Reconstruction of anorectal function through end-to-side neurorrhaphy by autonomic nerves and somatic nerve in rats

Anatomical feasibility of peripheral nerve transfer to reestablish external anal sphincter control - cadaveric study

PURPOSE

Motor deficits affecting anal sphincter control can severely impair quality of life. Peripheral nerve transfer has been proposed as an option to reestablish anal sphincter motor function. We assessed, in human cadavers, the anatomical feasibility of nerve transfer from a motor branch of the tibialis portion of the sciatic nerve to two distinct points on pudendal nerve (PN), through transgluteal access, as a potential approach to reestablish anal sphincter function.

METHODS

We dissected 24 formalinized specimens of the gluteal region and posterior proximal third of the thigh. We characterized the motor fascicle (donor nerve) from the sciatic nerve to the long head of the biceps femoris muscle and the PN (recipient nerve), and measured nerve lengths required for direct coaptation from the donor nerve to the recipient in both the gluteal region (proximal) and perineal cavity (distal).

RESULTS

We identified three anatomical variations of the donor nerve as well as three distinct branching patterns of the recipient nerve from the piriformis muscle to the pudendal canal region. Donor nerve lengths (proximal and distal) were satisfactory for direct coaptation in all cases.

CONCLUSIONS

Transfer of a motor fascicle of the sciatic nerve to the PN is anatomically feasible without nerve grafts. Donor nerve length was sufficient and donor nerve functionally compatible (motor). Anatomical variations in the PN could also be accommodated.

S1 nerve is the most efficient nerve rootlet innervating the anal canal and rectum in rats

Autonomic and somatic components participate in the defecation process in mammals, combining signals from the brainstem and forebrain. The innervation pattern involved in micturition in rats has been well studied, while defecation has been less studied. The aim of the present study was to identify the most important sensory and motor nerves of the anal canal and rectum involved in defecation. The amplitudes of evoked potential of the anal canal and rectum were higher when L6 and S1 ventral rootlets were stimulated, compared with the other segments (ANOVA and Tukey's post hoc test, all P < 0.05). The S1 segment was more strongly cholera toxin subunit B conjugated to horseradish peroxidase (CB-HRP) positive compared with the other segments (ANOVA and Tukey's post hoc test, P < 0.05). Ventral spinal rootlets of L6 and S1 mainly contributed to the pressure change in the anal canal and rectum when the ventral spinal rootlets from L5 to S3 were stimulated electrically. In conclusion, many afferent and efferent nerves innervate the anal canal and rectum and are involved in defecation, but the S1 nerve rootlet could be the most efficient one. These results could provide a basis for defecation reconstruction, especially for patients with spinal cord injuries.

Feasibility of neurovascular antropylorus perineal transposition with pudendal nerve anastomosis following anorectal excision: a cadaveric study for neoanal reconstruction

Purpose

Perineal transposition of the antropyloric valve following an anorectal excision as a substitute for a permanent colostomy has recently been reported in humans. However, the problem of neural control still remains in these patients. Our aim herein was to study the anatomical feasibility of an anastomosis between the pudendal nerve branches (inferior rectal nerve) innervating the external anal sphincter and the anterior vagal branches of the perineally-transposed antropyloric segment in cadavers.

Methods

The antropyloric segment, along with its carefully dissected branch of the anterior vagus, was mobilized based on the left gastroepiploic pedicle in six fresh human cadavers. The antropyloric valve was then transposed in the perineum after the pudendal nerve branches had been dissected out, and an approximation of these two nerves was performed to ascertain the technical feasibility of their neural anastomosis.

Results

The anterior vagus innervating the antropylorus could be harvested in all cadavers below the hepatic division of the main vagus trunk. The inferior rectal nerve or its branches were found consistently around the 3 or the 9 o'clock position in the ischioanal fossa. An anatomical tension-free approximation of the anterior vagus branch (of the transposed antropyloric segment) to the inferior rectal nerve in the perineum was feasible in all the cadavers studied.

Conclusion

An inferior rectal nerve anastomosis with the anterior vagal branch of the perineally-transposed antropyloric segment can be achieved anatomically. This preliminary step can be the basis for future animal studies and subsequent clinical application of the procedure for possible neural control of the transposed antropyloric segment in the perineum.