Increased innervation of the vulval vestibule in patients with vulvodynia.

BACKGROUND: Vulval vestibulitis is a condition characterized by the sudden onset of a painful burning sensation, hyperalgesia, mechanical allodynia, and occasionally pruritus, localized to the region of the vulval vestibulus. It is considered the commonest subset of vulvodynia. Pain precipitated in the absence of nociceptor stimuli might be triggered by previous peripheral nerve injury, or by the release of neuronal mediators, which set off inappropriate impulses in nonmyelinated pain fibres sensitizing the dorsal horn neurones. The pathophysiology of vulval vestibulitis is still unclear.
OBJECTIVES: The objective of this study was to evaluate the nerve fibre density and pattern, in specimens of vulval vestibulus, in normal subjects and in patients with vestibulitis, and provide objective diagnostic criteria for this condition. Methods Twelve patients with a history of the vestibulitis type of vulvodynia, and eight normal subjects underwent biopsy of the posterior wall of the vulval vestibule. Quantitative immunohistochemistry was performed, using antisera to the general neuronal marker protein gene product (PGP) 9.5, and to the neuropeptide calcitonin gene-related peptide (CGRP), on 15- microm sections.
RESULTS: There was a statistically significant increase of density and number of PGP 9.5 immunoreactive in the papillary dermis of patients with vulvodynia of the vestibulitis type, compared with those of controls. However, the distribution pattern of the innervation showed no significant change. There were no significant differences in CGRP staining between patients and controls.
CONCLUSIONS: It is concluded that the increase of PGP 9.5 immunoreactive nerve fibres, in patients with vulvodynia, may be either secondary to nerve sprouting, or may represent neural hyperplasia. Increased innervation may be applied as an objective diagnostic finding in vulval vestibulitis syndrome.