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Normative values for high voltage electrical stimulation across the brachial plexus
E Papathanasiou1, E Zamba, S Papacostas
1Department of Clinical Neurophysiology, Cyprus Institute of Neurology & Genetics, 6 International Airport Avenue, P.O. Box 23462, Nicosia 1683, Cyprus. neurophy@mdrtc.cing.ac.cy
Objectives:
To obtain normative values for High Voltage Electrical Stimulation across the brachial plexus between Erb's point, C8 root and T1 root. A case study of probable true thoracic outlet syndrome is used to illustrate the usefulness of the method.
Methods:
22 patients were tested for use in normative date pool with complaints unrelated to the ulnar nerve, the majority of which were pure carpal tunnel syndrome. High voltage stimulation was performed at Erb's point, C8 root and T1 root. Recording was from the abductor digit minimi muscle.
Results:
Upper limit for absolute latencies were 13.9 ms, 14.5 ms and 14.5 ms for Erb's point, C8 root and T1 root stimulation respectively. Corresponding lower limits of amplitude were 4.8 mV, 3.4 mV and 2.9 mV. Upper limits for interpeak latencies were 1.4 ms and 1.2 ms for C8 to Erb's point and T1 to Erb's point respectively. In a case of true thoracic outlet syndrome, the symptomatic side revealed prolonged interpeak and absolute latencies. The asymptomatic side remained within normal limits.
Conclusion:
Normative values for high voltage stimulation across the brachial plexus are useful in cases of suspected compression in this proximal location of the upper limb.