13 - An Investigation of the Autonomic Innervation of the Vulvar Vestibule Using Cadaveric Dissection: Clinical Implications for Provoked Vestibulodynia

Poster Board Number: 13
There are separate poster presentation times for odd and even posters.
Odd poster #s – first hour
Even poster #s – second hour

Abstract Body : Introduction: Provoked vestibulodynia (PVD) is a chronic pain syndrome characterized by pain localized to the vulvar vestibule, the tissue surrounding the vaginal opening, that is provoked by touch or insertion. The etiology of PVD is not fully understood, making treatment of this condition challenging. This may be due, in part, to an insufficient body of research which has characterized the innervation of the vulvar vestibule. Immunohistochemical markers of autonomic innervation have been identified in the vulvar vestibule mucosa, yet no studies to date have described the precise nerves that may be involved in this innervation. This study aimed to determine whether the inferior hypogastric plexus (IHP) contributes to the autonomic innervation of the vulvar vestibule. Given its central role in autonomic innervation of the pelvis, it is hypothesized that the IHP contributes to the autonomic innervation of the vulvar vestibule, though this has not yet been evaluated to our knowledge.
Materials and Methods: Detailed dissections of the IHP were completed using three female cadavers. Two cadavers were formalin-fixed, and one was fresh-frozen. In the formalin-fixed cadavers the IHP was traced from its origin to the external genitalia using gross dissection. A surgical microscope was then used for fine dissection of IHP nerve fibers toward the vulvar vestibule. Terminal branches of the IHP were investigated in the fresh-frozen cadaver. Measurements of the most distal location of the IHP were recorded. Samples were collected from the IHP and vulvar vestibule of each specimen for immunohistochemical analysis to validate patterns of innervation observed macroscopically.

Results: Gross fibres from the IHP were identified within approximately 3 cm of the vulvar vestibule in the region of the bladder neck. Microdissection of the periurethral tissue distal to the neck of the bladder did not reveal the clear presence of macroscopic IHP fibers in this region. Immunohistochemical analysis revealed that nerve fibres from both IHP and the vulvar vestibule both showed positive immunoreactivity for autonomic markers tyrosine hydroxylase and vasoactive intestinal polypeptide.
Conclusion: The results from this study indicate that the IHP could potentially innervate the vulvar vestibule via microscopic contributions, which may not be possible to identify using gross dissection approaches alone. These findings are valuable in supplementing current literature detailing the anatomy of the female external genitalia. These results are also useful for researchers studying the etiology and treatment of chronic vulvar pain syndromes such as PVD, though further research is needed to determine the potential role of this autonomic innervation in the normal functioning of the vulvar vestibule and associated disease pathogenesis.