CONGENITAL SUBGLOTTIC STENOSIS

20-Mark Answer | RGUHS ENT Examination

1. DEFINITION

• A cricoid diameter of < 4 mm in a full-term neonate (normal: 4.5-5.5 mm)
• < 3.5 mm in a premature infant
• Present in an airway with NO prior history of endotracheal intubation, surgery, trauma, or other acquired cause

2. INCIDENCE AND IMPORTANCE

• Third most common congenital laryngeal anomaly, after laryngomalacia (1st) and vocal fold immobility (2nd)
• Constitutes only ~5% of all SGS (the vast majority are acquired)
• True incidence is underestimated because many affected neonates are intubated for respiratory distress at birth, thus technically converting to "acquired" or combined stenosis
• Down syndrome (Trisomy 21) has a high association with congenital SGS (elliptical cricoid)
• 22q11 deletion (DiGeorge syndrome) is associated with anterior glottic webs with subglottic extension

3. EMBRYOLOGY AND PATHOGENESIS

• Defective canalization of the cricoid cartilage and/or conus elasticus
• Failure of recanalization of the epithelial plug that temporarily obliterates the laryngeal lumen during the 2nd-3rd month of fetal life
• Associated chromosomal anomalies affecting cartilage development

Normal laryngeal development
          |
  8th-12th week: Epithelial lamina dissolves → normal lumen
          |
 ┌────────┴────────┐
Failure of         Cartilage
canalization      malformation
     |                 |
 Membranous      Cartilaginous
   type SGS         type SGS

4. PATHOLOGICAL CLASSIFICATION

A. MEMBRANOUS TYPE (Soft / Fibrous)

• Fibrous soft tissue thickening of the subglottic mucosa
• Caused by increased fibrous connective tissue or hyperplastic dilated mucous glands without inflammatory reaction
• Usually circumferential, narrowest area 2-3 mm below the true vocal cords
• May extend upward to involve the true vocal cords
• Better prognosis; may respond to endoscopic treatment

B. CARTILAGINOUS TYPE (Hard / Structural)

1. Thickened/deformed cricoid - a shelf-like plate of cartilage partially filling the concave inner surface of the cricoid, extending posteriorly as a solid rigid sheet, leaving only a small posterior opening (most common)
2. Elliptical/small cricoid - narrow transverse diameter (seen in Trisomy 21); small anteroposterior diameter
3. Trapped first tracheal ring - may produce anterior subglottic shelf and lateral narrowing; clinically variable
4. Anterior cricoid thickening - gross thickening of the anterior cricoid lamina

5. CLINICAL FEATURES

Severe stenosis (Grade III-IV):

• Respiratory distress at birth - cyanosis, use of accessory muscles
• Biphasic stridor (both inspiratory and expiratory) - due to fixed narrowing
• Requires immediate airway intervention

Mild to moderate stenosis (Grade I-II):

• Inspiratory stridor emerging weeks to months after birth (increased activity, higher ventilatory needs)
• Recurrent "croup" (recurrent laryngotracheobronchitis) - caused by superimposed mucosal edema from URTIs in an already narrow airway
• Child may be symptom-free between episodes
• Key clinical pearl (Dhingra/Hazarika): Recurrent or atypical "croup" in an infant under 3 months should raise suspicion for underlying SGS
• Infants usually become symptomatic within 3 months of birth due to increased activity and greater ventilation requirements
• Feeding difficulties, failure to thrive (in severe cases)

Congenital SGS
      |
 ┌────┴─────────┐
Severe          Mild-Moderate
(Grade III-IV)  (Grade I-II)
   |                |
Stridor at      Stridor with activity
birth           or URTI ("recurrent croup")
Cyanosis        Well between episodes
Resp distress   Symptoms emerge 1-3 months
   |                |
Immediate       Watchful waiting
intervention    + symptomatic Rx

6. DIAGNOSIS

A. History

• Onset, severity, progression of stridor
• Episodes of "croup" or respiratory distress
• Birth history - gestational age, intubation history (absence required for congenital SGS diagnosis)
• Family history, syndromic features (Down syndrome, 22q11)

B. Physical Examination

• Biphasic stridor (fixed obstruction)
• Subcostal/intercostal retractions
• Cyanosis in severe cases
• Presence of other syndromic features

C. Investigations

• Subglottic narrowing on AP view ("steeple sign")
• Useful initial screening

• Office-based assessment
• Assess vocal cord mobility, supraglottic anatomy, dynamic collapse
• Does NOT adequately visualize the subglottis

• Under general anesthesia
• Exact location of stenosis measured relative to vocal cords, tracheostome, and carina
• Normal tracheal rings above tracheostome are counted
• Passing endotracheal tubes of known sizes to size the stricture (Myer-Cotton grading)
• Assessment of vocal cord mobility
• Identifies associated anomalies (laryngeal clefts, tracheomalacia)

• Assess cartilaginous integrity
• Multi-level disease, associated anomalies
• Virtual bronchoscopy

• Flow-volume loops show characteristic flattening of inspiratory limb in fixed upper airway obstruction

7. GRADING - THE MYER-COTTON CLASSIFICATION

8. DIFFERENTIAL DIAGNOSIS

9. MANAGEMENT

• Patient's age and overall health
• Severity grade (Myer-Cotton)
• Type (membranous vs. cartilaginous)
• Associated congenital anomalies
• Length and location of stenosis

A. CONSERVATIVE (WATCHFUL WAITING)

• As the child grows, the airway lumen expands proportionally
• Vigorous management of URTIs:
  • Inhaled/oral/parenteral corticosteroids (reduce mucosal edema)
  • Nebulized racemic epinephrine (vasoconstriction, reduces edema)
  • Antibiotics as indicated
• Regular follow-up with repeat MLB
• Less than half of patients with congenital SGS require tracheotomy

B. ENDOSCOPIC MANAGEMENT

1. Balloon dilation - applies radial pressure to the airway lumen; sized by patient age; preferred over rigid dilation which applies shearing force
2. CO2 laser / Cold steel radial incisions - incisions at 12, 3, and 9 o'clock positions through scar while preserving cricoid cartilage
3. Intralesional steroid injection - triamcinolone/mitomycin-C; controversial evidence for efficacy
4. Mitomycin-C topical application - inhibits DNA/protein synthesis; reduces scar reformation; most effective on fresh/young scar

C. ANTERIOR CRICOID SPLIT (ACS)

• Weight >1500 g
• Failed extubation x2
• No supplemental O2 required for >10 days
• No acute respiratory illness
• No congestive heart failure
• Steroid and diuretic therapy not required for >10 days

D. LARYNGOTRACHEAL RECONSTRUCTION (LTR) - MAINSTAY OF SURGICAL TREATMENT

E. PARTIAL CRICOTRACHEAL RESECTION (PCTR / CTR)

• Decannulation rate: 98% for primary PCTR
• Decannulation rate: 94% for salvage PCTR after failed prior reconstruction

F. TRACHEOTOMY

• Placed between 2nd and 3rd tracheal rings ideally
• Smallest tube permitting adequate ventilation to minimize further injury
• Long-term tracheotomy in children leads to speech delay, tracheomalacia, suprastomal collapse

Congenital SGS
        |
 ┌──────┬─────────┬────────────┐
Grade I  Grade II  Grade III   Grade IV
   |        |       |               |
 Observe   LTR    Mild III:     Ant + Post
            +     Ant graft +   grafts +
           Ant    Post split    prolonged
           graft  ± Post graft  stenting
                  Severe III:   OR PCTR
                  Ant + Post
                  grafts
                  OR PCTR

10. OUTCOMES

• Grade I and II: >90% success with LTR (Scott-Brown)
• Grade III and IV: 80-90% success with LTR
• PCTR: ~98% decannulation for primary; ~94% for revision surgery
• Congenital SGS generally has better prognosis than acquired SGS
• The best chance for successful repair lies in the initial operation - repeat surgery is more complex

11. ASSOCIATED CONDITIONS

12. RECENT ADVANCES (2021-2026)

1. Multidisciplinary team (MDT) approach - now considered essential: otolaryngology, speech-language pathology, gastroenterology (GERD management), pulmonology, anesthesia, and cardiology as needed
2. Balloon dilation as primary endoscopic tool - preferred over rigid dilation due to radial pressure application; used even for Grade III stenosis to defer or avoid open surgery
3. Propranolol for subglottic hemangioma (key differential) - oral propranolol has become first-line, avoiding tracheotomy and open surgery
4. Tracheal transplantation - emerging research area for severe/complex laryngotracheal stenosis; still experimental
5. 3D-printed costal cartilage scaffolds - under investigation as graft substitute in LTR
6. Revision airway surgery - increasingly recognized challenge as children age post-reconstruction; unique anatomical and functional considerations
7. Single-stage LTR expanding - more centers performing SSLTR avoiding long-term tracheotomy; requires dedicated anesthetic expertise
8. Thulium and fiber-based CO2 lasers - improved accuracy and access to difficult sites compared to conventional CO2 laser delivery systems
9. GERD management - anti-reflux therapy routinely used perioperatively (though direct causal evidence remains controversial); uncontrolled GERD is associated with worse LTR outcomes
10. Genetic testing - increasing recognition of chromosomal/syndromic associations (Trisomy 21, 22q11) warrants genetic workup in all congenital SGS cases

13. SUMMARY TABLE (Exam Quick Reference)

REFERENCES

• Cummings Otolaryngology Head and Neck Surgery, 7th Ed. - Chapters 206, 209
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, 8th Ed., Vol 2 - Chapter 30
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, 8th Ed., Adult Vol - Chapter 76
• KJ Lee's Essential Otolaryngology, 11th Ed.
• Myer CM, O'Connor DM, Cotton RT: Proposed grading system for SGS based on endotracheal tube sizes. Ann Otol Rhinol Laryngol 1994;103:319
• Cotton RT: Management of SGS in infancy and childhood. Ann Otol Rhinol Laryngol 1978;87:649
• Kennedy AA, Smith MM. Subglottic Stenosis. Otolaryngol Clin North Am. 2026. PMID: 42128760
• Smith MM, Buck LS. Update on diagnosis and management of pediatric laryngotracheal stenosis. Expert Rev Respir Med. 2022. PMID: 36347385
• Dhingra PL: Diseases of Ear, Nose and Throat & Head and Neck Surgery
• Hazarika P: Textbook of ENT and Head & Neck Surgery

RGUHS Examination Tip: For a 20-mark answer on congenital SGS, examiners expect: definition with measurements, embryological basis, pathological classification (membranous vs. cartilaginous), Myer-Cotton grading with the diagram, clinical features, MLB as the gold standard for diagnosis, and a logical management plan by grade (watchful waiting → ACS → LTR → PCTR). Always mention that cartilaginous type is a contraindication to dilatation. Recent advances should include propranolol for hemangioma, MDT approach, and tracheal transplantation research.