Episiotomy and innervation zones of the external anal Sphincter: A case series investigating the impact on neurological patterns

Objective: To investigate the impact of mediolateral episiotomy on the innervation zones of the External Anal Sphincter (EAS) in the absence and presence of direct muscular injury.

Methods: This case series examined four primiparous women, including three who underwent vaginal deliveries with mediolateral episiotomy and one cesarean section case for reference. Pre- and post-delivery assessments utilized surface electromyography (sEMG) and endoanal ultrasound to evaluate changes in the EAS's innervation zones and obstetrical EAS injuries, alongside the Wexner score for fecal incontinence.

Results: Mediolateral episiotomy can alter the innervation pattern of the EAS, with a significant reduction in innervation zones observed in the episiotomy cases compared to the reference cesarean section case. This alteration was evident even in the absence of visible EAS injury, suggesting episiotomy's potential to disrupt EAS functionality. Notably, the Wexner score indicated varying degrees of fecal incontinence among the episiotomy cases.

Conclusion: Mediolateral episiotomy may impact the EAS's innervation pattern, highlighting the importance of considering individual innervation zones in episiotomy planning. While the integration of sEMG into routine clinical practice is still evolving, this study underscores its potential as an additional tool for assessing neural integrity, particularly in cases of anal sphincter injury and reconstruction. Future research should explore the dynamics of re-innervation and the correlation between vascular injury and reduced innervation zones to enhance patient-specific care in pelvic floor dysfunction.