Intraoperative recording of electroneurographic signals from cuff electrodes on extradural sacral roots in spinal cord injured patients.

PURPOSE: A safe and reliable method for monitoring intravesical pressure on a long-term basis is needed for conditional electrical stimulation to be feasible as a treatment option for neurogenic detrusor overactivity in patients with a spinal cord injury. Therefore, we investigated the possibility of recording afferent nerve activity related to mechanical activity of the bladder and other pelvic organs from the extradural sacral nerve root in human.
MATERIALS AND METHODS: Nerve cuff electrodes were temporary placed on the extradural S3 sacral root in 6 spinal cord injured patients who underwent implantation of an extradural FineTech-Brindley Bladder System (Finetech Medical Lt., Welwyn Garden City, United Kingdom). The dorsal penile/clitoral nerve was electrically stimulated to evoke compound action potentials. Electroneurographic signals were recorded together with bladder and rectal pressure during mechanical stimulation of the dermatome rapid bladder filling and rectal distention, and during bladder contraction evoked by electrical stimulation of the contralateral sacral root.
RESULTS: Compound action potentials and electroneurographic responses during stimulation of the dermatome and rectum were present in all 6 patients and during bladder filling in 5 of 6. However, recorded responses from the bladder and rectum were small and mainly phasic in nature. Nerve responses following bladder contractions were present in 4 of 5 stimulated patients.
CONCLUSIONS: Afferent nerve activity from the dermatome, bladder and rectum can be recorded using cuff electrodes placed on the extradural S3 sacral root in humans but improvements in recording quality and sophisticated signal processing methods are needed for chronic application.