INTRODUCTION	Section 2 of 9
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Background: Stridor is a clinical sign characterized by musical, monophonic, audible breath sounds (noisy breathing) caused by oscillations of narrowed large extrathoracic airways. The presence of stridor indicates a partial obstruction of the upper airways, glottis, or trachea. The pitch of the stridor is determined by the degree of airway obstruction and the velocity of the airflow. The exact quality of the sound in terms of pitch and loudness varies depending on the specific cause. Congenital stridor is present at birth or within the first few weeks (4-6) of life.

Pathophysiology: Stridor results from partial obstruction of an airway with turbulent flow characteristics. Such respiratory tract areas are the upper airway, glottis, and trachea. The obstruction can be fixed or variable. Variable extrathoracic obstructions are primarily associated with inspiratory stridor. This is because during inspiration extrathoracic intraluminal airway pressure is negative relative to atmospheric pressure, leading to collapse of supraglottic structures. In contrast, stridor caused by intrathoracic obstructions tends to be more prominent on expiration. On expiration, intrathoracic pressure is positive and tends to collapse the airway.

Mortality/Morbidity: With the exception of bilateral vocal cord paralysis and subglottic hemangioma, congenital stridor is rarely caused by a life-threatening or fatal lesion. However, significant airway obstruction can lead to respiratory distress. Significant obstruction can also lead to failure to thrive secondary to increased work of breathing.

Age: Congenital stridor is present either at birth or shortly afterward.

	CLINICAL	Section 3 of 9
Author Information Introduction Clinical Differentials Workup Treatment Follow-up Miscellaneous Bibliography

History: The most common presentation for congenital stridor is chronic noisy breathing since birth. Most patients come to attention by the first 4-6 weeks of life.

The history can be helpful in determining the cause of stridor. Characteristics of stridor that should be elicited include the following:

• Association with position

• Association with feeding

• Persistent versus intermittent

• Abnormal phonation

• Foreign body exposure

• Presence of other congenital abnormalities

Physical: Physical examination should focus on examination of the respiratory tract, the quality and characteristics of the stridor, and other physical findings that may be associated with stridor.

• Characteristics of the patient's stridor

• Effect of position

• Effect of feeding

• Inspiratory versus expiratory

• Pitch and loudness

• Respiratory examination

• Lower respiratory tract sounds (eg, wheezes, crackles)

• Retractions

• Quality of voice or crying

• Other physical findings

• Skin lesions (eg, hemangiomas)

• Neurologic status

Causes: Differential diagnosis of stridor can be divided into supralaryngeal, laryngeal, tracheal, and nonanatomic categories.

• Supralaryngeal causes of stridor: Supralaryngeal causes include choanal atresia, vallecular cysts, thyroglossal cysts, and tongue dermoid or teratoma.

• Laryngeal causes of stridor

• Laryngomalacia is the most common cause of congenital stridor. Patients typically have high-pitched inspiratory stridor that increases with crying and when supine. It rarely interferes with feeding. Symptoms are usually present at birth or within the first 4-6 weeks of life. Laryngomalacia usually resolves of its own accord within 18-24 months.

• Vocal cord paralysis may cause a patient to have a weak cry. Patients may also be worse with feeding. Ruling out underlying conditions that may result in vocal cord paralysis, in particular neurologic conditions such as Arnold-Chiari malformation, is important. Bilateral paralysis is more commonly associated with neurologic problems and is a life-threatening emergency.

• Subglottic stenosis can be congenital or acquired. Stridor of subglottic stenosis typically is biphasic. Acquired forms usually arise from endotracheal (ET) intubation.

• Other laryngeal abnormalities leading to stridor include webs, cysts, hemangiomas, papillomata, and laryngotracheoesophageal clefts.

• Tracheal causes of stridor

• Extrinsic compression of the trachea by vascular abnormalities is a common cause of stridor. Anomalies that may lead to stridor include double aortic arch, innominate artery compression, aberrant right subclavian vein, and pulmonary artery sling.

• Bronchogenic cysts can also cause extrinsic compression of the trachea.

• Tracheomalacia may be observed in association with laryngomalacia or as an isolated lesion.

• Tracheal stenosis can be a complication of long-term ET intubation or a congenital lesion.

• Complete tracheal rings are a subset of tracheal stenosis with severe biphasic airway sounds.

• Nonanatomic causes of stridor

• Cardio-vocal syndrome occurs when cardiac abnormalities lead to compression of the recurrent laryngeal nerve.

• Foreign body may be present.

• Gastroesophageal reflux (GER) has been associated with stridor, although no controlled studies have been performed to demonstrate that GER is actually responsible for the stridor.