Anodal block V anodal stimulation. Fact or fiction

Anodal block and stimulation are poorly documented electrophysiologic phenomenon. Median and superficial radial nerves are examined in a prospective study to explore the significance of anodal block in routine nerve conduction studies. In addition, the anode's ability to stimulate the peripheral nervous system is evaluated. A monopolar stimulation technique is employed to achieve pure anode-generated responses. Additionally, a similar monopolar cathode stimulation technique is utilized and found to be equivalent to the traditional bipolar cathode stimulation. Based on the findings in this investigation, anodal block does not appear to occur during routine nerve conduction studies; however, transposition of the anode and cathode is clinically significant because the increased distance between the cathode and recording electrode results in predictably prolonged latencies. With higher levels of stimulus intensity, sensory, motor and F wave responses are generated by anodal stimulation in all cases. The actual mechanism of anodal stimulation remains uncertain and requires further study. Predicated on the results of this investigation, it appears that anodal block is an unlikely occurrence during routine electrodiagnostic medicine evaluations.