Subglottic stenosis is a

congenital A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

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 sit ...

. 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 or autoimmune 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 common 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 wh ...

. 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. Most commonly, intubation refers to tracheal intubation, a procedure during which an endotracheal tube is inserted into the trachea to supp ...

tracheostomy Tracheotomy (, ), or tracheostomy, is a surgical airway management procedure which consists of making an incision on the front of the neck to open a direct airway to the trachea. The resulting stoma (hole) can serve independently as an airway ...

, and an

endotracheal tube A tracheal tube is a catheter that is inserted into the trachea for the primary purpose of establishing and maintaining a patent airway and to ensure the adequate exchange of oxygen and carbon dioxide. Many different types of tracheal tubes are a ...

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,

tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

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 bacteria, bacterium ''Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild Course (medicine), clinical course, but in some outbreaks, the mortality rate approaches 10%. Signs a ...

, 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 ...

can cause it. Systemic diseases, such as

amyloidosis Amyloidosis is a group of diseases in which abnormal proteins, known as amyloid fibrils, build up in tissue. There are several non-specific and vague signs and symptoms associated with amyloidosis. These include fatigue, peripheral edema, weigh ...

granulomatosis with polyangiitis Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis (WG), after Nazi German physician Friedrich Wegener, is a rare, long-term, systemic disorder that involves the formation of granulomas and vasculitis, inflammatio ...

sarcoidosis Sarcoidosis (; also known as Besnier–Boeck–Schaumann disease) is a disease involving abnormal collections of White blood cell, inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph n ...

inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine, with Crohn's disease and ulcerative colitis (UC) being the principal types. Crohn's disease affects the small intestine and large intestine ...

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 systemic disease characterized by repeated episodes of inflammation and in some cases deterioration of cartilage. The disease can be life-threatening if the respiratory tract, heart valves, or blood vessels are affect ...

, and polyarthritis, 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, electricity, chemicals, friction, or ionizing radiation (such as sunburn, caused by ultraviolet radiation). Most burns are due to heat from hot fluids (called scalding), soli ...

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 scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

s and

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

(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 a high-resolution imaging technique with most of its applications in medicine and biology. OCT uses coherent near-infrared light to obtain micrometer-level depth resolved images of biological tissue or oth ...

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

Esophageal pH monitoring In gastroenterology, 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 ...

can help detect any acid reflux, which can worsen the condition. A laryngoscopy or an endoscope can be inserted and used to see the vocal cords, airway, and esophagus/trachea. 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 (), first recorded in ancient India, 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 ...

-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 membrane bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. For special purposes, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour or rice), ...

or rigid, incision via laser, and

stent In medicine, a stent is a tube usually constructed of a metallic alloy or a polymer. It is inserted into the Lumen (anatomy), lumen (hollow space) of an anatomic vessel or duct to keep the passageway open. Stenting refers to the placement of ...

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 Secondary metabolite, natural products isolated from ''Streptomyces caespitosus'' or ''Streptomyces lavendulae.'' They include mitomycin A, mitomycin B, and mitomycin C. When the name mitomycin ...

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 vertebra ...

s can be injected. Steroid injections may be used as an initial treatment, or as an on-going maintenance treatment. The treatment involves injecting a steroid through your neck into your airway. The doctor will use local anesthesia to numb the neck, airway and nose. Typically, people who have this treatment have a series of injections every four to six weeks. Idiopathic cases are usually treated via endoscopic balloon or laser dilation, and dilation may be improved by injecting

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...

s. Endoscopic balloon dilation is 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. Subglottic stenosis is a rare condition, affecting 1 in every 400,000 people. Idiopathic subglottic stenosis is even more rare, approximately 15-19% of all cases of subglottic stenosis are idiopathic and the vast majority of cases are found in women. The exact incidence and prevalence is unknown because people may go undiagnosed or misdiagnosed, determining the true frequency of idiopathic subglottic stenosis in the general population is difficult.

References

External links

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