A noninvasive method for recording the electrical activity of the human uterus in vivo

Development of an electrohysterograph (EHG) for recording the electrical activity of the uterus in vivo has been blocked for 60 years by problems with artifacts and extraneous/reactive electrical activity. This study reevaluates a method of cervical recording that does not appear to have these limitations. A set of cervical electrode cups was used to record uterine activity of 33 normal subjects and patients who had dysmenorrhea, endometriosis, or chronic pelvic pain. The electrode cups were atraumatic, able to be fitted to all subjects, and showed exceptional positional stability. Unipolar and bipolar recordings from the cervix showed the same infrequent spikes and spike bursts reported from other studies along with continuous, mildly irregular, undulating slow-wave activity, which was present throughout the recordings. The frequencies and amplitudes of these slow waves changed in relation to exogenous estrogen, diagnosis, intrauterine catheters, and the intensity of the subject's pain. Spikes and spike bursts were common only during menses and at midcycle. The cervical electrode cups proved easy to use and were well accepted by the subjects. The findings indicated that the spikes and slow waves were probably uterine in origin and not artifact or extraneous/reactive activity. There were also direct and indirect indications that the slow waves may represent the ionic propagation of uterine electrophysiologic activity through a network of uterine intercellular ionic channels (gap junctions). The limited but fairly consistent evidence from a number of perspectives indicates that recording spike and slow-wave activity from the cervix is a viable and practical EHG method.