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Updated: May 17 2021

Pronator Syndrome

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  • Summary
    • Pronator Syndrome is a compressive neuropathy of the median nerve at the level of the elbow.
    • Diagnosis is made clinically with pain at the proximal volar forearm, sensory changes over the palmar cutaneous branch, and positive Tinel's over the proximal volar forearm. 
    • Treatment involves a prolonged nonoperative course, and rarely, surgical decompression.
  • Epidemiology
    • Incidence
      • rare
        • < 1 per 100,000 annually
    • Demographics
      • female > male
      • common in 5th decade
    • Risk factors
      • associated with well-developed forearm muscles (e.g. weight lifters)
  • Etiology
    • Pathoanatomy
      • 5 potential sites of entrapment include
        • supracondylar process
          • residual osseous structure on distal humerus present in 1% of population
        • ligament of Struthers
          • travels from tip of supracondylar process to medial epicondyle
          • not to be confused with arcade of Struthers which is a site of ulnar compression neuropathy in cubital tunnel syndrome
        • bicipital aponeurosis (a.k.a. lacertus fibrosus)
        • between ulnar and humeral heads of pronator teres
          • considered the most common site of entrapment
        • FDS aponeurotic arch
    • Associated conditions
      • commonly associated with medial epicondylitis
  • Presentation
    • Symptoms
      • paresthesias in thumb, index, middle finger and radial half of ring finger as seen in carpal tunnel syndrome
        • in pronator syndrome paresthesias often made worse with repetitive pronosupination
      • should have characteristics differentiating from carpal tunnel syndrome (CTS)
        • aching pain over proximal volar forearm
        • sensory disturbances over the distribution of palmar cutaneous branch of the median nerve (palm of hand)
          • arises 4 to 5 cm proximal to carpal tunnel
        • lack of night symptoms
    • Physical exam
      • provocative tests are specific for different sites of entrapment
        • positive Tinel sign in the proximal anterior forearm but no Tinel sign at wrist nor provocative symptoms with wrist flexion as would be seen in CTS
        • resisted elbow flexion with forearm supination (compression at bicipital aponeurosis)
        • resisted forearm pronation with elbow extended (compression at two heads of pronator teres)
        • resisted contraction of FDS to middle finger (compression at FDS fibrous arch)
      • possible coexisting medial epicondylitis
  • Imaging
    • Radiographs
      • recommended views
        • elbow films are mandatory
      • findings
        • may see supracondylar process
  • Studies
    • EMG and NCV
      • may be helpful if positive but are usually inconclusive
      • may exclude other sites of nerve compression or identify double-crush syndrome
  • Differential
    • AIN compressive neuropathy 
    • Carpal tunnel syndrome
    • Pronator teres strain
  • Treatment
    • Nonoperative
      • rest, splinting, and NSAIDS for 3-6 months
        • indications
          • mild to moderate symptoms
        • technique
          • splint should avoid forearm rotation
    • Operative
      • surgical decompression of median nerve
        • indications
          • only when nonoperative management fails for 3-6 months
        • technique
          • decompression of the median nerve at all 5 possible sites of compression
        • outcomes
          • of surgical decompression are variable
            • 80% of patients having relief of symptoms
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