Morphometric data of canine sacral nerve roots with reference to electrical sacral root stimulation

Experiments to investigate restoration of lower urinary tract control by electrical stimulation of the sacral nerve roots are mostly performed on dogs, yet little morphometric data (such as canine root and fiber diameter distributions) are available. The aim of this study was to acquire morphometric data of the intradural canine sacral dorsal and ventral roots (S1-S3). Cross-sections of sacral roots of two beagle dogs were analyzed using a light microscope and image processing software. The cross-sectional area of each root was measured. The diameters of the fibers and the axons in the cross-sections of the S2 and S3 roots were measured and used to construct nerve fiber diameter frequency distribution histograms. The results show a unimodal diameter distribution for the dorsal roots and a bimodal distribution for the ventral roots. In addition the average ratio g of the axon diameter to fiber diameter was calculated for each roo

Selective sacral root stimulation for bladder control: acute experiments in an animal model

High bladder pressure is a potential side effect of poststimulus voiding, used to date for stimulation-induced bladder emptying in spinal cord injured patients. To prevent this side effect, selective activation of the bladder without activation of the urethral sphincter by selective stimulation of sacral roots was studied in a canine animal model. On-line registration of bladder, urethral and rectal pressure was performed, and EMG of tail muscles and urethral sphincter was recorded. After laminectomy, intradural left and right sacral root S2 were stimulated with a tripolar cuff electrode. A self-made stimulator generating adjustable pulse shapes was used. Using 200 microsec. rectangular pulses, contraction of bladder and urethral sphincter could be elicited. Selective activation of the bladder occurred with pulses of 600 to 800 microsec. due to anodal blocking of the large nerve fibers in the sacral roots. During acute animal experiments we were able to achieve selective activation of the detrusor without simultaneous activation of the external urethral sphincter, and complete, low-pressure voiding occurre

Selective detrusor activation by electrical stimulation of the human sacral nerve roots

The purpose of this study was to investigate the feasibility of selective detrusor activation without activation of the urethral sphincter by sacral root stimulation in patients. The sacral roots were stimulated using a tripolar electrode. An anodal block was used to prevent the urethral sphincter from contraction. Using square current pulses (700 microseconds, 6-7 mA), no increase in intraurethral pressure was measured, while a normal increase in intravesical pressure occurred. The minimum pulse duration to obtain a complete block was 550 microseconds. The study shows that anodal blocking of action potentials is possible in humans and can result in selective detrusor activation when used in sacral root stimulatio