Spinal Cord Injury: C4 Is a Crucial Level
Medical Author: Benjamin C. Wedro, MD, FAAEM
Nerves run from the brain through the spinal cord to the body. They connect to the muscles and tissues of the body, allowing them to function. Some functions are within our control, like moving an arm, making a facial expression or walking. Others are part of our unconscious system, things we take for granted, like breathing or swallowing saliva.
The fourth cervical vertebra is the level where nerves run to the diaphragm, the main muscle that allows us to breathe. It separates the chest from the abdomen, and when it contracts, air is sucked into the lungs like a bellows. No contraction, no sucking, no breathing. People who survive spinal cord injuries above this level need ventilators or machines to breathe.