The peripheral nervous system lies outside the central nervous system. Whereas the central nervous system controls the activities of the body, the peripheral nervous system sends messages from the extremities of the body to the central nervous system. Peripheral nerve injury is classified as damage to a nerve and its surrounding area without affecting the central spinal cord column, or the root from which the peripheral nerve stems from. With the damage to peripheral nerves, it is usually just a select area or muscle group that will be affected, rather than the large areas or whole limbs being affected which is often seen with spinal cord damage.
The nerves can be damaged in many ways, from wounds, which can sever nerve pathways, fractures that damage the nerves that wrap around different bones of the body, or even nerves, which are damaged necessarily in a surgical procedure. Peripheral nerves have the ability to regenerate, unlike those at the spinal cord, meaning that any numbness or weakness experienced after a peripheral nerve injury is likely to completely resolve.
When your nerves are injured, depending on the depth of the injury, you could experience two different symptoms. The most peripheral nerve route is the sensory aspect of the nerve. This is the nerve, which allows you to feel different objects touching your skin. It is the nerve most susceptible to damage because of its locations, often being compromised by positioning. For example, if you kneel for too long you will get temporary ‘pins and needles’ or numbness in your leg. This is when your nerves are starved of blood flow or oxygen. You will get the same or similar sensation when a peripheral sensory nerve is damaged, varying in intensity correlating to the severity of damage.
Sometimes where there is no visible injury to the body, it can be difficult to identify where the neural injury is arising. This is due to the nerves often branching, joining or crossing on their paths from the spine to their destination. Depending on the symptoms you are experiencing and their location on your body, your therapist can identify which nerves are likely to be damaged even without a visible injury site. Through extensive research, there has been a ‘map’ of which area of the body is supplied by a single nerve, known as a dermatome chart. Using this tool, your therapist can identify which nerve is likely to be responsible for the altered sensation, which you are experiencing. Another chart or ‘map’ has been created showing which nerves are responsible for each muscle action as well. This is known as a ‘myotomes’ map. Depending on the location of the wound (if any) and which action is affected by the damage of your peripheral nervous system, it will again identify the probable cause to your therapist.
By exercising the affected muscles, or stimulating the numb areas of your body, you can promote the regrowth of the nerve pathways. This will usually happen automatically, however working alongside your physiotherapist can reduce the severity of residual effects from severely damaged areas, and help with the rehabilitation of the affected muscles.