12 - An Exploratory Dissection of the Pudendal Nerve: Implications for the Understanding and Treatment of Provoked Vestibulodynia

Poster Board Number: 12
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Abstract Body : Introduction: The vulvar vestibule, the tissue surrounding the vaginal introitus, is a clinically significant region affected by localized pain syndromes, namely provoked vestibulodynia (PVD). Recent evidence suggests the importance of a sensory component in PVD pathogenesis, though the precise innervation of the vulvar vestibule is incompletely described. While it is assumed that the pudendal nerve, the main somatosensory nerve of the pelvis, innervates the vulvar vestibule, there is a paucity of literature which has validated this. Importantly, targeted pudendal nerve treatments have been proposed for PVD. This includes pudendal nerve blocks and surgical resection of pudendal nerve branches. Evidently, there is a need for the detailed study of the anatomy of the pudendal nerve in relation to the vulvar vestibule to support the use of these types of pudendal nerve-specific interventions.
Objectives: To confirm that the vulvar vestibule is innervated by terminal branches of the pudendal nerve.
Materials and Methods: Detailed dissections of the pudendal nerve were performed using six female cadavers. Four were formalin-fixed and two were fresh-frozen. The pudendal nerve was traced from its origin to distal terminations using gross and microdissection, noting any relationships of the pudendal nerve branches to the vulvar vestibule. Patterns of innervation were confirmed with subsequent histological and immunohistochemical analyses using general nerve marker PGP9.5 and sensory nerve marker calcitonin gene-related peptide (CGRP).
Results: Perineal branches of the pudendal nerve were traced to the external wall of the vulvar vestibule in all cadavers. Some heterogeneity in patterns of innervation was observed, including right-left variation in the existence of macroscopic vestibule-specific branches of the pudendal nerve. Nerve fibers immunoreactive for PGP9.5 and CGRP were identified in the pudendal nerve and accompanying vulvar vestibule tissue.
Conclusion: We confirmed that the vulvar vestibule is innervated by perineal branches of the pudendal nerve, though this study provides emerging evidence of anatomical heterogeneity in patterns of innervation across individuals. Such anatomical heterogeneity could result in insufficient targeting of the pudendal nerve during directed therapeutic interventions for PVD. Further characterization of this variability may help improve treatments for pain syndromes impacting this tissue.