Radial tunnel syndrome

Overview

Radial tunnel syndrome is a compressive neuropathy that affects the radial nerve as it passes through the radial tunnel near the elbow. It is often mistaken for lateral epicondylitis (tennis elbow) due to similar pain distribution, but it is a distinct condition caused by entrapment of the radial nerve in the forearm. The syndrome leads to pain and sometimes weakness in the posterior part of the forearm but typically does not cause numbness or tingling, since the radial nerve is primarily motor in this region.

The condition is relatively uncommon and tends to affect individuals who engage in repetitive arm and wrist movements, such as athletes, manual laborers, or people who perform repetitive desk work. Early recognition and management can prevent progression and reduce the risk of chronic pain or disability.

Causes

Radial tunnel syndrome is caused by compression or irritation of the radial nerve, particularly the posterior interosseous branch, within the radial tunnel. The radial tunnel is a narrow anatomical space in the forearm located just below the lateral epicondyle of the humerus. Several anatomical structures can contribute to nerve entrapment:

• Fibrous bands near the radial head

• The edge of the extensor carpi radialis brevis (ECRB) muscle

• The arcade of Frohse (a fibrous arch in the supinator muscle)

• Repetitive forearm rotation and extension movements

• Direct trauma to the lateral elbow or forearm

• Inflammation from overuse injuries or muscle hypertrophy

Occupational and recreational activities involving repetitive pronation and supination of the forearm increase the risk of developing this syndrome.

Symptoms

Symptoms of radial tunnel syndrome are primarily related to pain and motor disturbances, with sensory symptoms being rare. Common features include:

• Aching or burning pain on the top (dorsal) side of the forearm, especially 3 to 5 cm below the lateral epicondyle

• Pain that worsens with activities involving forearm rotation or wrist extension

• Tenderness over the radial tunnel during palpation

• Weakness in wrist and finger extension in some cases (posterior interosseous nerve involvement)

• Minimal or no numbness or tingling (as sensory branches are not typically affected)

• No swelling or redness

The pain may be persistent or intermittent and often mimics that of lateral epicondylitis, which can delay proper diagnosis and treatment.

Diagnosis

Diagnosing radial tunnel syndrome can be challenging due to its similarity to other elbow and forearm conditions. A thorough clinical evaluation is essential. Diagnostic steps may include:

• Physical examination: Palpation over the radial tunnel to elicit tenderness; resisted middle finger extension or resisted supination may reproduce symptoms

• Exclusion of lateral epicondylitis: Tenderness in radial tunnel is distal to the lateral epicondyle, differentiating it from tennis elbow

• Electromyography (EMG) and nerve conduction studies: May show nerve compression but are often normal in early or mild cases

• Imaging studies: MRI or ultrasound may be used to assess for structural causes such as masses or inflammation

A trial of conservative treatment may also help confirm the diagnosis if symptoms improve with nerve decompression strategies.

Treatment

Treatment of radial tunnel syndrome typically begins with conservative (non-surgical) measures. These include:

• Rest and activity modification: Avoiding repetitive forearm movements and reducing strain on the radial nerve

• Nonsteroidal anti-inflammatory drugs (NSAIDs): To reduce pain and inflammation

• Physical therapy: Stretching and strengthening exercises, nerve gliding techniques, ergonomic modifications

• Bracing or splinting: Wrist or elbow splints may help reduce nerve irritation

• Corticosteroid injections: May provide temporary relief if inflammation is contributing to compression

If conservative treatment fails after 3 to 6 months, surgical decompression of the radial nerve may be considered. This involves releasing the structures compressing the nerve within the radial tunnel.

Prognosis

The prognosis for radial tunnel syndrome is generally good, especially with early diagnosis and appropriate treatment. Most individuals respond well to conservative management and experience symptom relief within weeks to months. However, persistent or severe cases may require surgical intervention, which also has a high success rate in relieving pain and restoring function.

Delay in diagnosis or inadequate treatment may result in prolonged discomfort and decreased use of the affected arm. Long-term outcomes are best when treatment is initiated promptly and tailored to the patient’s specific occupational or activity-related needs.