Burning Mouth Syndrome

Background

• Primary burning mouth syndrome (BMS) is a chronic pain disorder characterized by burning sensations in the mouth that fluctuate in intensity and recur daily for > 2 hours/day over a period of > 3 months, without a clinically evident cause.
  • It usually affects peri- or postmenopausal women, but can also affect men.
  • Often associated with taste alterations (dysgeusia) and dry mouth (xerostomia).
  • Exact cause of primary BMS is unknown and likely involves an interaction between neurophysiological mechanisms and psychological factors.
  • Primary BMS has 3 distinct, subclinical neuropathic pain subtypes that may overlap in some patients.
  • Most literature uses the term "burning mouth syndrome" to refer to primary BMS.
• Secondary BMS is caused by other conditions (such as nutritional deficiencies and endocrine disorders) or oral/dental conditions (such as a poorly fitting dentures or an inflammatory reaction to an oral appliance) that must be ruled out.

Evaluation

• Patients typically report a burning sensation in the mouth that fluctuates in intensity and is often associated with taste alterations and dry mouth.
  • The most commonly affected site is the anterior two-thirds of the tongue (tip and edges), followed by the palate, however, the lips, cheek mucosa, or entire mouth can also be affected.
  • Onset can be spontaneous (and increases gradually in intensity) or after a precipitating event which can include dental procedures, such as dental cleaning or insertion of a denture.
• No universally accepted diagnostic criteria exists for primary burning mouth syndrome (BMS).
  • International Headache Society defines BMS an intraoral burning or dysesthetic sensation that recurs daily for > 2 hours/day for more than 3 months, without clinically evident causative lesions.
  • International Association for the Study of Pain defines burning mouth syndrome as burning pain of the tongue and/or other oral mucous membrane in the absence of clinical signs or laboratory findings.
• The diagnosis is usually made clinically following exclusion of other conditions or factors contributing to burning mouth symptoms.
  • Blood tests can be used to help rule out other factors contributing to burning mouth symptoms.
  • Patients with primary BMS can be classified into the peripheral or central type of BMS to help guide treatment; testing may include:
    • neurophysiologic and quantitative sensory testing (QST) (however, about 15% of primary BMS patients reported to have no abnormalities on neurophysiologic and QST)
    • blocking the lingual nerve with a local anesthetic (lidocaine) injection
      • persistence or exacerbation of symptoms following anesthesia may indicate central BMS
      • relief of pain may indicate peripheral BMS
  • Additional testing may include:
    • cytological smears if candidiasis is suspected
    • salivary flow rates to rule out xerostomia
    • skin patch tests if an allergic reaction is suspected
    • imaging studies
      • magnetic resonance imaging studies to rule any underlying central nervous system pathology if burning mouth symptoms are associated with numbness or dysesthesia
      • thyroid gland ultrasound if macroscopic thyroid lesions are suspected

Management

• Secondary burning mouth syndrome (BMS) requires treatment of the underlying cause.
• Treatment of primary BMS is challenging, and may only provide partial relief of symptoms.
  • Initial treatment includes both cognitive behavioral therapy (CBT) and topical clonazepam 0.5-1 mg 3 times/day (up to max 3 mg/day) dissolved in the mouth for 3 minutes then spit out with remaining saliva.
  • Determine if symptoms are due to a peripheral or central mechanism to help guide treatment in patients refractory to topical clonazepam and CBT.
    • If symptoms do not improve with initial therapy and a peripheral mechanism is suspected, consider:
      • topical capsaicin in Xylocaine gel (0.025-0.075% applied 2-3 times a day)
      • saliva substitute or inductor
    • If symptoms do not improve with initial therapy and a central mechanism is suspected, consider:
      • systemic clonazepam 0.5-1.5 mg/day orally in divided doses
        • efficacy of systemic clonazepam is generally conflicting among widely variable studies
        • success of treatment possibly depends on the level of the neuropathic disturbance
      • antidepressants, such as amitriptyline 10-25 mg/day
      • gabapentin 300-900 mg/day
      • amisulpride 50 mg/day for 24 weeks
      • duloxetine 20-40 mg/day for 12 weeks
      • alpha-lipoic acid or thioctic acid 600 mg/day
• Primary and secondary BMS can co-occur, so treatment may require identification and control of local factors contributing to burning mouth symptoms, including:
  • correct irritative parafunctional habits, such as teeth clenching or forcing of the tongue against the teeth
  • polish prominent or cutting palatal and lingual cusps
  • use a plastic dental protector that avoids direct tongue irritation caused by parafunctional movements
  • advise patients to avoid any foods/habits that can trigger or exacerbate symptoms, such as
    • eating acidic foods (pineapple, tomato, orange, lemon)
    • alcohol (including mouth rinses with alcohol)
    • smoking
    • toothpaste with abrasive substances