Median Nerve Injury

What the median nerve does

The median nerve forms in the armpit from nerve roots C6 to T1, runs down the inner upper arm, crosses the front of the elbow, passes through the forearm muscles, and enters the hand through the carpal tunnel at the wrist. It controls:

• feeling in the palm side of the thumb, index, middle and half of the ring finger
• forearm muscles that bend the wrist and fingers and turn the palm down
• thumb muscles that let the thumb move across the palm to touch the little finger (opposition), which is essential for pinching and fine grip

Types of median nerve injury by level

Carpal tunnel syndrome

This is by far the most common median nerve problem. The nerve is squeezed in the tight tunnel of bone and ligament at the wrist. Risk factors include pregnancy, diabetes, hypothyroidism, rheumatoid arthritis, obesity and repetitive wrist use. See carpal tunnel syndrome for full detail.

Traumatic injury

• Lacerations: a cut from glass or a knife at the front of the wrist can divide the nerve along with tendons. It needs surgical repair.
• Fractures: wrist fractures and supracondylar elbow fractures in children can stretch or trap the nerve.
• Dislocations of the elbow or wrist bones.

Symptoms

• numbness, tingling or burning in the thumb, index, middle and half of the ring finger
• weakness when pinching, opening jars or turning keys
• clumsiness and dropping objects
• shrinking (wasting) of the fleshy area at the base of the thumb (thenar eminence)
• forearm aching in higher compressions
• in long-standing cases, inability to bring the thumb across the palm ("ape hand")

If the little finger is numb, the ulnar nerve is involved instead; numbness on the back of the hand points to the radial nerve.

Diagnosis

1. Examination: mapping numbness, testing thumb opposition and pinch, the "OK" sign, and provocative tests (tapping the nerve, Tinel's sign; holding the wrist flexed, Phalen's test).
2. Nerve conduction studies and EMG: measure how fast and strongly signals travel, locate the level of injury and grade severity. Changes may take 2 to 3 weeks to appear after an acute injury.
3. Ultrasound: shows nerve swelling, compression, or a cut nerve.
4. MRI: for masses, unusual compression sites or to assess muscle denervation.
5. X-rays: after injury, to look for fractures.
6. Blood tests: glucose, thyroid function and others if a wider peripheral neuropathy is suspected.

Treatment

Compression injuries

• Wrist splint worn at night keeps the wrist straight and relieves carpal tunnel pressure.
• Activity changes: reduce forceful gripping, vibration and repetitive wrist bending; take breaks.
• Steroid injection into the carpal tunnel gives relief for weeks to months.
• Surgery to release the tight ligament (carpal tunnel release) or free the nerve in the forearm when symptoms are severe, constant, causing wasting, or not improving with conservative care.
• Anterior interosseous nerve palsy from inflammation often recovers on its own over months.

Cuts and traumatic injuries

• Direct nerve repair, ideally within days, under a microscope.
• Nerve grafts or conduits if there is a gap between the cut ends.
• Nerve or tendon transfers when recovery is incomplete, to restore thumb opposition or finger bending.
• Hand therapy to maintain joint movement, protect numb skin and retrain sensation.

Recovery and outlook

Recovery depends on how badly the nerve is damaged:

Younger people and injuries closer to the hand recover best. Muscles without a nerve supply for more than about 12 to 18 months may not recover, which is why timely assessment matters.

While feeling is reduced, protect the hand from burns and cuts: test bath water with the other hand and wear gloves for cooking and gardening.

Frequently asked questions

What are the symptoms of median nerve damage?

Typical symptoms are numbness and tingling in the thumb, index, middle and half of the ring finger, a weak pinch grip, clumsiness and dropping things. Long-standing damage causes wasting of the muscle at the base of the thumb. Forearm injuries can cause weakness without numbness.

Can a damaged median nerve heal on its own?

Mild injuries, where the nerve is bruised or briefly compressed, often heal on their own within weeks to a few months once pressure is relieved. A nerve that has been cut does not heal properly without surgical repair.

How long does median nerve damage take to heal?

Mild compression can improve within days to weeks. When nerve fibers are broken, they regrow at about 1 mm per day, so recovery of the hand after an injury near the elbow can take a year or more. Recovery after carpal tunnel release is usually faster.

What is the OK sign test for the median nerve?

You are asked to touch the tips of your thumb and index finger to make a round "O". If the tips cannot bend and the O collapses into a flat pinch, it suggests an anterior interosseous nerve injury, a branch of the median nerve in the forearm.

Is median nerve damage the same as carpal tunnel syndrome?

Carpal tunnel syndrome is one type of median nerve injury, caused by compression at the wrist, and the most common one. The median nerve can also be damaged by cuts, fractures and compression higher in the forearm or near the elbow.