Pronator teres syndrome

Overview

Pronator teres syndrome (PTS) is a rare compression neuropathy of the median nerve in the proximal forearm, specifically as it passes between the two heads of the pronator teres muscle. It is considered a form of median nerve entrapment and often presents with symptoms similar to carpal tunnel syndrome, but the site of compression is higher in the forearm. PTS can lead to forearm pain, weakness in certain hand muscles, and sensory disturbances in the hand. It typically affects individuals who perform repetitive pronation and gripping motions and may be seen in athletes, manual laborers, and office workers.

Causes

The main cause of pronator teres syndrome is compression of the median nerve at or near the elbow, particularly where the nerve passes through the two heads of the pronator teres muscle. Factors contributing to this compression include:

• Repetitive forearm activity: Activities involving repeated pronation (turning the palm downward), such as using screwdrivers or typing

• Muscle hypertrophy or tightness: Enlarged or tight pronator teres muscle due to overuse can compress the nerve

• Fibrous bands or fascial structures: Abnormal tissue bands may compress the nerve at the elbow or proximal forearm

• Trauma: Direct blow or injury to the proximal forearm can lead to inflammation or scarring around the nerve

• Occupational overuse: Prolonged or excessive gripping and forearm rotation in the workplace

Symptoms

Symptoms of pronator teres syndrome are often similar to those of carpal tunnel syndrome but tend to affect a wider area and may be aggravated by activity. Common symptoms include:

• Achy pain in the proximal forearm, especially over the pronator teres muscle

• Numbness or tingling in the thumb, index finger, middle finger, and lateral half of the ring finger

• Weakness in hand muscles innervated by the median nerve, such as the thenar muscles

• Increased discomfort during repetitive pronation or wrist flexion activities

• Tenderness over the pronator teres with pain on resisted forearm pronation or middle finger flexion

• Lack of nighttime symptoms (distinguishing it from carpal tunnel syndrome, which often disrupts sleep)

In severe or prolonged cases, muscle atrophy or significant functional weakness may develop.

Diagnosis

Diagnosis of pronator teres syndrome involves a combination of clinical examination, patient history, and diagnostic studies. Since it shares features with other median nerve compression syndromes, accurate diagnosis is critical.

• Physical examination: Includes palpation over the pronator teres, checking for tenderness, and performing provocative tests

• Resisted pronation test: Pain or paresthesia on resisted pronation of the forearm suggests PTS

• Middle finger flexion test: Symptoms may be reproduced with resisted flexion of the middle finger (indicating FDS arch compression)

• Tinel’s sign: Tapping over the proximal median nerve may elicit symptoms

• Nerve conduction studies (NCS) and electromyography (EMG): Help confirm the site and severity of nerve compression

• Ultrasound or MRI: May be used to visualize nerve entrapment, muscle hypertrophy, or fibrous bands

Ruling out carpal tunnel syndrome, anterior interosseous nerve syndrome, and cervical radiculopathy is essential during diagnostic evaluation.

Treatment

Treatment for pronator teres syndrome typically begins with conservative, non-surgical approaches. Surgical intervention is reserved for persistent or severe cases that do not respond to initial treatment.

Non-Surgical Management

• Activity modification: Avoiding repetitive pronation and gripping tasks

• Rest and immobilization: Use of forearm splints to reduce movement and allow healing

• Nonsteroidal anti-inflammatory drugs (NSAIDs): For pain relief and inflammation reduction

• Physical therapy: Focused on stretching, strengthening, nerve gliding exercises, and ergonomics

• Corticosteroid injections: May be used for short-term symptom relief in localized cases

Surgical Treatment

• Median nerve decompression: Surgical release of the pronator teres and any other structures compressing the nerve

• Postoperative rehabilitation: Involves gradual return to activity with supervised therapy

Surgery is generally successful in relieving symptoms when properly indicated, though full recovery may take weeks to months.

Prognosis

The prognosis for pronator teres syndrome is generally favorable, especially when diagnosed early and managed with conservative treatment. Most patients experience significant symptom improvement with rest, therapy, and ergonomic modifications. In chronic or severe cases requiring surgery, outcomes are typically good, with a high success rate for pain relief and functional recovery. However, delayed diagnosis or prolonged nerve compression may result in residual weakness or sensory changes. Ongoing attention to activity modification and proper ergonomics can help prevent recurrence.