Stridor

Congenital stridor, top 3 causes: #1 laryngomalacia, #2 vocal cord paralysis, #3 congenital subglottic stenosis/web. Flexible airway endoscopy is the best initial diagnostic procedure for evaluation of congenital stridor.

• Croup
  • Doubt if pt <4 months
  • Parainfluenza, influenza, RSV
• Tonsillitis
• Epiglottitis

Functional: Vocal cord paralysis (#2 cause of congenital stridor)

Structural

• Laryngomalacia (#1 cause of congenital stridor)
  • Better in upright position
  • Worse with crying
  • Self resolves usually by 1 year
• Tracheomalacia causes expiratory stridor, not biphasic
• Hemangioma
  • esp. if other hemangioma in “beard distribution”
• Subglottic stenosis: Congenital (#3 cause of congenital stridor) or post intubation
• Vascular rings/slings

Stridor is produced by rapid, turbulent flow of air through a narrow segment of the airway. Biphasic stridor suggests an anatomic location at the glottic or subglottic level. Inspiratory stridor typically is produced by an obstruction above the vocal cords; expiratory stridor is produced by an intrathoracic site of obstruction. 

The most common cause of congenital stridor is laryngomalacia, which typically presents as relatively benign inspiratory stridor without significant airway distress. Vocal cord paralysis is the second most common cause of congenital stridor and usually presents as predominately inspiratory obstruction. Infants who have vocal cord paralysis may present with respiratory distress, failure to thrive, and blue spells. The third most common cause of congenital stridor is congenital subglottic stenosis or glottic and subglottic web. Congenital subglottic stenosis is characterized by biphasic stridor that typically worsens with agitation, as described for the infant in the vignette. In severe cases that involve a very narrow airway, respiratory distress with retractions, desaturations, and bradycardia can occur. The presence of a weak cry suggests involvement of the stenosis up to the vocal cord level. Normal cardiovascular stability typically is maintained until end-stage airway crisis.

Flexible airway endoscopy is the best initial diagnostic procedure for evaluation of congenital stridor. Laryngomalacia and vocal cord paralysis are usually visible, subglottic narrowing can be evaluated, and tracheomalacia can be assessed easily. Endoscopy often reveals anterior pulsatile tracheal compression in innominate artery compression, demonstrates narrowing consistent with double aortic arch, and shows tracheoesophageal fistula or laryngeal cleft. CXR may reveal subglottic narrowing or tracheal narrowing that possibly are consistent with tracheal stenosis or tracheomalacia. Severe distal tracheal obstruction from a high-grade stenosis or foreign body frequently is suggested by air trapping and hyperexpansion on the affected side.

Cystic fibrosis often presents with meconium ileus at birth and the development of chronic cough, respiratory distress, and failure to thrive later in life. Stridor is uncommon. Patients who have hypoplastic left heart syndrome do not have obvious stridor; rather, they present with signs of cyanosis and hypoperfusion. Signs of congestive failure usually appear within the first few days or weeks of life. Tracheoesophageal fistula presents with excessive oral secretions, choking, coughing, and cyanosis when feeding is attempted. Tracheomalacia may cause expiratory stridor, but biphasic stridor is uncommon. Innominate artery compression, although usually mild and asym ptomatic, may cause expiratory stridor, cough, and recurrent pneumonias. Respiratory distress is uncommon.

References:
Brodsky L. Congenital stridor. Pediatr Rev. 1996;17:408-411
Cotton, RT, Reilly JS. Stridor and airway obstruction. In: Bluestone CD, Stool SE, Kenna MA, eds. Pediatric Otolaryngology. 3rd ed. Philadelphia, Pa: WB Saunders Co; 1996:1275-1287
Holinger LD. Etiology of stridor in the neonate, infant and child. Ann Otol Rhinol Laryngol. 1980;89:397-400