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Entrapment of Median nerve at the Elbow and Forearm


- See: Anterior Interosseous Nerve Sydrome:
       
- Site of Proximal Forearm Compression;
    - supracondylar process of the humerus and struther's ligament:
          - median nerve may be compressed as it passes under the bondy spur
          - pt c/o of weak hand grip and in pronating, & tingling in lateral digits;
          - there may be objective weakness in the pronator teres, FCR, FPL, FDS, and lateral half of FDP, and thenar mucles;
          - presence of pronator weakness distinguishes this syndrome from pronator and anterior interosseous syndromes;
          - nerve conduction studies may have shown slowing in the conduction velocity in the median nerve in the arm;
          - ref: Images in clinical medicine. Processus supracondylaris humeri.
    - lacertus fibrosus:
          - at front of elbow, median nerve lies behind bicipital aponeurosis (lacertus fibrosus) and in front of the brachialis;
          - one must suspect the lacertus fibrosis with pain in the forearm w/ resisted elbow flexion beyond 120 deg;
                 - it can also be caused by pressure from the origin of the FDS;
    - pronator teres: (pronator teres compression syndrome)
                 - w/ compression at this site, pts may complain of pain following resisted flexion of the FDS to the long finger;
                 - one should suspect compression of meidan nerve by head of pronator teres when a patient complains of pain with increased activity;
                 - check this with forced pronation and wrist flexion;
                 - elarged median artery can also cause the pronator syndrome as well as compress the median nerve at the wrist;
    - sublimis bridge:
                 - median nerve then passes under the fibrotendinous arcade that represents the origin of the FDS muscle;
                 - median nerve descends in the forearm adherent to the undersurface of FDS and lying superficial to the FDP;


- EMG may show denervation potentials in median innervated muscles in the forearm and hand;
    - clinical syndrome may be associated with symptoms and signs of ischemia in the distribution of the brachial artery;
    - bony process may or may not be palpable;
    - tangential or oblique views of humerus may show supracondylar process to greater advantage than routine AP & lateral views;
    - brachial arterogram may be necessary if vascular comprimise is possible
    - surgical therapy consists of excision of Struther's ligament and removal of the bony spur