Functional Reinnervation of the Canine Bladder after Spinal Root Transection and Immediate Somatic Nerve Transfer

Abstract

This study was performed to determine whether nerve transfer immediately after spinal root transection would lead to bladder reinnervation in a canine model. In one animal, the left T12 intercostal nerve was mobilized, cut and attached to the severed ends of sacral roots inducing bladder contraction using a graft from the T11 intercostal nerve. On the right side and bilaterally in two other dogs, coccygeal roots innervating tail musculature were cut and attached to the severed bladder sacral roots (coccygeal nerve transfer [CG NT]). In four other dogs, bladder sacral roots were transected in the vertebral column, and the genitofemoral nerve was transferred within the abdomen to the pelvic nerve (genitofemoral nerve transfer [GF NT]). After 14 months for CG NT and 4.5 months for GF NT, electrical stimulation of the pelvic nerve induced bladder pressure and urethral fluid flow on the intercostal nerve transfer side, in each of the five CG NT sites and bilaterally in three of the four GF NT animals. Reinnervation was further shown by retrograde labeling of spinal cord neurons following fluorogold injections into the bladder wall and by histological examination of the root/nerve suture sites. In all CG NT animals, labeled neuronal cell bodies were located in ventral horns in lamina IX of coccygeal cord segments. In the three GF NT animals in which pelvic nerve stimulation induced bladder contraction, abundant labeled cell bodies were observed in lamina IX and lateral zona intermedia of upper lumbar cord. These results clearly demonstrate that bladder reinnervation can be accomplished by immediate nerve transfer of intercostal nerves or coccygeal spinal roots to severed bladder sacral roots, or by transfer of peripheral genitofemoral nerves (L1,2 origin) to pelvic nerves.

Functional Reinnervation of the Canine Bladder after Spinal Root Transection and Genitofemoral Nerve Transfer at One and Three Months after Denervation

“…Since we cut the S1 and S2 roots, any anomalous S3 innervation to the bladder would have been spared. In our pervious reports (Ruggieri et al, 2008;Ruggieri et al, 2006) and in this current report, only two nerve roots on each side of the spinal cord (S1 and S2) were found to induce bladder contractions during electrical stimulation in all dogs studied. However, it is possible that a very few number of motor fibers innervate the bladder in some animals through S3 roots; however, these were apparently below the level needed to induce bladder pressure increases during conus medullaris stimulation.…”

“…A total of 13 dogs were used: four nerve transection with genitofemoral nerve transfer (GF NT) performed 1 month after nerve transection; six nerve transection with GF NT performed 3 months after nerve transection; and three sham-operated, nerve intact controls. These nerve intact sham-operated controls are the same animals as were included in a previous report (Ruggieri et al, 2008).…”

“…At 1 or 3 months after bladder denervation, the GF nerve was transferred to the pelvic nerve leading to the urinary bladder as previously described (Ruggieri et al, 2008). Briefly, the bladder vesicostomy was opened through a midline abdominal incision above and below the vesicostomy site.…”

“…Fluorogold retrograde neuronal tracing from the urinary bladder to the spinal cord was performed on all animals as previously described (Ruggieri et al, 2006;Ruggieri et al, 2008). Briefly, at 3 weeks before animals were euthanized, injections of 4% (w/v) fluorogold were made lateral to each ureteral orifice.…”

“…Similar nerve transection and immediate end-to-end suturing studies in pigs has demonstrated return of the micturition reflex in two animals at 14 and 20 weeks postoperatively (Conzen and Sollmann, 1982). Using the canine model, we have recently reported that, after transection of the spinal roots innervating the urinary bladder, reinnervation can be accomplished by immediate nerve transfer using either intercostal nerves or coccygeal nerve roots in the lumbosacral spinal column, as well as peripheral genitofemoral (GF) nerves in the lower abdomen (Ruggieri et al, 2008). In the clinical management of patients following SCI, patients are typically evaluated for a period of time to determine whether they will recover motor control of bladder function.…”