FEASIBILITY OF IMPLANT DRIVEN MICTURITION IN PARAPLEGIC DOGS

Objective- This study evaluates the feasibility of using existing tech nology for implant driven micturition in paralyzed dogs (part I) and a lso examines a less invasive technique for implant driven micturition (part II). Study Design- Part I. Sacral nerve root dimensions and blad der and urethral pressure responses to intradural and extradural sacra l nerve root stimulation were measured to determine the optimal locati on and size for sacral nerve root electrodes. Part II. Sacral nerve ro ots were stimulated via wire electrodes introduced into the S2 foramin a. Animals or Sample Population- Ten dogs (five dogs in part I and fiv e dogs in part II). Methods- Part I. Microtip pressure transducers wer e used to monitor bladder and urethral pressure responses to sacral ne rve root stimulation with tripolar hook electrodes. After euthanasia, sacral nerve root, and spinal canal dimensions were measured. Part II. Bipolar electrical stimulation of the sacral nerve roots was performe d by introducing wire electrodes into the S2 foramina. Bladder and ure thral pressures were recorded as in part I. Results- Part I. Stimulati on of S1 produced an increase in urethral, but not bladder, pressure. Stimulation of S2 or S3 produced increases in bladder pressure and dec reases in urethral pressure. Intradural and extradural nerve roots wer e not significantly different with respect to nerve dimensions or effe cts on nerve stimulation. Part II. High bladder pressures were achieve d, but effective voiding could not be produced, primarily because of u rethral resistance. Conclusions- Part I. Extradural implantation was d etermined to be the most appropriate site based on ease of dissection, nerve root dimensions, and decreased risk of iatrogenic trauma. Enoug h space is available to implant two to four tripolar spiral nerve cuff s. Part II. Transforaminal sacral nerve root stimulation did not effec tively empty the bladder. Clinical Relevance- Clinical trials in parap legic dogs are necessary to evaluate the number of sacral nerve cuff e lectrodes necessary to produce effective bladder emptying. (C) Copyrig ht 1997 by The American College of Veterinary Surgeons