Classification of Chronic Vulvar Pain

By Marek Jantos Ph.D.

The development of classification systems for medical diseases and disorders has been an ever evolving phenomenon (Levine, 2005). The classificatrion of chronic vulvar pain illustrates this process. The purpose of classifications is to provide a framework for identifying and grouping conditions, facilitating communication, both spoken and written, and guiding clinical practice as well as research (Merskey & Bogduk, 1994; APA, 2000). To achieve this goal, classification needs to accurately reflect current knowledge in a consistent and reliable manner (Merskey & Bogdul, 1994). However, if the diagnostic classification is erroneous or misleading, or if the foundations of its classification are faulty, treatment will be compromised and research misdirected (Klienplatz, 2005).

Uncertainty in relation to the classification of vulvodynia continues to the present day. To date three perspectives on the classification of vulvodynia have emerged: that of a sexual dysfunction (Basson, 2005; APA, 2000), a somatoform disorder (Mascherpa et al., 2007, Lynch, 2008), and that of a chronic pain syndrome (Binik et al., 1999, Pukall et al., 2003). These perspectives are linked, in varying degrees, to the following classification systems:

The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (APA, 2000) classification of pain under sexual disorders and somatoform disorder.
The International Association for the Study of Pain (IASP), Multi-Axial Classification of Chronic Pain (Merkesley & Bogduk, 1994).
The International Society for the Study of Vulvovaginal Disease (ISSVD), Terminology and Classification of Vulvodynia (Moyal-Barraco & Lynch, 2003).

Each of these diagnostic systems will now be discussed briefly.

The DSM System
The American Psychiatric Associations Diagnostic and Statistical Manual (DSM) classifies urogenital pain under Sexual Dysfunction or Somatoform Disorders. The text of the fourth edition of the DSM-Text Revision (DSM-IV-TR) version will form the basis of the discussion in this chapter (APA, 2000). Unless otherwise stated, all references will be made to the DSM-IV-TR, but referred to by the simplified acronym of DSM.

The DSM makes reference to two sexual pain disorders; dyspareunia, which is characterized by recurrent or persistent genital pain associated with sexual intercourse; and vaginismus, which is defined as a recurrent or persistent involuntary spasm of the pelvic musculature interfering with sexual intercourse (APA, 2000). Both of these conditions are discussed in the Sexual Pain Disorders section of the chapter on Sexual and Gender Identity Disorders.

In the DSM, the experience of pain in conjunction with sexual intercourse is most commonly classified as a sexual dysfunction. A sexual dysfunction refers to any “disturbances in sexual desire and in the psychophysiological changes that characterize the sexual response cycle and cause marked distress and interpersonal difficulty” (APA, p. 535). From the DSM perspective, sexual dysfunction is a disturbance in sexual desire and sexual response. This creates a conceptual problem, because sexual desire and sexual response in vulvodynia patients is no different to that of non-pain patients (Payne et al., 2007; Reed et al., 2000; Meana et al., 1997; Van Lankveld et al., 1996). It is the disabling impact of pain that makes intercourse difficult, if not impossible. Furthermore, as has been suggested elsewhere (Phillips, 2000; Marthol & Hilz, 2004), the most common causes of sexual dysfunction include psychological, pharmaceutical, medical, and physiological factors, which can be summarized as follows:

Psychological factors: intrapersonal conflicts arising from religious practices, guilt or social restrictions; historical factors including past or current abuse, rape, sexual inexperience; interpersonal conflict in the form of relationship difficulties, extra-marital affairs, abuse, desire differences, sexual communication problems; and life stressors arising from illness, depression, finances, family or job problems (Philips, 2000).
Pharmaceutical factors: medications that cause disorders of desire, psychoactive, antihypertensive, and hormonal preparations; medications that cause disorders of arousal, including anticholinergics, antihistamines, antihypertensives and psychoactives; medications that cause orgasmic dysfunction, such as tricyclic antidepressants, amphetamines, anorexic drugs, antipsychotics, narcotics and others (Phillips, 2000).
Medical conditions: a wide range of illnesses such as cancer, diabetes, gynecologic surgery, and procedures such as chemotherapy, radiation therapy and others (Phillips, 2000)
Physiological changes: including changes due to menopause, organ atrophy and muscle weakness. These changes can be lifelong, acquired, generalized or situational (Phillips, 2000).

These causes of sexual dysfunction, except in individual cases, have not been shown to be linked to vulvodynia and are not seen as relevant. The only characteristics that distinguish vulvodynia patients from controls and other chronic pelvic pain patients are pain sensitivity during sexual arousal, general severity of pain and the level of disability caused by pain (Payne et al., 2007; Reed et al., 2000; Meana et al., 1997).

Earlier versions of the DMS lacked clarity in relation to the specific role of pain in sexual dysfunction (First, 2005). Subsequently, the Text Revision (TR) qualifies the definition of sexual dysfunction by stating that a “sexual dysfunction is characterized by a disturbance in the processes that characterize the sexual response cycle or by pain associated with sexual intercourse” (APA, p. 535, italics added). Without this qualification, vulvodynia could not be considered a sexual dysfunction, since it does not directly affect any particular phase of the sexual response cycle (First, 2005; Schultz et al., 2005). Pain was identified as a separate cause of sexual dysfunction, quite apart from any other factors disrupting the sexual response cycle. The issue that remains unclear in the DSM classification is how pain, caused by sexual intercourse, can be the defining characteristic of a sexual dysfunction. It is the pain that causes the sexual dysfunction and not the reverse (White & Jantos, 1998; Pukall et al., 2003). As stated elsewhere, “it is tautological to define the pain as the symptom which causes pain” (Moser, 2005). To illustrate the point, it has been argued that lower back pain prevents people from working, but it is not appropriate to conceptualize back pain as a work disorder or a work pain (Pukall et al., 2003).

Finally, in order for a sexual dysfunction to meet the DSM classification criteria, it must cause marked distress and interpersonal difficulty. Vulvodynia, without a doubt, is a source of distress (Jantos, 2008; Pukall et al., 2002), impacting significantly on quality of life and on interpersonal relationships (Arnold et al., 2006; Desrosiers et al., 2008) but is not necessarily the cause of interpersonal difficulty or the result of relationship issues (Van Lankveld et al., 1996; Reed et al., 2000; Jantos & Burns, 2007).
Female sexual dysfunction in the DSM system is generally divided into four categories which are not mutually exclusive:

Hypoactive Sexual Desire Disorder – a low sexual desire – characterized by diminished interest in sexual activity.
Female Sexual Arousal Disorder – reflected in an inability to become aroused or maintain arousal during sexual activity.
Female Orgasmic Disorder – evidenced by a persistent or recurrent difficulty in achieving orgasm following a period of arousal and stimulation.
Sexual Pain Disorder – where pain is experienced in the urogenital area during sexual arousal or stimulation.

The two sexual pain disorders listed in the DSM are dyspareunia and vaginismus. Vaginismus is defined as an involuntary spasm of the muscles surrounding the outer third of the vagina when intercourse is attempted. Dyspareunia (from the Greek term for painful mating) is identified as a pain disorder, with no specific cause listed. These two pain disorders are further subclassified as Due to Psychological Factors or Due to Combined Factors (APA, p. 537). Pain can also be classified in the category of Sexual Dysfunction Due to a General Medical Condition (APA, p. 558).

Numerous psychological and medical conditions have been identified as possible causes of dyspareunia (Schultz et al., 2005), but the DSM provides few options for differentiating between causes of pain and provides limited inclusion and exclusion criteria (Meana et al., 1997; Pukall et al., 2003). By contrast, the current ISSVD definition of vulvodynia specifically states that it is a condition “occurring in the absence of relevant visible findings, or a specific, clinically identifiable, neurologic disorder,” and cannot be subtyped under any category for which there is a medical cause (Moyal-Barracco & Lynch, 2003; Lynch, 2008). In light of these exclusions, vulvodynia should not be classified as a sexual dysfunction due to medical causes, or combined factors (psychological and medical). According to the DMS this would leave only one remaining option, namely, to classify the disorder as being due to psychological factors. If that were to be the case all available evidence needs to be weighed to determine if indeed the etiology of vulvodynia is linked with psychological causes.

The DSM classification has been questioned for several other reasons as well. One of the major criticisms of its classification of sexual disorders is that it provides only descriptive information which is not based on empirical evidence (First, 2005; Binik, 2005). The descriptive and pragmatic nature of the classification system has been called into question by a range of research findings and is generally seen as lacking validity (Kaler, 2005; Kleinplatz, 2005; Moser, 2005). This is clearly illustrated in reference to vaginismus and dyspareunia.

The DSM classification lists vaginismus and dyspareunia as two sexual pain disorders. However, evidence shows that the distinction between vaginismus and dyspareunia is difficult to maintain (Binik et al., 2000; Binik, 2005; Ter Kuile et al., 2005; deKruiff et al., 2000; Binik et al., 1999; O’Donohue, 1993). Studies have shown that more than 50% of women presenting with primary vaginismus also meet the criteria for vulvodynia (Ter Kuile et al., 2005; deKruiff et al., 2000). Furthermore, in defining vaginismus as a “recurrent and persistent involuntary spasm of the musculature of the outer third of the vagina that interferes with sexual intercourse” (APA, 2000, p. 558), the diagnostic criteria do not specify that pain must be present, even though it is classified as a pain disorder. The DSM definition of vaginismus makes an assumption about the cause of pain. The spasm oriented diagnostic criteria for vaginismus have been widely questioned. Studies utilizing SEMG, have consistently failed to differentiate between normal controls and vaginismic women on the basis of muscle tension or spasm (Van der Velde & Everaerd, 1999; Van der Velde et al., 2001; Van der Velde & Everaerd, 2001). These studies showed no involuntary spasm in vaginismic women, who demonstrated equally good control of pelvic muscles, when compared with controls. The DSM provides no justification of why dyspareunia and vaginismus are listed as separate pain disorders, or why these pain conditions have been designated as sexual dysfunctions (Moser, 2005). The evidence raises questions about the validity of the DSM’s classification of sexual pain disorders (Binik, 2005) and other definitions of these disorders have been proposed (Basson et al., 2003).

Another section of the DMS relevant to vulvodynia is the section on Pain Disorder, in the chapter on Somatoform Disorder. This section of the DSM groups all physical manifestations of psychiatric disorders under Somatoform Disorders (Moser, 2005). To avoid the psychoanalytic overtures of the previous editions of the DSM, disorders previously seen as linked to hysteria, were grouped together on the basis of the predominant symptom of pain. Pain conditions, whether acute or chronic, were subtyped on the basis of factors that were seen to play a major role in its etiology. In the Somatoform Disorders section, three options exist: “Pain Disorder Associated With Psychological Factors”: “Pain Disorder Associated with Both Psychological and a General Medical Condition”; and “Pain Disorder Associated With a General Medical Condition”. Where psychological factors directly contribute to onset of pain the first two subclassifications are relevant. If pain is primarily due to a general medical condition, but psychological factors are present, they are not judged to have a major role in its onset, severity or maintenance. Medical conditions such as musculoskeletal problems, disc herniation, malignancies and neuropathies, are typical causes of pain due to medical cause. These conditions are judged not to arise from a “mental disorder” (APA, 2000, p. 499). Again, according to the ISSVD definition, if medical causes can be identified, they immediately exclude the diagnosis of vulvodynia. The only subtype remaining is Pain Disorder Associated with Psychological Factors. In this section of the DSM, there is no listing of any specific pain conditions, but the criteria apply where pain is shown to have a psychosomatic origin. According to DSM (IV-TR), the diagnosis of Pain Disorder is appropriate where “…psychological factors are judged to have a major role in the onset, severity and exacerbation, or maintenance of the pain” (APA, 2000, p. 499). If vulvodynia is to be classified as a pain disorder, emotional factors would need to be identified as having a primary role in its etiology (Moser, 2005). No such findings have been made to date.

From a psychiatric perspective, some pain conditions are seen as secondary to Axis I disorders (psychiatric disorders), or to an Axis III conditions (general medical conditions), providing there is a temporal relationship between the pain and potential triggers. However, in relation to chronic pain; “when chronic pain is the central or predominant feature, it fits somewhat uneasily into the framework… Because of its private and inferred nature, the frequent lack of demonstrable pathology, and its often obscure relationship to emotional stimuli, chronic pain does not fall readily under the traditional psychosomatic rubric…it is unlike other somatoform disorders, although that is the rubric under which it is currently classified.” (Blackwell, 1989, p. 1267)

Classification of chronic vulvar pain under the rubric of a somatoform disorder is often justified on the basis of a patient’s persistent search for a physical diagnosis, their rejection of psychological explanations, and their sexually dysfunctional status (Dodson & Friedrick 1978; Lynch, 2008). Yet, the search for a diagnosis, and the denial of psychological causes, are both features of patient behaviour that constitute appropriate efforts to resolve a health dilemma and in themselves do not warrant psychiatric labelling (Blackwell, 1989). Suggestions that sexual pain may be a form of anger displacement were also not supported by empirical evidence (Meana & Binik, 1994), which, leads to the conclusion that, “the explanation of sexual pain as a type of somatisation also has its roots in psychoanalytic theory and also has no empirical support (Binik et al., 1999). Until psychological factors are shown to have a major role in the onset of vulvodynia, its classification as a somatoform disorder is not justified.

It is evident that if vulvodynia is to be classified within the DSM framework, irrespective of whether it is subsumed under the sexual dysfunctions section, or under the pain disorder section, the primary cause of symptom onset, severity and maintenance, would need to be psychological. If indeed it can be shown to be psychological, than such a reclassification would have significant social and clinical implications. Thirty years ago, it was argued that vulvodynia was a psychosomatic pain disorder (Dodson & Friedrich, 1978). This argument was recently restated (Lynch, 2008). However, the research presented in this thesis and the research findings reviewed in the literature do not appear to support such a view. The relevance of the DSM to vulvodynia is questionable, unless the cause can be shown to be predominantly psychological. The DSM lacks empirical support and theoretical rational. As a result other classification systems have been suggested (Basson et al., 2003), with the specific purpose to “aid future research on women’s sexual dysfunctions by better delineating the clinical realities of women’s sexuality and by helping clinicians to minimize inappropriate classification and pathologizing of women” (Meston & Bradford, 2007).

The IASP multi-axial pain system
The most comprehensive classification of chronic pain was developed by the IASP (Mersky & Bogduk, 1994). This system classifies pain on the basis of body region, body system involved, pain characteristics, intensity and etiology. It lists the known generalized and localized pain syndromes (visceral, muscular, spinal and radicular) and includes pelvic and genital pain in its 700 and 800 code sections. The symptom characteristics in pain syndromes are rated along five axes:

Axis I: Regions: Identifying the main sites of the body affected by the pain (e.g., genital region).
Axis II: Systems: Identifying the physiological system whose abnormal functioning produces the pain (e.g., musculoskeletal, cutaneous, or nervous system).
Axis III: Temporal characteristics of pain and patterns of occurance (e.g., continuous, intermittent, recurring, or irregular).
Axis IV: Patient statement of intensity and time since onset of pain (e.g., mild or severe, of 6-12 months duration).
Axis V: Etiology: Identifying potential antecedents to pain (e.g., infection, physical trauma).

The IASP classification system is the most comprehensive taxonomy of chronic pain syndromes. Each category is rated on a nine point scale (0-8). This provides a five digit code which classifies the pain according to each of the five scales.

The IASP classification has been successfully applied to the study of vulvodynia (Pukall et al., 2003). Hypothetically, in the case of vulvodynia, the region of the body is clearly identified, affecting the vulvar region, or more specifically the vestibule, perineum or clitoris (Bergeron et al., 2001; Jantos, 2008). The physiological systems involved in vulvodynia can include the neuromuscular (White & Jantos, 1997; Glazer et al., 1995) and the autonomic nervous system (Payne et al., 2007; Granot et al., 2002). In relation to temporal patterns of occurrence, pain can be spontaneous or provoked by activities such as penetration and last for several hours post-intercourse (Meana et al., 1997; Reed et al., 2000); the quality of the pain is reported as burning, rawness, itching, or stabbing, and rated by most patients as severe (Bergeron et al., 2001; Jantos, 2008). The presumed etiology may be secondary to recurrent infections or inflammation (Friedrich, 1987; Saunders et al., 2008).

The classification of vulvodynia as a pain syndrome is becoming more widely accepted, with more reports referring to vulvodynia as a chronic pain syndrome, rather than a sexual dysfunction or somatoform disorder (Reed et al., 2000; Pukall et al., 2003; Binik, 2005). The IASP pain classification, with its primary focus on pain, enables clinical and research work to focus on the more objectively measurable symptom, than on interference with sexual activity and sexual response. This is a significant shift in focus as pain measures have been shown to be the most important predictors of patient-rated improvement (Bergeron et al., 1999), providing support for a pain-centered conceptualization of vulvodynia (Binik et al., 1999).

The ISSVD definition and classification of vulvodynia
With the prevalence of idiopathic vulvar pain increasing, the International Society for the Study of Vulvovaginal Disease (ISSVD) established a special task force in 1983 to review the terminology and classification of vulvar pain. The first report proposed two terms to designate chronic vulvar pain: vulvodynia and burning vulvar syndrome (Young et al., 1984). Following consultation with relevant specialist associations, including the IASP, the ISSVD adopted the term vulvodynia as a descriptive term for chronic unexplained vulvar pain (Moyal-Barracco & Lynch, 2004). The anatomical area referred to as the vulva includes the external portion of the female genital tract, consisting of the vestibule, hymen, urethral opening and Skene’s ducts, the greater vestibular ducts (Bartholin’s ducts), labia minora and majora, the clitoris, mons pubis and the perineum (McLean, 1988). The ISSVD defined vulvodynia as “vulvar discomfort, most often described as burning pain, occurring in the absence of relevant visible findings or specific, clinically identifiable, neurologic disorder” (Moyal-Barracco & Lynch 2004, p. 775). The ISSVD definition of vulvodynia meets the essential criteria for the definition of a chronic pain condition (Williams et al., 2004). It identifies the location of the pain, its sensory qualities, and its unknown but potentially multi-factorial nature. In relation to the location of the pain, the term vulvodynia is descriptive in that it identifies the anatomical area affected – namely the vulva, and the Greek term odyno points to pain as the primary symptom. Other terms such as dysesthesia and dysesthetic vulvodynia were not supported. The earlier term vulvar vestibulitis syndrome was also discontinued as it wrongly implied that vulvar pain was an inflammatory disorder.

The current classification system for vulvar pain was put forward and accepted at the 17th Congress of the ISSVD in 2003 (Moyal-Barracco & Lynch, 2004). The term vulvodynia was accepted as the most appropriate descriptor for chronic unexplained pain of the vulva. For purposes of consistency, the current ISSVD terminology will be used throughout this discussion, but earlier nomenclature used by authors will be acknowledged in parentheses.

To clearly differentiate between medical causes of vulvar pain and vulvodynia, the ISSVD proposed the following classification;

Vulvar pain related to specific disorder
Infectious (e.g., candidiasis, herpes, etc.)
Inflammatory (e.g., lichen planus, immunobullous disorders,etc.)
Neoplastic (e.g., Paget’s disease, squamous cell carcinoma, etc.)
Neurologic (e.g., herpetic neuralgia, spinal nerve compression, etc.)
Vulvodynia
Generalized
Provoked (sexual, nonsexual or both)
Unprovoked
Mixed (provoked and unprovoked)
Localized (vestibulodynia, clitorodynia, hemivulvodynia,etc.)
Provoked (sexual, non sexual or both)
Unprovoked
Mixed (provoked and unprovoked)

As is evident from the classification of vulvar pain, vulvodynia is a diagnosis of exclusion. Medical causes of vulvar discomfort are classified under four separate categories in Section A, covering infectious, inflammatory, malignant and neurological causes. Unexplained discomfort not accounted for by any of the medical diagnoses is classified in Section B under one of two categories, generalized or localized vulvodynia. Generalized vulvodynia accounts for the involvement of the whole vulva, and localized refers to the involvement of a specific portion of the vulva, such as the vestibule (vestibulodynia), clitoris (clitorodynia), or hemivulva (hemivulvodynia). Under each of the two categories (generalised and localised), provision is made to further identify if the discomfort occurs spontaneously or is provoked by physical triggers such as sexual intercourse, tampons, speculum, or tight clothing. There is very little research and empirical evidence supporting the sub-typing of vulvodynia (Masheb & Richman, 2005) and further work is required to clearly differentiate between different localizations, and to establish the significance of the generalised and localised sub-categories. Some reports have used further sub-classification to differentiate between primary (early onset) and secondary (later onset) vulvodynia, which may need to be considered in future reviews of terminology (Goetsch, 1991; Jantos & Burns, 2007; Sutton et al., 2009). The early onset of symptoms in primary vulvodynia, often predates, or is associated with, first attempts at intercourse, whereas, later onset in secondary vulvodynia, occurs after a period of pain free intercourse. The significance of a sub-classification based on time of onset needs to be further explored.

In terms of a medical assessment, the diagnosis of vulvodynia is established on the basis of reported discomfort and pain associated with vestibular touch and occurring in the absence of any other diagnosis. Cotton swab testing is used to localise painful areas and the degree of discomfort and pain can be classified as painless, mild, moderate or severe (Haefner et al., 2005). Concerning the common sensory descriptors used by patients, 88.1% chose adjectives that described a thermal quality and 86.6% chose adjectives that described an incisive pressure sensation, highlighting the involvement of peripheral sensory mechanisms (Bergeron et al., 2001; Jantos, 2008).

Finally, the ISSVD definition emphasizes the absence of any specific physical or neurological findings to account for the chronic pain. As a chronic pain condition, vulvodynia typifies the chronic pain syndrome anomaly where pain is not proportional to, or explained by, visible pathology (Steege, 1998). However, some have used the exclusion criteria to argue that if medical causes are excluded, the only alternative is to view psychosexual distress and psychopathology as the most likely cause of vulvodynia (Lynch, 2008; Schultz et al., 2005). The ISSVD classification is being accepted and, as a new classification system, needs to be reviewed and given time to evolve.

Reliability and validity of current classification systems
The DSM classification system in labelling pain in the urogenital area as a sexual dysfunction or a “sexual pain,” has inadvertently redefined this regional pain disorder in a manner which lacks validity and reliability (Moser, 2005). It has embedded the problem of pain in psychological concepts and discouraged the study of its major symptom, which is pain (Binik et al., 1999). Even though it has sought to remove the psychoanalytic language of the past versions, it has arbitrarily regrouped many of the disorders in a manner that still reflects its past history (Moser, 2005). As a result a growing number of researchers have been critical of the DSM classification (Kaler, 2005; Kleinplatz, 2005).

The IASP classification is a well validated system, providing the best model for the classification of chronic vulvar pain. It lists pelvic and genitourinary pain syndromes (including vaginismus and dyspareunia) in its classification, and can be adapted for the classification of chronic vulvar pain (Pukall et al., 2003). Many clinicians and researchers have called for the reclassification of vulvodynia as a chronic pain syndrome (Kaler, 2005; Binik, 2005) and have called specifically for the adaptation of the IASP classification in relation to vulvodynia. In recommending the IASP system, they are of the opinion that vulvodynia “fits nicely into this framework” and that a “de-sexualized” approach to pain “will lead to improved understanding and treatment of important and currently neglected women’s health problems” (Binik et al., 1999, pp. 230, 231).

For the diagnosis of vulvodynia two physical criteria show good reliability and validity: presence of pain on vaginal penetration and tenderness on pressure application to the vulvar vestibule (Bergeron et al., 2001; Masheb et al., 2004; Reed et al., 2006; Reed et al., 2008). Both of these criteria resulted in over 90% of cases being correctly classified (Bergeron et al., 2001). The IASP classification of chronic pain is focussed on the specific region affected by pain and on the physiological system producing symptoms of pain with an emphasis on objective diagnostic criteria such as reproducible tenderness on pressure application of the affected area. It appears to be the only system which can provide reliability and validity for the classification of chronic vulvar pain.

The ISSVD classification draws a clear distinction between medical and non-medical causes. In doing so it typifies a traditional dualism where visible pathology is equated with medical causes and lack of pathology with non-medical causes, which are often assumed to be psychological (Lynch, 2008). The ISSVD classification fails to make any mention of the possible physiological systems mediating pain, even though considerable evidence exists highlighting the involvement of the neuromuscular and neuropathic mechanisms (Bachmann et al., 2006). The ISSVD classification and definition of vulvodynia fails to address the emotional and subjective components of pain, as reflected in the definition of pain given by the IASP (Merskey & Bogduk, 1994, Jantos, 2008). These omissions contribute to confusion in the context of the current controversy on whether vulvodynia constitutes a sexual dysfunction, a somatoform disorder, or a regional pain syndrome. The ISSVD classification needs to be further developed and its sub-classifications updated.