Pronator syndrome

Pronator syndrome (pronator teres syndrome) is a compression neuropathy of the proximal median nerve as it passes between the two heads of the pronator muscle in the proximal forearm

• condition is rare compared with more distal compression of the median nerve (carpal tunnel syndrome)

Repetitive use of the pronator muscle as seen in people on factory assembly lines (especially hammering) and in some musicians is a key predisposing factor

• presents with pain over the proximal median nerve and sensory disturbance in the lateral three and a half fingers of the palmar aspect of the hand (median nerve distribution)
  • may be weakness of the flexor pollicis longus, the flexor digitorum profundus of the index finger and the pronator quadratus

Investigation

• condition can be made diagnosed clinically
  • key finding is tenderness over the proximal forearm, aggravated by resisted pronation of the forearm (opposite movement to Yergason's test)
    • click here for video of Yergason's test
      
      
  • weak flexor muscles of the thumb and index finger may lead to a weak pincer movement and there may be sensory loss in the median nerve distribution of the hand
    
    
  • Tinel's test at the wrist should be negative but positive over the proximal forearm
    
    
  • Phalan's test should be negative
    
    
• a nerve conduction study is useful in excluding the more common carpal tunnel syndrome

Management

• mainstay of treatment is physiotherapy. Referral for guided corticosteroid injections or surgical decompression should be considered in resistant cases or where there is significant weakness

Reference:

1. Arthritis Research UK (2011). Hands On (11) - upper limb in primary care.