Use of Electromyography (EMG) in Neuromodulation

Abstract

Neuromodulation is an emerging field that offers promise for patients with a variety of pelvic floor disorders; these include recalcitrant urge-frequency syndrome, urinary retention, and fecal incontinence. The use of neuromodulation continues to grow exponentially and more indications for neuromodulation will surely follow. For neuromodulation to be effective one has to deploy electrodes near the nerve target in a consistent fashion. Unfortunately, there is no clinical way to view the actual nerve targeted. Currently only surrogate markers of response are used, including visual cues of bellows response and great toe flexion. These markers are arbitrary and depend on personal interpretation. In many cases, adequate motor responses may not be possible due to medical disease or body habitus. Sensory responses are also used and are not consistent. These clinical responses are subjective, inaccurate, and leave room for interpretation. Recent studies show an 80% response rate to SNS [1, 2]. One reason that one in five do not respond may be due the subjective interpretation of responses. The use of Electroneurodiagnostics may aid in better use of neuromodulation. Electroneurodiagnostics include Electromyography (EMG), nerve conduction studies and evoked potentials. For this chapter, we will focus on use of EMG. The use of EMG allows recording of a Compound Motor Action Potential (cMAP). The use of Compound Muscle Action Potential (cMAP) monitoring objectifies the process of neuromodulation and may increase the success of the therapy. Currently there is a paucity of data evaluating the effectiveness of cMAP monitoring and most experts in the field are just implementing the use of this technology in clinical practice. In time, the use of cMAP evaluation will become standard care for the application of pelvic neuromodulation. This chapter focuses on a complete review of cMAP technology and cMAP applications for pelvic neuromodulation.