Diagnostic Classification of Orofacial Pain
| Key Points |
 Diagnostic systems are needed to assist with management of orofacial pain. |
 The complexity of the field of pain is reflected in the availability of many widely varying diagnostic schemes. |
 No diagnostic classification is without shortcomings and criticism. |
 There is still an urgent need for validation of classification schemes. |
 The diagnostic classification presented in this chapter is in accord with internationally accepted standards and should be useful for clinicians attempting to manage the patient suffering with orofacial pain. |
The ability to understand and investigate pathophysiologic processes underlying a disorder depends on a valid, reliable classification system and common terminology to facilitate communication among clinicians, researchers, academicians, and patients. Without a universal system of organization in place, discussion, investigation, and ultimately understanding of the disorder are difficult to achieve.
Classification begins by grouping disorders according to common signs and symptoms and dividing further by common pathophysiology and treatment approaches. In this manner, the diagnostic classification can assist the clinician in treatment selection. From a clinical perspective, it is not important to further divide subgroups when all the disorders within a given subgroup are managed by the same therapy. Therefore, from a therapeutic standpoint, subcategories are only useful when therapy demands it.
Another purpose of a common diagnostic classification system is to assist the researcher in gaining insight into the prevalence, etiology, and natural course of a specific disorder. Knowledge can only be advanced when agreement is met on specific disorders so that research efforts can be compared between patients and various research groups. At this time, it is uncertain whether diagnostic criteria for research purposes are compatible with diagnostic criteria for determining therapy. For example, it is quite reasonable to separate muscle disorders from intracapsular joint disorders for the purpose of studying the natural course of these disorders. However, merely identifying that a patient is suffering from one of these types of disorders may not be adequate to effectively manage the condition. The most useful classification system would provide both research and diagnostic advantages.
The process of developing a classification system begins by identifying a group of common signs and symptoms. Once these signs and symptoms have been identified, the disorder is named. The disorder, with its common signs and symptoms, is then investigated to learn more about its etiology so that effective treatment may be developed. It is very important that the signs and symptoms used to identify the disorder be unique to the disorder so that other, unrelated disorders are not misidentified. It is therefore important that specific inclusion and exclusion criteria are developed that will permit accurate grouping of similar disorders. In order to eliminate as much variability in diagnosis as possible, it is very important to be specific, avoiding words such as “usually,” “typically,” or “sometimes.” Testing is then necessary to determine if the diagnostic criteria are valid and reliable for determining the disorder. Once they are proven reliable, research efforts can be directed toward gaining better insight into etiology, eventually leading to more effective treatment.
In this chapter, past and present terminology and diagnostic classification systems for temporomandibular disorders (TMDs) and orofacial pain disorders are discussed, and a classification system for orofacial pain disorders is presented. To assist the reader, the ICD-10 and ICD-9 codes for each diagnosis, from The International Classification of Diseases, Tenth and Ninth Editions, will be provided throughout the next chapters. Some groups,1 however, feel that the ICD-10 codes do not adequately reflect the state of the art of pain research nor sufficiently support the clinical decisions in selecting proper pain management and have proposed that pain-specific classifications be addressed in the ICD-11. This is likely a reflection of the complexity of pain and our limited, yet growing ability to understand its many mechanisms.
Over the years, functional disturbances of the masticatory system have been identified by a variety of terms, which likely led to confusion in this area. In 1934, James Costen2 described a group of symptoms that centered around the ears and temporomandibular joints (TMJs) and called it Costen syndrome. In 1959, Shore3 used the term temporomandibular joint dysfunction syndrome for those symptoms. Later, the term functional temporomandibular joint disturbances was introduced by Ramfjord and Ash.4 Some earlier terms were based on possible etiologic factors, such as occlusomandibular disturbance5 and myoarthropathy of the temporomandibular joint.6 Other terminology stressed the featured pain symptom, such as temporomandibular pain-dysfunction syndrome7 and myofascial pain-dysfunction syndrome.8 Because the symptoms are not always isolated to the TMJs, some authors believe that the previously mentioned terms are too limited and a broader, more collective term should be used, such as craniomandibular disorders.9 Bell10 suggested the term temporomandibular disorders (TMDs), which has gained wide acceptance and popularity. As described in this text, this term not only includes problems related to the TMJs but also includes all functional disturbances of the masticatory system. TMDs are musculoskeletal disorders of the masticatory system.
Diagnostic Classification Systems
Many classification systems with varying advantages and disadvantages have been offered. Categories of division included etiologic factors, common signs and symptoms, and tissue origin or functional region of the body, or combinations thereof. Perhaps the first classification system for TMJ problems was offered by Weinmann and Sicher.11 In 1951, they classified TMJ problems into (1) vitamin deficiencies, (2) endocrine disorders, and (3) arthritis. Two years later, Schwartz12 introduced the term temporomandibular joint pain-dysfunction syndrome to distinguish organic disturbances of the joint proper from masticatory muscle disorders. In 1960, Bell13 developed a classification composed of six groups, recognizing both intracapsular and muscle (extracapsular) disorders. Acknowledging the need for a suitable classification for functional disorders of the masticatory system, the American Academy of Orofacial Pain (AAOP) published a position paper with a suggested classification system.9 Soon after, the American Dental Association (ADA) organized a national conference in which Bell suggested the term temporomandibular disorders, and a revised classification of TMDs consisting of five categories was introduced. Both the term and the classification were accepted by the ADA.14 Unfortunately, no diagnostic criteria were offered at that time.
In 1989, Stegenga et al15 proposed a system of classification emphasizing TMJ articular disorders. They divided their classification into inflammatory and noninflammatory articular disorders and nonarticular disorders. The subcategories of osteoarthrosis and internal derangements were further divided according to staging over time. Although this classification provided insight to intracapsular disorders, it placed little emphasis on masticatory muscle disorders. No diagnostic criteria were offered with this classification.
As the dental profession began to appreciate the similarity between many TMDs and other medical conditions, a need grew to include TMDs in a more inclusive medical classification for pain disorders. In 1986, the International Association for the Study of Pain (IASP)16 published a classification of pain conditions. Of the 32 categories of pain disorders, category III was designated as “Craniofacial pain of musculoskeletal origin.” Within this category were two subcategories: “Temporomandibular pain and dysfunction syndrome” and “Osteoarthritis of the TMJ.” This classification failed to recognize any pain disorders arising from the masticatory muscles.
Two years after the IASP classification was published, the International Headache Society (IHS)17 proposed a classification for headache made up of 13 broad categories. The 11th category was designated as “Headache or facial pain attributed to disorder of cranium, neck, eyes, ears, nose, sinuses, teeth, mouth, or other facial or cranial structures.” There were no specific subcategories related to TMDs, despite recommendations by the AAOP.18 The AAOP provided diagnostic criteria and subcategories in 199619 and again in 2008,20 although to date there have been no studies to determine the validity and reliability of these criteria.
In 1990, the American Academy of Head, Neck, Facial Pain and TMJ Orthopedics21 proposed a classification with five TMD categories and two non-TMD categories. The subcategories represented a mixture of both traditional and nontraditional disorders. Brief explanations for most subcategories were offered but not for all. There were 19 subcategories under the main category of “Myofascial disorders,” some of which were separated by the specific muscle or tendon involved. Some diagnostic categories, such as “Bruxism,” might better represent a precipitating or contributing factor of muscle pain and not necessarily a muscle pain disorder itself. No diagnostic criteria were offered to assist in classifying these disorders. Another classification suggested a much broader approach. Woda and Pionchon22 proposed the adoption of a unifying classification for “Idiopathic orofacial pain disorders.” Most clinicians who treat orofacial pain disorders recognize that there are certain patients who present with clinical symptoms that do not easily fit into the known and generally well-accepted classifications of orofacial pain disorders. The authors suggest that many of these unclassified conditions present with some common clinical symptoms. Because our understanding of these disorders is not complete, the profession has assigned such terms as atypical facial pain and atypical odontalgia. These atypical cases may present with common clinical symptoms associated with common pathophysiologic mechanisms. If common mechanisms do in fact exist, then it may be useful to group these conditions together. Yet until these mechanisms are better understood, grouping them into a large classification will not likely improve treatment selection. In fact, it would appear that placing TMDs with relatively known etiologies and treatment strategies into a group of idiopathic orofacial pain disorders would be taking a step in the wrong direction.
Recently, a group of researchers and clinicians attempted a new approach to the classification of orofacial pain.23 This new proposed taxonomy is based on ontology. Ontology is the study of the nature of being, such as whether an entity exists or not, how entities are similar and different as well as how they relate to each other within a hierarchy, and how these differences or similarities define their subgroup.24 Identifying a disorder or disease is dependent on several levels of evidence, such as reality, observations, interpretations, and/or beliefs. This new endeavor to classify orofacial pain has only attempted to look at a few orofacial pain conditions, and therefore a full classification is not available. This approach to nosology is unique, and its usefulness will need to be demonstrated.
A review of the literature regarding the classification of orofacial pain reveals little consensus regarding the most favorable diagnostic classification system. The IHS published the second edition of their classification in 2004.25 Over the past few years, many clinicians have embraced this classification because of its inclusive considerations for all head pains. This classification offers more than 230 types of headaches and thus requires the clinician to possess a very high level of appreciation for all head pain disorders before a diagnosis can be properly established. Temporomandibular joint disorder is grouped under category 11: “Headache or facial pain associated with disorder of cranium, neck, eyes, ears, nose, sinuses, teeth, mouth, or other facial or cranial structures.” The disorder is minimally defined, and masticatory muscle disorders are not addressed separately. The reliability and validity of the various diagnostic criteria have not yet been established. A third edition of this classification is expected within the next year.26 At this time, it is unclear whether a more thorough description of TMDs will be included.
Truelove et al27 proposed a classification system that allowed for multiple diagnoses within the same subject group. Required operational criteria were listed for each diagnostic group, allowing the researcher to investigate a sample population and determine the types and severity of disorders present. This concept was further elaborated through the Research Diagnostic Criteria (RDC) offered by Dworkin and LeResche.28 This classification not only provided very specific diagnostic criteria for eight TMD subgroups, but it also recognized another level or axis that must be considered when evaluating and managing TMD pain: the psychosocial level. For the first time in any classification system, a dual diagnosis was established that recognized the physical conditions (Axis I) and psychologic (Axis II) conditions that contribute to the suffering, pain behavior, and disability associated with the patient’s pain experience. (This Axis II should not be confused with the designated axis system endorsed by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) of the American Psychiatric Association.) This dual-axis classification approach has been incorporated in Bell’s classification for all orofacial pain disorders.29
The RDC28 offered what appeared to be reasonable diagnostic criteria, specifically for research purposes. Although the RDC have proven useful in standardizing research efforts in the field of TMDs, they have not proven as helpful for the clinician selecting appropriate therapy for the patient. Although some questioned whether these criteria were specific enough to accurately distinguish subgroups of TMD patients,30–32 the use of RDC/TMD for the most common TMDs has acceptable reliability.33 However, in a large-scale validation project for the RDC/TMD, no single diagnosis reached target validity.34,35 Over the past decade, researchers and clinicians have been working together to revise the RDC in an attempt to develop more specific and valid diagnostic criteria that would enhance both research and clinical usefulness. The International RDC-TMD Consortium from the International Association for Dental Research and the Special Interest Group on Orofacial Pain from the IASP joined forces to revise the RDC/TMD diagnostic algorithms to produce dual-axis diagnostic criteria (DC/TMD) that are evidence-based, have improved diagnostic accuracy, and are easy to use by both clinicians and researchers.36
Differential Diagnosis of Orofacial Pain
The diagnostic process is a clinical skill in which art and science are wed. The goals of the process are to determine the existence of any primary and/or secondary physical (Axis I) or psychologic (Axis II) diagnoses, the contributing factors, and the level of complexity of the patient’s problem(s), including the prognosis. Listing conditions that may be responsible for each of the presenting complaints of the patient, as well as other factors that may contribute to the complexity of the tentative diagnosis, usually facilitates the process. The diagnostic process involves defining the inclusion criteria that are specific to a disorder and ruling out specific disorders from a diagnostic classification that includes all possible disorders that can cause similar symptoms. It is important to rule out serious, life-threatening intracranial or extracranial disorders or diseases early in the diagnostic process, because these conditions may require immediate care. Pain sources should be pursued until all correct diagnoses are established using inclusive diagnostic criteria. The process of differential diagnosis is critical because an incorrect or omitted diagnosis is one of the most frequent causes of inapppropriate treatment or treatment failure.
Establishing the correct diagnosis in patients with orofacial pain is particularly difficult because of the complex interrelationship of physical (Axis I) and psychologic (Axis II) factors in the etiology of chronic pain syndromes. Many disorders have similar signs and symptoms. If the source of painful symptoms is uncertain, the appropriate diagnosis is “Pain, cause unknown or undetermined.” Although individual clinicians can be successful in diagnosing the simpler orofacial problems, a team approach is often required for diagnosing and managing complex chronic orofacial problems, especially when Axis II factors are present.37
The guidelines in this text use the classification structure proposed by the Taxonomy Committee of the International RDC-TMD Consortium Network and the Special Interest Group on Orofacial Pain, as presented in Table 3 of the DC/TMD36 (Box 3-1). This classification is a union of RDC/TMD and AAOP classification systems. The RDC/TMD criteria were employed for the more common TMDs. The AAOP criteria served as a basis for the less common TMDs.
| Box 3-1 Expanded TMD taxonomy36 |
| Temporomandibular joint disorders 1. Joint pain (ICD-10 M26.62; ICD-9 524.62) |
| A. Arthralgia B. Arthritis |
| 2. Joint disorders |
| A. Disc-condyle complex disorders (ICD-10 M26.62; ICD-9 524.63) |
| i. Disc displacement with reduction ii. Disc displacement with reduction with intermittent locking iii. Disc displacement without reduction with limited opening iv. Disc displacement without reduction without limited opening |
| B. Other hypomobility disorders (ICD-10 M26.61; ICD-9 524.61) |
| i. Adhesions/adherence ii. Ankylosis |
| a. Fibrous ankylosis b. Osseous ankylosis |
| C. Hypermobility disorders |
| i. Subluxation (ICD-10 S03.0XXA; ICD-9 830.0) ii. Luxation (ICD-10 S03.0XXA; ICD-9 830.0) |
| a. Closed dislocation (ICD-10 S03.0XXA; ICD-9 830.0) b. Recurrent dislocation (ICD-10 M26.69; ICD-9 524.69) c. Ligamentous laxity (ICD-10 M24.20; ICD-9 728.4) |
| 3. Joint diseases |
| A. Degenerative joint diseases (ICD-10 M19.91; ICD-9 715.18 localized/primary) |
| i. Osteoarthrosis ii. Osteoarthritis |
| B. Condylysis (ICD-10 M26.69; ICD-9 524.69) C. Osteochondritis dissecans (ICD-10 M93.20; ICD-9 732.7) D. Osteonecrosis (ICD-10 M87.08; ICD-9 733.45) E. Systemic arthritides (rheumatoid arthritis: ICD-10 M06.9; ICD-9 714.0) F. Neoplasm (benign: ICD-10 D16.5; ICD-9 213.1; malignant: ICD-10 C41.1; ICD-9 170.1) G. Synovial chondromatosis (ICD-10 D48.0; ICD-9 238.0) |
| 4. Fractures |
| A. Closed fracture of condylar process (ICD-10 S02.61XA; ICD-9 802.21) B. Closed fracture of subcondylar process (ICD-10 S02.62XA; ICD-9 802.22) C. Open fracture of condylar process (ICD-10 S02.61XB; ICD-9 802.31) D. Open fracture of subcondylar process (ICD-10 S02.62XB; ICD-9 802.32) |
| 5. Congenital/developmental disorders |
| A. Aplasia (ICD-10 Q67.4; ICD-9 754.0) B. Hypoplasia (ICD-10 M27.8; ICD-9 526.89) C. Hyperplasia (ICD-10 M27.8; ICD-9 526.89) |
| Masticatory muscle disorders 1. Muscle pain limited to the orofacial region |
| A. Myalgia (ICD-10 M79.1; ICD-9 729.1) |
| i. Local myalgia ii. Myofascial pain with spreading iii. Myofascial pain with referral |
| B. Tendonitis (ICD-10 M67.90; ICD-9 727.9) C. Myositis |
| i. Noninfective (ICD-10 M60.9; ICD-9 729.1) ii. Infective (ICD-10 M60.009; ICD-9 728.0) |
| D. Spasm (ICD-10 M62.838; ICD-9 728.85) |
| 2. Contracture |
| A. Muscle (ICD-10 M62.40; ICD-9 728.85) B. Tendon (ICD-9 727.81) |
| 3. Hypertrophy (ICD-10 M62.9; ICD-9 728.9) |
| 4. Neoplasms |
| A. Jaw |
| i. Malignant (ICD-10 C41.1; ICD-9 170.1) ii. Benign (ICD-10 D16.5; ICD-9 213.1) |
| B. Soft tissues of head, face, and neck |
| i. Malignant (ICD-10 C49.0; ICD-9 171.0) ii. Benign (ICD-10 D21.0; ICD-9 215.0) |
| 5. Movement disorders |
| A. Orofacial dyskinesia |
| i. Abnormal involuntary movements (ICD-10 R25.1 [tremor unspecified]; R25.2 [cramp and spasm]; R25.3 [fasciculations]; ICD-9 781.0) ii. Ataxia, unspecified (ICD-10 R27.0; ICD-9 781.3); muscular incoordination (ICD-10 R27.9; ICD-9 781.3) iii. Subacute, due to drugs; oral tardive dyskinesia (ICD-10 G24.01; ICD-9 333.85) |
| B. Oromandibular dystonia |
| i. Acute, due to drugs (ICD-10 G24.02; ICD-9 333.72) ii. Deformans, familial, idiopathic, and torsion dystonia (ICD-10 G24.1; ICD-9 333.6) |
| 6. Masticatory muscle pain attributed to systemic/central disorders |
| A. Fibromyalgia (ICD-10 M79.7; ICD-9 729.1) B. Centrally mediated myalgia (ICD-10 M79.1; ICD-9 729.1) |
| Headache disorders 1. Headache attributed to TMDs (ICD-10 G44.89; ICD-9 339.89; or ICD-10 R51; ICD-9 784.0) |
| Associated structures 1. Coronoid hyperplasia (ICD-10 M27.8; ICD-9 526.89) |
| Note: This box was adapted from work performed by the International RDC-TMD Consortium sponsored by the International Association for Dental Research and the Special Interest Group on Orofacial Pain of the International Association for the Study of Pain. |
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