AEMCA Practice Exam

What is a potential consequence of transection of C3 and above on the spinal cord?

1. Loss of sensory function

2. Respiratory arrest

3. Paralysis of the legs

4. Inability to move arms

The correct answer is: Respiratory arrest

Transection of the spinal cord at the level of C3 or above has significant implications for respiratory function. The C3, C4, and C5 spinal nerves are critical as they form the phrenic nerve, which innervates the diaphragm, the primary muscle used in breathing. When there is a transection at C3 or higher, the respiratory centers in the brain are unable to communicate with the diaphragm. As a result, this leads to respiratory arrest, a life-threatening condition where breathing stops completely. The other options may also occur based on the level and extent of spinal cord injury, but they do not directly address the most immediate and critical consequence associated with C3 transection. Loss of sensory function is a result of damage to the sensory pathways, and paralysis of the legs and inability to move arms would occur with lower-level injuries or involve additional motoneurons; however, neither can take precedence over the immediate life-threatening loss of respiratory control caused by a lesion at C3 and above. Thus, the primary and most pressing consequence of such an injury is respiratory arrest.