Intraoperative recording of neurographic signals from cuff electrodes on extradural sacral roots in human

The feasibility of conditional stimulation as a treatment option for neurogenic detrusor overactivity in spinal cord injury (SCI) patients depends on a reliable method for chronic monitoring of bladder activity. The purpose of this study was to investigate the possibility of recording afferent nerve activity related to mechanical activity of the bladder and other pelvic organs in human. In 6 SCI-patients, a nerve cuff electrode was temporary placed on the extradural S3 sacral root, and electroneurographic (ENG) signals were recorded during mechanical stimulation of the dermatome (manual tapping and stroking), rectum (balloon distension) and bladder (saline bolus infusion). Increases in ENG were present during stimulation of the dermatome and rectum in all 6 patients, and during bladder filling in 5 out of 6 patients. We therefore conclude that it is possible to record afferent nerve activity from the dermatome, rectum and bladder using cuff electrodes on the extradural sacral root in human. However, the low amplitude of recorded nerve responses indicates the need for improvements in recording quality and signal processing methods to distinguish signals from different afferent sources.