## 5 Discussion  
Several prior DBWS clinical studies have reported effective voiding; however, some patients have had side effects of pain, abdominal muscles contraction, urethral sphincter contractions preventing voiding, and limited detrusor responses [11; 12; 13; 14]. Our current test results highlight these potential problems. The primary limitation encountered in the current protocol was animal discomfort and aversive skeletal muscle contractions at levels of stimulating currents which were lower than necessary for inducing vesical wall contractions. Only with the administration of general anesthesia and the use of a high stimulating current (60 mA) were we able to induce moderate but reproducible bladder contractions. Several factors may have contributed to the adverse effects and the need for higher stimulating currents. The sacral spinal cord lesion was incomplete below the S2 level, and spinal sacral activity persisted at levels S3-S5 due to surgical difficulties. During the conus medullaris resection, it was observed to be at the level of the S2 vertebra. Using a two-level laminectomy, first in the lumbar and then in the sacral areas, it was difficult to resect the whole length of the conus, which reached almost the end of the dural sac; thus, there was remaining lower sacral reflex function. This  
Figure 5: Autopsy photographs of bladder wall electrodes and the sacral cord lesion. (**A**) The leads of two helical-wire hook electrodes are shown where they had been implanted on the right side of the bladder wall (black arrows); a forceps is attached to one electrode lead. Looping of the four electrode leads in the suprapublic area is also shown. (**B**) Sacral spine showing S1 and S2 levels of the lesion. The lower sacral levels, S3, S4, S5, were partially spared. was confirmed postoperativelyectively by a positive bulbocavernosus reflex and discomfort to passing a rectal catheter [21]. Moreover, we know from studies of the Brindley implant that it can only be applied in patients with complete spinal lesions, because electrostimulation causes pain in patients with preserved sensation [5]. Stimulating currents as low as 10 mA were causing the abdominal and leg muscles to contract, which may have been painful; however, all stimulation was stopped if there was any indication of animal discomfort. Several additional factors may have contributed to the poor detrusor responses to stimulation. First, the porcine models may have low detrusor contractility; for example, the empty bladder was observed as large and flacacid, being previously reported as a reason for non-response to DBWS in swine [18]. Other species, including cats, dogs, and humans, have shown higher detrusor responses to DBWS [15; 16; 17; 22]. Second, the use of general anesthesia with Propofol may have limited the maximal vesical responses to DBWS; however, higher vesical pressures have been induced during anesthesia in other species [15; 16; 17]. Third, this was a pilot study with the results limited to three animals. The lack of voiding during stimulation was another limitation encountered in this study. The high current which induced moderate vesical pressure increases could have produced voiding. In addition, resting vesical pressure before stimulation was moderately high, which could have resulted in voiding. Several mechanisms should be considered for the observed lack of voiding. First, detrusor sphincter dyssymergia, or detrusor bladder neck dyssymergia: the incomplete sacral lesion could have resulted in dyssymergia, which produces urethral sphincter contractions during bladder contraction. Moreover, during the stimulation studies on human subjects, [PERSON] performed bladder neck incisions to reduce this unwanted effect and promote voiding. Second, electrical stimulation of the urethral sphincter: the unwanted effect of electrical field spread during stimulation was inferred from the palpation of strong contractions of the anus and perineum.