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EMG in Cubital Tunnel Syndrome

- EMG - General Discussion:
    - conduction velocity in the ulnar nerve across the elbow is slowed compared with the velocity in the forearm segment;
    - as noted by Kaempffe and Farbach (1998), abnormal EMG results are associated w/ poor surgical outcome;
    - position of elbow during EMG/NCS:
           - remember that elbow flexion may cause greater than a 10% ulnar nerve strain in upto 25% of patients;
           - it is important to keep elbow flexed 70 to 90 deg during conduction measurements because in this position nerve is optimally stretched;
           - during extension nerve buckles upon itself & is redundant, factor that may lead to spuriously low computed values of conduction velocity;
    - amplitude of motor response in abductor digiti minimi is decreased and duration of response is prolonged w/ stimulation above elbow 
           compared w/ stimulation below the elbow;
    - motor conduction velocity:
           - look for slowing of more than 10 m/sec;
           - velocity less than 41 m / sec across the elbos is abnormal;
           - motor latency from above the elbow more than 10.2 sec;
    - sensory latency is prolonged;
    - motor latency:
    - when axonal degeneration of the ulnar nerve occurs, positive waves and fibrillation may be observed

A modified surgical procedure for cubital tunnel syndrome: partial medial epicondylectomy.