AEMCA Practice Exam

What is the primary result of transection of C4 and above on the spinal cord?

1. Loss of bowel control

2. Paralysis of the diaphragm

3. Loss of urinary function

4. Paralysis of the arms

The correct answer is: Paralysis of the diaphragm

The primary result of transection of the spinal cord at the level of C4 and above is paralysis of the diaphragm. The diaphragm is the main muscle involved in breathing, and its function is primarily controlled by the phrenic nerve, which arises from spinal nerves C3 to C5, with a significant contribution from C4. When the spinal cord is cut at C4, the signals from the brain that initiate and control breathing can no longer reach the diaphragm, leading to respiratory paralysis. This condition necessitates immediate medical intervention, often requiring mechanical ventilation support. While loss of bowel control, loss of urinary function, and paralysis of the arms are significant issues encountered in higher spinal cord injuries, the most critical and immediate threat resulting from transection at C4 is the compromised ability to breathe, making paralysis of the diaphragm the key outcome.