Laryngomalacia
The most likely diagnosis is laryngomalacia (option c), which is the most common congenital laryngeal anomaly and the most frequent cause of persistent stridor in children. 1, 2
Key Diagnostic Features Supporting Laryngomalacia
The clinical presentation strongly points to laryngomalacia based on several characteristic features:
Stridor present since birth: Laryngomalacia typically presents with high-pitched inspiratory stridor noticed within the first 14 days of life 3, 4
Improvement with thickened feeds: This is a pathognomonic feature of laryngomalacia, as thickened feeds help reduce aspiration and reflux symptoms that commonly accompany this condition 5. Approximately half of children with laryngomalacia have associated feeding difficulties 6
Absence of cyanosis: This indicates the airway obstruction is not severe, which is consistent with mild-to-moderate laryngomalacia that comprises the majority of cases 5, 4
Expiratory stridor: While laryngomalacia classically causes inspiratory stridor, the condition can present with variable stridor patterns depending on the degree of supraglottic collapse 1
Why Other Options Are Less Likely
Vascular compression of trachea (option a): This would typically cause persistent wheezing unresponsive to bronchodilators and would not improve with thickened feeds 1. The stridor would be more constant and not position-dependent.
Subglottic stenosis (option b): This presents with biphasic stridor and would not improve with thickened feeds 1. It is typically associated with a history of intubation or trauma, not present since birth in most cases.
Bilateral vocal cord palsy (option d): This is the third most common congenital laryngeal anomaly causing stridor 1, 2, but would present with severe respiratory distress, cyanosis, and would not improve with thickened feeds. It typically requires urgent intervention.
Clinical Reasoning
Laryngomalacia results from weakening of supraglottic laryngeal structures, causing them to collapse into the airway during inspiration 3, 6. The improvement with thickened feeds is explained by the frequent association with gastroesophageal reflux disease (GERD) and laryngopharyngeal reflux (LPR), which contribute to feeding symptoms 5. Thickened feeds reduce reflux and aspiration, thereby improving symptoms.
Expected Clinical Course
- Most cases (80-95%) are self-limited and resolve by 18-24 months of age without intervention 6, 4
- Only 5-20% require surgical intervention (supraglottoplasty) for severe disease 6
- The condition typically worsens with increased breathing effort and supine positioning, improving in prone position 3
Diagnostic Confirmation
Flexible fiberoptic laryngoscopy during symptomatic periods would definitively confirm the diagnosis by visualizing the collapse of supraglottic structures during inspiration 1, 6. The European Respiratory Society guidelines emphasize examining the larynx in physiological conditions when stridor is audible 1.