What is The Median Nerve?
The median nerve is one of the main nerves in the body and it originates from the brachial plexus. The nerve runs from the shoulder and passes along the bicep in the upper arm. The nerve continues past the elbow and down through the forearm.
The median nerve is the only one that travels through the carpal tunnel. After exiting the carpal tunnel the median nerve enters the hand, thumb, and fingers where it terminates.
The nerve has a motor and sensory function through the forearm and parts of the hand. It innervates many of the muscles in the forearm and controls muscles in the hand. The median nerve is responsible for feeling in part of the hand as well as the thumb and first three fingers.
Median Nerve Injuries
Due to its length, there are various places where the nerve can get damaged. The nerve is susceptible to injury at the elbow, forearm, wrist, and hand.
When the nerve is damaged it makes doing simple tasks hard. Holding a cup of coffee or brushing teeth is going to be difficult. Grip and strength are particularly affected when the median nerve is injured.
Various things lead to median nerve injury including trauma, fractures, pregnancy, and surgery. One of the most common conditions associated with median nerve injury is carpal tunnel syndrome.
Carpal Tunnel Syndrome
Carpal tunnel syndrome (CTS) is a condition that is a result of median nerve compression. As the nerve passes through the wrist and through the carpal tunnel it often gets compressed.
If the median nerve is compressed it will affect muscles and be feeling in the hand and fingers. Patients with CTS experience numbness and tingling in the forearm and the symptoms are usually worse during the night.
Typing on computer keyboards is thought to be one causes of carpal tunnel syndrome. The repetitive motion of typing combined with poor wrist posture often leads to nerve compression. Working with vibrating tools and machinery also affects the median nerve leading to carpal tunnel syndrome.
There are a few ways to prevent carpal tunnel syndrome and manage the symptoms. Taking breaks from typing, correcting wrist posture and wearing a brace will help. Doing some wrist strengthening exercises is another useful way to prevent CTS.
Median Nerve Palsy
An injury to the wrist, arm or forearm could lead to a condition called median nerve palsy. Penetrating or blunt trauma damage to the nerve can cause the condition. When the nerve has been damaged some of the muscles in the arm and hand will be affected.
Symptoms of median nerve palsy include muscle weakness, muscle paralysis, and sensory loss. Tendon transfers are often used in patients with median nerve palsy to restore some motor function. A tendon transfer replaces damaged muscles and tendons with healthy ones.
Blunt or penetrating trauma to the upper arm, elbow, forearm or wrist puts the median nerve at risk of injury. A heavy blow due to an accident or sports injury may lead to nerve compression or inflammation.
Piercing wounds or lacerations could also injure the median nerve. If the nerve gets severed it will not function resulting in loss of both sensory and motor function.
In rare cases, the median nerve is damaged by IV needles when taking blood or administering drugs. There are reported cases of patients that have permanent median nerve damage from an IV needle.
A fracture to any part of the arm puts the median nerve at risk of injury. When bones in the elbow, forearm or wrist are broken they could pinch the nerve and it will not function. In some cases, a fracture will sever the nerve which will then need time to heal or it will have to be repaired.
If a bone in a part of the arm is fractured there may be small fragments of bone near the median nerve. These tiny pieces of bone may press on the nerve and cause entrapment. Even when the fracture has healed the fragments are still there and could cause a problem.
Severe fractures are often repaired using wires and pins so that the bones knit together and heal. The metal pins used to repair fractured bones have been known to cause nerve damage. When bones in the arm are repaired with pins the median nerve is at risk of injury.
During pregnancy, there are hormonal changes that cause swelling which damages the median nerve. Pregnancy-induced carpal tunnel syndrome is not uncommon. The swelling causes compression due to excess pressure on the nerve.
Water retention often occurs during pregnancy and this is another cause of median nerve compression. The damage is not usually permanent and symptoms ease after giving birth.
The median nerve may get damaged during surgery to parts of the arm or hand. There is evidence that patients have sustained nerve damage during carpal tunnel surgery. The nerve may get severed during the surgery or it may suffer blunt trauma.
Scar tissue can compress the median nerve following the operation. This fibrous tissue has little elasticity and is known to cause nerve compression. There are ways to break up scar tissue including massage and laser treatment.
Some cancer treatments such as chemotherapy and radiation are harmful to nerves. The treatments are necessary to treat cancer but there are side effects.
The drugs used for chemotherapy target cancer cells but they damage healthy cells in the body. Platinum and taxane drugs used for chemotherapy are known to cause nerve damage.
Radiation therapy is often used to treat lung and breast cancer and high doses of radiation damages nerves. Nerves in the arms are particularly at risk during this type of treatment. The damage caused by radiation may be instant or symptoms will develop over a period of time.
The symptoms associated with median nerve injury include:
- Weak grip
- Wrist pain
- Aching hand and forearm
- Inability to rotate the wrist
- Numbness and tingling
How Are Median Nerve Injuries Diagnosed?
If a physician suspects a patient has median nerve damage there are various tests carried out. A sensory test will be done to determine whether any feeling is lost in the palm, thumb, and fingers.
Pinprick tests and grip tests are an effective way to assess median nerve damage. The physician will also assess hand and arm movement to determine the severity of the nerve damage.
Imaging tests are used to investigate median nerve damage in some cases. MRI scans, ultrasound, and X-rays are used to locate the injury.
Electromyography (EMG) is used to diagnose nerve damage and it measures the signals from nerves to muscles. A small needle is inserted into a muscle which records electrical activity. The physician is then able to make a diagnosis based on the reading that is picked up.
Can Median Nerve Injuries be Treated?
If the injury is not serious the nerve may regenerate without medical treatment. The median nerve is capable of regenerating over a period of time. Nerves regenerate at a rate of approximately one inch per month.
If the injury is more serious there are other treatment options. If the median nerve has been severed a surgeon may decide that end-to-end suturing is the best treatment. The two ends of the nerve will be connected which then allows it to heal.
Nerve grafting is another way to repair a severed nerve when end-to-end suturing is not an option. A section of the donor's nerve is harvested and used to carry out the grafting.
If the nerve is compressed there are a few ways that physicians can free it. Steroid injections are used to reduce swelling and inflammation to free a pinched nerve. Oral corticosteroids are used to manage pain and take down swelling around the nerve.
If non-invasive methods do not free the nerve the patient may need surgery. Surgical procedures are carried out to untrap the nerve which relieves the symptoms. If scar tissue or fragments of bone are causing the compression they will be removed by the surgeon.
When the damage to the nerve cannot be repaired the symptoms can be managed. Painkillers, anti-inflammatory drugs, and physiotherapy are used to help patients cope with nerve damage.
It clear to see how important the nerve is in order to maintain a quality of life. Any injury to the nerve is debilitating and in some cases very painful. Some median nerve injuries can’t be avoided and some can.
Fortunately, most nerve damage can be repaired or the associated symptoms controlled. In rare cases, there may be permanent damage to the nerve.