Reinnervation of atonic bladder after conus medullaris injury using a modified nerve crossover technique in canines

Neurogenic bladder represents a major cause of morbidity in patients with spinal cord injuries (SCI). Herein, we evaluated a novel reconstructive surgical technique designed to restore afferent and efferent nerve function in atonic bladder caused by conus medullaris injury.

A new reflex pathway was established by extradural transfer of the left L5 ventral root (VR) to the left S2 VR root together with extradural postganglionic spinal nerve transfer of the L5 dorsal root (DR) to the S2 DR with a nerve graft in a canine model. The corresponding nerves on the right side were kept intact and served as a control. After the new reflex pathway was reestablished, the early function of the reflex arc was evaluated by electrophysiologic study, intravesical pressure, and histologic examination.

Action potential (AP) curves were recorded with single focal stimulation of the left S2 DR before and after the spinal cord was destroyed horizontally between the L6 and S3 levels. Bladder contraction was successfully initiated by trains of stimuli targeting the left L5-S2 DR anastomosis. Achievable bladder pressures and the amplitude of bladder smooth muscle complex action potentials were unchanged before and after induced paraplegia and were comparable to those of the control. Prominent axonal sprouting was observed in the distal region of the nerve graft.

Both afferent and efferent nerve pathways in the atonic bladder were reconstructed by suprasacral motor-to-motor and sensory-to-sensory extradural nerve transfer in canines. Taken together, these findings suggest a new potential clinical approach for restoring bladder function in individuals with paraplegia.