Pectoral nerve conduction studies: technique in healthy subjects and evaluation of brachial plexopathy

OBJECTIVE: To define the optimal nerve conduction study (NCS) technique of the pectoral nerves and evaluate its clinical utility. DESIGN: Prospective electrophysiologic study with healthy controls. SETTING: Electrophysiologic laboratory in a large general hospital. PARTICIPANTS: Thirty healthy controls and 10 patients with cervical root or brachial plexus pathologies. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Correlation of pectoral NCS with electromyography and magnetic resonance imaging. RESULTS: For pectoral NCS, the mean values +/- standard deviation of onset latency, amplitude, and interside amplitude ratio (ratio of smaller over larger amplitude) were 2.01+/-0.22 ms, 11.75+/-2.21 mV, and .95+/-.04 mV, respectively. Subject age correlated significantly with both onset latency (r=.46, P<.001) and amplitude (r=-.34, P<.008). All 5 patients with brachial plexopathy had amplitude ratios below the normal limit of controls (.87). However, this was not seen for all 5 patients with cervical spondylotic radiculopathy. CONCLUSIONS: The pectoral NCS technique is feasible in healthy subjects. It is useful when differentiating brachial plexopathy from cervical root lesions.