Radial Tunnel Syndrome

The radial nerve and the radial tunnel

The radial nerve runs down the back of the upper arm (see radial nerve injury for damage higher up), wraps around to the outer side of the elbow, and then divides. Its deep branch passes through the radial tunnel, a 5 cm (2-inch) passage formed by forearm muscles, including the supinator muscle. Bands of tissue and blood vessels in this tunnel can squeeze the nerve, particularly during repetitive forearm rotation and gripping.

The same branch, called the posterior interosseous nerve, can also be compressed severely enough to cause weakness. That condition, posterior interosseous nerve syndrome, causes difficulty straightening the fingers and thumb without much pain.

Symptoms

• dull, deep, aching forearm pain in the top of the forearm, about 5 cm below the bony bump on the outer elbow
• pain worse with gripping, lifting, pushing, pulling or turning the palm up
• pain when straightening the wrist or middle finger against resistance
• fatigue of the forearm muscles
• sometimes pain spreading into the back of the hand or around the elbow
• usually no numbness or tingling, unlike carpal tunnel syndrome or cubital tunnel syndrome, because the nerve branch involved mainly controls muscles

Radial tunnel syndrome vs tennis elbow

The two conditions can occur together, and some people treated unsuccessfully for tennis elbow turn out to have radial tunnel syndrome.

Causes and risk factors

• repetitive forearm rotation and gripping, such as manual labor, using tools, racquet sports and lifting
• tight muscles or fibrous bands in the tunnel
• direct injury to the forearm
• swelling or masses such as ganglion cysts or lipomas (uncommon)

Diagnosis

• examination: pressing over the radial tunnel to find the point of tenderness, and testing resisted forearm rotation and middle finger extension
• diagnostic injection: a local anesthetic injected into the radial tunnel that relieves the pain supports the diagnosis
• nerve conduction studies and EMG: often normal in radial tunnel syndrome, but useful to rule out other nerve problems and to detect posterior interosseous nerve syndrome
• MRI or ultrasound: to look for masses or other causes
• neck examination and imaging if a pinched nerve in the neck (cervical radiculopathy) is possible

Treatment

Nonsurgical

Most people improve with conservative treatment over 3 to 6 months:

• rest from aggravating activities, especially repetitive twisting and gripping
• activity changes: lifting with the palm facing up, using tools with larger handles, taking regular breaks
• splint: a wrist splint, sometimes with an elbow brace, to rest the forearm muscles
• pain relief: acetaminophen (paracetamol) or anti-inflammatory medicine at the label dose
• physical therapy: nerve gliding exercises, stretching and gradual strengthening
• steroid injection into the radial tunnel to reduce inflammation

Surgery

If symptoms persist despite several months of treatment, radial tunnel release may be offered. The surgeon cuts the tight bands of tissue pressing on the nerve. Recovery takes several weeks to a few months, and full relief can take longer. Results are generally good, though less predictable than for carpal tunnel surgery.

Outlook

Most people improve with rest, splinting and activity changes. Some have recurring symptoms with repetitive work. Surgery helps many of those who do not respond to other treatments.

Frequently asked questions

What does radial tunnel syndrome feel like?

It feels like a deep, dull ache in the top of the forearm, a few centimeters below the outer elbow, worse with gripping, lifting and twisting the forearm. It usually does not cause numbness or tingling.

How is radial tunnel syndrome different from tennis elbow?

Tennis elbow pain is centered right on the bony bump on the outside of the elbow, where the tendon attaches. Radial tunnel pain is felt a few centimeters further down the forearm over the muscle, and comes from nerve compression rather than tendon damage.

How long does radial tunnel syndrome take to heal?

With rest, splinting and activity changes, symptoms often improve over 3 to 6 months. If they persist, surgery to release the nerve may help, with recovery over several weeks to months.

Can radial tunnel syndrome cause weakness?

Usually not. Weakness straightening the fingers or thumb suggests a more severe compression called posterior interosseous nerve syndrome, which needs prompt assessment by a hand or nerve specialist.