One of my college roommates was in an accident and the impact of her car crashing into a guardrail along the highway damaged her spine. She had to have several surgeries to correct the problems caused by the accident. The accident happened when she was a sophomore in high school, and by the time I met her she was a freshman in college.
To look at her you would never know she had a spine injury. The surgeries put her spine back in order. However, the tissue around one of her phrenic nerves was damaged during one of the surgeries, so her left or her right phrenic nerve (I don't remember which) had to do the work that both nerves would normally have been doing. Occasionally, she would have trouble catching her breath, but most of the time she had no symptoms.