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10 Articles in Volume 7, Issue #7
Burning Mouth Syndrome
Chronic Pain Program in a Primary Care Setting
Chronic Persistent Pain Can Kill
Education and Exercise Program for Chronic Pain Patients
Managing Pain in Intensive Care Units
Oxycodone to Oxymorphone Metabolism
Patulous Eustachian Tube: Part 1
Rational, Emotive, Ethical Approaches to Bio-psychosocial Pain Care
Smoking and Aberrant Behavior in Chronic Pain Patients
Structuring Opioid Therapy

Burning Mouth Syndrome

The large array of potential pathologies for this condition requires investigative skill, tenacity, patience, and empathy to differentially diagnose and treat.

The classic case of Burning Mouth Syndrome (BMS) is a constant burning sensation in the mouth with no obvious or visual tissue changes, lesions, or defects. BMS affects approximately 5% of the population. In 1,017 subjects, 4.6% of patients report burning mouth.1 The most common oral location of the pain is the tip of the tongue. The second most common presentation is a combination of the tip of the tongue and the anterior palate. It occurs more in females than males ( in a ratio of 7:1). Most of the females are over 60 years of age in post menopause.2 Besides burning, there is a wide array of other symptoms associated with BMS depending on the particular pathology or circumstance such as dry mouth, metallic taste, headache, tinnitus (ear ringing), difficult swallowing, difficult chewing, or various other symptoms. In most cases, the pain improves as the day progresses. So, the most common presentation is constant burning pain in the tip of the tongue in a 60-year old female with no visible signs of abnormality and may result from several diverse pathologies that can confound diagnosis.

The personality of this pain is “burning.” The term burning is rarely used by patients unless the nervous system is affected. Since the “burning mouth syndrome” (BMS) can be a pathology of the nervous system or pain reporting system; it can mimic pathology in the structures it reports from or to; structural damage to bone, skin, and connective tissue; along with many different systems malfunctions.

“In the mouth” directs the clinician to a specific area of the body, the mouth, thus excluding all non-mouth pathologies. With the mouth’s complex wiring, multiple fields of applicable science, specialized organs, and complex structures, it leaves a lot of room for an array of pathologies. Just in the dental field alone, there are subspecialties that encounter burning pains: dental, perio, endo, orofacial, oral path, and oral surgery. Likewise, in the medical field, specialties encountering burning pains include family practice, ENT, anesthesiology, allergy, gasteroentologist, endocrinologist, nutritionist, and rheumatology. A new specialty, orofacial pain—developed to treat the orthopedic jaw problem—is well trained at neuropathic pains in the chewing system since some of them mimic “TMJ syndrome.” Thus, the orofacial pain specialist can serve as a clearing house for BMS. This specialty is ideally positioned to diagnose BMS because it is already a blend of medicine and dentistry.

The “no visual presentation of BMS” gives rise to the difficulty in diagnosis. In the acute pain world, doctors diagnose most diseases visually. A broken leg on x-ray, a gum boil with large decay in tooth, clogged sinus by scope or image, and red inflamed ear drum are all examples of visual diagnostics. In chronic pain, a pathology without visual symptoms increases the differential list of possibilities and so puts more emphasis on searching for clues, data, and information. The key is to ferret out all the other symptoms to determine the proper diagnosis and the direction of care.

Etiology

There are many pathologies that can exhibit burning symptoms. The neurological pathologies can be categorized by location of nerve damage: central, intermediate, and peripheral. The central pathologies affect the nerve as it exits the brain and before it leaves skull. The central pathologies that have burning component are mostly tumors, trigeminal neuralgia, surgical damage, etc. The intermediate pathologies affect the nerve between skull and the nerve receptors and can be subdivided into neuralgia, neuritis, neuromas. There are various peripheral diseases affecting skin and skin receptors. BMS comes in all shapes, sizes, intensity of pain, vague or specific, superficial or deep structures and spanning both dental and medical fields. The burning can be constant or intermittent. They can mimicany structure along their path of innervation. Figures 1 and 2 illustrate innervation of the tongue and the distribution of the trigeminal nerve, respectively.

This vast array of pathologies and overlapping healthcare fields creates the necessity of a large differential diagnostic tree. An old-fashioned, but useful, technique is diagnosing by inclusion or exclusion. One starts with a differential list of pathologies based on patient presentation then, as the information and diagnostic test produce data, either exclude or re-enforce the possibility of a particular pathology.3 In using the diagnostic differential list, a clinician would also use statistics to help select the next clinical test, labs, images, or clinical trials. In a study several years ago—and before many of the tests we use today— it was found that the causes of BMS were grouped as follows:

Figure 1. Innervation of the tongue. Figure 2. Distribution of the Trigeminal nerve

BMS Causes

Medical (drugs & PMTOS*) ...............02%

Fungal .................................21%

Psycogenic..............................37%

Geographic tongue ......................26%

Multiple causes.........................12%

*Parotid masseteric traumatic occlusion syndrome

BMS can be caused by several different conditions either directly or indirectly. The burning pain can be created by a defect anywhere along the path of the nerves from the skin to the brain. The types of burning pains can be divided by the structure they affect: outside-peripheral-local-skin, intermediate-connective tissue-nerve bundles, or central or global pathologies. The types of BMS may be divided by frequency patterns:

  • constant,
  • constant with flares,
  • episodic, or
  • daily progressive.4

The burning pains may stay in the same location or wander from one location to another. Watching the pain’s patterns, we can glean knowledge of aggravators or perpetuators by looking at variables in and around the pain spikes or episodes of pain. Observing the time of day where pain increases, such as worse as the day progresses, worse at night, worse at meals, worse with stress, worse with spicy meals, etc. can provide clues to the cause of the pain. The burning pains may be categorized by associated symptoms: fatigue, dry mouth, dry eyes, altered skin condition, altered taste, tinnitus, difficulty chewing, difficulty swallowing, or other symptoms. The burning conditions may be analyzed from the historical data: recent impact of life events, depression or anxiety, menopause, diet, stimulant use, regular intake of over four major drugs, medical conditions, dental conditions, hormonal changes, allergies, nutritional, behavioral, psychological, digestive, rheumatological, surgery, intake major antibiotics, or viral infections. Each may contribute some or all of the causalgia for this confusing burning pain. In other words, there is no rule that says you cannot have more than one pathology. Therein lies one of BMS’ major areas of diagnostic confusion.

Common sense leads you to believe the peripheral, skin, outside, or local tissues such as skin receptors are more likely to be source of the burning pain than a central lesion. However, the central verses peripheral is not always easy to discern. The brain’s perception of pain is based on the area of the body the nerve connects to in the brain. Each nerve impulse is the same bioelectrical phenomena. So, a burning pain can be a defect anywhere along the path of the nerve: peripheral, intermediate, or central.

The list of BMS’ potential causes is exhausting:

  • Fungi
  • thyroid
  • glossodynia
  • stomatodynia
  • cancer
  • xerostomia
  • vitamin deficiency
  • allergies
  • Sjogren
  • Meniere’s
  • post radiation
  • reflux
  • bulimia
  • anemia
  • diabetes (only 2-10% of diabetics)
  • Lichen planus
  • Pemphigoid
  • Parkinson’s
  • interaction of 4 different drugs
  • drug reaction to anti-hypertensive
  • salivary gland dysfunction
  • neuroma
  • neuritis
  • sympathetic maintain pain, and
  • up-regulation sympathetic system.

Each specialist has a different set of diagnostic glasses and each pathology has a different set of parameters.

Diagnostic Approach

A systematic approach must be established to evaluate historical and clinical information, establish the differential diagnostic list. Other considerations include: impact on quality of life, cost of testing, impact of testing, patients ability to trust and compliance, path for ruling in and out the pathologies, and desire for success. The first step in the diagnosis is a thorough history and clinical examination looking for all signs and symptoms of pathology or pathologies. As they say in milking a cow, a cow does not give milk and neither does a patient give a history. Many times a doctor has to play detective when it comes to interviewing the patient. The differential list of pathologies are delineated as you collect the history and clinical findings. The pain patterns, associated symptoms, historical onset, aggravators, alleviators, images, lab work, and medical testing collected to date will guide you toward making the differential diagnosis. After the differential list is complete with all possibilities, the doctor will redefine the list according to priorities based on cost test, impact test, peripheral verse global, value of data, and statistical probability. Always try to start with the simple, inexpensive, and least invasive test when collecting more data for diagnosis. Use knowledge of statistical probability to help rank order the differential list.

For instance, if you suspect vitamin deficiencies as a causative factor, you may start with prescribing supplement of B series for BMS. This can be accomplished while you are setting up more sophisticated tests like imaging or a blood test. Another quick clinical test would be to suggest stopping tartar control products if you are suspicious of chemical sensitivity. Providing the patient with an NTI device (an enhanced anterior bite stop which prevents reciprocating posterior tooth contacts) to interfere with muscle contraction during day or night can be an easy and fairly inexpensive test for PMTOS. Any and all testing is guided by what you know and what you need to know, but the quickness, the expense, and the conservative nature should also guide you. After each clinical trial, the results are analyzed to help direct the doctor to the next level of testing. This type of evaluation is not very conducive to those patients who desire a fast, quick, and cheap fix, but with a syndrome of this complexity it is a necessity.

The moderate level of testing has an increase in cost, invasiveness, and need for detail. Many of these tests are directed by what you know, what you need to know, and the statistical probability of the pathology. For example, the suspicion of yeast infection even with no tissue changes can easily be ruled out or in by culture or an intake of an antifungal drug, especially if antibiotics were part of onset history. The use of blood studies is important due to its broad scope of data collection. The blood study can rule out so many pathologies at one time or it may give you a clue to lead you in a particular direction. The blood test can assist you with thyroid, vitamin deficiencies, diabetes, rheumatological, hormonal, viral infections, and anemia. The blood test may indicate a pathology that may be managed by the orofacial pain specialist or referred to an appropriate specialty.

It is assumed that all pathologies are from one cause, but this is not necessarily true. The first few tests may indicate a cause, but in the course of the treatment not all the pain is relieved, and the quest for answers continues. So, the patient needs to know the complexity of BMS and that all pain is managed to the best outcome. The goal of treatment is not “no pain,” but the least pain given the science we have today. So, a referral to a specialty does not always end the search. Sometimes, conservative therapy takes time to implement as in a parafunctional pathology such as PMTOS. Ruling out this pathology may require up to 1 to 2 months to fully evaluate the success. Allergy testing is safe and effective, but again takes time to implement fully. Sensitivity to minor allergens without obvious symptoms also takes time to test and implement. Reduction in pain from manipulation of any of the variables is the reason to include any modality in plan to solve the biodetective maze.

Each presentation of symptoms and history will generate a different beginning differential list. As the information and tests unfold, the steps of exclusion and inclusion will vary, with the endpoint being a treatment that improves the quality of life, stops the disease progression, and decouples the up-regulation of pain system (central sentization).

Differential Diagnosis

Many of the neurological pathologies of the head region produce a burning sensation and must be included in the differential diagnosis. The neurological pathologies are nerve injuries, defects, healing abnormalities, nerve entrapments, needle traumas, surgical traumas, radiofrequency lesions, gamma knife lesions, infections, or inflammation in the nerve tissues of mouth. Because the inflammation, infection, or defect involves the nerves of the body, it can mimic many different structural problems. The nerve damage can involve any part of the nervous system, the nerve receptors (peripheral), the nerve channels (intermediate), or nerves as they exit brain. It makes sense that the peripheral system is more prone to injury, infection, or inflammation; therefore, it is statistically more likely than deeper lesions—unless you discover, in the patient's history, that the deeper structures have been damaged by trauma, surgery, or infection. When the nerve is damaged, it conducts impulses without outside stimulus.

A burning sensation in the mouth can develop when the sympathetic system develops control over the pain system. The interplay between the sympathetic system and the nervous system is set up by long standing pain or excess stimulation of the sympathetic system. As the nervous system adapts to pain conditions:

  • connections develop between the pain system and the sympathetic system,
  • the sympathetic nerve cells change their neurotransmitters,
  • dorsal horn laminas interconnect between the pain and the sympathetic system,
  • nerve terminals produce new receptors sensitive to adrenalin (stress hormone) and thus we get a rewiring of the two systems allowing increase control of the stress system over pain system.

Sympathetic aggravated, maintained, or perpetutated pains usually have a burning component to the pain. This rewiring sets up a mind-body pathway thereby increasing confusion, misconceptions, and frustration for diagnostic clarification. A diagnostician used to treating organically-based acute pains that could easily be identified as stress aggravation to pain may brush off BMS as psychologically-induced.

Anxiety or significant stress sets up these patients to be non-compliant in the treatment regimens and makes it difficult to record accurate responses to clinical testing.5 Burning pain overlaps specialties such as oral pathology, orofacial pain, periodontal, psychology, medical, counseling, stress management, and neurology. These many different medical and dental specialties have little or no commonality, no integrated data system, and no organized referral system, and so reduces the amount of data that can be cross-correlated. Until the establishment of the orofacial pain specialty, no one had the range of knowledge to collect all the data together. With a limited number of champions for this syndrome, the patient may visit up to seven doctors before the orofacial pain doctor is consulted. Even the slowly evolving referral patterns are conducive for long lasting suffering of the BMS patient. Because of the seemingly small numbers of cases, limited publicity, and low morbidity, it has not received the attention it deserves. In other words, it is largely ignored by medicine and dentistry, making it the hot potato, or the black hole between professions. For many reasons, these pathologies are a bane to medicine and dentistry.

The differential diagnostic list for burning mouth syndrome (BMS) is a wide variety of medical or dental pathologies that are poorly defined with limited scientific data. The pathologies that are listed under “burning” lack a smooth flowing diagnostic tree for doctors to follow. The many different pathologies all share three similar parameters: burning, mouth, and no clinical sign. The general characteristics of burning mouth are:

  1. Gender: typically post-menopausal females
  2. Location: (one or more)
    • tip of the tongue alone (most common)
    • anterior palate (in addition to tongue)
    • or any other of lip, buccal mucosa, or throat
  3. No visual changes to normal tissue
  4. Pattern
    • constant (most common)
    • worse as day progresses
    • upon awakening
  5. Associated with:
    • autonomic dysfunction (high stress, anxiety, or
    • depression)
    • sleep disorders or dysfunction
    • deconditioned cardiovascular system
    • irritable bowel or gastric upset
    • parafunction (most common is clenching)
    • fatigue, loss of energy, low drive

In a study in 2002, this syndrome affected over 1 million women or 5% of the population.6 It may affect more than one site, but only the tongue is affected in the majority of the cases. Many cases involve both the anterior 1/3 of the tongue and the anterior palate. The distinct types of BMS have different and varied secondary symptoms.

The diagnostic path for most burning mouth patients is to first visit their dentist for the burning pain. The majority of dentist and medical doctors feel uncomfortable with this pathology from the start; therefore, they spend very little time and refer to a specialist after the exam. A few dentists will try their skills on the burning pain. They will prescribe one or two treatments such as miracle mouthwash (topical rinse). If this is ineffective, the dentist will refer to specialist. The difficulty is determining which specialist to refer the patient to for maximum success. The dentist or doctor may refer the patient to an ENT, allergist, gastroenterologist, periodontist, oral surgeon, or neurologist in their search for answers. The most prevalent referral is from the dentist to an oral surgeon. This referral to a specialist is usually without a lot of diagnostic guidance or reasoning regarding which specialist to choose. Each different field may involve one or more of the pathologies. So, after exhausting each specialist’s diagnostic and treatment strategies, it is on to the next specialist. Anywhere from 1 to 7 different doctors may try their skills and knowledge, before a specialist is seen that stumbles on the right diagnosis and treatment. Sometimes along the way, the treatment actually defines the diagnosis. Whoever or whatever the specialist, they typically have training or years of experience in “chronic pain,” creating knowledge, skill, tenaciousness, and ability to think in a diagnostic tree. Each of the different pathologies should be ruled out in as short time as possible due to the likelihood of central sensitization, since the pain system increases it’s irritability with time.

The top three pathologies with a burning component—based on their statistical probability—that affect the peripheral structures lay near the outside of the body and are more easily tested, observed, manipulated, or challenged. There are three highly publicized pathologies:

  • acid reflux,
  • candidia infections, and
  • post herpetic neuralgia.

Acid Reflux

The first pathology most doctors blame for burning mouth is acid reflux. The acid from the stomach increases in production or is pushed up the esophagus burning the throat and mouth. The acid reflux occurs in people who have up-regulated their stress system on regular basis. This constant and prolonged upregulation causes excess acid production in stomach back-flowing up the esphagous into the mouth. This is one of the most frequent causes of burning mouth syndrome. In severe states, it is also associated with irritation of tissue and unusual tooth damage, in other words, it is visual. In moderate to mild cases, or in tissue resistant cases, no tissue changes are evident. By the time the burning mouth symptoms occur, the patient may have had years of acid reflux, IBS, or ulcers as part of their history. Occasionally, acid reflux is well tolerated by the esophagus or mouth tissues have grown tolerant, so that the first symptom is a burning sensation in mouth tissues. Even though this sounds unusual, it is not an infrequent way to diagnose acid reflux.

Fungal Infection

The second pathology dentist think of with burning mouth is a fungal infection. Even though the typical yeast infection exhibits tissue changes, the burning sensation can occur without the visual tissue changes in early infections or in certain individuals. Yeast infection is more likely considered with a recent history intake of antibiotics. Many women are prone to yeast infections; so, a patient history of frequent yeast infections may lend a clue. Fungal infections are more prevalent than most patients suspect, especially with wide spread use of antibiotics. Since yeast infections are quite commonplace, it would stand to reason that this could be initially ruled with a round of antifungal medicine or ruled out by culture. In 1984 study of 57 BMS patients by Dr. David Zegarelli, 12 patients or 21.1% were diagnosed as having yeast infection. In almost all these cases there were local tissue changes to help with the diagnosis.7 Most were women (with the exception of 2 males) with ages ranging from 30 to 82. In the Gorsky 1987 study of 98 patients, 13 or 13.1% of the patients improved with antifungal medications.8 At best, brush biopsies are required for suspected yeast infections, but they take time for lab procedures. One may consider a clinical trial of anti-fungal medications.

Figure 3. Neuralgia Inducing Cavitational Osteonecrosis (NICO) or Osteomyletis

Post-Herpetic Neuralgia

The third type of burning pain is post herpetic neuralgia. The absence of vesicular lesion help rule out herpes, Pemphigus, and Pemphigoid. Unfortunately, in the early stage of infection of viral herpes, when burning pain can occur, there are no vesicles or ulcers to use as the diagnostic clue. The burning pain from frequent or subsequent infections of herpes produces a burning pain called Post Herpetic Neuralgia (PHN). When a virus invades the trigeminal nerve it causes neuritis or inflammation of the trigeminal nerve. In fact, the virus kills large diameter fibers which are part of the body’s way to obtund pain. Remember that when the dentist pressed on your lip before he injected the anesthetic, he was activating the large diameter fibers which speed to the spinal cord and block some of the pain nerves. The herpes virus kills these large diameter fibers.9 After several infections, a person may become deficient in these large diameter fibers thus allowing background pain that is usually blocked to get through to the brain. PHN is more common in older patients. Over the many years of life, one loses large diameter fibers due to a variety of causes. With each viral infection, it increases the chance of runaway pain in individuals after age 50.10 If the burning pain is from a viral infection, a clinical trial of anti-herpes medications may prove beneficial.

Peripheral Tissue Damage

The clinician will now turn his or her attention to the peripheral area because of its accessibility, ease of manipulation, non-invasive testing, and low cost of evaluation.

Since most peripheral tissue damage show visual changes to the tissues, it is easy to rule them out. Burning pain precedes the outbreak of vesicles in oral herpes (cold sores) due to damaged nerve receptors. By history of previous vesicles and patient perception, a diagnosis can be made or a diagnosis can be made just by waiting one to two days. Changes in the biochemistry of skin and connective tissue are not obvious. Burning pain can occur from changes due to sensitivities to drugs, chemicals, or biological changes such as: 1) age-related thinning skin interaction with hot spicy foods, 2) tartar control products (triclosan and bisphosphates) can set up burning discomfort, 3) bleaching teeth chemicals can chemically irritate tissues, 4) allergy to crown materials such as nickel can produce gum burning, or 5) denture and partial plastics can irritate tissues in some rare individuals. In one study, 5 of 23 patients were sensitive to the monomer in dentures and partials.11 Defects or changes in a person’s biochemistry can even predispose a person to a situation that normally does not cause burning pain.

Neuropathic Origin

Another class of pathologies is neuropathic pains: neuralgia, neuritis, and neuromas. These are deeper nerve problems going past the nerve receptors to the nerve bundles. Direct trauma from surgery, gamma knife lesions, radiofrequency lesions, injection needle trauma, infection irritation, glycerol injections, and invasive traumas can set up burning pain. Nerve irritations can occur from “Neuralgia Inducing Cavitational Osteonecrosis” (NICO) lesions (see Figure 3), drug induced osteonecrosis (bisphosphates), viral infections, chemical burns from glycerol injections, burning nerves by radiofrequency lesions, nerve compressions, or nerve entrapments. These can set up transmission of burning sensations.12

Burning pain can occur if a nerve is traumatized by anesthetic needle, anesthetic chemicals, or surgical trauma. This occurs most frequently in a nerve block of the inferior alveolar nerve used for a lot of dental procedures. It occurs in 1 in 26,762 injections (close to a lifetime number injections per dentist) and the lingual nerve is affected 79% of the time.13 Any nerve can be damaged by the needle or anesthetic anywhere in mouth with a probability of 3%.14 This occurs more often in a nerve that lies in the typical path of dental injections, a nerve that can be held firmly by connective tissue, scar tissue, or over-contracted muscles (parafunctional tense individuals). Most (94%) resolve without treatment in approximately 8 weeks,15 but a few do not. A nerve trauma from surgical or invasive trauma usually heals properly, but occasionally develops a neuroma.16 As the nerve heals, it reconnects to the nerve terminal, but occasionally, it’s pathway to reconnect is blocked by scar tissue and the nerve balls up and sometime forms ectopic eruption creating a burning sensation.16

Nerves subject to entrapment or irritation can produce a burning sensation. A nerve can be entrapped by tumor, artery, muscle, ligaments, or scar tissue. The nerve entrapments are rare and are usually accompanied by numbness. In the case of the auriculotemporal nerve being entrapped by lateral pterygoid muscle, it can even reduce saliva flow to mouth.17 This decrease in salivary flow by nerve compression can produce a drying effect which, in turn, could cause the burning pain. The burning pain can come from irritation to a nerve traveling through a bone lesion such as osteomyletis or NICO.18 The NICO lesion is thought to be a surgical defect that does not heal correctly and results in a osteomyletis. It is believed that a nerve traveling through such osteomyletis gets irritated.19 Most osteomyletis show on radiographs, but all of these lesions, and especially NICO, do not show in normal plane radiographic films. This sets up osteromyletis as a diagnostic challenge because they do not show up on standard dental or medical radiographic studies.20 A new form of burning pain comes from the ingestion of bisphosphates for osteoporosis and to prevent the spread of breast cancer to bone. These drugs— such as Aredia, Zometa, Boniva, and Fosomax—are becoming more popular every day for osteoprosis. These drugs have no way to be eliminated by the body and so accumulate. While the purpose of these drugs is to stop cancer metastasis to bone and osteoporosis, an accumulation can cause bone death in the mandible and thus osteomyelitis. Osteomyelitis is frequently found to have a burning component. The burning pain is felt most often under the tongue. The diagnose is assisted by Tech 99, MRI with contrast, or the new I-CAT scan.

Figure 4. Parotid duct enters in front of Masseter

Systemic Pathologies

The more global pathologies with a burning component affects the whole body such as diabetes, salivary gland diseases, parotid masseteric traumatic occlusion syndrome (PMTOS; see Figure 4), multiple drugs with drying effect, and hormonal changes.

Diabetes

A fragile, untreated, or significant diabetic may exhibit a burning sensation in the mouth. Known as diabetic neuralgia, it sets up irritation of nerves or nerve endings which presents as burning pain. A blood test for sugar or referral to endocrinologist can be recommended to see if the diabetes is under control.

Salivary Glands Malfunction

Burning pain can occur from a salivary glands malfunction. The pathologies that affect the salivary gland function are Sjogren syndrome, Meniere disease, radiation treatment to jaw area, salivary gland stone, and drug-induced salivary gland hypofunction.

Drug Sensitivity

There are medications that may induce a dry mouth which can also have the effect of burning sensation. A patient can be on as many as 8 different drugs with each contributing to some hypofunction or they may be taking one drug that diminishes mouth fluids. We know very little about how these drugs affect the autonomic system (sympathetic and parasympathetic systems) that control fluids. The patient may be hypersensitive to a particular drug that enhances it’s oral glandular hypofunction. Many people may have dry mouth without burning discomfort, but some people notice the burning and not the dry mouth. When asked about dry mouth, they will then let you know it is dryer than normal. A partial list of drugs that cause drying effects or even direct burning sensitivity are narcotics, anti-depressants, anti-histamines, anti-anxiety, diuretics, sedatives, anti-hypertensive, anti-psychotics, and etc. In patients over 50, some of these drugs may be taken for high blood pressure, cholesterol, heart conditions, diabetes, anxiety, etc. In fact, there are 400 drugs that maybe related to BMS. Even radiation therapy to the jaw have been associated with a few cases of BMS.

Mechanical Effects

The burning pain associated with mechanical hypo-secretion of the parotid gland is related to major grinding and clenching of the teeth. When the parafunctional habits such as grinding (bruxism) or holding teeth together (clenching) are frequent and significant, it can close off the parotid duct by hypercontraction of the Masseter. The parotid duct crosses over the Masseter entering the mouth just in front of this powerful clenching muscle (see Figure 4). In most people, the duct is not in the fascia of the Masseter, but just anterior to it. So, if there is significant grinding and clenching in a person where the duct crosses through the Masseteric fasica, the clenching effect on the duct may occlude the flow of salvia. It is a common misconception that parafunction occurs only at night, but many daytime habits exist such as clenching, tooth bracing, object biting, tongue biting, cheek biting, tongue gymnastics, and lip biting. This has been called Parotid Masseteric Traumatic Occlusion Syndrome (PMTOS).21 The clues here are significant Masseter Hypertrophy and/or severe wear to teeth. This decrease in salivary flow by PMTOS with it’s drying effect may lead to burning pain.

Hormonal Changes

Burning pain can stem from hormonal or nutritional deficiencies. The hormonal changes have been linked to BMS in 10 to 20% of women seeking menopausal treatment.22 The hormonal disturbance is believed to cause thinning of tissues or dryness of tissues. These conditions or circumstances can be a predisposing factor or the actual causalgia.

Nutritional Disorders

There are also systemic diseases that can exhibit burning discomfort such as nutritional disorders. Such nutritional deficiencies include B6, B12, iron, or foliate or anemia.23 These nutritional deficiences affect the health of skin, the health of the skin nerves, nerve receptors, and the health of the connective tissue in the mouth.

Figure 5. Production of receptors sensitive to adrenalin

Drug Sensitivity

BMS can occur from sensitivity to one or multiple drugs separate from any hypofunction to the salivary glands. These drug sensitivities set up neurological or biochemical changes in the nervous system resulting in burning. For example, Cyclospasmol, an anti-emitic, may cause intraoral burning in rare circumstances. These drugs cause a direct effect on the function of the nerves. As we age, many different doctors managing different pathologies prescribe various drugs. Sometimes even drugs are prescribed to manage the side effects of drugs. Most of the drugs have never been used in combination in studies; therefore, we know very little about the cumulative effect of the drugs or their effect on nerve biochemistry. The drugs that individually are known to cause some change in nerve bio-chemistry are antidepressants, narcotics, anti-histamines, anti-anxiety, diuretics, sedatives, anti-hypertensive, anti-psychotics, and ACE inhibitors. This is more difficult to rule out (or in) due to the multiple doctors prescribing, the existence of pathologies creating a need for drugs, and reversing most of these life style diseases (high blood pressure, high cholesterol, anxiety, etc) takes commitment and time to reverse. The paradigm shifts required for change in life style or life habits is the exact opposite of the habit that created the pathologies. The pathologies that these drugs treat must be reversed over long periods of time; so the question remains as to how to treat the burning pain in the meantime. For example, it may seem insurmountable to reduce 100 pounds of weight to reduce high blood pressure in order to prevent high blood pressure medicine precipitating burning pain. The best approach in most cases is to treat the burning pain symptom with Elavil and Stelaxine or Klonopin while an aggressive weight loss program is introduced.

Up-regulation of the Sympathetic System

Statistically the most likely, the most overlooked, and most unappreciated pathology is aberrant or defective nerve transmissions caused by upregulation of the sympathetic system (tension, stress, anxiety) in patients over 50. Under normal conditions, a stimulus affects a receptor in the periphery thus setting up the transmission of sensory information (including pain) to the spinal cord, to the thalamus, to the specific brain center, to the prefrontal cortex, mixes with the emotional aspect of perception, followed by reaction to the stimulus. For example, the brain registers pain when a tooth with recession is brushed or touched. Fortunately for doctors and patients, this is a normal body impulse in 98% of the time in regards to acute pain. In chronic pain—the other 2%—the stimulus on the receptor is normal or not even present, but the transmission of pain is still felt by the brain. After many years of exposure to normal transmissions of impulse with acute pain where the site and the source of pain are the same, the patient and the doctor assume the site of pain is always the source of pain. The fact is that the pain system is living tissue that is adapting, changing, or transforming in response to chronic pain stimulation.

For example, a Dworkin and Galer study shows that a severe or long term pain creates the production of a new receptor on pain nerves called an alpha adrenergic receptor. The alpha adrenergic receptor is not associated with a normal nerve. These receptors react to the stress molecule adrenalin (see Figure 5).24 The release of adrenalin during stress activates the alpha 1 receptor on the nerve which then incorrectly signals the brain that it has been activated by a normal stimulus. The brain thus perceives that the tongue has come into contact with a hot stimulus and is burning.

A second way that stress—fight or flight, or sympathetic system—can create false pain signals is when long term pain sets the stage for a new connection from the sympathetic system to the pain system in the spinal cord. The nerves in lamina 3 sprout (A Beta fibers) and connect with lamina 1 (C fibers) in the dorsal horn of the spinal cord.25 The sprouting of the sympathetic fibers to innervate the dorsal horn ganglion is the result of long term pain stimulation to the nervous system. It is thought to be an adaptive process to increase avoidance behavior to allow for healing. The body develops increased or enhanced control of the sympathetic system over the pain system.26 Increase in pain from the same stimulus, a nonpainful stimulus causing pain, or a phantom pain would set the stage for avoiding any stimulus to the pain system. Women seem to have the ability to enhance this process by the estrogen connection. In the presence of estrogen, the cell wall of the mast cell is weakened to release its contents more easily. The contents of the mast cell is inflammatory chemicals, but it also includes Nerve Growth Factor (NGF). Nerve growth factor, NGF, fertilizes the growth of nerve tissue.27 The mast cell’s inflammation chemicals could cause the burning pain itself or predispose a person to burning pain.

A third way that the sympathetic system causes burning pain is through long term pain stimulation that promotes excessive production of the the pain fibers’ neurotransmitter, substance P. Under normal conditions, a pain stimulus causes the release of substance P to communicate to the next nerve that a pain stimulation has occurred. In presence of long term or significant injury, the C fibers begin to produce increasing amounts of Sub-P. The production of copious amount of substance P increases the perception of the brain that more pain stimulus is occurring (eg. more exposure to pain conditions). The excess production of substance P produces a cascade of secondary hyperalgesia effects.28 All these biochemical and structural adaptive changes can set the stage for a burning sensation.

Local and Systemic Interactions

Some studies suggest that BMS can be a complex interaction of systemic and local factors.29 One of the more frequent sympathetic system global malfunction is chronic depression and anxiety. In fact in one study, up to 50% of BMS are associated with psychiatric disorders.30 In some literature psychosocial disturbances (stress, anxiety, or depression) are predisposing factors31 setting up changes in the nervous system. A significant life stressor is associated with a large number of the cases of BMS in mature female population, over 50 years of age.32 Depression is found in 31% of the cases and anxiety in 11% of the cases.33 In a Dutch study of 184 BMS using psychological testing, 154 (90%) had strong psychological component in their symptoms.34 In a British study of 25 patients with BMS, 11 (44%) had strong psychological symptoms based on clinical examination.35 In another British study of 47 patients using psychological testing, 24 (50%) had strong psychological symptoms.36 Some of the BMS cases are even associated with psychological disorders such as undiagnosed or diagnosed bipolar disorders. The central nervous system and especially the sympathetic system can adapt for many years of depression or anxiety before creating chronic burning pain. Unfortunately, many in this population of patients have difficulty focusing on a goal for long periods, irrationally expect quick fixes, or can’t maintain a doctor-patient relationship long enough to manage this biochemical and or neurological defect. It can be difficult for patients to accept the mind body connection to some of these pains. In suggesting mind body techniques or coaching, it is not uncommon to hear, “I really hurt, I’m not crazy” just from the suggestion to treat this aspect of the pain. It may be difficult for the depressed patient to accept the idea of counseling. The very person who needs mind-body therapy or coaching the most has the least capacity to understand it. If the sympathetic system can stop a heart due fear, it is not farfetched that it can cause burning pain in the presence of long term anxiety in older females.

Testing

Without a definitive diagnosis with primary and moderate levels of testing, we begin invasive or expensive testing. The reason for the need for this level of testing is diagnostic resolution and lack of definitive diagnosis. In times like these, the need for images such as CT, MRI, or Tech 99 scans are suggested. The need for blood test, surgical biopsies, testing for NICO, drugs with significant side effects, or 2nd opinions with Tier 3 level specialist (Mayo clinic, Saper clinic, or university researcher doctor) may be warranted. Even exploratory surgery fits into this level of invasiveness such as apicoectomy, extraction, injection of steroids, nerve blocks, among other things.

The amount of research, lab test, images, 2nd opinions may depend on results of each test and the statistical possibility of pathology. These expensive and invasive tests are considered when necessary when the need for data outweighs the cost.

Treatment Options

If the sympathetic system is suspected, the use of medication is one of the fastest ways to identify the sympathetic system as part of patho-physiology. Here we are discussing the use of medications as a diagnostic tool, but in reality it can be a treatment tool. The medications most used in burning pain are the TCA’s, the benzodiazepines, psychotropic drugs, and antihistamines.37 The use of Elavil has a long history of use in neuropathic pains such as burning pain. To enhance it’s effectiveness, we sometimes add Stelazine to the Elavil. The use of Klonopin38 is also widely discussed in the literature for burning pain. A reasonable benefit or reduction in pain gives rise to the suspicion of autonomic system imbalance. When the pain system or sympathetic system is involved, one of the management techniques is to enhance inhibition of pain impulses to the central computer. The pain inhibitory system can be enhanced by medications like the TCA’s. Many years ago it was found that TCA’s could help with burning pain.39 A variety of drugs have been added to enhance the pain inhibitory system such as Neurotin,40 Lyrica, Trileptal,39 and even some psychotropic drugs.41

This is not complete or exhaustive list for there are many different drugs used in neuropathic pain.42 It is interesting to note that combinations of these different drugs are sometimes more beneficial than the base drug depending on nature or cause of the neuropathic pain.43 The benefit of the drug—and the realization that the sympathetic system is involved in burning pain —initiates the use of behavior modalities to enhance the pain inhibitory system, reduces pain impulses, reverses central sensitization, etc. Many modalities have been added to our list of treatments for sympathetically-maintained or initiated BMS such as biofeedback, cognitive behavior training, stress coaching, abuse counseling, positive thinking, and other ways to calm the sympathetic system. Typically, the final treatment plan is a combination of medications, topicals, behavioral modification, nutrition, stress management, biofeedback, exercise, etc.

“If the sympathetic system is suspected, the use of medication is one of the fastest ways to identify the sympathetic system as part of patho-physiology.”

The pain inhibitory system may be enhanced by drugs, but it can also be enhanced by behavioral modalities. When the sympathetic system is up-regulated to point it is involved in a burning mouth pain, the pain can be reduced or effected by behavioral therapies, anxiety or depression management, change in attitude, thought therapy, anger management, abuse counseling, cognitive behavioral therapy, stress coaching, and other pain management techniques. The main focus of any burning mouth therapy associated with the sympathetic system is to balance, refine, improve, and re-regulate the basic four (good sleep, nutrition, thinking, exercise). The pain management that affects the mind-body connection is more conservative, but requires acceptance, commitment, and compliance to be effective. Many in this group have trouble accepting that their habits have anything to do with this pain; therefore, some problems may arise in implementing the therapy. Despair, hopelessness, and uncertainty have been shown to have a negative impact on an individual’ internal body chemistry at the cellular level.10 Stress makes most global pains worse and stress management improves pain outcomes in most of these pathologies.44 A partnership with mutually shared goals of improved quality of life between the medical team and the patient is necessary for these to be effective.9 Biofeedback, one type of pain management, is aimed at helping patients acquire improved self-regulation of specific body physiology to reduce pain conditions.45 This is a major paradigm shift in thinking for a patient, in adjusting from the quick fixes of acute pain world to the time contingent and active participation of mind-body therapies in the chronic pain world.

Some of the up-regulators sympathetic system must be uncovered through long hours of counseling or coaching to develop alternative thought and habit patterns to emotional hijacking, overpowering emotional postioning, and break down of cognitive abilities. Emotional hijacking can occur by one small part (sight, sound, smell, look, feeling, situation) of the past triggering a primordial protection system called the lower highway.37 The lower highway is an impulse path through the amgdyla to prefrontal cortex not allowing for cognitive processing or even cognitive recognition. The short, powerful primitive impulse loop allows for powerful reactions against life threatening events; unfortunately, we empregnate some memories in this pathway because of the emotional damage, such as child abuse. Unfortunately, the sympathetic system is hijacked when the one aspect of the abuse (only one impregnated aspect of memory imprinted on the hypocampus) is registered by the sensory systems. To facilitate changes in the primitive protection systems, the psychologist, biofeedback specialist, counselor, and other professionals must provide long term coaching to deal with this aspect of the sympathetic system. The coaching is to repetitively challenge the lower highway and re-divert it through the upper highway (cognitive brain).

One treatment option is to block the pain receptors at the periphery level. To block these receptors, one can use topicals, injections, neurosensory shields, temperature, iontophoresis, phono-phoresis, or electrical devices. Blocking the receptors reduces transmission of the nerve impulse from the receptor to the brain. The receptors can be blocked by topicals with lidocaine46 as one of the ingredients. Other ingredients such as Gabapentin, Tricyclic Antidepressants (TCA), Selective Serotonin Reuptake Inhibitors (SSRI), anti-convulsants, Klono-pin, etc. may also be added to lidocaine depending on the presentation of symptoms. Many professionals in the chronic pain arena add drugs to the topical mix based on the pain or symptoms. The topical may include capsaicin29 to deplete substance P, a pain neuro-transmitter, thereby reducing pain transmissions. The topical drugs are added to a penetrating substance to help the drug cross the skin barrier. The topicals can be applied as an adhesive patch, tray, lozenge, or as a topical with applicator. Klonopin lozenges have been used in one study to provide short term relief.47 The receptors can also be blocked by injection. Injecting lidocaine as a nerve block upstream from the damaged nerve has become standard of anesthesiology practice.48 A surprising finding occuring with neuropathic pains is that the injection can reduce the pain for hours, days, weeks, or months, long after the anesthetic has worn off. The more invasive procedures are surgical resection of nerves and blocking the sympathetic system in the head region. The sympathetic nerve blocks in the head neck region are called stellate ganglion nerve blocks and are performed by an anesthesiologist. The ganglion is in the neck region near the carotid triangle. Surgical resection of a nerve can be accomplished by chemicals, burning, and cutting. The problem with blocking transmissions by burning or cutting the nerve is that the pain can return with more severity. The surgical approach is one of the last procedures performed usually, and only, when all else fails.

Conclusion

The most important aspect of burning mouth pain management is to determine the cause of the pain. By directing the treatment to the cause, we improve the success of the treatment, but most importantly reduce the amount of suffering. With this syndrome, sometimes the only way to diagnosis is to provide directed treatment, starting with a conservative approach and working toward invasive, but always keeping in mind the symptoms at hand, results of testing, and professional intuition. The pain treatment is directed to locations where access to the nerve or synapse is possible; at the receptor, nerve trunk, spinal cord, sympathetic system, and the pain inhibitory system. By ruling out conflicting diagnostic possibilities and ruling in the nerve system pathology, it is possible to manage the burning pain successfully. The sympathetic system may be managed long term by behavioral management, habit reversal training, or even counseling.49 The management is hopefully short term, but the level and chronicity of the pain, skill of the pain physician, and patient compliance all contribute to the battle against refractory pain. The level of commitment and effort by the patient goes a long way to developing a successful outcome. The management of chronic pain is an art based on a science, so the pain physician must relate assurances not guarantees and, in the meantime, offer the hardest working, knowledgeable, and caring team.

The burning mouth syndrome implies a collection of confusing pathologies that exhibit burning pain in the mouth. The BMS may be periphery to central, episodic or continuous, specific or variable location, superficial or deep, single or multiple pathologies, single or variety of insults, intense or mild, classic or varied symptoms having sudden or gradual onset. BMS presents a confusing array of pathologies that require investigative skill, tenacity, patience, and an empathetic nature to delineate all possible pieces of data, develop a differential and a “rule out-rule in” system, develop ways to provide more data, and follow the diagnostic tree. The diagnostic tests used are chosen based on the likelihood of a particular pathology, the cost, impact, selectivity of data collected, invasiveness of the test, the intuition of the diagnostician, and other factors.

Last updated on: February 26, 2013
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