Increased innervation of the vulval vestibule in patients with vulvodynia

Vulvodynie

Vulvodynia (vulvar dysesthesia) refers to vulvar pain (burning, irritation and rawness) of the external female genitalia for more than 3 months without other dermatological or gynecological causes. The term primary vulvodynia should be reserved for vulvar vestibulitis and essential (dysesthetic) vulvodynia. Vulvar vestibulitis is characterized by dyspareunia, allodynia and vulvar erythema. Most patients are Caucasian, premenopausal and sexually active. The prevalence is estimated as high as 15%. Damage to the sympathetic nerves with an increased pain sensitivity is the likely explanation for the burning sensation. Psychological impairment, which is common in many patients, rather seems to be the consequence of the chronic disease than a primary condition. Essential vulvodynia is characterized by vulvar burning, which is characteristically not limited to the vestibulum. The patients are generally older and dyspareunia is less severe. The prevalence of essential vulvodynia is 1-3%. Various interdisciplinary approaches to these two rather frequent genital diseases are discussed.

Estrogen Regulates Vaginal Sensory and Autonomic Nerve Density in the Rat1

Vaginal function is strongly influenced by reproductive hormone status. Vaginal dysfunction during menopause is generally assumed to occur because of diminished estrogen-mediated trophic support of vaginal target cells. However, peripheral neurons possess estrogen receptors and are potentially responsive to gonadal steroid hormones. In the present study, we investigated whether sensory and autonomic innervation of the vagina varies among rats during the estrus phase of the estrous cycle, following chronic ovariectomy, and after sustained estrogen replacement. Relative to rats in estrus, ovariectomized rats showed a 59% elevation in nerve density, as determined using the panneuronal marker PGP 9.5. This increase persisted even after correcting for differences in vaginal tissue size, indicating true axonal proliferation after ovariectomy rather than changes secondary to altered volume. Increased total innervation after ovariectomy was attributable to increased densities of sympathetic nerves immunostained for tyrosine hydroxylase (70%), cholinergic parasympathetic nerves immunoreactive for vesicular acetylcholine transporter (93%), and calcitonin gene-related peptide-immunoreactive sensory nociceptor nerves (84%). Myelinated primary sensory innervation revealed by RT-97 immunoreactivity did not appear to be affected. Sustained 17beta-estradiol administration reduced innervation density to an extent comparable to that of estrus, implying that estrogen is the hormone mediating vaginal neuroplasticity. These findings indicate that some aspects of vaginal dysfunction during menopause may be attributable to changes in innervation. Increased sympathetic innervation may augment vasoconstriction and promote vaginal dryness, while sensory nociceptor axon proliferation may contribute to symptoms of pain, burning, and itching associated with menopause and some forms of vulvodynia.

Vulvodynia

CONTEXT

Vulvodynia is a term used to describe chronic burning and/or pain in the vulva without objective physical findings to explain the symptoms. The terminology and classification of vulvodynia continue to evolve, and much remains to be understood about the prevalence, pathogenesis, natural history, and management of this distressing condition.

STARTING POINT

James Aikens and colleagues showed that chronic vulval pain (vulvodynia or vulvar dysaesthesia) is associated with worse depressive symptoms (Am J Obstet Gynecol 2003; 189: 462-66). However, the increased scores for depression in this case-control study were attributed to sexual disinterest and experience of chronic pain rather than to features of depressive disorder. These results lend weight to the increasing need for better understanding of the pathogenesis of vulval pain and how to manage it appropriately. WHERE NEXT? The aetiology of vulvodynia and effectiveness of treatments need further study. Appraising the available literature, we have formulated a useful approach to patients with chronic vulval pain. There is a pressing need for further case-control studies of potential causes of vulvodynia and for randomised trials of interventions.

Vulvodynia

PURPOSE OF REVIEW

An increasing number of patients present with symptoms of vulvar pain, soreness, burning or irritation, which become chronic. Clinicians are often uncertain of the diagnosis. Terminology and an understanding of aetiology and therapy are evolving.

RECENT FINDINGS

Previous descriptions of vulvodynia have grouped patients according to whether pain is provoked by coitus (vulvar vestibulitis syndrome) or generalized and neuropathic pain (dysesthetic vulvodynia). Recent terminology debates have questioned whether 'vulvodynia' should be replaced by 'dysesthesia' and the term 'vestibulitis' avoided. Definitions of pain provocation, quality, duration, and distribution vary. Prevalence studies suggest one in six women may experience vulvodynia, although such a figure reflects clinic, patient or author reporting bias. Symptoms are as likely to be found in non-white as in white women. Although infection is often blamed, evidence for its role or that of inflammation is minimal. Immunohistochemistry has shown altered density of nerve endings and oestrogen receptors. There may be overlap with other pain syndromes. Several reviews have examined the many therapies available. Pharmacological alteration of nerve conduction (tricyclic antidepressants, gabapentin, local anaesthetics), biofeedback and sometimes surgery are helpful, but not always. Counselling and an understanding between patient and clinician/therapist are important for long-term results.

SUMMARY

Gynaecologists should be aware that they will encounter patients with vulvodynia who will need assessment and management. There are increasing numbers of clinics or clinicians with expertise to whom these patients can be referred.