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.
What are the clinical features or burning mouth syndrome?
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.
- Medications – some dry the mouth
- Dental care – denture hygiene
- General health especially risk of diabetes
- Skin conditions – they may affect the mouth
- Diet – iron and vitamins are required for good oral health
- Hormonal status – burning mouth may begin around the time of menopause
The three key symptoms of burning mouth syndrome are:
- Oral pain
- Abnormal taste
- Dry mouth feeling.
|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:
|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.
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:
- The complaint that dentures don't fit properly even though the dentist finds they fit well
- Aggravation or relief of symptoms with specific food items
- Bad breath (halitosis) — needs to be confirmed by questioning relatives as this can be socially incapacitating for the patient
- Difficulty swallowing (dysphagia)
- A sensation of having a lump in the throat when nothing is there
- Symptoms of jaw clenching or tooth grinding may present as headache, ear pain, pain in muscles or joints around the jaw, face and neck.
- Tongue ulcers are usually related to inflamed tongue papillae.
The examination of the mouth
A thorough clinical examination should be performed, including 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.
The oral mucosa looks normal in burning mouth syndrome. Clues may be noted on examination that may help to confirm the diagnosis.
- Worn teeth or damaged dental enamel may indicate tooth grinding and clenching
- Scalloping along the sides of the tongue caused by tongue thrusting
- Protruding teeth or malocclusion may indicate tongue thrusting
- Tender muscles around the jaw and neck due to jaw clenching
- Frothy saliva pooling in the floor of the mouth indicating excessive mucoid submandibular saliva that does not clear easily with swallowing
- Mild redness on the symptomatic areas such as the tongue, hard palate, inside lower lip near the incisors
- Exposure of the filiform papillae (taste buds) on the tongue due to traumatic abrasion on teeth
How is burning mouth syndrome 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:
- Screening for nutritional deficiencies (folate, iron, vitamin B12, zinc)
- Hormone levels (especially for thyroid and menopause), autoimmune conditions
- Blood sugar — diabetes mellitus
- Mucosal scraping for candida
- Patch tests for contact allergy
- Sialometry for saliva production
- Mucosal biopsy, but this is rarely indicated.
What is the 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.
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 causes 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:
- Other medications
- Anti-depressants, particularly tricyclics, are the most commonly used treatment and should be started in low dose as dry mouth is a common side effect e.g. amitriptyline starting with 10mg before bed, increasing slowly up to a maximum of 150mg as tolerated or required.
- Anxiolytic medications such as benzodiazepines, in low dose, can be useful for confirmation of the diagnosis as there is usually a mild perceived improvement eg clonazepam starting at 0.25mg before bed, increasing up to a maximum of 2mg as tolerated or required
- Anti-convulsants eg gabapentin starting at 100mg before bed and increasing as tolerated or required.
- Hormone replacement therapy
- Topical local anaesthetics
- Topical capsaicin
- Behaviour therapies including relaxation and exercise therapies
- Physical therapies including massage, acupuncture and laser
- Empiric treatment for known causes of mouth pain such as nystatin for candidiasis
These treatments may be used alone or in combination, particularly with cognitive behaviour therapy.