Nerve supply of the vulva.
The pudendal nerve supplies both the anal and urinary sphincters, whereas the muscles of the pelvic floor are mostly innervated via direct branches from the sacral plexus (S3–S5) with some input from the pudendal nerve, both voluntarily from higher centres in the brain and reflexly via the spinal cord.
It is known that there is a relationship between muscle function in the pelvis and pain, and studies have demonstrated that patients with pelvic pain have higher levels of resting muscle tone than other persons.
The convergence in the spinal cord of afferent impulses from viscera, skin and muscle can also lead to the phenomenon of referred pain. We are familiar with this when it comes to sciatica, but it is less well known that pain may also be referred to the vulva and distal vagina.
This convergence can also lead to alterations of sensation to nearby viscera, particularly the bladder. It is not uncommon for patients with vulval pain to complain of urinary frequency and urgency, lower abdominal pain and burning on urination.
Autonomic dysfunction may lead to loss of control of the vascular system of the vulva. The result is a variable degree of erythema of the vulval skin and the epithelium of the introitus. This is often misinterpreted as a rash and treated with cortisone creams. The vasoconstricting action of these medications is followed by a reflex vasodilatation, which may increase erythema and produce discomfort.
Chronic Pain
Pain sensation is mediated by three types of afferent nerve fibres: the large myelinated type Aβ fibres, which are responsible for touch, the smaller myelinated type A fibres, and the poorly myelinated or non-myelinated type C fibres. These latter fibres are responsible for pain perception, and the pain mediated by type C fibres in particular often has a burning quality. Type A fibres can, however, become involved in pain sensation, and when this occurs patients may develop allodynia. In this condition, stimuli that would normally elicit sensations of touch or pressure are perceived as pain. This explains why patients with vulval pain often find pressure from clothes difficult to cope with.
When patients experience chronic pain, afferent sensory processes mediated by type C peripheral nerve fibres via the dorsal horn spinal cord neurones appear to become sensitised, discharging more easily to lower levels of stimulation and at lower thresholds. They may even discharge spontaneously. This phenomenon has been termed ‘wind-up’. There may be associated pathological changes in the dorsal horn connection and perhaps also in higher centres. It is helpful to understand this when there is no apparent noxious stimulus present. We also know that depressed and anxious patients have more problems with chronic pain, and that mental state is integral to pain experience.
It is important as a doctor to have a concept of how pain can occur in the absence of observable abnormality, particularly when it comes to explaining the diagnosis to the patient and indeed accepting it oneself.
Presentation of Vulval Pain
Broadly speaking, patients presenting with vulval pain tend to present either with something observable that explains their pain or with a normal-looking vulva.
They can be divided into two main groups:
Pain that is directly attributable to an observable vulval or vaginal lesion or disease via cutaneous nociceptors: this is termed lesional pain
Pain that is experienced in the absence of any observable vulvovaginal pathology and where the physical examination is normal for the patient’s age and ethnic group: this is termed non-lesional pain
It must be remembered that the presenting symptoms may sometimes be due to co-existing lesional and non-lesional aetiologies.
Non-lesional Pain
We believe that the most likely explanation for non-lesional pain is neuropathy and/or referred pelvic muscular dysfunction. The source of this neuromuscular pain can include visceral pelvic problems such as prolapse, irritable bowel (particularly with chronic constipation), irritable bladder, uterine pain whether due to endometriosis or other pathology, or neuromuscular problems such as spinal or hip disease or dysfunction. A patient may have pain caused by both. Sometimes, a patient presents with pain that seems to have started with an episode of vulval skin disease (especially genital herpes or chronic thrush) but that persists after the skin problem has been resolved. Even though there has been a physical historical trigger for the pain, it should still be treated in this group.
Conversely, if a skin disease is present, it should always be considered initially as the cause of the patient’s symptoms, even if this eventually proves not to be the case.
Non-lesional pain usually has the qualities of neuropathic pain. It is poorly localised and usually has a burning quality. It is spontaneous but can also be worsened by the sort of physical stimuli that would not normally cause pain, such as pressure from tight clothes or the application of topical therapy. There is a subgroup of non-lesional pain that is well localised. This tends to be more musculoskeletal in origin, rather than purely neuropathic.
Any form of chronic painful vulvovaginal or pelvic condition can predispose a patient to non-lesional pelvic pain. This includes period pain, bowel pain, chronic irritable bladder and any painful vulvovaginal condition. The reason is that chronic pain of any sort not only causes painful muscle spasm but also changes the way the brain perceives pain so that the threshold for experiencing pain becomes lower with time. This is called neuroplasticity.
Very occasionally, patients with psychiatric conditions can experience vulval pain as a symptom of their condition, and malingering patients may also sometimes complain of vulval pain. Our experience is that vulval pain due primarily to psychiatric disease is no more common than in any other part of the body.
Non-lesional pain has the following characteristics:
It typically is best on first arising, becomes worse throughout the day, and is improved with rest at night.
It is often positional: worsened by prolonged sitting and tight trousers.
Hyperalgesia is characteristic of neuropathic pain and describes severe pain experienced from mild pain stimuli such as light touch. This can cause extra confusion because application of diverse topical therapies all seems to cause pain. This is inevitably attributed to the products themselves but is actually hypersensitivity to touch.
Poor localisation of pain is often a feature of neuropathic pain. When asked to localise this sort of pain, patients are often unable to do so, and are only able to indicate the general area where the pain is experienced.
Well-localised and especially unilateral pain is usually referred from the spine. Patients will localise a portion of skin on the affected side, but examination will show normal skin and no tenderness at this site.
When patients describe non-lesional vulvovaginal pain, they use the following words:
Lesional Pain
Pain due to an observable lesion or dermatosis is often caused by dermatological conditions that cause inflammation, ulceration, blisters, fissures and adhesions, and by conditions that cause vaginitis:
It is frequently provoked by physical stimuli such as friction during intercourse or when inserting or pulling out a tampon, rubbing, scratching or wearing tight clothes.
It is often accompanied by the symptoms of the causative dermatosis.
It is usually bilateral.
It is often worse during the night, when there are fewer external stimuli.
It resolves promptly when the underlying condition resolves.
Lesional pain is usually well localised and has the familiar qualities of pain induced by injury.
Application of cream, which contain irritating substances such as preservatives, may sting. Changing from a cream to an ointment (which has no preservatives) usually solves this problem, and also helps to confirm that the pain is lesional.
This sort of pain resolves promptly when the underlying condition resolves.
When patients describe lesional pain they usually use the following words:
Which Skin Diseases of the Vulva Are Likely To Be Painful?
Dermatological conditions that affect the vulva tend to present with itch. Pain may be present, but it is usually sharp, easily localised pain that is due to excoriation from scratching or fissuring, which may occur in any dermatosis. Dyspareunia, if present, is usually due to friction involving raw areas.
Dermatological conditions that are predominantly painful rather than itchy are uncommon and include lichen planus, desquamative inflammatory vulvovaginitis, aphthous ulcers, erythema multiforme and fixed drug eruption. Bullous diseases such as bullous pemphigoid and cicatricial pemphigoid (see Chapter 5) can cause painful erosions but are extremely rare. Crohn’s disease can present with painful erosions associated with oedema (see Chapter 5).
Vulval varicose veins may cause a dull ache, particularly after long periods of standing.
Infections such as genital herpes (see Chapter 5), vulval staphylococcal cellulitis and hidradenitis suppurativa (Chapter 7) are characteristically painful.
Atrophic vulvovaginitis tends to present with dyspareunia and a sensation of dryness (see ‘Dyspareunia due to oestrogen deficiency’ below).
Vaginal Dyspareunia
It is important to differentiate vaginal (superficial/entry) dyspareunia (felt in the vagina) from abdominal (deep) dyspareunia (felt in the abdomen). The first is usually caused by problems in the lower pelvis, and the second by problems in the upper pelvis or abdomen. There is widespread confusion about what constitutes ‘deep’ dyspareunia, with many doctors assuming this means ‘deep in the vagina’. Our experience is that the important distinction is between abdominal as opposed to vaginal dyspareunia, and that it does not matter (in a diagnostic sense) how deep in the vagina it is felt. In the context of this book, we are discussing vaginal dyspareunia.
We find it most helpful to consider vaginal dyspareunia as a subset of vulval pain. Dyspareunia is usually primarily physical in origin, and therefore needs to be assessed in the context of the wider pelvis. Most often, it is part of a syndrome of non-sexual vulval pain, and it is the history of this background pain that will help in making a diagnosis. Dyspareunia can, however, occur as the only presenting symptom. In other words, the patient has no symptoms except pain during intercourse and/or tampon insertion.
Like more generalised vulval pain, vaginal dyspareunia may also be lesional or non-lesional. Lesional dyspareunia clearly occurs because the vulva and vagina is raw and inflamed.
Non-lesional dyspareunia occurs in the absence of any observable disease that could explain it. We believe that it is most often due to neuromuscular dysfunction. Rarely, it may be a somatoform disorder. This type of dyspareunia may be triggered by an underlying lesional disease but may remain long after the disease resolves. It may also appear in the absence of any lesional disease.
When discussing dyspareunia, it is important to explain pubococcygeal muscular dysfunction. This is found in many patients who have experienced vulval conditions that have caused dyspareunia for any reason. It can also occur as a primary problem in response to emotional stress and anxiety.
In this situation, the pubococcygeus muscle (the muscle that attaches anteriorly to the pubic bone and meets within the substance of the perineal body) goes into spasm as soon as any pressure is applied to the introitus. The patient describes a sharp, tearing sensation on intromission and immediate relief as soon as intercourse ceases. Tampon insertion often causes the same symptoms. It is unusual for this pain to linger for long after intercourse ceases unless there is also a lesion that has been irritated during intercourse.
Pubococcygeus muscle spasm is detectable on vaginal examination. It may be virtually impossible to insert an examining finger into the vagina because of this spasm, and any attempt to do so is described as severe pain by the patient. However, a patient who is relaxed with you as a doctor but apprehensive about intercourse may appear deceptively normal.
Lesional Group (nociceptive pain)
When dyspareunia is due to an ulcer or fissure, patients usually complain of the sort of pain that we would all experience if we cut a finger. This is known as ‘nociceptive pain’, in other words mediated by nociceptors in skin. This pain is usually well localised and is often accompanied by a small amount of bright post-coital bleeding. If the patient has a skin condition that is prone to fissuring, for example lichen sclerosus, this may occur as a result of intercourse. In this situation, the pain may not be immediate but may develop during intercourse. It then typically lasts for several days, until the fissure has healed.
Dyspareunia due to local physical causes usually improves promptly when the underlying dermatological condition is healed. However, it must be recognised that by the time effective treatment for the dermatosis is initiated, it may have caused secondary pubococcygeus muscle dysfunction that continues to cause dyspareunia.
Non-lesional Group (non-nociceptive pain)
In these patients, there is often a background of poorly localised or unilateral vulval pain. Some patients with non-lesional vulval pain deny dyspareunia but say they no longer want to have sex due to low libido or fear of being hurt. Those who do experience dyspareunia are usually either experiencing hyperalgesia or the same secondary pubococcygeus muscle dysfunction that occurs in patients with nociceptive pain.
Dyspareunia due to Oestrogen Deficiency (atrophic vaginitis)
Atrophic vaginitis is due to oestrogen deficiency and may present with dyspareunia alone, which patients often correctly identify as being associated with dryness. These women are lactating, post-menopausal or very thin.
Some patients, particularly those with a tendency to dermatitis elsewhere or who are atopic, may also develop a mild dermatitis of the introitus and labia minora. They may then complain of itching or irritation.
Post-menopausal women, who are prone to the vulvovaginal effects of post-menopausal oestrogen deficiency, are however also the group who may suffer from neuropathic vulval pain. As a result, an observation of atrophy may not be the cause of their vulval pain.
Examination
Examination shows a pale mucosa, with little lubrication and loss of normal rugosity. In younger lactating patients, however, there may be little to see other than a somewhat dry surface.
Management
Management should be initiated with topical treatment using oestrogen cream or pessaries, initially daily for 2 weeks and then twice weekly. Long-term use will be required if a beneficial response is achieved.
If dermatitis is present, hydrocortisone 1% ointment twice daily should be used concurrently, and the patient should use a soap substitute. Bland emollients and non-irritating lubricants during intercourse are helpful adjuncts to treatment. This condition should respond promptly to topical oestrogen cream or pessaries within a month. If there is no response, consider an alternative cause for the dyspareunia.
Approach to the Patient with Constant Vulval Pain
History Taking
Most patients with vulval pain will not volunteer the symptoms that help to make a diagnosis. They will, for example, complain about ‘reduced libido’ instead of dyspareunia; similarly, a patient is unlikely to volunteer that her vulval pain started during an episode of acute generalised psoriasis. A careful and comprehensive history is therefore essential, and should include the following:
Duration of current episode of pain
History of similar pain previously
Historical triggers
Exacerbating/relieving factors
Associated symptoms, e.g. itch, vaginal discharge
History of skin disease, either vulval or elsewhere
History of menstrual pain
History of bladder pain
History of irritable bowel or chronic constipation
History of hip and/or back pain or injury
Leisure activities such as cycling, horse riding, skating
Pain descriptors:
Sharp/dull/burn/sting/formication/stabbing
Associated itch, bleeding or abnormal vaginal discharge
Length of episodes
Triggers for episodes
Pain location:
On/within the labia majora
Central
Bilateral/unilateral
Anterior/posterior
Referral patterns
Previous treatments:
Effective
Ineffective
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