Pain syndromes that involve the face are very common in clinical practice. Many facial pain syndromes are also unique, given the complex anatomy and specialized sensory innervation of the head, face, and neck. These syndromes represent a clinical diagnostic challenge and deserve special attention. The common descriptive terms for facial pain complaints are frequently misleading. To avoid confusion, pain clinicians should be familiar with the International Headache Society’s Diagnostic Classification for Head, Face, and Neck Pain Disorders¹ (Table 36-1). Clinicians should be comfortable distinguishing painful conditions that arise from structural pathology, headache syndromes, oral and facial structures, temporomandibular joint disorders, myofascial pain disorders, and primary cranial neuralgias.

Temporomandibular disorders are defined as a subgroup of craniofacial pain problems that involve the temporomandibular joint (TMJ), masticatory muscles, and associated head and neck musculoskeletal structures.² Patients with temporomandibular disorders most frequently present with complaints of pain, limited or asymmetric mandibular motion, and TMJ sounds.^3,4 The pain or discomfort is often localized to the jaw, TMJ, and muscles of mastication. Common associated symptoms include ear pain and stuffiness, tinnitus, dizziness, neck pain, and headache. In some cases, the onset is acute and symptoms are mild and self-limiting. Other patients develop a chronic temporomandibular disorder with persistent pain in association with physical, behavioral, psychological, and psychosocial symptoms similar to those of patients with chronic pain syndromes in other areas of the body^5–7 (e.g., arthritis, low back pain, chronic headache, fibromyalgia, and chronic regional pain syndrome), all requiring a coordinated interdisciplinary diagnostic and treatment approach.

Temporomandibular disorders are classified as one subtype of secondary headache disorder by the International Headache Society (IHS), Classification of Headache Disorders II (2004).¹ The American Academy of Orofacial Pain has expanded upon this IHS classification, as shown in Tables 36-2 and 36-3.²

There are at least three distinct and separate dysfunctions that create or affect the symptoms described by the TMD patient.⁸ These are as follows:

1. 
   

   Muscle disorder (myofascial pain dysfunction, MPD)

   
   

   MPD is related to muscle dysfunction, often leading to muscle spasms, pain, and dysfunction. This type of dysfunction can occur in any skeletal muscle. The triggering area lies in the fascial coverings and attachment zones of the muscles—thus the term myofascial. This syndrome is sometimes incorrectly referred to as myofascial pain dysfunction.

   
   
2. 
   

   Temporomandibular joint articular disorder (TMJD)

   
   

   TMJD is related to specific problems in the temporomandibular joints. These problems may range from joint sounds to locking, pain, and degenerative changes of the joints themselves. Invariably, muscle dysfunction is a secondary effect of true TMJD.

   
   
3. 
   

   Cervical spinal dysfunction (CSD)

   
   

   This syndrome is related to the spinal column, the vertebrae, the ligaments, and the muscles related to them. The majority of symptoms not directly related to the jaw muscles are triggered or affected by the CSD syndrome.

The prevalence among adults in the United States of at least one sign of temporomandibular disorders is reported as 40% to 75%, and those with at least one symptom, as 33%.^7,9,10 TMJ sounds and deviation on opening the jaw occur in approximately 50% of otherwise asymptomatic persons and are considered within the range of normal and do not require treatment.¹⁰ Other signs, such as decreased mouth opening and occlusal changes, occur in fewer than 5% of the general population.¹¹ Temporomandibular disorders are most commonly reported in young to middle-aged adults (age 20–50). The female-to-male ratio of patients seeking care has been reported to be from 3:1 to as high as 9:1.^10,12 Despite the high prevalence of temporomandibular disorders, signs and symptoms, only 5% to 10% of symptomatic people require treatment, given the wide spectrum of symptoms and the fact that the natural history of this disorder suggests that many patients (up to 40%) undergo spontaneous resolution of their symptoms.^7,13

ETIOLOGY

In 1934, Costen, an otolaryngologist, evaluated 13 patients who presented with pain in or near the ear, tinnitus, dizziness, a sensation of ear fullness, and difficulty swallowing.¹⁴ He observed that these patients had many missing teeth, and, as a result, their mandibles were overclosed. The patients seemed to improve when their missing teeth were replaced and the proper vertical dimension of the occlusion was restored. The malocclusion and improper jaw position was perceived to be the cause both of “disturbed function of the temporomandibular joint” and the associated facial pain. Thereafter, the emphasis of treatment was on altering the affected patient’s occlusion.

More recently, advances in the understanding of joint biomechanics, neuromuscular physiology, autoimmune and musculoskeletal disorders, and pain mechanisms have resulted in changing concepts of the etiology of temporomandibular disorders. These disorders are now considered multifactorial in etiology, with biologic, behavioral, environmental, social, emotional, and cognitive factors alone or in combination contributing to the development of signs and symptoms of temporomandibular disorders.^2,15

Various forms of trauma to the TMJ structures (ligaments, articular cartilage, articular disc, bone) can lead to intraarticular biochemical alterations that have been demonstrated to produce oxidative stress and the generation of free radicals. Subsequent inflammatory changes in synovial fluid with the production of a variety of proinflammatory cytokines can then lead to alteration in the functioning of normal tissues and degenerative disease in the TMJ.^16–20

Genetic marker studies involving catecholamine metabolism and adrenergic receptors suggest that certain gene polymorphisms (e.g., in the catechol-O-methyl transferase [COMT] gene) might be associated with changes seen in pain responsiveness and pain processing in patients with chronic temporomandibular disorders.^21–23

Differences in pain modulation have been reported between women and men with temporomandibular disorders; women have been observed to demonstrate decreased thresholds to noxious stimuli and more hyperalgesia. In addition, in women with temporomandibular disorders, some studies suggest that the affective component of pain may be enhanced during the low-estrogen phase of the menstrual cycle.^24–27

Functional brain imaging studies demonstrating changes in cortical circuitry support the concept that temporomandibular disorders are very similar to other chronic pain disorders and may be related to abnormal pain processing in the trigeminal system.^28,29 In particular, muscle pain disorders appear to have little, if any, abnormality of the muscles or peripheral tissues and may represent a central sensitization pain producing process.

Lastly, numerous biobehavioral studies support a connection between chronic temporomandibular disorders and comorbid psychopathology (anxiety and depression disorders; posttraumatic stress disorder; and childhood physical, sexual, and psychological abuse).^29–36

CLINICAL EVALUATION

Although temporomandibular disorders are a common cause of craniofacial pain, it is imperative for the health care provider to obtain a comprehensive history, perform a careful physical examination, and obtain appropriate diagnostic studies to exclude other potentially serious disorders. The differential diagnosis should include odontogenic (caries, periodontal disease) and nonodontogenic causes of facial pain, primary or metastatic jaw tumors, intracranial tumors and skull base tumors, disorders of other facial structures (including the salivary glands), primary and secondary headache syndromes, trigeminal neuropathic pain disorders, and systemic disease (cardiac, viral, autoimmune, diabetes, temporal arteritis).

The most common complaint of patients with temporomandibular disorders is unilateral facial pain. The pain may radiate into the ear, to the temporal and periorbital regions, to the angle of the mandible, and, frequently, to the posterior neck. The pain is usually reported as a dull, constant ache that is worse at certain times during the day. There can be bouts of more severe, sharp pain typically triggered by movements of the mandible. The pain may be present daily or intermittently, but many patients have pain-free intervals. Mandibular motion is usually limited, and attempts at active motion (chewing, talking, yawning) increase the pain. Patients frequently describe “locking” of the jaw, either in the closed-mouth position with inability to open (most common) or in the open-mouth position with inability to close the jaw. These complaints are often worse in the morning, particularly in patients who clench or grind their teeth during sleep. Clenching, grinding of the teeth, and other nonfunctional, involuntary mandibular compensatory movements (so-called oral parafunctional habits) are common.

Along with limitation of motion, there is often deviation to the affected side of the mandible on opening and a “clicking” or “popping” noise in the joint. While some of the preceding differential diagnoses can present with facial pain, temporomandibular disorders often have a stereotypical presentation (as described earlier), which helps in the diagnostic process. It is well appreciated that pain of cardiac origin (ischemia or myocardial infarction) may present with neck, jaw, and face pain, but cardiac pain is generally acute in nature with very different associated signs and symptoms.³⁷

Other commonly associated symptoms of TMD are discussed in the following sections.

Headache

Symptoms of bilateral head and face pain involve multiple postural muscles and/or the muscles of mastication. The pain is typically moderate in intensity, dull and aching in quality, and usually described as deep and constant.^38–42 Pain exacerbations are often provoked by functional use of the affected muscles. Morning headaches may be related to nocturnal bruxism and or sleep disorders,⁴³ while increasing pain during the day may be related to masticatory muscle use or head posture.⁴⁴

1. 
   

   Front of Head

   
   

   Patients complaining of pain in the front of the head often refer to it as “sinus headache.” There is usually accompanying pressure along the upper anterior teeth, bridge of the nose, and pressure behind the eyes. Chronic front-of-the-head pain and facial pain are generally not due to chronic sinus disease but are a primary headache disorder. This can also be due to a reduction in posterior occlusal dimension causing heavy incisal contact, resulting in pain of pressure in the anterior vortex of the face. A bandlike feeling of the front of the head can also be brought about by posterior neck muscle contractions or muscle tension of the frontalis muscle.

   
   
2. 
   

   Side of Head

   
   

   Temporal headaches are mainly related to muscle contraction and fiber spasm of the temporalis muscle. The temporalis muscle has three groups of muscle fibers: anterior, middle, and posterior. The anterior fibers function to bring the lower jaw up and forward, while the middle and posterior fibers swing the jaw to full closure and retract the mandible.

   
   

   Clenching, grinding, or biting on objects while the jaw is in an anterior displaced position (edge-to-edge) generally creates pain in the anterior temporal group—that is, the patient has pain in the “temple” area. Individuals who work at desk jobs where the head is forward and down tend to clench and grind in this forward position due to gravity affecting the mandible. This would be further aggravated by habits such as pencil or pen biting, pipe smoking, or gum chewing.

   
   

   Clenching or grinding during sleep or clenching in a posterior position tends to tire the middle and posterior group of fibers, and the pain is more posteriorly located. Generally, the temporalis is affected in any dysfunction of the lower jaw.

   
   
3. 
   

   Back of Head

   
   

   Deep dull pain, constant and aggravating in the back of the head, is usually a result of fiber spasms within the trapezius and sternocleidomastoid muscles. These muscles have strong large bodies that, when under tension, pull on their bony attachments to the sill—the occiput and mastoid areas. This leads to soreness in the bone and deep, dull pain radiating up the back of the head and down the neck. The muscle tension may be independent of, or secondarily related to, vertebral displacement in the cervical and upper thoracic region.

Face Pain

Pain in the sides of the face, or pain described by the patient as “sinus” pain in the zygomatic or orbital area, may also have a musculoskeletal origin.⁸ Clenching; acute or chronic stress; reduction of dental vertical dimension (height) related to loss of posterior teeth, combined with daytime tooth clenching; and acute or chronic stress can create muscle trigger points or muscle fatigue. This is particularly noticed by the patient after meals and is reported as “a heavy and tired feeling” in the jaw muscles. Face pain related to sinuses and other pathologies are discussed separately in this chapter.

Eye Pain

Orbital pain symptoms are often described as unilateral and constant and “boring.” This is frequently seen in patients with TMD complaints, which include pain symptoms involving the eye and periorbital region.^8,45–47 Patients with a history of trauma or chronic upper cervical vertebral subluxations or nerve root impingements related to the occiput and the atlantoaxial region may present with orbital symptoms. In addition, entrapment of the greater occipital nerve at the occiput level can also produce this type of pain, which is often diagnosed as occipital neuralgia. This is frequently amenable to physical medicine, along with changes in head posture and mandibular position through the use of dental bite appliances.

Ear Symptoms

Pain, stuffiness, and tinnitus may have a musculoskeletal etiology.^48,49 Mandibular posture related to the maxilla affects the masticatory elevator muscles. The medial pterygoid muscles help stabilize the left-to-right balance of the mandible on tooth closure. Innervation from the nerve to the medial pterygoid also supplies the middle ear muscles. The tensor tympani and tensor palati are actually one muscle with a raphe that wraps around the hamulus notch of the maxilla. Growth and development problems related to the proper expansion of the maxilla can affect Eustachian tube function and have been known to precipitate middle ear infections in children as well as ear stuffiness with changes in pressure in the ear in adults. Maxillary and mandibular dysfunctions aid in the development and maintenance of such symptoms.

Tinnitus and other types of ear sounds may also have a peripheral musculoskeletal etiology. Specifically, cervical factors and mandibular postural factors have been seen in subjects with tinnitus. A combination of physical medicine and dental jaw appliance therapy has been effective in some cases where there has been a history of trauma or childhood growth and development affecting the proper expansion of the maxilla.

Ear pain that is sharp and jabbing upon movement of the mandible is frequently seen in patients who have an internal derangement of the temporomandibular joint. Usually, it presents unilaterally and ipsilateral to the joint in question.

Ear pain and symptoms such as stuffiness in the absence of positive otologic findings are among the most common reasons to evaluate the patient for dental and maxillo mandibular imbalance. Treatment can often alleviate the symptoms completely or reduce the impact on the patient in conjunction with standard medical intervention.^50–54

Neck Pain

Neck stiffness and pain are commonly part of the TMD complex.^55–57 Trauma, habitual posturing, and musculoskeletal tension will chronically affect the cervical area, creating pain, stiffness, and trigger point flare-up in the muscles of the head and neck. It is well documented that the trigeminal and cervical nerve systems are interactive in the maintenance of head neck and jaw posture.⁵⁸ The act of mastication and jaw function relies on all the anterior and posterior cervical muscles to interact with the jaw closing and opening muscles. In addition, mandibular and head posture interacts to maintain the airway space during function and in sleep.

Studies on the relationship between the maxillo-mandibular position and the cervical spine have shown that loss of vertical dimension of the teeth and a deep bite can adversely affect cervical muscle function, leading to chronic stiffness, pain, and reduction of range of motion.⁵⁹ It is, therefore, important to assess the dental factors in patients with chronic neck pain.

Arm and Back Symptoms

Patients presenting with TMD may also commonly present with shoulder pain or pain radiating down the arm that may or may not be accompanied by tingling and/or numbness. Physical medicine assessments frequently are positive for thoracic outlet syndrome, costoclavicular syndrome, vertebral subluxations or nerve impingement of the brachial plexus of nerves, and even rotator cuff injuries previously undiagnosed.⁶⁰

Physical examination should include observation and measurement of mandibular motion (maximal interincisal opening, lateral movements, and protrusion), palpation of the muscles of mastication (masseter, temporalis, medial and lateral pterygoids) and the cervical musculature, and palpation and/or auscultation of the TMJ, as well as examination of the oral cavity, dentition, occlusion and salivary glands, and inspection and palpation of the anterior and posterior neck. Auscultation of the carotids and examination of the cranial nerves, with special attention to the trigeminal system, should also be part of the physical examination.

As already noted, noise in the TMJ on mandibular movement is frequently present in patients with temporomandibular disorders. However, noise alone is also a very common finding in completely asymptomatic people and may represent a range of normal rather than intraarticular pathology. Muscle tenderness, producing pain or discomfort, is generally found on both extraoral and intraoral palpation of the masticatory muscles. Tenderness may also be present in the anterior neck muscles (suprahyoid muscles and sternocleidomastoid muscles), posterior cervical paraspinal muscles (semispinalis capitus, splenius capitus, and suboccipital muscles), and upper shoulder muscles (trapezius and levator scapulae). There may be mandibular hypomobility and deviation on opening. Finally, the neurological examination is typically normal, without any objective neurosensory or motor deficits of the trigeminal nerve or other focal cranial nerve abnormalities.