Laryngomalacia, tracheomalacia and vocal-cord dysfunction: SAQ

This infant has the classic picture of mild laryngomalacia: position-dependent inspiratory stridor beginning in the first fortnight, worse with feeding, crying and supine posture, in a thriving baby with a normal cry and no red flags. The task is to recognise the benign natural history, localise the airway lesion by the phase of the noise, and give a clear safety-net without over-investigating. ^[2]

Question 1 (10 marks)

How do you localise a noisy airway in an infant, what is the most likely diagnosis here, and how would you confirm it? (5 marks for the localisation principle; 3 marks for the diagnosis and its supporting features; 2 marks for confirmation.) ^[3]

A noisy airway is localised by the phase of the respiratory cycle in which the noise occurs. Inspiratory stridor points to the extrathoracic airway at the larynx or above, because the negative intraluminal pressure of inspiration draws the walls inward; expiratory noise points to the intrathoracic trachea and bronchi, which are compressed as pleural pressure rises in expiration; and a biphasic noise points to a fixed lesion at or near the glottis or subglottis. This single rule organises the whole assessment. ^[3]

The most likely diagnosis is laryngomalacia, the commonest cause of stridor in infancy. The supporting features are the onset at around two weeks rather than at birth, the high-pitched inspiratory quality, and the characteristic worsening with feeding, crying and the supine position with improvement when prone. The normal cry, the absence of biphasic stridor, and the good weight gain all point toward benign disease rather than a fixed or additional lesion. ^[2]

Confirmation is by awake flexible nasolaryngoscopy in the clinic, which shows the dynamic supraglottic collapse — an omega-shaped epiglottis, short aryepiglottic folds and redundant arytenoid mucosa prolapsing into the airway on inspiration. It must be performed with the infant awake and spontaneously breathing, because the collapse is dynamic and would be missed under deep anaesthesia. In a thriving infant with a typical history and no red flags, some clinicians observe and reserve laryngoscopy for atypical or severe features. ^[1]