Pressure-specified sensory device versus electrodiagnostic testing in brachial plexus upper trunk injury.

Brachial plexus upper trunk injury is associated with winged scapula owing to the close anatomical course of the long thoracic nerve and upper trunk. Needle electromyography is a common diagnostic test for this injury; however, it does not detect injury in most patients with upper trunk damage. The pressure-specified sensory device may be an alternative to needle electromyography. Thirty patients with winged scapula and upper trunk injury were evaluated with needle electromyography (EMG) and pressure-specified sensory device (PSSD) tests. EMG testing of the biceps muscle was compared with PSSD testing of the dorsal hand skin (C6 damage), and EMG testing of the deltoid and spinati muscles was compared with PSSD testing of the deltoid skin (C5 damage). PSSD pressure values were significantly higher on the affected arm. On the basis of published and calculated threshold values the PSSD was found to be significantly more sensitive than EMG. The PSSD tests consistently identified injuries that were not detected by needle EMG tests. These findings provide strong evidence that the PSSD is more effective than needle EMG in the detection of brachial plexus upper trunk injury.