Injury at C1–C3 commonly causes which respiratory finding?

• A. Apnea and no cough
• B. Normal breathing with preserved cough
• C. Diaphragm function intact with intercostal paralysis
• D. Regular breathing with strong cough

Answer: (A)

High cervical spinal cord injuries disrupt the nerves that drive the diaphragm and the expiratory muscles. The diaphragm, the main muscle for inspiration, is innervated by the phrenic nerve from C3–C5. When the injury is at or above C3, this input is lost, causing diaphragmatic paralysis and the person cannot breathe on their own—apnea. In addition, the muscles used to force a cough (the intercostals and abdominal muscles) are also weak or paralyzed with such high injuries, so an effective cough cannot be produced. That combination explains why apnea with no cough is the typical respiratory finding after injury at the C1–C3 level.