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 nerve injury to a more severe, permanent nerve injury. The extent of the injury depends on the amount of stretch.
The signs and symptoms of a nerve injury can be different depending on the nerve injured, the type of injury, and the severity of the injury. Some may include:
Symptoms of nerve injury may be intermittent, if the injury repeats itself; or they may be constant, if the injury is severe enough. There are many other signs of nerve injury: muscles that get smaller, color change in the skin, and changes to the amount of sweat in certain areas.
An example of a nerve injury that can recur is carpal tunnel syndrome. Carpal tunnel syndrome occurs when the median nerve has too much pressure on it as it crosses the wrist. The symptoms of numbness in the hand, pain in the hand, pain in the wrist, pain in the forearm, or weakness (particularly in the thumb) can be present. The symptoms of carpal tunnel syndrome can be intermittent or, if severe enough, can occur all of the time.