What is Radial Tunnel Syndrome

Radial tunnel syndrome happens when the nerve that extends from the back of your upper arm to your forearm (radial nerve) gets squeezed (compressed).

Radial tunnel syndrome is an entrapment of the posterior interosseous branch of the radial nerve at the proximal forearm.

The condition is usually caused by inflammation, an injury, or a tumor that puts pressure on the nerve and traps it. Radial tunnel syndrome can cause stabbing pain in the hand and arm.

In fact, it is often mistaken for tennis elbow. It is a rare syndrome, and although tennis elbow is so common, radial tunnel syndrome should still be added to the differential diagnosis.

Radial tunnel syndrome is an uncommon cause of lateral elbow pain that has the unique distinction among entrapment neuropathies of almost always being initially misdiagnosed. The incidence of misdiagnosis of radial tunnel syndrome is so common that it is often incorrectly referred to as resistant tennis elbow. As seen from the following discussion, the only major similarity that radial tunnel syndrome and tennis elbow share is the fact that both clinical syndromes produce lateral elbow pain.

Characteristics of Radial Tunnel Syndrome and Lateral Epicondylitis

Modified from Mileti J, Largacha M, O’Driscoll SW. Radial tunnel syndrome caused by ganglion cyst: treatment by arthroscopic cyst decompression. Arthroscopy . 2004;20:e39–e44.

Characteristic	Radial Tunnel Syndrome	Lateral Epicondylitis (Tennis Elbow)
Frequency	Rare (2% of all peripheral nerve compressions of the upper limb)	Common cause of lateral elbow pain
Cause	Compression of the radial nerve	Caused by overuse of the extensor and supinator muscles
Characteristic patient	Anybody with repetitive, stressful pronation and supination (e.g., tennis players, Frisbee players, swimmers, powerlifters)	Tennis players
Pain location	Pain over the neck of the radius and lateral aspect of the proximal forearm over the extensor muscles themselves (distal to where the pain is located in lateral epicondyle)	Pain and tenderness over the lateral epicondyle and immediately distal to it (at the origin of the extensor muscles)
Pain radiation	Pain can radiate proximally and (more commonly) distally	Usually localized without radiation
Provocative tests (much overlap between the two entities)	Pain with resisted extension of the middle finger with the forearm pronated and the elbow extended. Pain with resisted forearm supination with the elbow fully extended	Pain with resisted wrist extension or elbow supination with the elbow extended. Pain with forceful wrist flexion or forearm pronation

The lateral elbow pain of radial tunnel syndrome is aching and localized to the deep extensor muscle mass. The pain may radiate proximally and distally into the upper arm and forearm. The intensity of the pain of radial tunnel syndrome is mild to moderate, but it may produce significant functional disability.

In radial tunnel syndrome, the posterior interosseous branch of the radial nerve is entrapped by a variety of mechanisms that have in common a similar clinical presentation. These mechanisms include aberrant fibrous bands in front of the radial head, anomalous blood vessels that compress the nerve, extrinsic masses, or a sharp tendinous margin of the extensor carpi radialis brevis. These entrapments may exist alone or in combination.

What are the causes?

This condition may be caused by:

• Repeatedly using your forearm too much, especially to twist or extend your arm.
• Muscle inflammation.
• An injury.
• A mass of nerve tissue (ganglia).
• Noncancerous fatty tumors (lipomas).
• A bone tumor.

This may be due to an aberrant fibrous band, sharp tendinous margin, or a blood vessel.

What increases the risk?

This condition is more likely to develop in people who:

• Play sports that involve moving their forearm a lot, such as tennis.
• Have a job that involves using their forearm a lot, such as some factory jobs.

What are the symptoms?

Symptoms include pain in the proximal and lateral forearm similar to tennis elbow.

Symptoms of this condition include:

• Aching pain on the top of the forearm, back of the hand, or side of the elbow.
• Pain while straightening the wrist or fingers.
• Weakness in the forearm muscles and wrist.

Regardless of the mechanism of entrapment of the radial nerve, the common clinical feature of radial tunnel syndrome is pain just below the lateral epicondyle of the humerus. The pain of radial tunnel syndrome may develop after an acute twisting injury or direct trauma to the soft tissues overlying the posterior interosseous branch of the radial nerve, or the onset may be more insidious, without an obvious inciting factor. The pain is constant and worsens with active supination of the wrist. Patients often note the inability to hold a coffee cup or hammer. Sleep disturbance is common. On physical examination, elbow range of motion is normal. Grip strength on the affected side may be diminished.

In the classic text on entrapment neuropathies, Dawson and colleagues note three important signs that allow the clinician to distinguish radial tunnel syndrome from tennis elbow: (1) tenderness to palpation distal to the radial head in the muscle mass of the extensors, rather than over the more proximal lateral epicondyle, as in tennis elbow; (2) increasing pain on active resisted supination of the forearm owing to compression of the radial nerve by the arcade of Frohse as a result of contraction of the muscle mass; and (3) a positive result on the middle finger test. The middle finger test is performed by having the patient extend the forearm, wrist, and middle finger and sustain this action against resistance. Patients with radial tunnel syndrome exhibit increased lateral elbow pain secondary to fixation and compression of the radial nerve by the extensor carpi radialis brevis muscle

How is this diagnosed?

This condition may be diagnosed based on your symptoms, your medical history, and a physical exam. During the exam, you may be asked to move your hand, fingers, wrist, and arm in certain ways so your health care provider can find the source of your pain. Your health care provider may also order one or more tests to rule out other conditions. The tests may include:

• An electromyogram (EMG). This test can show how well the radial nerve is working.
• A nerve conduction study. This test measures how well electrical signals pass through your nerves.
• An MRI. This test checks for causes of nerve problems, such as scarring from an injury, pressure on a nerve, or a tumor.
• An ultrasound. This test can show certain injuries, such as tears to ligaments or tendons.

Because of the ambiguity and confusion surrounding this clinical syndrome, testing is important to help confirm the diagnosis of radial tunnel syndrome. Electromyography helps distinguish cervical radiculopathy and radial tunnel syndrome from tennis elbow. Plain radiographs are indicated in all patients who present with radial tunnel syndrome to rule out occult bony pathology.

Based on the patient’s clinical presentation, additional testing, including complete blood cell count, uric acid, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated.

Magnetic resonance imaging (MRI) of the elbow is indicated if internal derangement of the joint is suspected and may help identify the factors responsible for the nerve entrapment, such as ganglion cysts or lipomas. The injection technique of the radial nerve at the elbow with a local anesthetic and steroid may help confirm the diagnosis and treat the syndrome.

Differential Diagnosis

Cervical radiculopathy and tennis elbow can mimic radial tunnel syndrome. Radial tunnel syndrome can be distinguished from tennis elbow because with radial tunnel syndrome, the maximal tenderness to palpation is distal to the lateral epicondyle over the posterior interosseous branch of the radial nerve, whereas with tennis elbow, the maximal tenderness to palpation is over the lateral epicondyle.

Increased pain with active supination and a positive middle finger test (see earlier discussion) helps strengthen the diagnosis of radial tunnel syndrome. Acute gout affecting the elbow manifests as a diffuse acute inflammatory condition that may be difficult to distinguish from infection of the joint, rather than a localized nerve entrapment.

How is this treated?

Treatment for this condition may include:

• Avoiding activities that cause your symptoms to get worse or flare up.
• Taking steroids or anti-inflammatory medicines, like ibuprofen, to help with symptoms.
• Wearing a splint or brace for support until your symptoms go away.
• Doing exercises to regain strength and maintain movement and range of motion in your hand and arm.
• Surgery to release the radial nerve.

Usually, surgery is not needed unless other treatments fail and symptoms last longer than 3 months.

Initial treatment of the pain and functional disability associated with radial tunnel syndrome should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. The local application of heat and cold also may be beneficial. Patients should avoid the repetitive movements that incite the syndrome.

For patients who do not respond to these treatment modalities, injection of the radial nerve at the elbow with a local anesthetic and steroid may be a reasonable next step. If the symptoms of radial tunnel syndrome persist, surgical exploration and decompression of the radial nerve are indicated.

Follow these instructions at home:

If You Have a Splint or Brace:

• Wear it as told by your health care provider. Remove it only as told by your health care provider.
• Loosen it if your fingers tingle, become numb, or turn cold and blue.
• Do not let it get wet if it is not waterproof.
• Keep it clean.

Activity

• Return to your normal activities as told by your health care provider. Ask your health care provider what activities are safe for you.
• Do exercises as told by your health care provider.

General Instructions

• Do not use any tobacco products, including cigarettes, chewing tobacco, or e-cigarettes. If you need help quitting, ask your health care provider.
• Take over-the-counter and prescription medicines only as told by your health care provider.
• Keep all follow-up visits as told by your health care provider. This is important.

How is this prevented?

• Warm up and stretch before being active.
• Cool down and stretch after being active.
• Give your body time to rest between periods of activity.
• Make sure to use equipment that fits you.
• Be safe and responsible while being active to avoid falls.
• Do at least 150 minutes of moderate-intensity exercise each week, such as brisk walking or water aerobics.
• Maintain physical fitness, including:
  • Strength.
  • Flexibility.
  • Cardiovascular fitness.
  • Endurance.

Contact a health care provider if:

• Your symptoms do not improve within 12 weeks.
• Your symptoms get worse.
• Your wrist gets weak or droopy.

Get help right away if:

• Your pain is severe.
• You cannot move part of your hand or arm.

Radial Tunnel Syndrome Rehabilitation

Ask your health care provider which exercises are safe for you. Do exercises exactly as told by your health care provider and adjust them as directed. It is normal to feel mild stretching, pulling, tightness, or discomfort as you do these exercises, but you should stop right away if you feel sudden pain or your pain gets worse. Do not begin these exercises until told by your health care provider.

Stretching and range of motion exercises

These exercises warm up your muscles and joints and improve the movement and flexibility of your forearm. These exercises also help to relieve pain, numbness, and tingling.

Exercise A: Wrist flexion, active-assisted

1. Extend your left / right arm in front of you, and point your fingers downward.
2. If told by your health care provider, bend your left / right elbow.
3. Gently tip the palm of your hand toward your forearm.
4. If told by your health care provider, use your other hand to move your palm closer to your forearm.
5. Hold this position for __________ seconds.
6. Slowly return to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise B: Wrist flexion

1. Stand over a tabletop with your left / right hand resting palm-up on the tabletop and your fingers pointing away from your body. Your arm should be extended, and there should be a slight bend in your elbow.
2. Gently press the back of your hand down by straightening your elbow. You should feel a stretch in the top of your forearm.
3. Hold this position for __________ seconds.
4. Slowly return to the starting position.

Repeat __________ times. Complete this stretch __________ times a day.

Strengthening exercises

These exercises build strength and endurance in your forearm. Endurance is the ability to use your muscles for a long time, even after they get tired.

Exercise C: Wrist flexors

1. Sit with your left / right forearm supported on a table and your hand resting palm-up over the edge of the table. Your elbow should be below the level of your shoulder.
2. Hold a __________ weight in your hand. Or, hold a rubber exercise band or tube in both hands, keeping your hands at the same level and hip distance apart. There should be a slight tension in the exercise band or tube.
3. Slowly curl your hand up toward your forearm.
4. Hold this position for __________ seconds.
5. Slowly lower your hand to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise D: Radial deviators

1. Stand with a __________ weight in your hand. Or, sit with your healthy hand supported, and hold onto a rubber exercises band or tube. There should be a slight tension in the exercise band or tube.
   1. If you are holding a weight, move your thumb toward your forearm, raising your hand as far as it will go.
   1. If you are holding an exercise band or tube, pull on it as far as it will go with your thumb facing your forearm.
2. Hold this position for __________ seconds.
3. Slowly return to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise E: Grip

1. Hold one of these items in your hand: a dense sponge, a tennis ball, or a large, rolled sock.
2. Squeeze as hard as you can without increasing any pain.
3. Hold this position for __________ seconds.
4. Slowly release your grip.

Repeat __________ times. Complete this exercise __________ times a day.

Complications and Pitfalls

The major complications associated with radial tunnel syndrome fall into two categories: (1) iatrogenically induced complications resulting from persistent and overaggressive treatment of “resistant tennis elbow” and (2) the potential for permanent neurological deficits as a result of prolonged untreated entrapment of the radial nerve. Failure of the clinician to recognize an acute inflammatory or infectious arthritis of the elbow may result in permanent damage to the joint and chronic pain and functional disability.

Clinical Pearls

Radial tunnel syndrome is a distinct clinical entity that is often misdiagnosed as tennis elbow, and this fact accounts for the many patients with “tennis elbow” who fail to respond to conservative measures. Radial tunnel syndrome can be distinguished from tennis elbow because with radial tunnel syndrome, the maximal tenderness to palpation is over the radial nerve, whereas with tennis elbow, the maximal tenderness to palpation is over the lateral epicondyle.

If radial tunnel syndrome is suspected, injection of the radial nerve at the humerus with a local anesthetic and steroid gives almost instantaneous relief. Careful neurological examination to identify preexisting neurological deficits that may later be attributed to the nerve block should be performed on all patients before beginning radial nerve block at the humerus.