Sensory Nerve Conduction Study of Upper Trunk Lesion in Brachial Plexopathy

J Korean Assoc EMG Electrodiagn Med 2011;13(1):1-5.
Published online June 1, 2011.

Abstract

Objectives: Localizing or evaluating lesions of upper trunk brachial plexopathy using conventional nerve conduction studies is not accurate. This study examined whether sensory nerve conduction studies are useful for detecting upper trunk brachial plexopathy. Methods: Sixty eight patients with upper trunk brachial plexopathy based on the intra-operative findings were selected among 162 cases of brachial plexopathy revealed by electrodiagnostic tests. All subjects were evaluated by extensive sensory nerve conduction studies including the lateral antebrachial cutaneous nerve, median nerve recorded at the 1st, 2nd and 3rd finger and superficial radial nerve, bilaterally. The following abnormalities were identified: lower amplitude or prolonged onset latency compared to the normal value or a decrease in amplitude more than 50% compared to the contralateral uninjured limb in the sensory nerve action potentials (SNAP). This study analyzed the percentage of abnormal latency and amplitude in the SNAP of lateral antebrachial cutaneous nerve, median nerve and superficial radial nerve. Results: The percentage of cases who showed abnormal findings of the nerve conduction studies in the lateral antebrachial cutaneous nerve, median nerve recorded from the 1st, 2nd and 3rd finger and superficial radial nerve group was 88.2%, 69.2%, 48.5%, 44.4% and 66.2%, respectively. Compared to the uninjured limb, the abnormal findings of nerve conduction studies in the lateral antebrachial cutaneous nerve, median nerve recorded from the 1st, 2nd and 3rd finger and superficial radial nerve group was 92.6%, 88.4%, 64.7%, 55.5% and 82.4%, respectively. Conclusion: Various nerve conduction studies, including the lateral antebrachial cutaneous nerve, median nerve recording at 1st digit and superficial radial nerve, are needed to diagnose upper trunk brachial plexopathy. Because most brachial plexopathy is axon loss, a comparison of the injured and uninjured limb is recommended even if the amplitude of SNAP is within normal limits.

Key Words: Brachial plexopathy, Upper trunk, Nerve conduction study