Burning Mouth Syndrome

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

First published on: September 1, 2007