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ORGAN SYSTEMS Otolaryngeal system (ENT)

Subglottic stenosis

Narrowing of upper airway between the vocal folds and the lower border of the cricoid cartilage.

Narrowing of upper airway between the vocal folds and the lower border of the cricoid cartilage.


Anatomy

Subglottic lumen:

  • Normal: 4.5-5.5 mm (term neonate) or 3.5 mm (premature neonate)
  • Narrow ≤ 4 mm (in term neonate)
Subglottic stenosis, sagittal view. | Aravena, C., Almeida, F. A., Mukhopadhyay, S., Ghosh, S., Lorenz, R. R., Murthy, S. C., & Mehta, A. C. (2020). Idiopathic subglottic stenosis: a review. Journal of thoracic disease, 12(3), 1100–1111. https://doi.org/10.21037/jtd.2019.11.43

Aetiology

Congenital subglottic stenosis:

No history of endotracheal intubation or any other acquired cause of the stenosis.
  • Pallister Killian syndrome: Tetrasomy 12p mosaicism and presents phenotypically with multisystem morphologic defects involving the respiratory system and progressive subglottic stenosis

Acquired subglottic stenosis:

More common than congenital due to the introduction of prolonged intubation in the 1960s, and does not improve with time.
  • Trauma (M/C cause of the acquired subglottic stenosis)
    • External trauma (common in adults): Roadside accidents and clothesline injuries.
    • Internal trauma: Iatrogenic, secondary to endotracheal intubation (90% cases in children due to completely cartilaginous ring in upper airway and the pseudostratified, ciliated, columnar respiratory epithelium with loose areolar tissue)

Idiopathic subglottic stenosis (very rare):

Characterized by circumferential stenosis in the subglottic region and upper trachea. Signs and symptoms range from recurrent croup and exertional stridor to complete airflow obstruction requiring tracheostomy. Symptoms of idiopathic subglottic stenosis can be misinterpreted as asthma. When asthma medication fails to treat symptoms, the patient is diagnosed with an endoscopic evaluation.
Idiopathic Subglottic Stenosis in a 55-year-old female. Note concentric web-like nature of the lesion. | Aravena, C., Almeida, F. A., Mukhopadhyay, S., Ghosh, S., Lorenz, R. R., Murthy, S. C., & Mehta, A. C. (2020). Idiopathic subglottic stenosis: a review. Journal of thoracic disease, 12(3), 1100–1111. https://doi.org/10.21037/jtd.2019.11.43

Clinical features

In congenital subglottic stenosis, symptoms usually appear shortly after birth. In acquired subglottic stenosis, there is a history of laryngeal insult, and symptoms usually occur 3 to 4 weeks after the insult.

  • Vocal cord involvement: Biphasic stridor, abnormal cry, aphonia, or hoarseness
  • Laboured breathing: Dyspnea, air hunger, Suprasternal, intercostal, and diaphragmatic retractions

Case study:


Diagnosis

Pulmonary function test:

Flow-volume loop reveals fixed upper airway obstruction when patients develop severe stenosis. This observation is also associated with a reduction in maximal voluntary ventilation despite preserved muscle strength and patient effort
Flow-volume loop is demonstrating fixed upper airway obstruction [Inner loop]. Dots denote predicted values. Outer loop depicts near normalization of the flow rates following appropriate treatment. | Aravena, C., Almeida, F. A., Mukhopadhyay, S., Ghosh, S., Lorenz, R. R., Murthy, S. C., & Mehta, A. C. (2020). Idiopathic subglottic stenosis: a review. Journal of thoracic disease, 12(3), 1100–1111. https://doi.org/10.21037/jtd.2019.11.43

Imaging:

Locate exact location and length of stenotic segment
  • Computed tomography (CT)
  • Magnetic resonance imaging (MRI)
Axial (A,B), coronal (C) and sagittal (C) CT scan of the trachea depiction Subglottic Stenosis. | Aravena, C., Almeida, F. A., Mukhopadhyay, S., Ghosh, S., Lorenz, R. R., Murthy, S. C., & Mehta, A. C. (2020). Idiopathic subglottic stenosis: a review. Journal of thoracic disease, 12(3), 1100–1111. https://doi.org/10.21037/jtd.2019.11.43

Optical coherence tomography (OCT):

Minimally invasive endoscopic imaging modality capable of monitoring the progression of subglottic mucosal injury. OCT and texture analysis help in the early detection of mucosal injury, which helps with better management of the airway and limits its progression to stenosis.

Endoscopic examination:

Direct endoscopic visualization with flexible fiberoptic endoscopy assesses the dynamics of the vocal cord function and the upper airway plus the esophagus. The rigid telescope carries importance in children for better visualization of the small larynx.

Gastroesophageal reflux disease (GERD) evaluation:

Gastroesophageal and gastrolaryngopharyngeal reflux plays a role in the exacerbation of subglottic stenosis and adversely affect the successful outcomes of laryngotracheal outcomes
  • 24-hour oesophageal pH probe using dual-probe technique (M/reliable)

Meyer-Cotton classification:

  • Grade 1 stenosis: Lumen obstruction < 50%
  • Grade 2 stenosis: Lumen obstruction 51-70%
  • Grade 3 stenosis: Lumen obstruction 71-99%
  • Grade 4 stenosis: Complete lumen obstruction

Management

Prevention:

Avoidance of tracheostomy in patients with subglottic stenosis is paramount and this is possible by advances in balloon dilation and endoscopic cricoid split techniques. Tracheostomy decannulation can be more likely with laryngotracheal reconstruction and cricotracheal resection.

Surgical management:

There are 3 main surgical approaches for subglottic stenosis, including endoscopic, open neck surgery, and tracheotomy. The goal of these approaches is to improve the patency of the airway in the long term and avoid dyspnea symptoms.

Endoscopic dilation:

Endoscopic dilation is ideal due to being non-invasive
  • Balloon or rigid dilation
  • Radical incision using CO2-laser and scar excision using a cold knife, without dilation
  • Endoscopic stent placement
  • Adjunctive therapies (for endoscopic surgery): Topical mitomycin-C and glucocorticoid injection. Mitomycin has antifibrogenic and antineoplastic activity.

Tracheostomy:

In an infant born with subglottic stenosis, traditional management is to do tracheostomy and access the child’s airway every 3 months to decide for the need for reconstructive surgery. The second option is to perform anterior or posterior cricoid split under general anesthesia to enlarge the cricoid lumen.

Laryngotracheal reconstruction:

Optimal treatment for acquired subglottic stenosis

Separate incision above tracheostomy at level of cricoid is made, and larynx is exposed from the hyoid above to the tracheostomy below. The lumen is entered above the superior thyroid notch, and the larynx is incised strictly in the midline. The graft is taken from costal cartilage and inserted to widen the cricoid ring. A silastic stent is used to prevent the collapse of the graft. During the closure of the incision, it is very important to oppose the anterior commissure accurately.

  • Evaluation of swallowing is a must before airway reconstruction to avoid the risk of aspiration postoperatively.

Summary:

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