Subglottic Stenosis (SGS)

What is Subglottic Stenosis (SGS)?

Subglottic stenosis (SGS) is a narrowing of the lowest part of the voice box, just below the vocal cords. This area is unique, as it is the smallest part of the entire airway at the time of birth, and the only part of the airway that is surrounded by a complete ring of cartilage, called the cricoid cartilage. These factors make this part of the voice box particularly prone to injury from a breathing tube at birth or later in childhood, as well. This area can be small at the time of birth (congenital SGS), which generally becomes apparent early in childhood. The narrowing can be mild, moderate, or severe, and if moderate or severe the patient may need to have a tube, called a tracheostomy tube, inserted in the neck below the obstruction to ensure comfortable and safe breathing.

A grading system is used to measure the severity of the SGS condition:

• Grade 1 -  0 - 50% narrowing
• Grade 2 - 50 – 70% narrowing
• Grade 3 – 70 – 99% narrowing
• Grade 4 – No opening/complete obstruction

Generally, Grade 1 SGS patients will display no symptoms or very mild and many children with this level of stenosis will not have problems and may never be diagnosed. Grade 2 SGS patients often have some symptoms, the severity of which can range from mild difficulty with strenuous physical activity to some more severe symptoms at the higher end of that spectrum. Many children with Grade 2 SGS can carry on for some time without the need for intervention, but often need the stenosis repaired. Grade 3 and 4 SGS patients usually present with symptoms significant enough to warrant intervention, and many children in this group need tracheostomies to safely breathe, before they ever get to the airway specialist.

Typical Symptoms of Subglottic Stenosis (SGS)

• Stridor (squeaky, noisy, or wheezy breathing), which worsens with crying or activity
• Recurrent croup that gets worse with age, not better
• Retractions (pulling of neck, chest, or belly muscles to breath)

History more frequently associated with SGS:

• History of prolonged intubation or multiple intubations
• Genetic/chromosomal syndromes (including Down Syndrome)

How is Subglottic Stenosis (SGS) Diagnosed?

SGS should be diagnosed by an otolaryngologist (ENT) who is trained in complex airway evaluation and management. A detailed history is performed in the clinic, and generally the voice box is viewed with a small, flexible fiberoptic camera, called a Laryngoscope, which can assess vocal cord movement and any other abnormalities at and above the vocal cords. Sometimes the subglottis can be seen with this camera, but this view is not good enough to fully diagnose SGS. If the otolaryngologist feels that the child is high enough risk, then he/she may recommend looking at the subglottis with a camera in the operating room, which gives the surgeon an ideal view and allows them to fully diagnose and measure the SGS.

How is Subglottic Stenosis (SGS) Treated?

Depending on how the SGS looks, it may be treated endoscopically through the mouth, with a camera and long instruments, possibly with a balloon to dilate it open. Some medications can be applied as well to try and help keep the stenosis from re-scarring. Once an endoscopic approach has begun, these patients usually need repeat evaluations and dilations in the operating room to ensure that the area stays open enough for the child to breath easily.

Aerodigestive Evaluation

If SGS does not respond to dilation and keeps re-scarring, or if it is thick and hard and the surgeon is not able to treat it endoscopically, there are more thorough options to surgically treat SGS. This begins with the aerodigestive evaluation to ensure that this surgery will be successful. The surgery for SGS, called Laryngotracheal Reconstruction (LTR), is highly successful if certain conditions are ruled out or treated before the operation. Patients who are undergoing an LTR must be tested for these conditions, which is performed by members of the multidisciplinary Aerodigestive Team. This team includes an otolaryngologist (airway surgeon), a pediatric pulmonologist (lung doctor), a pediatric gastroenterologist (esophagus, stomach, and intestines doctor), a speech and language pathologist (feeding and swallowing specialist), and a pediatric general surgeon. The Aerodigestive Team also provides social work and case management support.

All these specialists meet with the family and the patient during a single clinic visit, and once completed, collaborate to discuss their collective view of the patient’s needs.

Conditions that can affect success of an LTR :

• Gastroesophageal reflux (GERD) – stomach acid coming up the esophagus and sometimes into the throat
• Eosinophilic esophagitis (EoE) – allergic inflammation of the esophagus
• Dysmotility conditions – problems with the way feeds move through the gut
• Chronic lung disease – from prematurity, asthma, chest wall deformities, and many other conditions
• Other airway abnormalities – tracheomalacia, vocal cord paralysis, and others
• Dysphagia and Aspiration – food going into the airway during swallowing
• Bacterial cultures – from the nose and the lower airways

Triple Endoscopy

For SGS, the patient will undergo the full aerodigestive evaluation, and will likely be booked for “Triple Endoscopy”, in which the otolaryngologist, pulmonologist, and gastroenterologist once again team up in the operating room to place cameras in their respective areas of specialty to gather information about all of the above possible conditions. During these procedures, the patient is under general anesthesia, usually breathing on their own. Sometimes a tube must be placed in the airway for parts of the procedures.

• Rigid Microlaryngoscopy and Bronchoscopy: Performed by the pediatric otolaryngologist/airway surgeon, with long rigid instruments through the mouth. These instruments provide a very detailed view of the voice box and trachea, and can pass into the upper part of the lower airways, where the lungs begin. This is generally used to evaluate the airway’s size, shape, and patency (how “open” it is). Rigid instruments also allow for intervention, if necessary.
• Flexible Bronchoscopy: Performed by the pediatric pulmonologist, this flexible camera is very long and narrow, and can be inserted through the nose to enter through the voice box, or through a breathing tube or a tracheostomy tube. This lets the doctors examine the airways lower down in the lungs, searching for any anatomic abnormalities, and allowing them to get samples of mucus from the lower airways, on which several helpful lab tests can be run.
• Esophagogastroduodenoscopy (EGD): Performed by the pediatric gastroenterologist, with a long flexible camera inserted through the mouth and into the esophagus, stomach, and upper intestines. This allows visual examination of the lining of these structures, and the GI doctor will biopsy various areas from each of these structures, giving more information about the health of the upper digestive tract.

Based on the results of the testing and the evaluations from the Aerodigestive Team, the patient may need treatment for a while and a re-evaluation, or they may be considered ready to undergo Laryngotracheal Reconstruction. If it is determined that surgery is the best option, the team discusses the surgical procedure in detail with the family.

Laryngotracheal Reconstruction Surgery  

This surgery involves taking a piece of cartilage from somewhere else in the body, usually a rib, and carving it into a graft (or grafts) that can be inserted to make the airway larger. This can be placed in the front of the airway, the back of the airway, or both, depending on the needs of the patient. The procedure can be performed with or without a tracheostomy tube, and the airway surgeon will decide in advance whether to complete the surgery with a tracheostomy left in place. Generally, a patient undergoing LTR who did not have a tracheostomy tube in advance will not have one afterwards, and often, a tracheostomy opening is closed during the procedure; this is called a “Single Stage” LTR. Sometimes, a tracheostomy that was in place before the surgery is left in place afterwards for healing purposes; this is called a “Double Stage” LTR, referring to the brief second procedure to remove the stent.

What is the Recovery Like After LTR Surgery?

After LTR, the patient will be in the Intensive Care Unit (ICU) for at least a few days, depending on the situation. The amount of time spent in the ICU is dependent on many factors and will be decided based on the details of surgery and the needs of the child. After about a week, the airway surgeon will look at the airway endoscopically to see how well it is healing, and to determine next steps. Endoscopy (in the OR under anesthesia) is usually done weekly for a few weeks to ensure good healing and to address any “touch-ups” that need to be done. Once the surgeon feels the airway is healing well, endoscopy is spaced out further and further, eventually occurring yearly to ensure that the airway is growing with the child.

LTR can affect swallowing at times, especially a posterior graft and especially in the weeks following the surgery. Swallow testing is performed for most kids before and after LTR, to ensure that they are not aspirating (food and liquid going down the wrong way) when they swallow. The voice may also be affected by an LTR, depending on the details of the procedure the child needs. Airway surgeons try to balance the breathing and voice needs of patients, but if one of these needs to be compromised, it is the voice, which could result in hoarseness after the procedure. This hoarseness may be lifelong, but if it means a safe airway and no tracheostomy tube, this is considered an acceptable outcome. Sometimes this hoarseness can be addressed when the child gets older and the airway is fully grown.

Success rates in treating subglottic stenosis are very high, whether treated endoscopically or through  Laryngotracheal Reconstruction. A vast majority of children can have the tracheostomy tube removed, and almost all can grow into adulthood with minimal or no symptoms.