Nerves are the body’s “telephone wiring” system that carries messages between the brain and the rest of the body. Some nerves carry messages from the brain to muscles to make the body move. Other nerves carry messages about pain, pressure, or temperature from the body to the brain. Many small fibers are bundled inside each nerve to carry the messages. There is an outer layer that insulates and protects the nerves (Figure 1). Sometimes, nerves can be damaged.
Nerves can be damaged by too much pressure, by stretching, or by a cut. Carpal tunnel syndrome is an example of a problem that arises from too much pressure on the median nerve in the hand. Carpal tunnel syndrome can injure the median nerve slowly over time or, in the case of trauma to the area, it can occur much more quickly.
A cut to the nerve can cause it to no longer transmit signals, because the signal cannot jump through a gap in the nerve. Stretch injuries to the nerve can range from mild, temporary injury to a more severe, permanent injury. The extent of the injury depends on the amount of stretch.