Uncommon syndrome of pain, easy fatigability, and/or sensory deficits resulting from entrapment of the median nerve near the elbow.
Potential sites of impingement include:
- lacertus fibrosus
- between the two heads of a hypertrophied pronator teres muscle
- intramuscular tendinous bands
- fascial bands between the superficial and deep heads
- vascular leashes
- fibrous arch of the flexor digitorum superficialis.
Common in weight lifting and occupations requiring repetitive pronation of the forearm
Patient History and Physical Findings
- forearm dysesthesias
- dysesthesias in the palmar triangle and or thenar eminence
- easy fatigability of forearm muscles
- signs of median neuropathy localized to the forearm and hand
- Numbness in median nerve distribution after repetitive pronation
- nocturnal awakening due to pain/numbness is uncommon, in contrast to carpal tunnel syndrome
- Provocative tests:
- Resisted pronation with the elbow in extension
- Resisted elbow flexion
- Resisted contraction of the FDS to the long finger.
- Anterior interosseous nerve function is typically spared, despite the fact this nerve branches from the median nerve near the sites of potential impingement.
- Carpal tunnel provocative tests are negative
- Tenderness in proximal portion of pronator teres muscle
- Positive Tinel sign at proximal edge of pronator teres muscle
Imaging and Diagnostic Studies
- Useful for distinguishing other peripheral nerve disorders with similar presentations
- In 15-20% of patients with pronator teres syndrome, electrophysiologic testing will identify a non-localizable median nerve lesion. In fewer cases it will localize the site of the lesion
- If EMG ordered, request a needle placed in the flexor pollicus longus
- cervical radiculopathy
- thoracic outlet syndrome
- brachial plexus neuritis (Parsonage Turner Syndrome)
- overuse injury
- carpal tunnel syndrome
- Anterior interosseus syndrome (Kiloh-Nevin syndrome)
- Surgery is usually not necessary as this condition can typically be treated with activity modification.
- Surgical exploration and release of impinging structures. Potential sites of impingement include the lacertus fibrosus, between the two heads of a hypertrophied pronator teres muscle (requires release of the humeral head), intramuscular tendinous bands, fascial bands between the superficial and deep heads, vascular leashes, fibrous arch of the flexor digitorum superficialis.
- One series of 36 patients treated surgically, 8 had excellent results, 20 had good results, 5 had fair results and 3 remained unchanged
Pearls and Pitfalls