Q & A: RADIAL TUNNEL SYNDROME

by Lorenzo G. Walker, M.D.

Surgery of the Hand and Upper Extremity

QUESTION: Over the past several months, I have developed a deep aching on the outside of my forearm which occurs at night and is exacerbated by twisting and gripping. Activities such as turning a screwdriver and opening doorknobs cause significant pain and I am persistently troubled by a "toothache" feeling at night, which makes it difficult for me to fall asleep. Occasionally, I have a feeling of tingling which radiates from my elbow into the back of my hand. I have tried rest, ice, and Advil without significant relief. What can I do?

ANSWER: Most people have heard of carpal tunnel syndrome, which is an affliction of the median nerve which causes numbness on the palm side of the hand and emanates from compression at the wrist. Patients with entrapment of the radial nerve in the forearm are often initially thought to have carpal tunnel syndrome and treatment directed towards that disorder is obviously ineffective. While patients with carpal tunnel syndrome primarily complain of a lack of feeling, numbness, and tingling, patients with radial nerve entrapment complain primarily of pain. This pain is well localized to the outside of the elbow and is initiated and intensified by repetitive movements with the forearm in a palm-down (pronated) position. Weakness of grip can also be present, owing to the fact that an increase in muscular tension in the forearm may indeed exacerbate symptoms. Patients with radial tunnel syndrome are also often confused with those presenting with lateral epicondylitis (tennis elbow). While patients with tennis elbow complain of primarily activity related pain, the nocturnal aching and unrelenting rest pain are more characteristic of radial nerve compression. The primary cause of radial nerve entrapment is repetitive motion of the extensor muscles of the forearm. These muscles create a scissor-like effect with those responsible for turning the forearm into a palm-up (supinated) position, eventually causing nerve compression.

Physical examination of the patient with radial tunnel syndrome reveals tenderness to palpation over the lateral elbow. Pain and numbness/tingling can also be elicited by resisted supination and resisted extension of the middle finger. These maneuvers place increased pressure upon the radial nerve and often reproduce symptoms. Electrodiagnosis, including measurements of nerve conduction velocity and electromyogram, are normal within the vast majority of cases. While these studies are very helpful in the diagnosis of both carpal tunnel syndrome (entrapment of the median nerve) and cubital tunnel syndrome (entrapment of the ulnar nerve), they are only valuable in this setting when significant denervation (an indicator of atrophy) is found in the forearm muscles, which derive their energy from the radial nerve.

Unfortunately, although therapy and cortisone injections are often helpful in relieving the symptoms of lateral epicondylitis, they are virtually useless in the treatment of radial tunnel syndrome. There is also no documented evidence that bracing or anti-inflammatory agents are useful in cases documented by physical examination and/or electrodiagnostic studies.

Those patients with persistent symptoms, therefore, become a candidate for release of the radial nerve, which can be performed on an outpatient basis under a regional anesthetic. The nerve can either be approached from the front of the elbow, where the surgical scar is often lengthy, and at times, unsightly, or via a 6 cm. cosmetically acceptable incision over the outside of the forearm, which requires significant surgical skill but minimal rehabilitation postoperatively. Utilizing this incision (as depicted), the extensor muscles are not cut but are merely spread, exposing the thin fibers of the supinator muscles, which is released, providing adequate nerve decompression.

After surgery, a soft bandage is placed and mobilization is begun immediately. Your symptoms may be relieved immediately or in a short period of time. Tenderness at the incision site may persist until healing is complete, and any amount of residual numbness and/or muscle weakness should resolve over a matter of weeks. Initially, home exercises are prescribed and should weakness or incisional tenderness hamper progress, formal hand therapy is then prescribed.

As mentioned above, radial tunnel syndrome often coexists with lateral epicondylitis. In chronic situations where conservative treatment has failed to relieve either set of symptoms, both corrective surgeries can easily be combined through the same incision. The only difference in this instance is that the tennis elbow procedure requires a 3-4 week period of immobilization to allow healing of the muscle back to the bone and rehabilitation is therefore delayed. In this instance, formal hand therapy is instituted immediately once casting has been discontinued.

Many patients seen in my practice have already had unsuccessful surgery for carpal tunnel syndrome or lateral epicondylitis alone before the diagnosis of radial tunnel syndrome has been made. This occurs frequently due to the fact that patients continue to complain of numbness, electrodiagnostic studies yield variable results, and it is wrongfully assumed that carpal tunnel syndrome or lateral epicondylitis alone is responsible for their persistent complaints of pain. In the overwhelming majority of cases, a radial tunnel release is well accepted and provides the already frustrated patient with an upper extremity which has been relieved of its pain and had its function restored.