Orofacial Pain: How to Evaluate and Treat, Part 1

Most pain in or around the oral cavity is attributable to tooth or mucosal pathology. However, tooth or muco-sal pain may also be caused by a variety of other conditions, including brain pathology; vascular inflammatory and cardiac disease; jaw infection or neoplasm; neuropathic abnormality not associated with central pathology; pathology in the neck and thoracic region; myofascial and temporomandibular joint pathology; and disease of the ear, eye, or nose, or of the paranasal sinuses, lymph nodes, and salivary glands. Accurate diagnosis is facilitated when the features of pain presentation in this region are understood.

Classification of and criteria for nondental conditions that can cause tooth pain appear in a number of sources.^1-4 Clinical factors, including the patient's description of pain; its intensity, quality, and location; what relieves or exacerbates it; and the presence (or absence) of additional symptoms (eg, dysesthesia) may help establish the diagnosis when oral examination findings are negative.Additional imaging studies may be necessary to rule out problems such as salivary or central disease.

In my 2-part series, I review some of the more significant nondental conditions that cause tooth and mucosal pain; I also address treatment options. Here the focus is on temporal arteritis (TA), trigeminal neuralgia, burning mouth syndrome, postherpetic neuralgia (PHN), vascular conditions, masticatory myofascial conditions, and salivary gland pathology. In an upcoming issue, I will discuss oral cancer, maxillary sinus disease, and nonmalignant disorders of the oral mucosa.

TEMPORAL ARTERITIS

The approximate annual incidence of TA varies by region but was reported in one study to be 4.1 cases per 100,000 persons.⁵ The typical patient is older than 50 years and looks and feels quite ill at presentation.

Dental pain associated with TA is usually localized to the maxillary posterior teeth (the first or second molar) or the maxilla, including the palate. Pain may also be perceived in or radiate to the frontal-temple region. The intensity of pain is described as moderate to severe and the quality as throbbing or aching/throbbing. It may be bilateral or unilateral. Pain may develop slowly or suddenly but, once established, it is unremitting.⁶

Chewing may worsen tooth pain as well as general pain--hence the presumption of a dental cause. However, in contrast to pain of pulpal (ie, dental) origin, the pain of TA is often associated with exquisite tenderness (hypersensitivity) of the scalp and face. Patients often report that hair combing or very light touching of the frontal-temple area is painful. Patients may also present with a number of more generalized symptoms, such as malaise or low-grade fever, that are not typically associated with dental pain (unless there is frank infection and cellulitis). There may also be ocular symptoms.

Additional factors that help establish the diagnosis include a significantly elevated erythrocyte sedimentation rate and hardness of the temporal artery on palpation. Temporal artery biopsy confirms the diagnosis. Early diagnosis is crucial because vision loss may result from delayed treatment.⁷ Treatment consists of high-dose corticosteroids (40 to 60 mg/d) with rapid taper over 7 to 10 days. In some cases, long-term therapy is required.

TRIGEMINAL NEURALGIA (TIC DOULOUREUX)

The pain of trigeminal neuralgia is typically felt in the anterior maxillary or mandibular anterior teeth (within the second and third division of the fifth cranial nerve) or, if the patient is edentulous, in the attached mucosa overlying the alveolar bone or a healed extraction site.⁸ Less frequently, it is perceived in the posterior teeth.

This pain, which is described as electrical, shocklike, or stabbing, is triggered by light touch and typically radiates along the mandible toward or into the ear on the ipsilateral side of the trigger or, if perceived in the maxillary region, superiorly into the eye or the maxillary sinus. The pain may be severe or excruciating. Unlike the pain of TA, however, the pain of trigeminal neuralgia is episodic, with paroxysms that last for seconds to minutes. A more generalized low-grade pain sometimes follows the severe attack. The severe paroxysmal pain is followed by a variable pain-free interval. Although pain may sometimes remit for months or years, recurring pain may be incapacitating.

Often, patients think that trigeminal neuralgia represents a dental problem because touching a tooth or adjacent mucosa in the trigger zone will initiate the paroxysm. Paroxysms can also be triggered by chewing or drinking, presumably because of the manipulation of the trigger point during these activities. However, in contrast to a patient with tooth pathology, a patient with trigeminal neuralgia often (but not always) reports an additional trigger on the external face (nose, lip, or cheek), so that touch or manipulation of an extraoral area during showering, smiling, shaving, or applying makeup also triggers pain.

Unlike patients with TA, those with trigeminal neuralgia do not have malaise or fever. Laboratory results are normal. A trial of an anticonvulsant medication such as carbamazepine or gabapentin may be useful in establishing the diagnosis.⁹In a patient whose pain does not respond to medication, or who reports additional sensory abnormality, such as facial numbness or tingling, additional evaluation should include gadolinium- enhanced MRI to rule out central tumor. In a person with neuralgia who is younger than 45 years, consider multiple sclerosis and brain tumor in the differential diagnosis.¹⁰

BURNING MOUTH SYNDROME

This condition preferentially affects postmenopausal women older than 50 years.¹¹ Pain may involve the palate, tongue, lips, attached mucosa, oropharynx, or a combination of these. Pain is not typically perceived in the teeth, but severity is comparable to that of mild to moderate toothache. Involvement is usually bilateral, and there may be associated dysgeusia (alteration in taste).

The differential includes such conditions as tongue muscle hyperactivity; oral candidiasis; salivary hypofunction; Sjögren syndrome; denture-related causes; hematinic deficiency states (iron, vitamin B, and folate deficiencies); allergic reactions or reactions to chemical irritants; medication side effects; peripheral neuropathy; and a variety of intraoral diseases, such as migratory glossitis or lichen planus.¹² Less likely, but still possible, is undiagnosed or poorly controlled diabetes, a psychological disorder, malignancy, or central pathology. If the burning is unilateral and is associated with dysesthesia (eg, numbness or tingling) in the absence of trauma, consider a neoplasm such as adenocystic carcinoma of the posterior tongue or the vestibule, PHN (see below), or ventral pontine infarction.¹³

Once these conditions have been ruled out, moderate relief of symptoms can be obtained with clonazepam, 0.25 to 2 mg/d. The combination of gabapentin and clonazepam is also effective.¹⁴ Some patients respond to topical anesthetics, such as lidocaine (2%) or dyclonine hydrochloride (1%). I have found that having patients rinse with doxepin elixir every 4 to 6 hours and swallow the last dose at bedtime sometimes relieves pain. About one half to two thirds of patients will experience spontaneous pain remission within 6 to 7 years, with or without treatment. Psychological intervention may also be helpful.¹⁵

POSTHERPETIC NEURALGIA

In elderly patients who have PHN involving the face, the condition is typically localized to the first division of the fifth cranial nerve. Some patients experience significant pain in the region of initial involvement several months after the original infection has subsided. Patients describe this chronic pain as moderate to severe and burning.¹⁶ There may be dysesthesia, such as facial itching, or other unusual sensations involv-ing the intraoral mucosa (eg, the sensation that something is stuck between the teeth). Pain is often exacerbated by mechanical contact. Intraoral pain, when present, is also constant and is perceived as arising in the mucosa or teeth; it may be aggravated by chewing.

Figure 1

Figure 2

Unlike the pain of burning mouth syndrome, the pain of PHN is unilateral and restricted to the appropriate dermatome. The history is likely to include a previous vesicular outbreak on the ipsilateral side (Figure 1). However, if the primary lesions occur in the mouth with minimal facial involvement (a rarer variation that affects the second and third division of the fifth cranial nerve), the patient may not be aware of the connection between the postzoster pain and the original episode. Hence, it is important to ask whether the current pain was preceded by an eruption of multiple painful intraoral vesicles that lasted 14 to 21 days.

Another herpetic condition that causes oral (including tooth) pain and dysesthesia is recurrent intraoral herpes.¹⁷ The clinical presentation of primary herpes stomatitis and the secondary recurrent lip lesion that typically follows the initial infection are familiar. However, the characteristic extraoral lesion may occur in the mouth as well (Figure 2). With intraoral expression of the disease, pain is also described as burning, but it occurs within a well-localized region of attached gingival tissue around a tooth or teeth, or on the palate. Generalized facial pain located ipsilateral to the lesions is often preceded by a sensory prodrome that may include mild to moderate tooth pain that typically persists only during the phase of vesicular eruption (7 to 10 days).

Therapeutic options for PHN include systemic antiviral medication (acyclovir or famciclovir) and tricyclic antidepressants (amitriptyline or nortriptyline, 10 to 50 mg/d).¹⁸ Topical capsaicin (applied as a cream, 0.025% or 0.075% tid) may also be effective. The combination of tricyclic antidepressants and antiviral medication, when used during the initial zoster episode, may reduce the risk of PHN.¹⁹

VASCULAR CONDITIONS

This group of conditions can cause pain that is perceived in the maxillary teeth, lateral nose, or palate.

Paroxysmal hemicrania. Diagnostic criteria from the International Headache Society include at least 20 attacks of severe pain, each lasting 2 to 20 minutes, followed by pain-free intervals.¹ Attacks occur with ipsilateral autonomic features, such as conjunctival injection and lacrimation, nasal congestion, and slight ptosis or miosis. Pain is described as throbbing.²⁰ For unknown reasons, indomethacin completely eliminates pain.

Hemicrania continua, an unremitting mild to moderate ache/ throb, can also occur in the midface region and include the maxillary bicuspid teeth. It is usually unilateral but, unlike the pain of paroxysmal hemicrania, it does not remit. It is appreciably relieved, but generally not eliminated, by indomethacin.

Cluster headache, which primarily affects men, occurs in the periorbital or temple region but may also be perceived initially in the maxillary posterior teeth or palate. The pain is quite severe and usually unilateral, although some bilaterality has been reported. Pain typically occurs in seasonal/circannual or circadian patterns with extended periods of remission. Autonomic involvement may include facial sweating and nasal congestion; ocular symptoms such as tearing, lid edema, ptosis, conjunctival injection, and miosis; and general restlessness.²¹ Pain usually awakens the patient.

Patients may benefit from 100% oxygen delivered via a nonrebreathing mask at 10 L/min for 15 minutes. Subcutaneous sumatriptan, 3 to 6 mg, or intravenous, subcutaneous, or intramuscular dihydroergotamine, 0.5 to 1 mg, may also be effective.²²

MASTICATORY MYOFASCIAL CONDITIONS

Trigger points within the muscles of mastication, particularly trigger points located in the lateral pterygoid, masseter, and temporalis muscles, may refer pain to the maxillary and mandibular teeth.²³ Pain is usually described as a mild to moderate dull ache that is exacerbated by jaw movement. It may be worse in the morning in patients with nocturnal bruxism. Palpation of the tender area of the offending muscle should reproduce the tooth pain.

Pain is often ameliorated by application of cold or heat to the face and head. Pharmacologic options include time-dependent use of muscle relaxants (cyclobenzaprine, 10 to 20 mg, tid or hs; diazepam, 5 mg bid or hs; or methocarbamol, 500 to 750 mg qid) or NSAIDs. Patients with chronic myofascial pain may use low-dose tertiary tricyclic antidepressants, such as amitriptyline or nortriptyline.²⁴

Myofascial conditions that cause facial pain are generally thought to be self-limited²⁵; recrudescence is tied to parafunctional jaw activity, sleep disturbance, and stress. Chronic muscle pain develops in only about 10% of patients. Hence, facial pain associated with the jaw musculature is usually managed effectively with a variety of self-care treatment options, including jaw relaxation, habit modification, jaw exercises (including stretching), jaw activity limitation, and intraoral appliance therapy. Only rarely do patients with myofascial conditions require dental treatment such as tooth equilibration, reconstruction, or orthodontics. If patients do not respond to conservative management within 4 to 6 weeks, consider further medical and behavioral assessment to rule out more serious disease or psychosocial confounders.²⁴

SALIVARY GLAND PATHOLOGY

Diseases of the major salivary glands (parotid, submandibular, and sublingual) may cause generalized facial pain in the area of the gland, although referral to the lower jaw and neck is not uncommon. In these cases, perceived pain is thought to arise from ductal obstruction that produces saliva retention and compression of adjacent tissues. In acute cases, the offending agent is likely to be a mucous plug or stone. In these settings, pain and swelling of the gland occur when the patient begins to eat or drink. Facial swelling accompanied by pain may also be confused with tooth infection. Infrequency of symptoms suggests chronic glandular inflammation or infection (which causes recurrent stone or mucous plug formation). If pain and swelling persist, however, the differential should also include neoplasm.²⁶ Pain is a significant finding in parotid gland tumors.²⁷

Sialography is useful in ruling out chronic inflammation of the parotid gland; MRI can help identify a possible tumor. Other conditions that may cause salivary gland abnormalities and dry mouth include Sjögren syndrome, scleroderma, systemic lupus erythematosus, hypothyroidism, and infection (eg, with HIV or hepatitis C virus). The latter conditions,however, do not typically cause orofacial pain.

CHRONIC PAIN

Regardless of the cause, chronic pain increases the complexity of the patient's condition. For patients with orofacial pain that persists for more than 6 months, as with other types of chronic pain, the sensory experience may be confounded by such factors as altered pain processing (which can produce central sensitization and expansion of the receptive field); psychological factors such as depression and anxiety; and psychosocial or behavioral problems, including disability, excessive treatment seeking, and medication abuse. The longer the pain persists, the greater the potential for emergence of comorbid physiologic and psychosocial abnormality.

Concomitant acute or chronic stress, as well as anxiety, may affect the pain experience through a variety of mechanisms, including activation of the hypothalamic-pituitary-adrenal axis, up-regulation of the sympathetic nervous system, disruption of sleep and, in the case of masticatory muscle abnormality, an increase in bruxism. Interaction among these factors can complicate the diagnostic picture. Thus, a complete evaluation of persistent orofacial pain, including chronic "dental" pain of unknown origin, should also include biobehavioral assessment. This is particularly important for patients who need long-term pharmacologic therapy (especially with narcotics) and for those who exhibit signs of depression or another psychological disorder.

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