Subtle Stridor: Seen in the ED

History of present illness. A teenager is brought to the emergency department by his parents for 2-3 months of progressive shortness of breath following an admission to the ICU after a bad car crash. At that time he had multiple rib fractures, a pneumothorax and a splenic laceration. His mom says his breathing is “noisy” at times, especially when he exerts himself or is talking a lot.

Vital signs and physical examination. Vital signs and pulse oximeter reading were normal. There was very subtle stridor while talking. Oral and pulmonary exams were otherwise unremarkable.

Initial diagnostic testing:

  • Findings on basic laboratory studies all normal
  • Chest X-ray showed healed rib fractures but was otherwise normal
  • Neck X-ray image shown here

What is the most accurate diagnosis?