conditions, such as relapsing polychondritis.

Who Treats Idiopathic Subglottic Stenosis?

An otolaryngologist treats idiopathic subglottic stenosis in the majority of cases, but for comprehensive and effective care, a multidisciplinary team with interventional pulmonology, otolaryngology, thoracic surgery, and anesthesiology specialists is also necessary.

How to Treat Idiopathic Subglottic Stenosis?

Mild cases that do not show symptoms may not require immediate treatment and can be periodically observed for symptom development or further narrowing. However, for symptomatic cases, the following treatment options will be considered:

• Endoscopic Dilation With or Without Incisional Techniques and Steroid Injection: This is performed as an outpatient procedure under general anesthesia. It involves dilating the narrowed area using a balloon or rigid bronchoscope. Incisions may be made to reduce trauma. Repeat procedures are typically required every 9 to 12 months. Endoscopic dilation provides temporary relief but may have a high recurrence rate, requiring additional treatments.

• In-Office Transcutaneous Steroid Injections: This is done in patients who can tolerate some airway swelling. It involves injecting steroids directly into the inflamed area through the skin of the neck. Multiple injections are usually required, spaced a few weeks apart.

• The Maddern Procedure: This is a relatively new endoscopic procedure involving scar removal and the placement of a split-thickness skin graft from the thigh. Its effectiveness and long-term outcomes are still being studied, and it is recommended for patients who do not respond to other treatments.

• Cricotracheal Resection (CTR) With Primary Reconstruction: This is a more invasive procedure where the narrowed section of the windpipe is removed, and the ends are rejoined. It is typically performed on patients with difficult-to-control inflammation or complications from previous surgeries. The success rate is approximately 75 percent, but there is a risk of voice changes and recurrence.

• Surgical Procedures: Surgical procedures include endoscopic resection (with prolonged medical therapy afterward) or open neck surgery with resection and reconstruction of the affected tracheal segment. During surgery for ISS, Triamcinolone is injected into the stenotic mucosa. Then, the stenotic lesion is vaporized with a CO2 (carbon dioxide) laser, and Mitomycin C is put on the area. Research that appeared in laryngoscope in 2014 supported this strategy. Typically, same-day discharge follows the surgery under general anesthesia.

• Medications: Medications such as corticosteroids can be used to treat inflammation associated with idiopathic subglottic stenosis, either inhaled, injected, or taken orally. The medicines include inhaled Glucocorticoids, Trimethoprim-Sulfamethoxazole, and proton-pump inhibitors.

• Anti-reflux Therapy: This is for gastroesophageal reflux disease (GERD) and has shown improvement in certain cases, often combined with dietary and lifestyle changes.

Conclusion

To conclude, any symptom related to breathing should not be ignored. No medicine should be taken on its own if symptoms like difficulty breathing or shortness of breath persist. Idiopathic subglottic stenosis is one of the rare diseases that can be left undiagnosed due to its similarities in symptoms with other respiratory diseases. Therefore, knowledge about this disease can help an individual know it better.