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 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