Subglottic stenosis is a congenital or acquired narrowing of the subglottic airway. It can be congenital, acquired, iatrogenic, or very rarely, idiopathic. It is defined as the narrowing of the portion of the airway that lies between the vocal cords and the lower part of the

cricoid cartilage The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...

. In a normal infant, the subglottic airway is 4.5-5.5 millimeters wide, while in a premature infant, the normal width is 3.5 millimeters. Subglottic stenosis is defined as a diameter of under 4 millimeters in an infant. Acquired cases are more common than congenital cases due to prolonged intubation being introduced in the 1960s. It is most frequently caused by certain medical procedures or external trauma, although infections and systemic diseases can also cause it.

Signs and symptoms

Symptoms may range from stridor during exercise to complete obstruction of the airway. In idiopathic cases, symptoms may be mistaken for

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...

. In congenital cases, symptoms occur soon after birth, and include difficulty breathing, stridor, and air hunger. If the vocal cords are affected, symptoms may include inability to make sound, and an unusual cry.

Causes

Most commonly, acquired cases are caused by trauma or certain medical procedures. The condition is more often caused by external trauma in adults. External injuries occur from vehicular accidents or clothesline injuries. Iatrogenic cases can occur from

intubation Intubation (sometimes entubation) is a medical procedure involving the insertion of a tube into the body. Patients are generally anesthetized beforehand. Examples include tracheal intubation, and the balloon tamponade with a Sengstaken-Blake ...

tracheostomy Tracheotomy (, ), or tracheostomy, is a surgical airway management procedure which consists of making an incision (cut) on the anterior aspect (front) of the neck and opening a direct airway through an incision in the trachea (windpipe). The r ...

, and an

endotracheal tube A tracheal tube is a catheter that is inserted into the Vertebrate trachea, trachea for the primary purpose of establishing and maintaining a patent airway and to ensure the adequate Gas exchange, exchange of oxygen and carbon dioxide. Many diffe ...

cuff pressure that is too high. 17 hours of intubation in adults and 1 week of intubation in neonates can cause the injury. Infants born prematurely can be intubated for a longer amount of time due to the fact that they have more flexible cartilage and a larynx located high in the airway. 90% of acquired cases in children are due to intubation, due to the ring of cartilage in the upper airway. Less commonly, infections, such as

bacterial tracheitis Tracheitis is an inflammation of the trachea. Although the trachea is usually considered part of the lower respiratory tract, in ICD-10 tracheitis is classified under "acute upper respiratory infections". Symptoms * Increasing deep or barking cro ...

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, i ...

histoplasmosis Histoplasmosis is a fungal infection caused by '' Histoplasma capsulatum''. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can ...

diphtheria Diphtheria is an infection caused by the bacterium '' Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks more than 10% of those diagnosed with the disease may die. Signs and s ...

, and

laryngeal papillomatosis Laryngeal papillomatosis, also known as recurrent respiratory papillomatosis (RRP) or glottal papillomatosis, is a rare medical condition in which benign tumors (papilloma) form along the aerodigestive tract. There are two variants based on the ag ...

can cause it. Systemic diseases, such as amyloidosis,

granulomatosis with polyangiitis Granulomatosis with polyangiitis (GPA), previously known as Wegener's granulomatosis (WG), is a rare long-term systemic disorder that involves the formation of granulomas and inflammation of blood vessels (vasculitis). It is a form of vasculitis ...

sarcoidosis Sarcoidosis (also known as ''Besnier-Boeck-Schaumann disease'') is a disease involving abnormal collections of inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph nodes. Less commonly a ...

, inflammatory bowel disease,

scleroderma Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas ...

relapsing polychondritis Relapsing polychondritis is a multi-systemic condition characterized by repeated episodes of inflammation and deterioration of cartilage. The often painful disease can cause joint deformity and be life-threatening if the respiratory tract, heart ...

, and

polyarthritis Polyarthritis is any type of arthritis that involves 5 or more joints simultaneously. It is usually associated with autoimmune conditions and may be experienced at any age and is not sex specific. Causes Polyarthritis is most often caused by an au ...

, can also cause it. Other causes may include aspiration of foreign bodies,

burn A burn is an injury to skin, or other tissues, caused by heat, cold, electricity, chemicals, friction, or ultraviolet radiation (like sunburn). Most burns are due to heat from hot liquids (called scalding), solids, or fire. Burns occur ma ...

s, and exposure to occupational hazards. Very rarely, the condition may also have no known cause, in which case it is known as idiopathic subglottic stenosis.

Mechanism

High cuff pressure or long-term intubation can cause damage to the tracheal mucosa, causing inflammation, ulceration, and breakdown of cartilage. When the injury heals, scarring occurs, narrowing the airway. Treatment-related risk factors include repeated intubation, the presence of a nasogastric tube, and size of an endotracheal tube. Person-related risk factors include systemic diseases, the likelihood of infection, and inadequate perfusion. Acid reflux may cause narrowing due to scarring resulting from stomach acid damaging the tracheal mucosa. 10-23% of causes result due to narrowing arising from granulomatosis with polyangiitis. In these cases, it is believed that this is more common in people under the age of 20. Around 66% of sarcoidosis cases involve the airway.

Diagnosis

CT scans and

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

(magnetic resonance imaging) can help in diagnosis. X-rays can determine the location and size of the narrowed airway portion.

Optical coherence tomography Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to capture micrometer-resolution, two- and three-dimensional images from within optical scattering media (e.g., biological tissue). It is used for medica ...

(OCT) can help observe the progression of the injury.

Esophageal pH monitoring Esophageal pH monitoring is the current gold standard for diagnosis of gastroesophageal reflux disease (GERD). It provides direct physiologic measurement of acid in the esophagus and is the most objective method to document reflux disease, assess t ...

can help detect any acid reflux, which can worsen the condition. An endoscope can be inserted and used to see the vocal cords, airway, and esophagus. Spirometry is a useful way to measure respiratory function. People affected by subglottic stenosis have a

FEV1 Spirometry (meaning ''the measuring of breath'') is the most common of the pulmonary function tests (PFTs). It measures lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry is h ...

of over 10. Subglottic stenosis is graded according to the

Cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...

-Myer classification system from one to four based on the severity of the blockage. Grade 1 is up to 50% obstruction, Grade 2 is 50-70% obstruction, Grade 3 is 70-99% obstruction, and Grade 4 is with no visible lumen. File:Subglottic stenosis 04.png, Grade 1 subglottic stenosis File:Subglottic stenosis 03.png, Grade 2 subglottic stenosis File:Subglottic stenosis 02.png, Grade 3 subglottic stenosis File:Subglottic stenosis 01.jpg, Grade 4 subglottic stenosis

Treatment

The goal of treatment is to relieve any breathing difficulty and to ensure that the airway remains open in the long term. In mild cases, the disease can be treated with endoscopic balloon dilation. In severe cases, open surgery is done. Owing to the risk of complications, tracheostomy is avoided if possible.

Surgery

In severe cases, the condition frequently recurs after dilation, and the main treatment is open surgery. There are three main surgical procedures that are used when treating subglottic stenosis. These include endoscopy, open neck surgery, and tracheotomy. Endoscopic procedures include dilation via

balloon A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and air. For special tasks, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour or rice), or light so ...

or rigid, incision via laser, and

stent In medicine, a stent is a metal or plastic tube inserted into the lumen of an anatomic vessel or duct to keep the passageway open, and stenting is the placement of a stent. A wide variety of stents are used for different purposes, from expandab ...

placement.

Other

In mild cases, such as cases with only granuloma or thin, web-like tissue, dilation is able to remove the lesion. In severe cases, dilation and laser treatment only works temporarily, and the condition frequently recurs. Repeated procedures, especially stents, come with the risk of increasing the damaged area. Also, laser resection has a risk of damaging the cartilage underneath. For this reason, surgery is typically done. In addition to surgery,

mitomycin The mitomycins are a family of aziridine-containing natural products isolated from ''Streptomyces caespitosus'' or ''Streptomyces lavendulae.'' They include mitomycin A, mitomycin B, and mitomycin C. When the name mitomycin occurs alone, it usually ...

can be applied topically and

glucocorticoid Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every verteb ...

s can be injected. Idiopathic cases are usually treated via endoscopic balloon dilation, and dilation may be improved by injecting corticosteroids. It is also the safest and main treatment in pregnant women. It allows dilation via noninvasive measures such as expanding a balloon catheter via ventilation.

Prognosis

The condition frequently recurs after dilation. The prognosis after surgery is good if it is done carefully to avoid complications.

Epidemiology

The condition has decreased in frequency over time, due to improved management of people on a ventilator. The condition occurs in around 1% of endotracheal tube users.

References

External links

{{DEFAULTSORT:Subglottic Stenosis Congenital disorders of respiratory system Larynx disorders Rare diseases