Median Nerve Injury

What is Median Nerve Injury?

The median nerve is also known as the ‘eye of the hand’ because it plays a key role in how our hand functions. This nerve stimulates the muscles in our forearm and most of the muscles in the thumb-side of the hand, enabling us to move our thumb away from our hand, fold our hand at the wrist, and bend the fingers. This nerve also enables us to sense touch on the palm-side of the thumb, index, middle, and part of the ring finger, as well as the entire half of the palm that is closest to the thumb. It also lets us sense touch on the back skin of the last two joints of the index and middle fingers.

The median nerve originates from the neck area of the spinal cord. From there, it runs beside the main artery in the arm, and enters the forearm between two muscles, one of which turns the forearm so that the palm faces down. It continues to the palm, passing under a band of tissue near the heel of the hand, a path that leaves it quite exposed. Damage to the median nerve can occur anywhere along its length.

In the arm, the median nerve does not stimulate any muscles. In the forearm, it does stimulate several muscles including those that help flex the wrist, rotate the forearm, and bend the fingers. In the hand, it stimulates the muscles of the thumb and a few other muscles, plus it lets us sense touch on the skin over the base of the thumb and the two fingers closest to the thumb.

The median nerve can get damaged due to sudden injuries, repeated minor injuries, or conditions that compress the nerve at enclosed spaces. It can also get damaged due to multiple causes that wear down nerves and their protective lining, mainly affecting the part of the nerve near the hand. In particular, the median nerve can get squeezed under a band of tissue at the wrist, causing pain, numbness, or a tingling sensation (referred to as neuropathic pain). This condition is known as carpal tunnel syndrome, which is often described as a needle and pin sensation spreading from the wrist to the hand. The exact cause of this syndrome is unknown, but it is often associated with conditions like hypothyroidism, pregnancy, and diabetes. Loss of sensation over the base of the thumb suggests damage to the median nerve before it enters the carpal tunnel, a narrow passageway in the wrist.

Although a patient’s symptoms and history can suggest damage to the median nerve, several diagnostic tools can help confirm this. These tools include x-rays, ultrasound, and electromyography (a test that measures muscle response to nerve stimulation). Non-invasive treatments such as braces, physical therapy, and changes in lifestyle to avoid repetitive stress are usually tried first. If these fail, surgery may be considered.

What Causes Median Nerve Injury?

The median nerve, which runs through your upper arm, can be damaged in a variety of ways and at different points along its path. It’s often injured during shoulder or elbow dislocations, fractures of the arm bones, stab wounds, or from the repeated use of crutches. Sometimes it can get hurt from having a tourniquet placed on it for too long.

Sometimes, these injuries happen together with damage to the radial or ulnar nerves, which are nerves located in your arm too. The most common causes of median nerve injury are:

Trauma directly to the wrist and elbow joints
Accidental injury to the areas surrounding the armpit, wrist, and palm during surgery
Injury from a suicide attempt
Being connected to a fracture of the upper arm bone
Compression at the elbow or under a band of tissue at the front of your wrist (this is known as carpal tunnel syndrome)}

The median nerve can also be affected by diseases that cause a gradual degeneration or demyelination (damage to the protective sheath around a nerve) of the nerve tissue, and neuropathy (nerve damage) caused by chemotherapy.

Most of the time, we don’t know why carpal tunnel syndrome happens. But some conditions can cause or contribute to it. For example, during pregnancy, fluid retention can cause carpal tunnel syndrome. A few other things that can cause carpal tunnel syndrome include tumors, bone abnormalities resulting from an injury, bone spurs, and thickened tissue around the joints. Medical conditions such as an underactive thyroid, rheumatoid arthritis, and infections can also contribute. Even habits like drinking alcohol or a genetic predisposition can make it more likely.

Certain diseases that affect connective tissues can increase the risk of carpal tunnel. Also, repetitive activities requiring repeated bending and straightening of the wrist, obesity, and going through menopause can make it more likely to develop carpal tunnel syndrome. This syndrome occurs because the pressure inside the ‘carpal tunnel’, a narrow passageway in the wrist, increases. This leads to compression and damage to the median nerve. Activities such as performing the same motion over and over or using equipment that vibrates a lot, can also increase the risk.

Risk Factors and Frequency for Median Nerve Injury

Emergency room visits for peripheral nerve injuries are often due to median nerve injuries. In the United States, there are around 8,000,000 reported cases of such injuries per year. The most common condition related to this is carpal tunnel syndrome, which impacts about 3% of the general population. Every year, carpal tunnel syndrome is diagnosed in 105 out of every 100,000 people.

Carpal tunnel syndrome affects more women than men, with 149 cases in women and 52 cases in men per 100,000 people.
About 1% of men and 7% of women have carpal tunnel syndrome, contributing to the overall prevalence of 3% in the general population.
Most cases of carpal tunnel syndrome are diagnosed between ages 45 and 54.
Up to 65% of people with carpal tunnel syndrome have it in both hands.
Women between 65 and 74 years of age are four times more likely than men of the same age to have carpal tunnel syndrome.

Carpal tunnel is a common condition where the median nerve is trapped, but 7 to 10% of median nerve entrapments occur further up the arm. Other less common locations for median nerve entrapment include bone spurs on the humerus, the pronator teres muscle, and the flexor digitorum superficialis muscle. Conditions with similar symptoms to median nerve entrapment, like Martin-Gruber anastomosis, can also occur. To identify and isolate nerve damage and its location, electromyography is used.

Signs and Symptoms of Median Nerve Injury

Traumas can affect the median nerve, which runs through the hand, forearm, arm, and underarm (axilla). The impact of the injury on the nerve can cause problems with movement, feeling, and the function of blood vessels. Most commonly, these injuries happen at the wrist, where several conditions can harm the nerve. These issues can start from the wrist and continue up to the underarm and the network of nerves in the shoulder (brachial plexus).

Wrist Lesions

At the wrist, the median nerve often gets injured during wrist fractures. The nerve can be compressed by fractured bones, bruised or, in rare cases, torn. Since it’s exposed at the wrist, the median nerve can also be cut by sharp objects, leading to full or partial splits in the nerve. The small nerve branch in the palm, which carries sensations from the nerve, and surgeries on the wrist can also damage the nerve and cause painful growths (neuromas).

Carpal Tunnel Syndrome

In the wrist, there’s a space known as the carpal tunnel, formed by a ligament and the wrist bones, where the median nerve and some tendons run. Symptoms of carpal tunnel syndrome can localize to the wrist or the entire hand and can even go up into the forearm. These symptoms include weakness in the thumb, numbness in the fingers, and a pins-and-needles sensation. Other symptoms include a burning pain in the area supplied by the median nerve. The symptoms might get worse at night and wake patients up. Special tests can help diagnose carpal tunnel syndrome: Tinel and Phalen tests, as well as the hand elevation and flick sign.

Mild carpal tunnel syndrome: numbness and tingling in the area supplied by the median nerve, without any loss of function or sensation affecting sleep or daily activities.
Moderate carpal tunnel syndrome: Includes all mild symptoms plus loss of sensation in the area supplied by the median nerve, disrupted sleep, and some changes to hand function.
Severe carpal tunnel syndrome: Includes all mild and moderate symptoms, weakness in the area supplied by the median nerve, and changes to daily activities.

Pronator Syndrome

Pronator syndrome or pronator teres syndrome is a condition where the muscle in the forearm compresses the median nerve. This often mirrors symptoms of carpal tunnel syndrome. Patients suffering from pronator syndrome often feel discomfort in their forearm during activities. They might experience numbness and tingling in the thumb and the first two fingers, along with a loss of sensation over the thenar eminence (the rounded area at the base of your thumb).

Anterior Interosseous Neuropathy

Anterior interosseous neuropathy is another type of median nerve injury. This condition affects a branch of the median nerve near the elbow. The affected nerve controls several muscles in the forearm and has no branches to the skin, so symptoms involve muscle weakness with no sensation changes. Patients might find it challenging to press their thumb and index finger together or make an “OK” sign. This problem often occurs due to complicated trauma.

Elbow Lesions

In the scenario of elbow injuries or dislocations, the median nerve can be damaged directly by fractured bones, stretched by the injury, or compressed by masses of clotted blood (hematomas). After the injury, the healing process might lead to the nerve being trapped and squeezed. The nerve can also be injured during routine elbow surgeries, leading to painful nerve symptoms and muscle weakness.

Arm, Axillary, or Upper Lesions

In rare cases, fractures in the upper arm (humerus) could lead to paralysis of the median nerve. More commonly, these severe symptoms result from acute trauma such as deep wounds, gunshot wounds, or major accidents. These more severe injuries could cause nerve lesions higher up in the underarm or shoulder and could lead to paralysis and sensory impairment.

Testing for Median Nerve Injury

The Tinel and Phalen tests play a significant role in diagnosing carpal tunnel syndrome. If your doctor can’t confirm the diagnosis from your medical history or physical examination, they may recommend additional tests like electromyography (EMG) or a nerve conduction study. These tests can help distinguish if the nerve damage is in the nerve root or further along the nerve path in the hand.

A nerve conduction test checks how well the median nerve, which passes through the carpal tunnel in your wrist, sends signals. If this nerve sends signals properly except when in the carpal tunnel, this indicates carpal tunnel syndrome. An EMG test, on the other hand, checks the health of muscles controlled by the affected nerve. This test helps rule out other conditions like polyneuropathy or radiculopathy.

Based on the nerve conduction test, carpal tunnel syndrome can be categorized into four levels:

Mild: This involves a slight delay in sensory responses and a very small decrease in nerve signal speed. No nerve damage is expected.
Moderate: This is characterized by abnormal sensory signal speeds and reduced motor signal speeds. There is still no expected nerve damage.
Severe: This involves no sensory responses and significantly delayed motor responses.
Extreme: In this case, both sensory and motor responses are absent.

An imaging test called a musculoskeletal (MSK) ultrasound, which measures the size of the median nerve, can also be conducted. This test is pretty good at identifying carpal tunnel syndrome. The size of the nerve is typically larger, at 9 mm or more, in cases of this condition.

Usually, a magnetic resonance imaging (MRI) scan or a standard x-ray is not needed unless the condition is expected to have other complications like a trapped nerve at the wrist. In such situations where the patient’s condition diverges from the standard recovery path, these imaging tools can be handy. They can identify abnormal growth of the joint lining (synovium) or a mass like a ganglion cyst.

Treatment Options for Median Nerve Injury

When treating median nerve damage, strategies are based on the underlying cause. For mild to moderate carpal tunnel syndrome, a common condition affecting the median nerve, a common initial treatment is wearing a splint. Current research suggests this helps more than doing nothing, although it’s unclear if one specific type of splint works best. One study has found that a splint keeping the wrist in a neutral position (straight, not bent) helps to relieve symptoms twice as effectively as a splint that positions the wrist in extension (bent backwards). If wearing a splint at night fails to provide results after a month, it’s suggested to add another non-invasive treatment to the plan while using the splint for another one to two months. Splints can be worn continuously or only during sleeping, but it’s not proven which method is more effective.

Additional non-surgical treatments include physical therapy, yoga, and treatments using sound waves known as therapeutic ultrasound. First-line treatments for mild to moderate carpal tunnel syndrome often involve corticosteroid injections and wearing splints at night. Treatments are usually combined because they are more successful when used together than on their own. A local corticosteroid injection can delay the need for surgery up to one year after the injection. However, this treatment carries the risk that the medication might be accidentally injected into the nerve, which can cause damage, or that a tendon may rupture. To minimize these risks, the injection should be done under the guidance of an ultrasound. Notably, the study does not show significant differences in the likelihood of surgery one year following an injection between two tested corticosteroid dosages, 40mg and 80mg, both were lower than the control group.

Although the best injection technique isn’t clear, those guided by ultrasound appear to be more effective than blind techniques. If symptoms return, the injection may be repeated six months after the first one. If symptoms still persist after the second injection, surgery is typically recommended. Taking oral prednisone (an anti-inflammatory medication) for ten to fourteen days can improve the patient’s carpal tunnel syndrome-related pain and hand function for up to eight weeks. The effectiveness of physical therapy, ultrasound treatment, and carpal bone mobilization might be limited. However, yoga was once found to be an efficient treatment, providing symptom relief for up to eight weeks.

For patients with severe carpal tunnel symptoms who have not improved following four to six months of non-surgical treatment, a surgical procedure to relieve the pressure on the median nerve (known as decompression) should be considered. Before undergoing surgery, it is advised to conduct electrodiagnostic tests to help determine the severity of the condition and what the likely outcome might be. Compared to non-treatments or treatments using wrist splints, surgical release has been found to generally produce better clinical results. Both endoscopic (using a camera and tiny instruments) and open (making larger incision to access the nerve) techniques show improvement in patient symptoms, although patients undergoing endoscopic surgery return to work approximately a week earlier. There is emerging evidence that supports ultrasound-guided carpal tunnel release.

The outcome of non-surgical strategies varies widely, from 20% to 93%, depending on the severity of symptoms. Symptoms with mild compression tend to worsen over ten to fifteen months, while moderate or severe cases show a tendency to improve. Treatment with either splinting or surgical decompression can lead to complete or significant improvement at one year following therapy in 70 to 90 percent of patients.

When managing pronator teres syndrome, another condition affecting the median nerve, it is recommended to minimize activities that provoke symptoms. Nonsteroidal anti-inflammatory drugs (NSAIDs), local corticosteroid injections into the tender points of the affected muscle, and median nerve decompression surgery have also been shown to be effective treatments.

When a doctor is trying to make a diagnosis, they may consider several possible ailments that may be causing your symptoms. These could include:

Cervical radiculopathy (pinched nerve in the neck)
Motor neuron diseases (diseases affecting the nerves that control muscle movement)
Fibromyalgia (widespread muscle pain and tenderness)
Compartment syndrome (increased pressure in a muscle compartment)
Brachial plexopathy (nerve damage in the brachial plexus, which sends signals from the spine to the arm and hand)

Furthermore, the following specific conditions may also be considered:

Dislocation of joints in the fingers or base of the thumb
General diseases that cause nerve damage
Infection in the deep spaces of the palm
Local muscle injuries around the thumb
Rheumatoid arthritis affecting the thumb joints
Tenosynovitis (inflammation of the tendon lining) affecting the tendons in the thumb

What to expect with Median Nerve Injury

The outcome of nerve injuries largely depends on how severe the injury is and when it’s treated. Smaller cuts that are quickly treated with surgery and additional care tend to have the best results, reducing related deformities.

Carpal tunnel symptoms often go away about six months after they start. The younger the patient, the better the chances of improvement. If both wrists show a positive result from a certain test known as a Phalen test, the condition could be more serious. In most cases, carpal tunnel that develops during pregnancy goes away on its own after the baby is born.

Conservative therapies, or non-surgical treatments, usually start to improve symptoms within two to six weeks, with the most benefit coming around the three-month mark. If after six weeks of treatment the symptoms don’t improve, it might be time to consider a different treatment approach.

Certain factors can suggest that non-surgical treatments might not work. These include having symptoms for more than six months, constant tingling sensations, being older than 50, not being able to distinguish two close points when touched, a positive Phalen’s test in less than 30 seconds, and certain results from a nerve test known as an EMG.

Surgery to relieve pressure (decompression) works in about 70 to 90% of cases. Most patients see a significant improvement within a week and can get back to their normal activities within two weeks after surgery. However, in some cases, it can take up to a year for a full recovery.

Possible Complications When Diagnosed with Median Nerve Injury

Sensory nerve fibers, which allow us to feel touch and pain, are more likely to be harmed by nerve squeezing than motor nerve fibers, which control our muscles. So, the first signs of carpal tunnel syndrome are often strange sensations like tingling, numbness, and prickling. As the condition gets worse, motor fibers get affected too. Patients may feel weakness in moving their thumb or conducting fine motor skills, such as buttoning a shirt or opening a jar. When these motor and sensory nerve fibers die, patients experience less pain, but the muscles begin to shrink. They might also lose the ability to tell the difference between two items that are 6 mm (a quarter of an inch) apart.

Pain in the area around the surgery is common after carpal tunnel surgery. If the surgery doesn’t work, it’s often due to the growth of scar-like tissue or failure to fully cut the flexor retinaculum, which is the band of tissue holding the tendons in the carpal tunnel. In these cases, another surgery may be required.

Here are some complications that can occur after carpal tunnel surgery:

Not completely cutting the transverse carpal ligament, which forms the roof of the carpal tunnel
Damaging the recurrent motor and palmar cutaneous branches of the median nerve, which provide feeling and movement in the hand
Injuries to the blood vessels of the superficial palmar arch
Cuts to the median and ulnar nerve trunks, which control sensation and movement in the hand
Wound infections after surgery
Painful scar formation
Developing complex regional pain syndrome, which is a chronic pain condition

Preventing Median Nerve Injury

The median nerve, which runs down the arm and hand, can often be damaged due to bad posture, workplace-related stresses, injuries, or even during conditions like pregnancy.

Your doctor will first look at your medical history and perform a physical exam to diagnose this issue. Specifically, if your symptoms get worse at night, but better when you shake your hand, it suggests that the median nerve might be trapped. This is often referred to as the “flick sign”.

During your physical exam, your doctor might conduct two specific tests, known as the Phalen sign and Tinel sign. If these tests produce certain results, it might suggest that your nerve is trapped.

In addition to the physical exam, your doctor might also use imaging techniques like X-rays and ultrasound to help confirm the diagnosis. They might also use a test called electromyography (EMG), which helps to find out where and how much your nerve has been damaged.

If the median nerve is found to be damaged, the treatment plan is typically quite straightforward starting with easy changes like adjusting your workplace setup, wearing braces, or physical therapy.

If you develop this condition during pregnancy, then it usually gets better on its own after childbirth. In cases where the symptoms aren’t relieved with the general treatment, steroids injections can be highly effective. If even that does not work, then your doctor might recommend surgery to relieve the trapped nerve by releasing a part of the wrist called the transverse carpal ligament.

Frequently asked questions

Median nerve injury refers to damage or compression of the median nerve, which can occur anywhere along its length. This can result in symptoms such as pain, numbness, or tingling sensation in the hand and wrist. Diagnostic tools such as x-rays, ultrasound, and electromyography can help confirm the injury, and non-invasive treatments are usually tried first before considering surgery.

Emergency room visits for peripheral nerve injuries are often due to median nerve injuries. In the United States, there are around 8,000,000 reported cases of such injuries per year.

Signs and symptoms of Median Nerve Injury include: - Weakness in the thumb - Numbness in the fingers - Pins-and-needles sensation - Burning pain in the area supplied by the median nerve - Worsening symptoms at night that can disrupt sleep - Discomfort in the forearm during activities (in cases of Pronator Syndrome) - Numbness and tingling in the thumb and first two fingers (in cases of Pronator Syndrome) - Loss of sensation over the thenar eminence (the rounded area at the base of the thumb) (in cases of Pronator Syndrome) - Difficulty pressing the thumb and index finger together or making an "OK" sign (in cases of Anterior Interosseous Neuropathy) - Muscle weakness without sensation changes (in cases of Anterior Interosseous Neuropathy) - Painful nerve symptoms and muscle weakness (in cases of elbow injuries or dislocations) - Paralysis and sensory impairment (in severe cases of upper arm fractures or acute trauma)

The median nerve can be damaged in a variety of ways and at different points along its path. It can be injured during shoulder or elbow dislocations, fractures of the arm bones, stab wounds, or from the repeated use of crutches. It can also get hurt from having a tourniquet placed on it for too long. Additionally, diseases that cause degeneration or demyelination of the nerve tissue, as well as neuropathy caused by chemotherapy, can affect the median nerve.

The doctor needs to rule out the following conditions when diagnosing Median Nerve Injury: - Cervical radiculopathy (pinched nerve in the neck) - Motor neuron diseases (diseases affecting the nerves that control muscle movement) - Fibromyalgia (widespread muscle pain and tenderness) - Compartment syndrome (increased pressure in a muscle compartment) - Brachial plexopathy (nerve damage in the brachial plexus, which sends signals from the spine to the arm and hand) - Dislocation of joints in the fingers or base of the thumb - General diseases that cause nerve damage - Infection in the deep spaces of the palm - Local muscle injuries around the thumb - Rheumatoid arthritis affecting the thumb joints - Tenosynovitis (inflammation of the tendon lining) affecting the tendons in the thumb

The types of tests that are needed for Median Nerve Injury include: 1. Tinel and Phalen tests: These tests play a significant role in diagnosing carpal tunnel syndrome. 2. Electromyography (EMG): This test checks the health of muscles controlled by the affected nerve and helps rule out other conditions. 3. Nerve conduction study: This test checks how well the median nerve sends signals and can help distinguish if the nerve damage is in the nerve root or further along the nerve path in the hand. 4. Musculoskeletal (MSK) ultrasound: This imaging test measures the size of the median nerve and can be conducted to identify carpal tunnel syndrome. 5. Magnetic resonance imaging (MRI) scan or standard x-ray: These imaging tools are usually not needed unless there are other complications expected, such as a trapped nerve at the wrist. They can help identify abnormal growth or masses.

Median nerve injury is treated based on the underlying cause. For mild to moderate carpal tunnel syndrome, wearing a splint is a common initial treatment. Research suggests that wearing a splint in a neutral position helps relieve symptoms twice as effectively as wearing a splint in an extended position. If wearing a splint at night does not provide results after a month, another non-invasive treatment can be added to the plan. Additional treatments include physical therapy, yoga, corticosteroid injections, and therapeutic ultrasound. For severe carpal tunnel symptoms that do not improve with non-surgical treatment, surgical decompression may be considered. The outcome of non-surgical strategies varies depending on the severity of symptoms, with 70 to 90 percent of patients experiencing complete or significant improvement at one year following therapy. For pronator teres syndrome, minimizing activities that provoke symptoms, NSAIDs, corticosteroid injections, and median nerve decompression surgery are effective treatments.

The side effects when treating Median Nerve Injury include: - Not completely cutting the transverse carpal ligament, which forms the roof of the carpal tunnel - Damaging the recurrent motor and palmar cutaneous branches of the median nerve, which provide feeling and movement in the hand - Injuries to the blood vessels of the superficial palmar arch - Cuts to the median and ulnar nerve trunks, which control sensation and movement in the hand - Wound infections after surgery - Painful scar formation - Developing complex regional pain syndrome, which is a chronic pain condition

The prognosis for median nerve injury largely depends on the severity of the injury and how quickly it is treated. Smaller cuts that are promptly treated with surgery and additional care tend to have the best results, reducing related deformities. Surgery to relieve pressure works in about 70 to 90% of cases, with most patients seeing significant improvement within a week and being able to return to normal activities within two weeks after surgery. However, in some cases, it can take up to a year for a full recovery.

A neurologist or an orthopedic surgeon.