Investigations on urinary bladder reinnervation. Historical perspective and review.

Although nerve crossover surgery to bypass a spinal cord lesion and recentralize the decentralized bladder was first conceptualized in 1907, surprisingly few studies concerning this goal have been reported since. In addition to direct implantation of nerves into the detrusor, the studies reviewed have investigated the crossover of mixed roots (with and without nerve grafts), dorsal roots, ventral roots, pelvic, obturator and hypogastric nerves both in animal models, in human cadavers, and in human patients. Restoration of the micturition reflex through the use of nonsacral nerves has been achieved in cats. In addition, we have shown that the axons of a suprasacral mixed root (L7) when anastomosed to a sacral mixed root (S1) via a nerve graft can regenerate and recentralize the unilaterally decentralized bladder in the cat. The return of the micturition reflex after reconstruction of severed pelvic nerves has been documented, while the results of obstruction or hypogastric crossover have given diminished returns of bladder function. The direct implantation of nerves into the detrusor has not resulted in restoration of function. In addition, return of useful bladder function in humans after nerve crossover surgery has not been predictable. In part, present inability to achieve restoration of urinary bladder function may be a consequence of the complexity of micturition reflex organization and the inability to use techniques in humans that have given success in animals. Although, some of the technical aspects of nerve crossover surgery to bypass a spinal cord injury and restore functional micturition in those with neurogenic bladder dysfunction have been elucidated, further work is required to develop techniques that will enhance appropriate axonal regeneration to achieve reinnervation and return of useful function. Indeed, restoration of function may be limited by current microsurgical methodologies. Studies directed at understanding the neuropathophysiology of nerve injury and nerve surgery may be more fruitful in identifying factors than can be manipulated to achieve consistent return of useful function. In general, however, the results of the animal and human studies surveyed may be viewed with cautious optimism.