Innervation of parasympathetic postganglionic neurons and bladder detrusor muscle directly after sacral root transection and repair using nerve transfer

Aims This is a continuation of studies examining the effectiveness of root repairs and nerve transfers for bladder reinnervation. Our previous retrograde fluorogold tracing studies from the bladder to the spinal cord found regrowth of axons from the spinal cord through the nerve repair site to the bladder which was confirmed electrophysiologically [Ruggieri et al. J Neurotrauma 25:214–24, 2006]. The current study determines whether the pattern of axonal regrowth from the repaired nerves or roots to the bladder is different between the surgical reanastomosis methods. Methods The canine bladder was denervated by transection of all nerve roots from the sacral spinal cord mediating bladder contraction. Reinnervation surgeries included end‐on‐end repair of transected sacral ventral roots, transfer of coccygeal to sacral ventral roots (CG NT), or transfer of genitofemoral to pelvic nerves (GF NT). Results Postmortem dialkylcarbocyanine dye tracing with Neurotrace DiI from the distal pelvic nerve to the bladder wall, combined with PGP9.5 neuronal immunohistochemistry, demonstrated innervation by DiI‐labeled axons of only parasympathetic postganglionic intramural ganglia in normal controls and sham operated controls, but reinnervation of both intramural ganglia and detrusor muscle directly after repair of sacral ventral roots. GF NT and CG NT also resulted in reinnervation of both intramural ganglia and detrusor muscle, although to a lesser extent than repaired roots. Conclusions Bladder reinnervation with either the same nerve (orthotopic reinnervation) or with either a primarily somatic nerve (coccygeal) or a primarily sensory nerve (genitofemoral) results in reinnervation of both intramural ganglia as well as direct innervation of detrusor muscle. 30:599–605, 2011. © 2011 Wiley‐Liss, Inc.