A comparative study of electromyogram and the findings on operation in patients with peripheral nerve lesions

Objective To evaluate the clinical value of preoperative EMG examinations in diagnosis of peripheral nerve injury and to analyze the reasons of misdiagnosis. Methods From January 2000 to April 2003, the results of electrophysiological examinations of 69 nerves in 63 inpatients for operation were compared with the findings on operation. Results In the open injury group, the diagnostic accuracy rate of EMG was 73.08%, which was significantly different from the findings on operation. In the close injury group, the location and quality of injury as diagnosed by EMG examination were all confirmed on operation. In the brachial plexus injury group, the diagnostic accuracy rate for complete root avulsion was not significantly different from that of MRI (68.52% vs 55.56%). With regard to the evaluation of axon regeneration after repair operation of peripheral nerve injuries, EMG examinations of 3 nerves were consistent with the operative findings, while 2 nerves in 5 nerves were not. The general diagnostic accuracy rate of EMG examinations of peripheral nerve lesions was 85.51%. The false positive rate was 4.49%, while the false negative rate was 22.73%. Conclusion EMG is valuable in detecting the location, characteristics and axon regeneration in patients with peripheral nerve injury. But the false positive and false negative results should be watched out. There is no statistical significant difference between preoperative EMG and MRI in detecting the complete brachial plexus root avulsion. A combinative use of EMG and MRI can improve the diagnostic accuracy of brachial plexus roots injuries.