Paralysis occurs when a disease or injury to the nervous system causes the loss of muscle function in one or more body areas. People with paralysis can’t move parts of their bodies because their nerves can’t tell their muscles what to do.

The nervous system is in charge of transmitting nerve impulses from the brain to other body regions. For example, when you move, your nervous system sends messages to your arms and legs, instructing the muscles in them what to do.

When a medical condition or traumatic injury damages the nervous system, it cannot send nerve signals throughout the body or some parts, causing paralysis.