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Electrodiagnostic Studies
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
In the motor nerve conduction study (MNCS), surface electrodes are used to record the activity from a muscle innervated by the tested nerve. Figure 46.6a illustrates the setup for a median motor NCS. e “active” recording surface is over the belly of abductor pollicis brevis (APB) muscle, and a “reference” electrode is placed distally over the thumb. e rst stimulation site for the median nerve is at the wrist where the nerve is quite supercial. At minimal stimulus intensity, the electrical eld is insucient to depolarize any nerve bers. Hence, no response is registered. When the intensity is increased, some axons in the nerve will be stimulated (i.e., they will adequately depolarize to generate the AP). eir APs will propagate to the muscle and activate the muscle bers innervated by them. One may recognize a small twitch and a concomitant low-voltage electrical response on the display. When the intensity is increased, more nerve bers will be stimulated and the response will become larger (Figure 46.6b). One continues to increase the intensity until the amplitude (i.e., signal voltage) is maximized. is indicates that all nerve bers are stimulated. To ensure that the response is maximal, the intensity is increased further by 10-20% and the resulting potential is accepted for analysis. e signal is a sum of MUP of all MUs in the muscle and is called the “compound muscle action potential (CMAP)” (Figure 46.6c). In motor nerve conduction studies, the recording electrode is placed over the end-plate zone of the muscle. Since there is no approaching volley of APs, the CMAP does not have an initial positive phase. An initial negative (i.e., upward) deection is used as an indication of proper electrode placement.
MR neurography of the brachial plexus in adult and pediatric age groups: evolution, recent advances, and future directions
Published in Expert Review of Medical Devices, 2020
Alexander T. Mazal, Ali Faramarzalian, Jonathan D. Samet, Kevin Gill, Jonathan Cheng, Avneesh Chhabra
The signs and symptoms of brachial plexopathies are highly variable depending on the lesion location and etiology (Table 1). Due to its anatomic complexity, accurate localization of lesions within the brachial plexus can be challenging. Furthermore, among patients with scarring or fibrosis secondary to prior surgery or irradiation to the axilla, physical examination findings can be quite difficult to interpret. Diagnosis of brachial plexopathy is generally multi-modal, and may involve any combination of electromyography (EMG), nerve conduction studies, MR imaging, or CT myelography, in association with clinical exam findings. F wave indices using nerve conduction studies have recently shown some promise in facilitating early detection of peripheral neuropathy; however, due to the deep location of the brachial plexus, an inability to characterize regional anatomy, and challenges in differentiating radiculopathy from brachial plexopathy, this technique suffers from several limitations [10].
Forearm muscle activation, ulnar nerve at the elbow and forearm fatigue in overhand sports
Published in Sports Biomechanics, 2020
Lin-Hwa Wang, Kuo-Cheng Lo, I-Ming Jou, Fong-Chin Su
Nerve conduction studies for evaluating neuromuscular disease were performed as a physiological assessment of the peripheral nerve. Small electrical stimuli were applied to the nerves and responses were recorded. Standard median and ulnar sensory and motor nerve conduction studies were completed according to the methods reported by Jackson and Clifford (1989).