Infantile laryngeal stridor caused by weak and lax laryngeal tissues, collapse of tissues during inhalation, and narrowing of the laryngeal cavity is called congenital laryngeal stridor, also known as laryngomalacia. It often occurs shortly after birth and gradually disappears as the laryngeal cartilage develops with age.

bubble_chart Etiology

Due to malnutrition during pregnancy, fetal calcium deficiency leads to weak laryngeal cartilage. The increased negative pressure during inhalation causes the edges of the epiglottic cartilage to curl inward and make contact, or the epiglottic cartilage becomes overly large and soft, bringing the aryepiglottic folds closer together and narrowing the laryngeal cavity into a valve-like tremor, resulting in laryngeal stridor. Inspiratory arytenoid cartilage prolapse is another cause. In such cases, the laryngeal stridor is not due to weak laryngeal cartilage but occurs when the arytenoid cartilage rotates forward and downward during inhalation, causing the surrounding loose tissue to protrude into the anterior glottis and obstruct the airway, leading to stridor.

bubble_chart Clinical Manifestations

The baby breathes normally at birth, but gradually develops laryngeal stridor within 1 to 2 months after birth. The stridor is mostly persistent or intermittently worsens. It occurs only during the inspiratory phase and may be accompanied by inspiratory dyspnea. In some cases, the stridor is not obvious under normal conditions but appears immediately after slight stimulation. Some cases are related to body position, worsening when lying supine and improving when prone or on the side. Most infants are in good general condition, and their crying is not hoarse.

Based on a history of laryngeal stridor shortly after birth, with no history or signs of respiratory foreign bodies or other diseases, normal lateral neck X-rays, loud crying, and good swallowing, a diagnosis can usually be made without direct laryngoscopy.

During direct laryngoscopy, the epiglottis cartilage may appear long and pointed, curling backward on both sides and touching each other; or the epiglottis may be large and soft, with its sides and the aryepiglottic folds closely approximated. In some cases, the loose tissue on the arytenoid cartilage may protrude into the glottis, causing obstruction. When the epiglottis is lifted with a direct laryngoscope, the laryngeal stridor disappears, confirming the diagnosis.

Congenital laryngeal stridor must be differentiated from other congenital abnormalities of the larynx and trachea, such as laryngeal webs, laryngeal clefts, and tracheomalacia, as well as from various acquired laryngeal conditions like inflammation, foreign bodies, and trauma.

bubble_chart Treatment Measures

If the symptoms are mild, congenital laryngeal stridor usually resolves on its own by the age of 2 to 3. Therefore, the family can be reassured and advised to prevent colds and fright to avoid respiratory infections and laryngospasm, which may worsen laryngeal obstruction. If the episodes are severe with difficulty in breathing, adjusting the infant's position to a lateral decubitus position can alleviate symptoms. In rare cases of severe laryngeal obstruction, a tracheotomy may be required.