The contribution of the interosseous muscles to the hypothenar compound muscle action potential

Nerve conduction topography in geriatric hand assessment

“…This variation explains why CMAP parameters are so sensitive to electrode position [26] and why larger electrodes, averaged over a wider area, reduce variability. Lateva et al and McGill et al used mathematical models and volume conductor theory to describe the way the electrical potential field throughout the limb evolves in space and time during the action potential [23,27]. Their results explain the differences in CMAP shapes associated with different recording montages and different joint configurations.…”

Origin of far‐field potentials in the ulnar compound muscle action potential

“…Kincaid et al1 first reported the presence of a potential recorded over the conventional distal reference electrode for the ADM CMAP when it was referenced to a proximal electrode. These reference electrode potentials are now considered to be FFPs and contribute to the second peak of the routine ADM CMAP 2–4. Previous investigators have proposed hypotheses regarding the origin of these FFP components.…”

“…van Dijk et al2 deduced the origin of the ADM CMAP from the distribution over the hand, and concluded that the second peak (i.e., the P1 FFP component in this study) might be generated mainly by the dorsal interosseous muscles. McGill and Lateva3 investigated this issue by changing the muscle length and by using direct muscle stimulation. They identified the “I–N1–P1–N2–P2” components when the proximal electrodes were referenced to the distal ones, which must correspond to our N1–P1–bilobed N2 components, because the polarity was the opposite.…”

“…It is believed that the compound muscle action potential (CMAP) is generated at the active electrode over the muscle belly. However, several researchers have documented the contribution of the reference electrode to the CMAP, especially for tibial and ulnar nerves, and have proposed that far‐field potentials (FFPs) may be responsible as a mechanism 1–4. Regarding the ulnar nerve CMAP recorded at the abductor digiti minimi (ADM) muscle, a major contribution of the interosseous muscles to the FFPs has been suggested 2, 5.…”

Physiologic basis of potentials recorded in electromyography

“…Thus, the CMAP derived from the ADM under routine conditions is a combination of near-field potential from the ADM and far-field potentials from additional ulnarinnervated intrinsic hand muscles. 47,58 Finally, a slow sweep-speed following ulnar nerve stimulation while recording from the ADM also demonstrates a total waveform duration approaching 60 ms for reasons described above for the APB (Fig. 9E).…”