ENT: Clinical Approach to Stridor
High-Yield Diagnostic & Clinical Reasoning for Board Review
Stridor is a high-pitched, musical sound resulting from turbulent airflow through a narrowed upper airway. It is a symptom, not a diagnosis, and always indicates a significant reduction in the airway lumen.
1. Localization by Timing
| Timing | Anatomical Site | Common Causes |
|---|---|---|
| Inspiratory | Supraglottic / Glottic | Laryngomalacia, Croup, Vocal cord paralysis |
| Expiratory | Tracheal / Bronchial | Tracheomalacia, Foreign body |
| Biphasic | Subglottic / Glottic | Subglottic stenosis, Fixed mass |
2. Pediatric Stridor: The “Big Four.”
- Laryngomalacia: Most common cause in infants. Characterized by inspiratory stridor that worsens with agitation or supine position and improves with prone positioning. “Omega-shaped epiglottis” is the classic finding.
- Croup (Laryngotracheobronchitis): Viral (Parainfluenza). Presents with a barking cough and “Steeple sign” on neck X-ray.
- Acute Epiglottitis: Bacterial (H. influenzae type b). Medical Emergency! Features “Tripod position,” drooling, and “Thumbprint sign” on lateral neck X-ray.
- Vascular Ring: External compression of the trachea causes biphasic stridor and feeding difficulties.
3. High-Yield Board Points
| Point | High-Yield Detail |
|---|---|
| The Rule of Thumb | Never attempt a blind oral exam or instrumentation in a child suspected of **Acute Epiglottitis**—risk of total airway obstruction. |
| “Steeple Sign” | Subglottic narrowing seen on AP neck X-ray; hallmark of **Croup**. |
| “Thumbprint Sign” | Swollen epiglottis seen on lateral neck X-ray; hallmark of **Epiglottitis**. |
| Most Common Site | The subglottis is the narrowest part of the pediatric airway and thus the most vulnerable to edema. |