Inspiratory stridor is found in what kind of lesions:

Correct Answer: A. Supraglottic

Inspiratory stridor is the pathognomonic finding in supraglottic lesions. The supraglottis (epiglottis, aryepiglottic folds, arytenoids, false vocal cords) lies above the true vocal cords. During inspiration, negative intraluminal pressure causes the supraglottic structures to collapse inward into the airway lumen, creating the characteristic high-pitched, musical breathing sound heard without a stethoscope. This is the hallmark of supraglottic obstruction. Common supraglottic causes in Indian clinical practice include epiglottitis (now rare post-Hib vaccination but still seen), lingual thyroid, laryngomalacia (most common cause of stridor in infants), peritonsillar abscess with extension, and angioedema. The key discriminator is that supraglottic lesions are above the glottis, so they obstruct the airway during the negative-pressure phase of inspiration. This contrasts sharply with fixed lesions (tracheal stenosis) which cause biphasic stridor, and subglottic lesions which typically cause expiratory or biphasic stridor due to their location below the vocal cords where dynamic collapse occurs differently.

Why the other options are wrong

B. Bronchus — Bronchial lesions are far distal to the larynx and do not cause stridor at all. Bronchial obstruction produces wheeze (polyphonic or monophonic) on auscultation, not stridor. Stridor is by definition a laryngeal or upper airway phenomenon. This is a distractor testing whether students confuse upper airway obstruction (stridor) with lower airway obstruction (wheeze). C. Tracheal — Tracheal lesions (stenosis, malacia, tumours) cause biphasic stridor (both inspiratory and expiratory) because the trachea is a fixed structure without dynamic collapse. The fixed narrowing obstructs airflow in both phases. This is the NBE trap—students may think 'trachea = stridor' without recognizing that tracheal stridor is biphasic, not purely inspiratory. D. Subglottic — Subglottic lesions (subglottic stenosis, croup, haemangioma) typically cause expiratory or biphasic stridor, not pure inspiratory stridor. The subglottis lies below the vocal cords; during expiration, positive intrathoracic pressure causes dynamic collapse of these structures. Croup, the most common subglottic condition in Indian paediatric practice, presents with barky cough and expiratory stridor, not inspiratory.

High-Yield Facts

Mnemonics

STRIDOR SITE Supraglottic → Inspiratory; Subglottic → Expiratory; Tracheal → Biphasic. (Supraglottic = Inspiratory; Subglottic = Expiratory; Tracheal = Biphasic.) Pressure-Collapse Rule Supraglottis collapses during negative pressure (inspiration) → inspiratory stridor. Subglottis collapses during positive pressure (expiration) → expiratory stridor. Fixed trachea → both phases → biphasic.

NBE Trap

NBE pairs "stridor" with "trachea" to lure students into choosing tracheal lesions, but the question specifies inspiratory stridor—the key discriminator that points uniquely to supraglottic pathology. Students who know only that tracheal lesions cause stridor (without the biphasic qualifier) will fall into this trap.

Clinical Pearl

In Indian paediatric practice, a crying infant with inspiratory stridor and no fever is laryngomalacia until proven otherwise—reassure parents that it self-resolves. But if the child is febrile, drooling, and tripoding, think epiglottitis and secure the airway immediately; this distinction between benign laryngomalacia and life-threatening epiglottitis hinges on recognizing the supraglottic anatomy.

_Reference: Bailey & Love Ch. 36 (Larynx); Robbins Ch. 16 (Respiratory System)_