Warren M. Grill1,2 and Graham H. Creasey2,3
1Department of Biomedical Engineering, Case Western Reserve University
CB Bolton Bldg., Rm. 3480, Cleveland, OH 44106-4912 USA
2Louis Stokes VA Medical Center, Cleveland OH
3MetroHealth Medical Center, Cleveland, OH
Spinal Cord injury causes bladder paralysis, bladder hyper-reflexia and bladder-sphincter dysynergia. Electrical stimulation of the sacral ventral roots provides safe and effective bladder emptying. Hyper-reflexia and dysynergia are sometimes treated at present by surgical transection of the sacral dorsal roots. The objective of this project is to develop an electrical alternative to surgical transection for control of bladder hyper-reflexia. Specifically, we sought to determine whether electrical recordings of sensory neural activity could detect changes in bladder pressure associated with hyper-reflexia, and whether electrical stimulation of sacral afferent nerve fibers could arrest nascent hyper-reflexive contractions. All protocols were reviewed and approved by the Institutional Review Board of MetroHealth Medical Center, and subjects gave informed consent.
Recording cuff electrodes were implanted on the S3 dorsal root during surgical procedures in which the roots were thereafter transected. During slow bladder filling, there was an increase in the S3 electroneurogram (ENG) at the onset of filling, but not during the fill. Rapid injections of saline into the bladder were used to evoke hyperreflexia-like increases in bladder pressure. These rapid increases in bladder pressure led to robust increases in the S3 ENG. The ENG exhibited a large onset response, during the initial increase in bladder pressure, followed by decay to an increased baseline value during the maintained pressure. There was no apparent off-response during decreases in pressure induced by removal of saline, only a return to the pre-injection baseline ENG.
These results parallel our earlier studies in an animal model and demonstrate that electrical recording of sensory nerve activity can detect hyperreflexia-like increases in bladder pressure in human SCI. We have also shown that electrical stimulation of sacral afferent nerves in human subjects with chronic spinal cord injury can abolish nascent hyper-reflexive contractions of the bladder, increase bladder capacity and reduce incontinence of urine, particularly if this stimulation is applied at the onset of the contractions. These results indicate that electrical recording and stimulation can be used to detect and abolish bladder hyper-reflexia and may provide an alternative to surgical transection of the sacral dorsal roots.