ELECTROMYOGRAPHIC MOTOR TINELS SIGN IN ULNAR MONONEUROPATHIES AT THE ELBOW

A novel test for localizing ulnar mononeuropathies (UM), the electromy ographic (EMC) motor Tinel's sign, has been developed. While recording with a monopolar needle from the abductor digiti minimi, the ulnar ne rve is lightly rolled at multiple sites across the elbow, and the test is considered positive if a burst of EMG activity is observed simulta neously with nerve compression. To determine the use of the EMG Tinel' s sign, we evaluated 70 control nerves and 50 clinically suspected UMs . The EMC Tinel's sign had a 78% sensitivity and a 79% specificity for suspected UM at the elbow. The clinical Tinel's sign was present in 6 8% of suspected UM cases, and the combined sensitivity of the EMG and clinical Tinel's sign was 96%. Using nerve conduction study (NCS) valu es derived from the control nerves, 62% of UM nerves had abnormal NCS/ EMG findings, and 28% of UM nerves had NCS/EMG abnormalities that coul d be localized to the elbow. The development of motor axon mechanosens itivity at the site of nerve injury is a new finding, not previously o bserved in electrophysiologic studies of animal nerve injury models or reported in the electrodiagnostic literature.