For more than a decade it was used the 2003 International Society for the Study of Vulvovaginal Disease (ISSVD) terminology as a guide to diagnosing vulvar pain (see Table 20-3) [1].

The 2003 terminology divides vulvar pain into the following two overarching categories: vulvar pain related to a specific disorder, and vulvodynia, defined as “vulvar discomfort , most often described as burning pain, occurring in the absence of relevant visible findings or a specific, clinically identifiable, neurologic disorder”.

Since 2003, the category of “identifiable causes” for vulvar pain has evolved substantially, as have factors “potentially associated” with vulvodynia. Vulvodynia is likely not one disease but a constellation of symptoms of several (sometimes overlapping) disease processes, which will benefit best from a range of treatments based on individual presentation [17, 18]. The vulvar organ can therefore be differently affected.

In 2015, the International Society for the Study of Vulvovaginal Disease, the International Society for the Study of Women’s Sexual Health, and the International Pelvic Pain Society adopted a new vulvar pain and vulvodynia terminology that acknowledges the complexity of the clinical presentation and pathophysiology involved in vulvar pain and vulvodynia, and incorporates new information derived from evidence-based studies conducted since the last terminology.

The 2015 terminology of vulvar pain reflects key developments in understanding vulvar disorders and chronic pain over the recent years. The main difference between the 2015 terminology and the 2003 terminology is the addition of “potential associated factors” [1]. The inclusion of the associated factors emphasizes that treatment should be chosen according to the characteristics of the individual case and the possible associated factors , rather than as a “one-size-fits-all” approach (see Table 20-4).

Vulvodynia is not a rare condition: many studies now suggest that up to 15% of gynecologic clinic populations have the disorder at any given time [19]. Up to 14-million women are affected with vulvodynia at some point during their lifetimes, and the condition accounts for 10-million doctor visits annually. Results from research on the epidemiology (the study of the distribution and causes) of vulvodynia have helped to clarify the magnitude of the problem. Its frequency is underestimated partially because not recognized by doctors (some physicians dismiss this problem as psychological and relatively unimportant), and also because many affected women are reluctant to discuss their symptoms, which are perceived as unusual and possibly “all in the head.”

Dyspareunia is the word currently more used in the epidemiological research when pain as intercourse is considered. Prevalence of dyspareunia is 14% in Europe (Figure 20-1) with data collected from a mail survey (Women’s International Sexuality and Health Survey [WISHeS] Study) of 2467 women aged 20–70 years from Germany, UK, France and Italy and USA, where coital pain is reported by 21% of women aged 18–55 years of age (Figure 20-2).

Other researches indicate a prevalence of 16%: as indicated by a 2001 study of women in the Boston area, chronic burning, knifelike pain, or pain on contact that lasted at least 3 months or longer in the lower genital tract occurred frequently. These symptoms were reported by White, African-American, and Hispanic women of all ages, and nearly 40% of these women chose not to seek treatment. Of the women who sought treatment, 60% saw three or more doctors. These researchers estimate that up to 16% of women will experience symptoms consistent with vulvodynia in their lifetimes. The incidence of symptom onset was highest between the ages of 18 and 25 and lowest after age 35. Compared to controls, women with vulvar pain were seven times more likely to report difficulty and pain with their first tampon use. Almost 40% never sought medical care; 60% of those who sought medical care reported visiting more than three providers to receive a diagnosis and 40% remained undiagnosed after three medical consults. Although the reproductive age was the most affected, it was found that almost 4% of women between the ages of 45 and 54, and another 4% aged 55 to 64 years, reported burning or knifelike vulvar pain or pain on contact; in 50% of cases, pain limited sexual intercourse [22]. Lifelong mild vaginismus contributing to lifelong dyspareunia may occur in 10–15% of women.

Compared to controls, women with vulvodynia were significantly more likely to report chronic medical conditions, including bladder pain syndrome/interstitial cystitis (BPS/IC) , fibromyalgia and irritable bowel syndrome . It was estimated that among women with urologist diagnosed IC, more than half (51.4%) were diagnosed with vulvodynia. This strong link may be related to a common etiology for these two conditions. The vulva and bladder are both derived from the embryonic urogenital sinus and share common sacral nerve innervation pathways. Conditions that affect the bladder may therefore lead to symptoms in the vulva, and vice versa [23]. Between 12 and 68% of patients diagnosed with BPS/IC report vulvodynia symptoms [24].

Current available epidemiological data do not differentiate between introital and deep dyspareunia, nor in terms of leading etiology.

Chronic pain is associated with changes in the central nervous system (CNS), which may maintain the perception of pain in the absence of acute injury. Recent evidence from human studies has significantly expanded the understanding of pain perception and has demonstrated that a complex series of spinal, midbrain, and cortical structures are involved in pain perception [16].

Pain transmission from the periphery to the higher brain centers via the spinal cord is not a simple, passive process involving exclusive pathways. The relationship between a stimulus causing pain, and the way it is perceived by an individual, is dramatically affected by circuitry within the spinal cord and the brain. The sensation of pain is modulated as it is transmitted upwards from the periphery to the cortex. It is modulated at a segmental level and by descending control from higher centers, with the main neurotransmitters involved being serotonin, noradrenaline, and endogenous opioids [25].

The peripheral nociceptors are simple bare-endings nerve fibers and they are widespread in the superficial layers of the skin. Nociceptors are classified Aδ, which are small diameter, lightly myelinated, and C-fibers, which are not myelinated. The nociceptors neurons pass in the peripheral nerves and enter the spinal cord at the dermatomal level ascribed by their insertion. Innervation to the vulva is via the pudendal nerve, which originates from the S2-4 nerve roots and the ileoinguinal and genitofemoral nerves, arising from L1-2. The two latter nerves are predominantly sensory, but the pudendal nerve contains motor, sensory, and sympathetic fibers, which supply the complex autonomic reflexes of the pelvic organs. The vagina itself is relatively insensitive to pain, while the vulva and particularly the vulvar vestibule have an high level of free nerve endings.

Spinal cord . Following spinal cord integration of afferent inputs there are neurons (second-order neurons) that transmit the information to the higher centers via ascending pathways. The classical ascending pathway ascribed to pain is the spinothalamic one; other pathways relevant in pain modulation include the spinomesencephalic, spinoreticular, and dorsal column pathways.

Cerebral cortex . Cortical pain perception can be roughly divided into a lateral, somatosensory system involved in discrimination of pain location and intensity, and a medial system which mediates the anticipatory, fearful, affective quality of pain through limbic structures. In broad terms, pain has elements that are sensory and localizing with other elements that are involved with memory, cognition, and affect.