What can be the clinical impact of a cervical spinal cord injury at C3-C5?

A cervical spinal cord injury at the C3-C5 vertebrae can significantly affect respiratory function due to the involvement of the phrenic nerve, which innervates the diaphragm. The diaphragm is the primary muscle responsible for breathing, and when the spinal cord is injured at this level, the ability to breathe effectively can be severely compromised. This can lead to respiratory distress and challenges in maintaining proper ventilation, necessitating immediate medical intervention and often advanced supportive measures such as mechanical ventilation.

The other options reflect conditions that are not typically associated with cervical spinal cord injuries at this level. Increased mobility in the lower limbs is unlikely, as such injuries can lead to paralysis or significant motor deficits due to impaired neural signals. Chronic back pain can occur but is not an immediate clinical impact of injuries at C3-C5 and generally relates more to chronic conditions rather than acute spinal cord injuries. Complete recovery without complications is very rare in cases of significant injuries to the spinal cord, particularly at critical levels such as C3-C5, where vital functions like breathing are at risk. Thus, the choice identifying potential respiratory distress accurately captures the most critical impact of this injury.