Is stridor originating from the larynx rather than the pharynx?

Stridor Originates from the Larynx

Stridor is a respiratory sound caused by turbulent airflow through narrowed airways located in the larynx, not the pharynx. 1

Anatomical Origin and Mechanism

• The location of airflow restriction causing stridor is limited to the larynx, which includes both the vocal folds and supraglottic structures, according to the ERS/ELS/ACCP 2013 International Consensus Conference. 1

• Stridor represents turbulent airflow through the trachea from upper airway obstruction, specifically at the laryngeal level. 2, 3

• The larynx serves as the primary site of obstruction that generates the characteristic high-pitched sound, with the pharynx not being the source of stridor itself. 4, 5

Clinical Characteristics Based on Timing

• Inspiratory stridor typically results from supraglottic or glottic obstruction (structures within the larynx above or at the level of the vocal cords). 2

• Expiratory stridor originates from obstruction at or below the glottic level and/or indicates severe upper airway obstruction. 2

• Biphasic stridor suggests lesions at the glottic or subglottic level, such as subglottic stenosis or fixed laryngeal lesions. 1, 6

Common Laryngeal Causes

• Laryngomalacia is the most common cause of chronic stridor in infants, representing the most frequent congenital laryngeal anomaly, and involves collapse of supraglottic laryngeal structures during inspiration. 7, 4, 5

• Subglottic hemangiomas cause stridor as they enlarge in the subglottis (the narrowest portion of the pediatric laryngeal airway), typically presenting with biphasic stridor and barky cough. 1

• Vocal cord paralysis is the third most common congenital laryngeal anomaly causing stridor. 7, 8

• Laryngeal edema from croup, trauma, or post-extubation causes stridor by narrowing the laryngeal airway. 1, 6

Important Clinical Distinction

• While the pharynx is part of the upper airway, stridor specifically indicates laryngeal-level obstruction with at least 50% narrowing of the airway. 6

• Pharyngeal pathology (such as peritonsillar abscess or retropharyngeal abscess) typically causes muffled voice, dysphagia, and drooling rather than stridor. 4

• The consensus definition of inducible laryngeal obstructions explicitly states that airflow restriction is "limited to the larynx" and not the pharynx. 1