Perineal pudendal neurotomy versus selective neurotomy of the S2 somatic contribution to the pudendal nerve. Effects on sacral-root-stimulated bladder and urethral responses in the dog.

In 10 dogs that underwent bilateral electrode implantation on the S2 ventral root, 5 then underwent a bilateral total perineal neurotomy of the pudendal nerve (group A) at 3 months and 5 bilateral division of the S2 somatic contribution to the pudendal nerve (group B). The effects of these 2 types of neurotomy on the bladder and urethral responses to electrostimulation were compared after another 3 months. In group A, the proximal and mid-urethral responses decreased significantly [69.1% (p = 0.004) and 79.6% (p = 0.002), respectively]. A decrease in bladder response [26% (p = 0.089)], although not significant, was also found. In group B, the decrease in the proximal urethral response was significant [67.8% (p = 0.012)]; the mid-urethral response (56.8%) was not statistically significant (p = 0.134). The bladder response decreased by 73.6% (p = 0.034). Thus, although pudendal neurotomy can be effective in reducing the outlet resistance, the pudendal nerve may have an important role in the regulation of micturition in the dog. Preoperative testing of the effect of a pudendal neurotomy by temporary nerve blocks is warranted to avoid undesirable side effects such as a decrease in bladder excitability.