Burning mouth syndrome

Author: Dr Delwyn Dyall-Smith FACD, Dermatologist, 2010.

What is burning mouth syndrome?

Burning mouth syndrome is a chronic pain syndrome strictly defined as a burning painful sensation in the mouth (oral dysaesthesia) with normal clinical examination and no obvious organic cause. It is therefore a diagnosis made only after excluding recognised organic causes of mouth pain.

It is currently thought to be neurological in origin, and not psychogenic as previously believed. Many other names have been given to this condition including orodynia (burning mouth) and glossodynia (burning tongue).

Who gets burning mouth syndrome?

Burning mouth syndrome is seen predominantly, but not exclusively, in peri- and post-menopausal women. Males can be affected. The incidence increases with advancing age. It is rarely seen before the age of 30 years. No racial or ethnic differences have been reported. It probably affects approximately 1% of the general population, rising as high as 30% in selected populations such as post-menopausal women.

Burning mouth syndrome may be associated with personality or mood disturbances, particularly anxiety and depression. It is not clear if these are due to the mouth symptoms or if they contribute to the development of the problem. Tooth grinding, tongue thrusting and jaw clenching are also commonly associated and may only be identified by asking family members.

Clinical features: history and symptoms

A careful history is important, as underlying organic causes must be searched for and excluded to make this diagnosis. Questions should cover the following points.

The three key symptoms of burning mouth syndrome are:

  1. Oral pain
  2. Abnormal taste
  3. Dry mouth feeling
Oral pain Oral pain is the major symptom and is most commonly described as a burning sensation in the mouth like a scald from a hot drink, or as tingling or numbness. The tongue is the most common site involved, followed by the inside of the lower lip and the hard palate. The pain rarely causes awakening from sleep.
Three patterns of oral pain have been identified:
  • Type 1: pain absent on waking and developing during the day
  • Type 2: pain present day and night
  • Type 3: intermittent pain, with pain-free days
Abnormal taste Abnormal taste (dysgeusia, parageusia) is either a metallic or bitter taste in the mouth or altered perception of taste particularly of salty or sweet/sour foods.
Dry mouth feeling Although the patient may perceive a dryness of the mouth, reduced saliva production is not confirmed on testing.
Symptoms of burning mouth

In burning mouth syndrome, symptoms persist for many months and often years. Not everyone with this condition describes all three key symptoms and the absence of any of these does not exclude the diagnosis.

Many other symptoms may also be described and may include:

Clinical features: examination

A thorough clinical examination should be performed, including of the oral cavity where local organic causes, such as oral candidiasis (thrush) and oral cancer, must be excluded. The top of the tongue should have a complex architecture (i.e. it should not be smooth as is seen in anaemia). All surfaces in the mouth should be checked for ulceration which may represent a spectrum of causes from trauma, idiopathic recurrent aphthous stomatitis, autoimmune diseases such as pemphigus to oral cancer.

Examination of the skin and nails should look for systemic causes of oral pain including nutritional deficiences, lichen planus and hormonal disturbance (e.g. diabetes mellitus, thyroid disease).

The oral mucosa looks normal in burning mouth syndrome. Clues may be noted on examination that may help to confirm the diagnosis.

How is it diagnosed?

Burning mouth syndrome is a diagnosis of exclusion, therefore history taking, clinical examination and tests are aimed at finding an organic explanation for the symptoms.

Tests may be required based on the findings of history and examination. However in burning mouth syndrome these are all normal/negative.

Investigations may include:

Treatment of burning mouth syndrome

In a small number of patients (3%) the condition resolves spontaneously. Over 6-7 years, half to two thirds of patients experience some improvement. There is no definitive cure.

A list of symptoms and signs of burning mouth syndrome may help the patient accept the diagnosis as this is an important step in order to make progress. For some, recognition and explanation only is required.

However for many, the condition is disabling and active treatment is required. Realistic expectations of response to treatment are important. Often the first sign of response is an improvement in the altered taste. However improvement is unpredictable – it may be incomplete and slow, taking several years for some. The feeling of dryness (xerostomia) is often resistant to therapy. Referral to a specialist multidisciplinary oral medicine unit may offer the best chance at mid- to long-term relief.

Few studies have been conducted on treatment and only cognitive behaviour therapy, topical clonazepam, oral capsaicin and alpha lipoic acid (+/- cognitive behaviour therapy) have been shown to have a positive impact in properly conducted trials. Oral capsaicin however caused significant abdominal pain that may outweigh any benefit. Cognitive behaviour therapy may exert its effect through better pain-coping mechanisms.

Placebo-controlled studies have failed to show any benefit using topical steroids, benzydamine hydrochloride oral rinses or trazodone (serotoninergic antidepressant), the latter causing most patients to withdraw from the trial due to side effects, in particular dizziness.

Reported treatments include:

These treatments may be used alone or in combination, particularly with cognitive behaviour therapy.

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