Are You Confident of the Diagnosis?

The International Association for the Study of Pain defines glossodynia as burning pain in the tongue or other oral mucous membrane, lasting at least 4 to 6 months, associated with normal signs and laboratory findings.

The International Headache Society defines glossodynia as an intraoral burning sensation for which no medical or dental cause can be found.

There is controversy as to whether glossodynia is a syndrome or a disorder. A syndrome is defined as a disease unto itself and a disorder is defined as a condition manifesting symptoms of other diseases such that the symptom is the cause of the disease. It appears that the term “syndrome” is justifiable, as there are several other subjective symptoms, such as dry mouth, oral paresthesia, and taste alteration, or other associated symptoms such as headache and sleep disturbances, that often accompany glossodynia.

Glossodynia may be pragmatically categorized into two categories: primary (essential/idiopathic) glossodynia, where there is a lack of evidence for any other diseases, and secondary glossodynia, where symptoms have been identified through clinical abnormalities, or systemic and/or psychologic conditions

Characteristic findings on physical examination

Individuals experiencing glossodynia describe it as an annoying sensation that may be burning, tender, tingling, hot, scalding, numb, dry, sandy, or rough. The oral burning pain is most often continuous, providing a chronic discomfort. In certain individuals, there may be spontaneously induced acute periods; however, to date, there is no clearly identifiable precipitating factor. The etiology of oral burning pain in primary glossodynia is unknown but may be related to an upper respiratory tract infection, previous/recent dental procedure, medication use/change in medication, or traumatic life stressors.

The oral burning pain is usually bilateral and symmetrical, involving the anterior two-thirds of the tongue, dorsum and lateral borders of the tongue, the anterior part of the hard palate, the labial mucosa, and gingiva. However, it may appear at multiple locations, with location having no effect on the course of the disease or the response to interventions. If a unilateral location, then this may be due to an injury or tumor, warranting further investigation.

The oral burning pain increases progressively throughout the day, with maximum intensity at the end of the afternoon or early evening, and usually not presenting during sleep, although patients report difficulty in getting to sleep. Common associations with glossodynia are mood changes, including irritability, anxiety, and depression. Glossodynia often coexists with other symptoms such as xerostomia (subjective dry mouth), dysgeusia, metallic taste, bitter taste, or combinations thereof, and/or changes in the intensity of taste perception.

Symptoms occur continuously for months or years without periods of cessation or remission, with the intensity of oral burning pain being moderate to severe. Patients describe it as comparable to the intensity of toothache pain in regard to severity, not quality. Intensity of oral burning pain often increases in the presence of personal stressors such as fatigue, or during the consumption of hot or spicy foods. Approximately 50% of individuals who use distraction techniques, or take food or liquid, have a reduction in, or alleviation of, the symptoms.

There do not appear to be any objective findings of decreased salivary flow rates, yet there are findings of qualitative changes to saliva composition. Nonspecific health complaints and more severe menopausal symptoms are seen more frequently than in healthy controls. Headaches, dizziness, neck and back pain, dermatologic disorders, irritable bowel syndrome, anxiety, depression, personality disorders, and other psychiatric disorders are more frequent.

It is still questionable as to whether comorbidities are risk factors for the development of glossodynia or a consequence of the chronic pain.

Diagnosis confirmation

Primary glossodynia is a diagnosis of exclusion, and so it is essential to rule out local, systemic, and psychological factors.

Who is at Risk for Developing this Disease?

The prevalence of glossodynia is difficult to establish due to variation in study methodology (questionnaire, survey or clinical assessment) and geographic location. However, the prevalence of glossodynia is between 0.7% to 5% in the general population. It is most commonly reported in perimenopausal middle-aged to elderly females, with a female-to-male ratio of 3:1. It rarely manifests before 30 years of age and has not been studied in children or adolescents. To date, there are no studies on occupational, educational, or social grouping.

What is the Cause of the Disease?

  • Etiology

  • Pathophysiology

Causes include the following:

  • Poorly fitting prostheses, leading to microtrauma or local erythema. Poor denture design may restrict the normal action of tongue muscles; however, denture replacement rarely leads to resolution of symptoms.

  • Parafunctional habits such as tooth clenching, bruxing, tongue posturing, continual rubbing of the tongue over the teeth or prosthesis, lip sucking or licking, or mouth breathing

  • Local allergic reactions (allergic contact stomatitis) due to high levels of uncured or residual monomer in dentures

  • Allergens such as nylon, ascorbic acid, nicotinic acid esters, benzoic peroxide, 4-toyl diethanolamine, N-dimethyl toluidine, nickel, sulfate, and certain foods, preservatives, additives, and flavorings. However, when epicutaneous tests are performed by eliminating contact with allergen, there may be a decrease in burning in some individuals. There is the possibility, though, that the positive results are due to a subclinical case of contact dermatitis.

  • Galvanic reactions caused by intraoral use of dissimilar metals

  • Oral infections with the main pathogen being a fungal organism (Candida albicans). Other bacteria implicated are Enterobacter, Klebsiella, Staphylococcus aureus, and Helicobacter pylori.

  • Oral mucosal diseases such as lichen planus, benign migratory glossitis (geographic tongue), and scalloped or fissured tongue

  • Alterations in salivary composition may be present; however, this may be a result of the underlying condition rather than a causative factor.

  • Anxiety, depression, somatization, and certain aberrant personality traits or disorders are implicated. At least one-third of glossodynia individuals have an underlying psychiatric diagnosis. This indicates that these comorbid psychological factors may require treatment, but it does not prove causality, as association does not equate to a causal relationship. Furthermore, chronic pain conditions and psychological issues are very common, and psychological issues may be the result of the constant pain and its effect on the quality of life rather than its cause.

  • Cancerphobia is often a concern, and manifests with repeated self-examinations (hypochondriasis) and multiple office visits.

  • Xerostomia (subjective sensation of dry mouth) is commonly reported and may be related to medication-induced xerostomia.

  • Direct irritant effect on oral mucosa due to physical, chemical, or biological (bacterial, fungal, or viral) mechanisms

NEURAL ALTERATIONS

Glossodynia may be a neuropathic disorder caused by neuropathological mechanisms involving the peripheral and/or the central nervous system (CNS). The mechanisms involved may be peripheral receptor dysfunction or a central dysfunction, or a dysfunction in the transmission of sensory impulses from the trigeminal system. To date, a definitive anatomic location for changes is unknown.

The following is evidence to support alterations in the nervous system:

  • Reduction in thermal sensation and low scores for tonic painful stimuli intraorally, which is similar to other neuropathies

  • Reduction in heat and pain tolerance at the tip of the tongue

  • Anomalies in the blink reflex response (altered sensory threshold or reaction) to applied stimulation and quantitative sensory testing, suggesting a trigeminal neuropathy

  • Alterations in salivary composition

  • A lower density of epithelial and subpapillary nerve fibers in tongue biopsies, suggesting axonal degeneration, implicating a sensorial neuropathy of the small trigeminal fibers

  • Cerebral activity similar to that occurring in other neuropathic conditions

  • Alterations to normal functioning of the dopaminergic system

TASTE AND SENSORY SYSTEM INTERACTIONS

Taste anomalies have been reported in glossodynia. There appears to be a relationship between glossodynia and “supertasters.” These are people, mainly females, who have the ability to perceive low levels of bitter taste 6-n-propylthiouracil [PROP]); this involves an interaction between taste and nociceptive mechanisms in the CNS. The proposed mechanism involves pathology of both the central and peripheral nervous systems, leading to an alteration in the taste system at the level of the chorda tympani and/or glossopharyngeal nerves. This results in a loss of central inhibition and hyperactivity of the trigeminal nociceptive pathway, which leads to an intensification of responses to oral irritants, and the potential for phantom oral pains (oral burning sensations, dysgeusia, or subjective oral dryness).

This hypothesis, however, lacks definitive data from large populations and is unable to account for all of the various manifestations of glossodynia, or for the fact that many supertasters experience glossodynia.

STEROID DYSREGULATION

Females undergoing menopause who are also experiencing either chronic anxiety or posttraumatic stress may be at greater risk for glossodynia. Chronic anxiety or posttraumatic stress can result in a dysregulation of the adrenal production of steroids, leading to a decreased or modified production of precursors for neuroactive steroid synthesis in the nervous system. Furthermore, menopausal females, due to alteration in ovarian steroid production, could experience neurodegenerative alteration in small nerve fibers, both peripherally and centrally. The combination of these two events may lead to glossodynia.

Clinical aspects of glossodynia

To deliver a definitive diagnosis for glossodynia, it is imperative to take perform a thorough and comprehensive history taking and to perform a clinical examination to differentiate primary from secondary glossodynia, as follows:

HISTORY TAKING

1. Past and current symptoms (seeking information regarding duration, intensity, character, location, onset, and factors that improve or worsen the oral burning pain and its course)

2. Numeric rating scale or visual analog scale regarding pain intensity and dry mouth

3. Current and past health status regarding systemic disorders, allergies, immunologic disorders, and current and past medication

4. Current or previous information regarding psychological or psychiatric issues

CLINICAL EXAMINATION

1. Assessment of extraoral and intraoral regions

2. Palpation of the temporomandibular joints, masticatory muscle, and lymph nodes

3. Assessment of oral mucosa, tongue, lips, hard and soft tissues, and prosthetic devices

ADJUNCTIVE DIAGNOSTIC TESTS

1. Hematologic tests: Complete blood cell count/differential, fasting blood glucose, thyroid levels, nutritional factors, and autoimmune panel

2. Oral cultures, if infections are suspected (bacterial, fungal, viral)

3. Imaging such as magnetic resonance imaging (MRI), computed tomography (CT) scans, and nuclear imaging to rule out systemic considerations and other pathologies

4. Salivary uptake scans, if salivary flow rates are reduced or there is suspicion of connective tissue disorders

5. Measurement of salivary flow rates (by weight) for whole unstimulated saliva (normal=0.3-0.4gm/min) and whole stimulated (using unflavored paraffin wax) saliva (normal=0.75-2.0gm/min)

6. Allergy testing for dental panel and allergens

7. Discontinuation of certain medications thought to be implicated in glossodynia

8. Gastric reflux studies

9. Psychometric tests such as the SCL-90R, Multidimensional Pain Inventory, Hospital Anxiety and Depression Scale, and Beck Depression Inventory

Systemic Implications and Complications

Depression, anxiety and somatisation appear to have an association with glossodynia. Furthermore, many personality characteristics and personality disorders within the domains of neuroticism, extraversion, openness, phobias, socialization skills, and conscientiousness have been reported in patients with glossodynia when compared with the general population. This may lead the clinician to believe these individuals require purely psychiatric and/or psychologic counseling; however, these same studies could not determine whether the development of glossodynia precedes or follows the development of these psychological/psychiatric conditions.

Elevated levels of psychological disturbances are not unusual or unique to patients with glossodynia. It has been reported that glossodynia patients are more frequently concerned about bodily functions, emotionally repressed, angry, distrustful, and socially isolated; however, these traits were also displayed by other chronic pain patients and tended to increase with increased pain. Apparently, personality characteristics among patients with chronic pain, be it glossodynia or other pain conditions, share many similarities. Furthermore, many medications used in the treatment of these psychological conditions (be it a misdiagnosis for glossodynia or an accurate diagnosis) can cause side effects such as dry mouth and taste alterations that may induce or exacerbate the oral burning.

Treatment Options

There has been minimal research evidence to provide clear and concise recommendations for management of primary glossodynia. Therefore, a trial and error strategy is utilized with the goal of individual adaptation. Currently, there are three approaches, which may be employed individually or in combination.

BEHAVIORAL INTERVENTIONS

(These have variable success rates, but may be included as a component of a multidisciplinary approach to management.)

1. Cognitive behavioral therapy—three randomly controlled trials (RCTs) indicate decrease in symptoms

2. Psychotherapy—one RCT indicates decrease in symptoms

3. Electroconvulsive therapy—one case report showed decrease in symptoms

TOPICAL THERAPY

1. Clonazepam 1mg—one RCT indicates decrease in symptoms, 1mg tablet TID, let tablet dissolve and hold fluid in mouth in area of most intense burning for 3 minutes, then expectorate.

2. Lidocaine viscous gel 2%—no published evidence for glossodynia. Rinse 5ml QID for 2 minutes and expectorate.

3. Capsaicin .025% cream—no published evidence for glossodynia. Apply to burning area TID or QID.

4. Doxepin 5% cream—no published evidence for glossodynia. Apply to burning area TID or QID.

SYSTEMIC THERAPY

1. Clonazepam 0.25 to 2mg/day—one open trial indicates decrease in symptoms. At bedtime, use 0.25mg and increase dose by 0.25mg every 4-7 days until burning is relieved or side effects occur. As dose increases, medication is taken in three divided doses.

2. Pregabalin 50mg—one case report indicates decrease in symptoms. Use 50mg for duration of burning.

3. Milnacipran 15 to 100mg/day—two open trials indicate decrease in symptoms. Use 15mg/day and increase to 100mg/day, if needed.

4. Gabapentin 300 to 2400mg/day—one case report indicates decrease in symptoms, one RCT indicated no effect. At bedtime, use 100mg and increase dose by 100mg every 4 to 7 days until burning is relieved or side effects occur. As dose increases, medication is taken in three divided doses.

5. Topiramate 50mg BID—one case report indicates decrease in symptoms. Start at 50mg BID, if burning is not relieved in 4 weeks then increase to 100mg BID, and then 2 weeks later increase to 150mg BID.

6. Tricyclic antidepressants (nortiptyline or amitriptyline) 10 to 75mg/day—no published evidence for glossodynia but commonly used for neuropathic pain. At bedtime, 10mg, increase dose by 10mg every 4 to 7 days until burning is relieved or side effects occur.

7. Alpha lipoic acid 200mg TID—several RCTs indicate decrease in symptoms, several RCTs indicate no effect. Use 200mg TID for 2 months. Also prescribe gastroprotection.

8. Serotonin-specific reuptake inhibitors (SSRIs)—Sertraline 50mg/day with maximum dose of 200mg/day or paroxetine 20mg/day with maximum dose of 50mg/day—two RCTs and one open trial indicate decrease in symptoms.

9. Duloxetine 30 to 60mg/day—one open trial indicates decrease in symptoms.

Optimal Therapeutic Approach for this Disease

When an individual presents with oral burning symptoms, a history, clinical examination, lab evaluations, and imaging, when deemed necessary, are required. If there are positive findings, then this is considered secondary glossodynia, whereby the symptoms of the underlying condition are managed accordingly. If there are negative findings, then this is considered primary glossodynia.

A trial of topical therapies (in order as listed) should ensue. If this is only partially successful in symptom alleviation, then a trial of systemic therapies (in order as listed) and/or behavioral interventions should be instituted.

RATIONALE FOR TOPICAL THERAPY

Topical therapies have minimal side effects (other than an unpleasant taste) or adverse events and have minimal interactions with other medications. If used concomitantly with systemic medications, there may be a reduction in dose of systemic medication with the potential for decreased side effects and adverse events due to systemic medication use.

RATIONALE FOR SYSTEMIC THERAPY

Systemic therapies used in glossodynia are similar to approaches used to manage other chronic neuropathic pain conditions. Unfortunately, there is an increased risk of side effects and adverse events, which may limit use. Also, there is an increased risk of interactions with other medications, again, potentially limiting their use. Furthermore, side effects from these medications can exacerbate symptoms such as an increase in oral dryness, somnolence, taste alteration, etc.

RATIONALE FOR BEHAVIORAL THERAPY

Behavioral interventions have minimal side effects or adverse events. This approach may be used as a single strategy and/or as an adjunct to a medical approach. It will certainly be of assistance in managing quality-of-life issues and enhancing coping skills and strategies.

Patient Management

Of primary importance in the management for glossodynia is the need to educate and reassure patients, and to explain the disease’s benign nature, as this is a not a life-threatening disease but is a disease that presents quality-of-life issues. The need to address quality-of-life issues and to provide coping skills to the sufferer and strategies for individual and family members is important. It is essential the individual have acceptance of “management” rather than definitive “cure,” with an understanding that improvements are variable, with an unpredictable pattern that may occur over many months to years, as this is a chronic pain condition.

Monitoring, while using topical and/or systemic medications, should be done every 2 weeks to assess pain control. If there is inadequate pain control, then the clinician can consider increasing the dose and/or frequency until pain is controlled or undesirable side effects/toxicity occur. If there is pain control, then maintain medical strategy. If side effects occur, then there should be reassessment, with reconsideration of other options. If there is an adverse event, then discontinue immediately and follow with a trial from a different class of medication. There should be continuous monitoring of all psychosocial issues. Recall, and if pain control is established, then the individual may be seen every 3 months for reevaluation.

Unusual Clinical Scenarios to Consider in Patient Management

Glossodynia is enigmatic and may be associated with other idiopathic pain conditions. There may be a shared etiology and pathophysiology between glossodynia and burning feet syndrome. Burning feet has been described as a condition disseminated throughout the foot, with severe diffuse burning, most frequently affecting the plantar aspect of the foot and distal portions of the digits. It is possible that both conditions are secondary to peripheral nerve damage, with postmenopausal females at higher risk for both conditions due to deafferentation process secondary to hormonal changes.

Glossodynia may also have pathways similar to other persistent idiopathic facial pain conditions such as atypical odontalgia (constant tooth pain in the absence of any pathology). Based on the taste-sensory interaction model, minor injury to the chorda tympani may be able to release inhibition on the trigeminal nerve and cause oral pain because of increased sensory input and increased activity in the masticatory muscles, caused by increased motor output. Interestingly, some reports have found selective taste loss at the fungiform papillae in atypical odontalgia similar to that in glossodynia patients and especially in those who might satisfy the criteria of supertasters.

Glossodynia has been associated with vulvodynia, which is another idiopathic pain condition described as vulvar burning pain occurring in the absence of relevant visible findings or a specific clinically identifiable neurologic disorder. There are cases reported whereby there is the combination of burning pain in both the oral and urogenital regions, thus resulting in a condition with the term vulvostomatodynia. It appears that this condition, once again, presents most commonly in perimenopausal females with delays in diagnosis greatly affecting the quality of life.

Temporal arteritis, or giant cell arteritis, is a systemic granulomatous disease that predominantly affects branches of the carotid artery. Claudication of the muscles of mastication and a painful burning tongue may develop during temporal arteritis, or be the initial presenting symptoms. This may be confused for primary glossodynia and therefore incorrectly managed, thus delaying appropriate treatment and increasing the risk of permanent ocular damage and blindness. Since the orofacial manifestations may be part of the disease process, they should be considered a secondary glossodynia, and therefore treatment must be directed at the underlying systemic condition.

What is the Evidence?

Grushka, M, Epstein, JB, Gorsky, M. “Burning mouth syndrome”. Am Fam Physician. vol. 65. 2002. pp. 615-20. (A review article that provides a synopsis of all aspects regarding burning mouth syndrome. Etiology, diagnosis, and management are discussed.)

Klasser, GD, Fischer, DJ, Epstein, JB. “Burning mouth syndrome: recognition, understanding and management”. Oral Maxillofacial Surg Clin N Am. vol. 20. 2008. pp. 255-71. (An in-depth article reviewing the current concepts relating to the etiology, pathophysiology, diagnosis, and management of this enigmatic condition.)

Suarez, P, Clark, GT. “Burning mouth syndrome: an update on diagnosis and treatment methods”. J Calif Dent Assoc. vol. 34. 2006. pp. 611-22. (A clinically orientated article providing a thorough review of the current concepts for the diagnosis and treatment strategies employed in this condition.)

Sardella, A, Lodi, G, Demarosi, F, Bez, C, Cassano, S, Carrassi, A. “Burning mouth syndrome: a retrospective study investigating spontaneous remission and response to treatments”. Oral Dis. vol. 12. 2006. pp. 152-5. (A research study outlining the potential for the spontaneous remission of burning mouth syndrome with a follow-up period of at least 18 months, and the response of burning symptoms to various treatments.)

Mignogna, MD, Fedele, S, Lo Russo, L, leuci, S, Lo Muzio, L. “The diagnosis of burning mouth syndrome represents a challenge for clinicians”. J Orofac Pain. vol. 16. 2002. pp. 305-11. (This article evaluated the effect of professional delay [by both medical and dental practitioners] in the diagnosis, referral, and treatment of patients with burning mouth syndrome.)

Carlson, CR, Miller, CS, Reid, KI. “Psychosocial profiles of patients with burning mouth syndrome”. J Orofac Pain. vol. 14. 2000. pp. 59-64. (An investigation into the psychosocial profiles of burning mouth syndrome patients, utilizing standardized psychologic assessment instruments such as the McGill Pain Questionnaire, the Revised Symptom Checklist [SCL-90R] and the Multidimensional Pain Inventory, during an initial clinical evaluation session, with comparison to a chronic pain population and a normal nonclinical sample.)

Patton, LL, Siegel, MA, Benoliel, R, De Laat, A. “Management of burning mouth syndrome: systematic review and management recommendations”. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. vol. 103 Suppl. 2007. pp. S39 e1-13. (The most recent systematic review regarding the management of burning mouth syndrome.)

Grushka, M, Bartoshuk, L. “Burning mouth syndrome and oral dysesthesias”. Can J Diagnosis. 1999 June. pp. 99-109. (This article discusses the possibility of burning mouth syndrome being considered an oral dysesthesia and proposes an etiological theory of a taste-sensory interaction for its manifestations.)

Woda, A, Dao, T, Gremeau-Richard, C. “Steroid dysregulation and stomatodynia (burning mouth syndrome)”. J Orofac Pain. vol. 23. 2009. pp. 202-10. (The theory that burning mouth syndrome may be related to steroid dysregulation is proposed and discussed in detail.)

Zakrzewska, JM, Forsell, H, Glenny, AM. “Interventions for the treatment of burning mouth syndrome”. Cochrane Database Syst Rev. 2005. pp. CD002779(The original systematic review, using an evidence based approach regarding the treatment of burning mouth syndrome.)

Ducasse, D, Courtet, P, Olie, E. “Burning mouth syndrome: current clinical, physiopathologic, and therapeutic data”. Reg Anesth Pain Med. vol. 38. 2013 Sep-Oct. pp. 380-90. (A systematic review to identify clinical features, pathophysiology, and therapeutic strategies for BMS. The results of randomized clinical trials for each treatment are discussed through a pathophysiologic approach.)

de Moraes, M, do Amaral Bezerra, BA, da Rocha Neto, PC, de Oliveira Soares, AC, Pinto, LP, de Lisboa Lopes Costa, A. “Randomized trials for the treatment of burning mouth syndrome: an evidence-based review of the literature”. J Oral Pathol Med. vol. 41. 2012 Apr. pp. 281-7. (A systematic review of randomized controlled trials (RCTs) investigating the effectiveness of therapeutic interventions for BMS.)

Kuten-Shorrer, M, Kelley, JM, Sonis, ST, Treister, NS. “Placebo effect in burning mouth syndrome: a systematic review”. Oral Dis. vol. 20. 2014 Apr. pp. e1-6(A systematic review of randomized controlled trials (RCTs) which included a placebo arm in the management of BMS.)