Stridor (Pediatric)

What is stridor?

Stridor is an abnormal sound that can be heard during breathing.  It occurs as a result of a partial blockage of the breathing passageway, which creates a turbulent flow of air and noise.  Depending on the location, type, and degree of blockage, the stridor can be heard when breathing in (inspiratory stridor), when breathing out (expiratory stridor), or both (biphasic stridor).  Potential sites of narrowing which result in stridor include the larynx (voicebox), trachea (windpipe), and bronchi (smaller air passages that bring air to the lungs).

Here is a list of some common causes of stridor:

• Laryngomalacia – collapsibility of the soft tissues of the voice box.  Typically presenting  with inspiratory stridor, this is the most common cause of stridor in newborns.  As the soft tissues gain tone with maturation, the sound usually diminishes and clears by one year of age.  When severe, it can cause breathing and feeding issues, and surgery at times may be recommended.
• Vocal cord paralysis – lack of movement of one or both vocal cords.  Typically presents with inspiratory stridor (normally the vocal cords both move into the open position to allow air to enter the windpipe).  Sometimes paralysis of both vocal cords presents with biphasic stridor.  This may be present at birth, or may be a complication of heart surgery or other surgeries.  Treatment depends on the cause and severity of the problem.
• Congenital cyst – a fluid-filled mass that is present at birth and can enlarge.  The type of stridor depends on the location of the cyst; however, these commonly occur behind the tongue at the top of the voicebox and present with inspiratory stridor
• Neoplasm – tumor or growth.  The type of stridor depends on the location of the neoplasm.  Although rare, the most common example of neoplasm in the infant airway is a subglottic hemangioma.  This is an area of abnormal blood vessels that typically occurs in the upper trachea, and presents with biphasic stridor.  Diagnosis may be made with a scoping procedure or an MRI, and treatment may involve surgery or medication. 
• Laryngeal papilloma are tumors of the voicebox as a result of exposure to the HPV virus.  These are becoming less common secondary to the HPV vaccine.
• Infections – these may occur anywhere in the airway.  The most common example is croup, a viral infection of the voice box and upper trachea that presents with barky cough and biphasic stridor.  Less common infections include epiglottitis (infection of the top of the voicebox, presents with fevers and inspiratory stridor, can quickly result in respiratory distress) and tracheitis (bacterial infection of the trachea, presents with fevers, and biphasic stridor).
• Vocal cord dysfunction – the vocal cords stay closed instead of opening during breathing.  This presents with inspiratory stridor and may be associated with acid reflux.
• Foreign body –An inhaled object can occur anywhere in the airway, and there is often a history of the child having a choking episode.  The type of stridor depends on the location of the foreign body; the most common location is the bronchi of the lung, and this presents with expiratory stridor or wheezing. X-rays may play a role in diagnosis.
• Small lower jaw – this can result in the tongue falling back over the voice box and airway and commonly presents with inspiratory stridor
• Laryngeal Stenosis – narrowing of the voicebox.  Can be congenital (born with it), or acquired (usually secondary to having a breathing tube in the airway).  Typically presents with biphasic stridor, and sometimes hoarseness.
• Tracheomalacia and bronchomalacia – weakening and collapse of the trachea (windpipe), or bronchi (smaller air passages that bring air to the lungs).  Typically presents with expiratory stridor.
• Vascular ring or sling – compression of the windpipe by an artery.  Typically presents with expiratory stridor and a barky cough
• Tracheal stenosis – narrowing of the trachea.  Typically presents with biphasic stridor.