Investigation of anodal stimulation and its implications for F‐wave examinations

Abstract

In this work we identified detailed features of anodal stimulation and potential influence on F-wave examinations. Muscle Nerve 56: 51-56, 2017.

Interaction of cathodal and anodal stimulations in nerve conduction studies

“…These interactions may influence actual NCS examinations. In our preceding study, we documented that, when F‐wave examinations are performed with a cathode‐distal setting, anodal stimulation may shorten the F‐wave latency. We also found that the threshold for the anodal stimulation decreased when the cathode was placed away from the nerve trunk.…”

“…6 During this investigation, we noticed that the anodal stimulation was easy to elicit when the cathode was placed away from the nerve trunk. 6 In ordinary NCSs, we observed that cathodal stimulation becomes difficult to elicit when the anode is moved away from the nerve during the effort to optimize the baseline. These findings suggest that cathodal stimulation and anodal stimulation may interact with each other.…”

“…The stimulus intensity at the proximal anode was set at 0, 2, 4, 6, 8, or 10 mA. At these settings, the anodal stimulation did not usually elicit the CMAP because the threshold of anodal stimulation is much higher than that of cathodal stimulation . At each setting, we checked the stimulus current necessary to achieve the following while the distal cathode stimulus intensity was gradually increased: (1) the threshold for the CMAP (“cathodal threshold”); (2) half size of the maximal CMAP (cathodal half”); and (3) the maximal CMAP (“cathodal max”).…”

“…In our preceding study, we investigated the characteristics of anodal stimulation in detail and demonstrated that anodal stimulation occurs about 20 mm away from the anode and has a potential influence on F‐wave examinations . During this investigation, we noticed that the anodal stimulation was easy to elicit when the cathode was placed away from the nerve trunk . In ordinary NCSs, we observed that cathodal stimulation becomes difficult to elicit when the anode is moved away from the nerve during the effort to optimize the baseline.…”

“…I t has long been believed that anodal block occurs during bipolar stimulation in nerve conduction studies (NCSs), although recent studies have demonstrated that anodal stimulation, that is, the action potential generated from the anode itself, occurs instead of anodal block . In our preceding study, we investigated the characteristics of anodal stimulation in detail and demonstrated that anodal stimulation occurs about 20 mm away from the anode and has a potential influence on F‐wave examinations . During this investigation, we noticed that the anodal stimulation was easy to elicit when the cathode was placed away from the nerve trunk .…”