When a nerve is injured, sometimes you may not be able to move the affected muscle at all. Nerve injuries can take a long time to heal, and in the worst cases, the affected muscle or muscle group can remain paralyzed permanently.
Description: Nerve Injuries
Before discussing nerve injuries, it’s important to understand what nerves are and what they do:
Nerves transport information to and from the brain (similar to cables connecting a computer to a printer or scanner). Like a cable, a nerve has a protective layer (a ring of tissue). There are motor nerves and sensory nerves:
- Motor nerves tell your muscles what to do (how to contract, etc.).
- Sensory nerves send information back to the brain, such as pain, pressure, and temperature.
Motor and sensory nerves are often located close together inside the same protective tissue—just like in the computer-printer analogy: the computer says, “Print this picture,” and the printer responds, “Sorry, no paper.”
What Happens When a Nerve is Injured
Nerves are fragile, like very thin wires. They can be damaged by overstretching, pulling, cutting, and other trauma. A nerve can be cut with its protective tissue (insulation) or without it. In both cases, information cannot travel to or from the brain, but it is much worse if the nerve and its protective tissue are both damaged.
- When nerve fibers are cut, the distal portion (farthest from the brain, closest to the muscle) may die.
- The proximal portion (closest to the brain) survives and over time, nerve fibers begin to grow along the remaining protective tissue.
- Nerve fibers grow very slowly—about 1 cm per month—and the farther the injury from the brain, the longer it takes to heal (leg nerve injuries take longer than shoulder nerve injuries).
If the protective tissue is also damaged, nerve fibers may form a tangled ball at the end of the insulation. This is very painful and is called a neuroma.
Nerve Injury Treatment
- If the protective tissue is intact, the main treatment is to wait. Sensation may return after months or even years.
- During this time, avoid excessive movement of the affected area to protect your joints. In some cases, other muscles may compensate for the lost function, causing the affected muscle to shrink or atrophy, regardless of whether the nerve eventually recovers.
- If the protective tissue is cut, a doctor may need to expose the entire nerve to sew the ends of the insulation together.
- If the wound is contaminated, the doctor may need to wait until the skin and tissues heal before performing the nerve repair.
- In severe cases, when the nerve ends are too far apart, a nerve graft from another sensory nerve may be required. Only sensory nerves are used for grafts, so motor function is not lost.
While the nerve is non-functional:
- Physical therapy is necessary to maintain joint mobility. Joints that are immobile for several months can become stiff, and forcing them too aggressively can lead to permanent joint damage.
- Electrical muscle stimulation (EMS) therapy can help prevent muscle degeneration, but do not attempt EMS therapy on your own, as it can cause joint injury.
Even after nerve function returns, the brain must relearn to control incoming and outgoing signals to the affected muscles.
