Nerve Injury

Nerves are the wires that carry messages back and forth 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. Some nerves have only fibers that control muscles, called motor nerves. Other nerves have only fibers that carry messages about feeling and touch, called sensory nerves. Others have both and are called mixed nerves. The fibers in a nerve are protected by an outer covering (Figure 1). This layer protects the nerve fibers and helps messages be sent faster.

Sometimes, nerves can be damaged. This damage can affect part of the nerve or the whole nerve. The injury can be to the outer layer of the nerve – the insulation – or to the fibers within the nerve, or both. Symptoms, treatment, and expected recovery depend on the type of damage.

Figure 1

Nerve with bundles of individual nerve fibers and surrounding outer sheath (“insulation”)

Figure 2

A nerve repair with realignment of bundles

Causes

Nerves can be damaged by too much pressure, by excessive stretching of the nerve, or by a cut.

Pressure
Pressure on a nerve can come from a tight spot in your body, from certain activities or positions, or from an injury. When nerves are damaged by pressure, it can affect the outer layer of the nerve only or the nerve fibers that are inside as well. 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 because of a tight spot in your wrist. Carpal tunnel syndrome can also happen quickly after trauma that causes swelling in the area of the median nerve, which causes pressure to build up in a short period of time.

Stretching or Bruising
Like other parts of your body, a nerve can be stretched or bruised. This can be caused by a traumatic injury that does not cut the skin. Bruising can also happen with injuries that do break the skin but do not cut the nerve. When this happens, the nerve might not work normally. A finger being crushed is an example of an injury that might cause bruising of the nerves that give feeling to your finger.

Cut
Like an electrical wire, a nerve that is no longer connected cannot carry information. Even a small cut in the skin can cause a cut to the nerves beneath the skin. For example, if you accidentally stab your hand while cutting an avocado, you could cut a nerve in your palm.

Signs and Symptoms

The signs and symptoms of nerve injuries are different depending on which nerve is injured, but can include:

Numbness: If a nerve that gives feeling to an area is injured, that area will lose feeling. To you, this might feel like numbness. It can also feel like tingling or buzzing, like when your arm falls asleep.
Weakness: If a nerve that controls muscles is injured, the muscles controlled by that nerve can be weak or not work at all. If muscles are weak or do not work for a long time, they get smaller. This is called atrophy.
Pain: Injuries to nerves often cause pain. This can be at the place the nerve was injured. Pain can also be along the entire nerve all the way up the arm to the spinal cord.
Changes in the skin: Nerve injuries are not the only thing that can cause skin changes, but if there is a concern your nerve might have been injured, your doctor will look for these signs. Skin changes can include color, texture, and sweating.

Symptoms of nerve injury will also depend on the cause and severity of the injury. Some symptoms of a nerve injury come and go, others are constant. Injuries from pressure can be intermittent (“come and go”). If the pressure has been there for a long time or has gotten more severe, the symptoms can become constant. Symptoms of stretching or bruising are usually constant but can get better over time as the nerve recovers. Symptoms from a cut nerve are usually constant, but pain can vary a lot, even with a cut nerve.

Treatment

Treatment for nerve injuries depends on many things, including:

Which nerve was injured
Type of injury
Severity of injury
How long it has been since the injury happened or symptoms began
Severity of symptoms
Patient factors: Your age, overall health, what you do for a living, and how bothered you are by your symptoms are examples of things that can impact the treatment for your nerve injury.

Some nerve injuries can get better on their own, but other injuries need treatment. Treatment can be non-surgical, such as splinting or physical therapy. Other injuries require surgery to treat symptoms or repair a nerve. Depending on your injury, your doctor might recommend waiting to see if your symptoms will get better on their own before recommending other treatments.

If an injury does not get better on its own or does not recover completely, there are several types of surgical treatments that might be recommended. The treatment will depend on the factors listed above. Examples of surgical treatments include:

Decompression: This is the word for releasing pressure on a nerve. There are spots along the path of a nerve where the anatomy causes pressure on the nerve. By removing these pressure spots, the nerve is decompressed.
Neurolysis: This is a type of surgery where all the scar tissue is removed from around the nerve. This can include the removal of insulation, or outer layer of the nerve, as well, to take pressure off the fibers inside the nerve.
Nerve repair: If a nerve has been cut or very badly bruised, your surgeon might recommend repair of the nerve. This means putting the nerve back together so the two ends of the cut nerve are touching one another (Figure 2). If the nerve ends cannot reach one another, your surgeon will sometimes use another piece of nerve to bridge the gap. This is called a nerve graft.
Nerve or tendon transfer: Some nerve injuries do not improve after decompression or cannot be repaired. If this happens, your surgeon will try to reconstruct the functions of that nerve. The purpose of these surgeries is to try to replace the function of the injured nerve using nerves or muscles that still work. There are many different types of nerve or tendon transfers depending on which nerve is injured.

Recovery After Surgery

When nerve injuries are repaired, the signals do not flow immediately to the body or the brain. The nerve needs to regrow from the spot it was injured out to the body before it will work again. This means that even after your surgery, you will still have symptoms until the nerve regrows. If the nerve injury was only to the outer lining of the nerve, recovery is usually faster than if the fibers of the nerve were injured. Regrowing the inner fibers of the nerve is a slow process. Nerves usually grow about one inch per month, so it can take a long time for your nerve to start working again.

Results after nerve surgery depend on many factors, and you should discuss your injury with your surgeon. In general, injured nerves can have complete recovery, partial recovery, or no recovery, depending on the injury. Talk with your surgeon about what you can expect for your injury and treatment.

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