Novel method for restoration of anorectal function following spinal cord injury via nerve transfer in rats

Objectives Nerve transfer has been developed to restore partial function after serious nerve injuries, for example, restoring bladder control after spinal cord injury (SCI). Our aim here was to establish a preclinical proof-of-concept model using nerve transfer for restoring anorectal function after SCI. Setting We used laminectomy to model SCI, and bilateral spinal ventral and dorsal nerve root anastomosis to re-establish connectivity to the anorectal musculature. Methods Multidisciplinary methods were used to assess the anatomical and functional integrity of the alternative spinal-to-anorectal nerve circuit. Adult rats were used to establish the model. Bilateral anterior and posterior L5 nerve roots were surgically matched with anterior and posterior of S1 nerve roots by microscopic anastomosis to establish an artificial rectal reflex arc with complete sensory and motor pathways. Twelve weeks later, we used retrograde nerve tracing and neurohistomorphological analysis to assess anatomical integrity of the new artificial rectal reflex arc. Anorectal manometry was used to assess the function of the new nerve circuit. Results Retrograde tracing with recombinant attenuated pseudo rabies virus indicated that the new neural pathway was successfully established to the anorectal musculature after experimental SCI. Toluidine blue-stained sections of the anastomosis site revealed normal-appearing nerve fiber morphology and regeneration, and transmission electron microscopy revealed myelinated axons. Anorectal manometry revealed significant anorectal functional recovery. Conclusion These results suggest that our model is a feasible first step in developing an alternative reflex pathway after laminectomy at L4 to S2 and shows promise for effective restoration of anorectal function.