**Question:** Most common cause of stridor in children is

A. Obstructive sleep apnoea
B. Epiglottitis
C. Foreign body aspiration
D. Anterior mediastinal mass

**Core Concept:**
Stridor is a high-pitched, hoarse, and rapid inspiratory sound heard during breathing in the neck or trachea. It is a clinical sign indicating airway obstruction. In children, the most common causes of stridor can be categorized into mechanical, infectious, or foreign body aspiration.

**Why the Correct Answer is Right:**
D. Anterior mediastinal mass (e.g., lymphangioma, teratoma, hemangioma) is the most common cause of stridor in children due to compression of the trachea or bronchi. These masses can cause airway obstruction, leading to stridor.

**Why Each Wrong Option is Incorrect:**
A. Obstructive sleep apnoea (OSA) typically presents with choking episodes, apnoea, and hypoxia during sleep, rather than stridor.
B. Epiglottitis is an inflammation of the epiglottis causing swelling and airway obstruction, but it is less common than anterior mediastinal masses.
C. Foreign body aspiration usually presents with choking, cough, and stridor immediately after the event, whereas the stridor in anterior mediastinal masses usually develops gradually.

**Why the Correct Answer is Right:**
D. Anterior mediastinal masses are the most common cause of stridor in children due to compression of the trachea or bronchi. These masses can cause airway obstruction, leading to stridor.

**Why Each Wrong Option is Incorrect:**
A. Obstructive sleep apnoea (OSA) typically presents with choking episodes, apnoea, and hypoxia during sleep, rather than stridor.
B. Epiglottitis is an inflammation of the epiglottis causing swelling and airway obstruction, but it is less common than anterior mediastinal masses.
C. Foreign body aspiration usually presents with choking, cough, and stridor immediately after the event, whereas the stridor in anterior mediastinal masses usually develops gradually.

**Clinical Pearl:**
A foreign body aspiration should be considered in children who present with acute onset of stridor and a history of choking or cough immediately after an event, whereas the stridor in anterior mediastinal masses usually develops gradually. This can help clinicians narrow down their differential diagnosis and initiate appropriate management.