Tuesday
Dec282010

Subglottic Stenosis

By Joe Edmonds, M.D.
see bottom of document for "Clinical Photographs"

Subglottic stenosis can be congenital or acquired. The congenital form is related to inadequate recanalization of the laryngeal lumen after completion of the normal epithelial fusion at the end of the third month of gestation. It can be membranous or cartilaginous. The membranous type often involves the true vocal cords. The cartilaginous type is usually shelf-like at the level of the cricoid and easy to diagnose endoscopically. In other instances the subglottic appearance is normal and only after "sizing" the airway can the appropriate diagnosis be made. The cartilaginous variety of stenosis is very rarely managed successfully with dilation or with laser techniques.

Acquired subglottic stenosis is related to an inconsistent cascade of events that causes 1-8% of infants to develop the condition after prolonged intubation. The most commonly affected area in these children is the cricoid. Proposed theories regarding the etiology and pathogenesis agree many factors are important (i.e. small cricoid, reflux, infection, tube movement and replacement, among others). All forms of subglottic stenosis can be assigned a grade. The most widely used scale is found in Table 1 (Cotton, 1199).

Table 1: Grading Scale of Laryngeal Stenosis

GRADE PERCENT OBSTRUCTION

Grade 1 

Less than 50%

Grade 2 

50 - 70%

Grade 3 

Greater than 90%, with some lumen

Grade 4

 100%

Diagnosis of the condition depends on the clinical examination, history, radiology evaluation, and endoscopic exam. Congenital subglottic stenosis usually presents very early in the child’s life with symptoms of airway distress. Acquired or less severe congenital cases often present with airway compromise after development of a URI. The stridor in these patients is biphasic. Abnormal or absent cry and hoarseness are present with laryngeal involvement. Feeding abnormalities and FTT syndromes may also be present. In the intubated child, the main clinical feature is the inability to extubate with apparently normal pulmonary function.

The lateral soft tissue x-ray is the single most important view in children. The high voltage A-P view and xeroradiography also have merit. A chest x-ray is essential. It is necessary to rule out pulmonary causes for respiratory compromise and to evaluate the effects of the upper airway anomaly on the lower airway.

Flexible examination of the dynamic larynx is essential in the workup of a child with possible upper airway pathology. However, it is insufficient to assess the nature and extent of a subglottic stenosis. Direct laryngoscopy under general anesthesia is the definitive diagnostic test or exam. A key portion of the DL is "sizing" the airway. In other words, it is necessary to obtain an accurate and reliable measurement of the airway. This can be done by passing sequentially larger bronchoscopes or endotracheal tubes through the stenotic area. The normal diameter of the full-term neonate is 4.5 to 5.0 mm. In a premature child the normal diameter is much smaller, and ranges from 3.5 to 4.0 mm.

Once the diagnosis of subglottic stenosis is made, the multitude of management possibilities must be examined for the needs of the individual pt. These possibilities include observation, systemic drug therapy, reintubation, tracheotomy, endoscopic surgical treatments, dilation and open surgical management. Each patient requires a tailor-made treatment plan consisting of one or many of these treatments. A brief review of these possibilities are discussed.

A minimally symptomatic child may be successfully managed with observation in anticipation of growth which will obviate the need for further therapy. All children should be started on medication that may alleviate exacerbating conditions. These may include antibiotics, antacid medication and GI promotility agents. Some children may require antireflux surgical management as well.

In the child who has failed extubation several times and in whom other possible etiologies (choanal atresia, severe laryngomalacia, tracheomalacia, oropharyngeal airway obstruction) have been ruled out, several possible treatment options exist. It may be appropriate to reintubate the child with edema of the subglottis. Treatment of the child might include antibiotics, antireflux medications and steroids. 

These children, and others with slightly more severe cases, may also be managed with a procedure pioneered by Drs. Cotton and Seid in the early 1980s, termed the anterior cricoid split. This procedure has become less widely used recently.  Many favor a more definitive initial strategy.  Advantages to proceeding with the anterior cricoid split include :avoiding the mortality risk of a tracheotomy dependent child; increased ability to develop spoken language; and simplifying the care needs. Many factors dictate the appropriate time to perform the procedure. Some are listed in Table 2 (Cotton, 1197). The procedure is simple. It involves exposure of the anterior trachea, followed by a vertical midline incision through the inferior two-thirds of the thyroid cartilage, the cricoid and the first two tracheal rings. The patient is left intubated for seven to ten days. If this does not result in successful extubation, endoscopic laser surgery, dilatation, repeat anterior cricoid split, tracheotomy and more extensive laryngotracheoplasty are possible next steps in the management of the child.

Table 2: Criteria for performing an Anterior Cricoid Split Procedure

·Extubation failure on at least two occasions, secondary to laryngeal anatomy

·Infant weight greater than 1500 gm

·No assisted ventilation for at least ten days

·Minimal supplemental oxygen requirements

·Absence of CHF

·Absence of URI

·No need for antihypertensives

Grade 1 lesions are usually managed with success endoscopically. Grade 2 lesions may be amenable to endoscopic or open treatments. Factors associated with endoscopic failure are included in Table 3(Cotton, 1199).

Table 3: Factors Associated with Endoscopic Failure

·Failure of previous endoscopic management

·Cartilage framework loss

·Both laryngeal and tracheal stenosis

·Circumferential scarring

·Scar in the interarytenoid area.

·Vertical scar greater than 1 cm

·Bacterial infection of the trachea

If extensive glottic and tracheal pathology are found (grades 3 and 4) primary tracheotomy should be performed. After tracheotomy is performed the child should be considered for open surgical management. A contraindication to open surgical management which deserves special mention is an incompetent glottic sphincter. In this setting, a reconstruction would case chronic aspiration. In contemporary practice, there are generally four modifications of the open procedure which together make up the Laryngotracheoplasty (LTP) armamentarium. These are: the anterior cricoid split; the anterior laryngofissure with augmentation; the combined anterior laryngofissure with augmentation and a division of the posterior cricoid lamina with augmentation; and the four quadrant division of the cricoid. The anterior cricoid split has already been reviewed. The other three LTP procedures will be briefly reviewed.

If the patient is found to have fibrocartilaginous subglottic stenosis without significant loss of cartilaginous support, laryngofissure and anterior autogenous costal cartilage graft is indicated. This procedure is similar to the anterior cricoid split but the defect is filled with autologous cartilage. The cartilage is most abundant and highest quality from the rib, and the graft is usually taken from the fifth right costal cartilage. When making the vertical incision in the thyroid, care is taken not to disturb the anterior commissure. The inferior aspect is dictated by the inferior aspect of the stenosis and may or may not reach the trach site. No attempt is made to remove the scar. After the incision, the tracheotomy is removed, and the patient is intubated with an appropriate size tube. The graft is made to be elliptical in shape, and is beveled at the edges (to prevent setting into the lumen). It is positioned and secured into place with the perichondrium surface facing the lumen. 

Anterior laryngofissure with augmentation is combined with a posterior cricoid split when the subglottic stenosis is found to coexist with: posterior glottic stenosis; upper tracheal stenosis with loss of cartilaginous support; or is associated with severe structural damage to the cricoid cartilage with complete stenosis. This procedure incorporates division of the midline posterior airway to the depth of the tracheoesophageal septum to the previously described anterior grafting technique. The posterior incision extends from the interarytenoid area to 1 cm below the cricoid. The posterior halves are separated 1 mm per year up to 10 mm. A stent is used to hold open the posterior surgical airway. Preferably, an Aboulker stent is wired to a Holinger style metal tracheotomy tube for the dual purpose of stenting and airway maintenance. The stent is positioned just superior to the arytenoids. When the procedure is done for combined glottic and subglottic stenosis, posterior cartilage grafting is performed. In this instance, the stent is left in place for one month. For moderate subglottic stenosis, posterior grafting is unnecessary as may be anterior grafting. The stent is left in for four months in this setting. I the case of substantial loss of cartilaginous framework, an anterior graft is often difficult to secure. In this situation, no tracheal closure is attempted and the stent is left in place for six months.

In the instance of grade 4 complete stenosis, especially congenital, a four quadrant division is indicated. Failure of other procedures with subsequent ossification may also lead one to this management option. In this procedure, the lateral incisions are made after the anterior and posterior ones. Cartilage grafting is unnecessary. The stents are left in for six months.

The last surgical management option to be discussed is a modified tracheal resection, or the cricotracheal resection with primary reanastomosis. It shares the same indications as the four quadrant procedure. It is gaining increased popularity. It involves resection of the cricoid in continuity with the upper trachea and subsequent anastomosis of the tracheal to the inferior thyroid cartilage. It is particularly applicable to posttraumatic management and caustic ingestions.

Works Cited

Cotton, Robin T. "Management and Prevention of Subglottic Stenosis in Infants and Children." Pediatric Otolaryngology. Ed. Charles Bluestone and Sylvan Stool. 2nd ed. Vol 2. Philadelphia: W.B. Saunders, 1990. 1194-1203.

References

Cotton, Robin T. "Management and Prevention of Subglottic Stenosis in Infants and Children." Pediatric Otolaryngology. Ed. Charles Bluestone and Sylvan Stool. 2nd Ed. Vol 2. Philadelphia: W.B. Saunders, 1990. 1194-1203.

Cotton, R. and Myer, C. Contemporary surgical management of laryngeal stenosis in children. Am J. Otolar. 5:360-368, 1984.

Cotton, R. and Seid, A. Management of the extubation problem in the premature child: Anterior cricoid split as an alternative tracheotomy. Ann. Otol. Rhinol. Laryng.. 89:508, 1980.

Gerwat, J. and Bryce, D. The management of subglottic laryngeal stenosis by resection and direct anastomosis. Laryng. 89:940-957, 1974.

Hawkins, D. Pathogenesis of subglottic stenosis from endotracheal intubation. Ann. Otol. Rhinol. Laryng. 96:116-117, 1987.

Holinger, L., et. al. Anterior cricoid split: the Chicago experience with an alternative to tracheotomy. Laryng. 97:19-23, 1987.

Clinical Photographs

Grade 1

 Grade 2

 

Grade 3

 

Lateral "Shelves"

Circumferential Scarring

Endotracheal tube injury to the glottis and subglottis, which can lead to subglottic or glottic scarring.