An 8-month-old infant has had biphasic stridor since birth, with several episodes of acute worsening treated elsewhere as 'recurrent croup'. There is no feeding difficulty and the cry is normal. Flexible endoscopy shows normal supraglottis and mobile cords. Which investigation will best establish the diagnosis?
- A Rigid endoscopic assessment of the subglottis under anaesthesia with sizing of the airway ✓
- B Barium swallow to exclude vascular ring
- C Lateral neck radiograph looking for thumb sign
- D MRI brain stem to exclude bilateral vocal cord paralysis
Correct answer: A. Rigid endoscopic assessment of the subglottis under anaesthesia with sizing of the airway
Explanation
Congenital subglottic stenosis is the third commonest cause of congenital stridor and classically presents with biphasic stridor plus recurrent episodes mislabelled as croup, with a normal cry and normal feeding. Diagnosis requires rigid endoscopy of the subglottis under anaesthesia, graded by the size of endotracheal tube that passes (Myer-Cotton classification). A barium swallow is indicated when vascular compression is suspected, but the recurrent croup pattern points to the subglottis first.
Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.