What is burning mouth syndrome, particularly in middle-aged to elderly women with a history of anxiety or depression?

What is Burning Mouth Syndrome?

Burning mouth syndrome (BMS) is a chronic neuropathic pain disorder characterized by a continuous burning, stinging, or itchy sensation of the oral mucosa—most commonly affecting the tongue tip bilaterally, lips, palate, and buccal mucosa—in the absence of any visible mucosal abnormalities, predominantly affecting peri- and post-menopausal women. 1, 2

Pathophysiology and Classification

BMS is now understood as a disorder of peripheral nerve fibers with central nervous system changes, confirmed through neurophysiological testing, biopsies showing significantly lower density of epithelial nerve fibers, and functional MRI findings. 2 The condition is classified into two distinct forms:

Primary (Idiopathic) BMS

• Essential neuropathic disorder where no organic local or systemic causes can be identified 2, 3
• Diagnosis is made by exclusion of all secondary causes 1, 2
• Represents a true neuropathological condition rather than a psychological disorder 2

Secondary BMS

• Caused by identifiable local, systemic, or psychological factors 3
• Treatment or elimination of causative factors typically results in significant clinical improvement 3

Clinical Presentation

Primary Symptoms

• Continuous burning sensation with severity ranging from mild to severe, most commonly bilateral on the tongue tip, lateral tongue borders, lips, palate, and buccal mucosa 1, 4
• Pain may worsen during the day, with stress and fatigue, excessive talking, or consumption of spicy/hot foods 5
• Symptoms may improve with cold food, during work, or leisure activities 5

Associated Symptoms

• Dry mouth (xerostomia) is frequently reported 1, 3
• Abnormal taste (dysgeusia) or unpleasant taste sensations 1, 3
• Depression and poor quality of life are common comorbidities 1, 6
• Unremitting oral mucosal pain 3

Demographic Profile

BMS predominantly affects middle-aged to elderly women, particularly those who are peri- or post-menopausal. 1, 2, 3 In population studies:

• Overall prevalence is approximately 3.7% 6
• Women are affected 3-4 times more frequently than men (5.5% vs 1.6%) 6
• In men, prevalence increases from 0.7% in ages 40-49 to 3.6% in the oldest age groups 6
• In women, prevalence increases from 0.6% in ages 30-39 to 12.2% in the oldest age groups 6

Secondary Causes That Must Be Excluded

Before diagnosing primary BMS, the following must be systematically ruled out:

Local Factors

• Oral candidiasis (diagnosed by scraping and KOH preparation) 2
• Traumatic lesions from sharp edges of residual tooth roots/crowns, ill-fitting dentures, thermal burns, or chemical injury 2, 4
• Dental causes and allergic reactions 5

Systemic Factors

• Nutritional deficiencies: vitamin B12, iron deficiency anemia, zinc deficiency 2, 4, 3
• Autoimmune diseases: Sjögren's syndrome, sicca syndrome 2
• Thyroid disorders, particularly hyperthyroidism 2, 4
• Endocrine disorders and connective tissue diseases 5
• Hematological disorders identified through complete blood count 2

Neurological Causes

• Post-herpetic neuralgia following herpes zoster 2, 4
• Post-traumatic trigeminal neuropathic pain developing 3-6 months after dental procedures or facial trauma 2, 4

Pharmacological

• Medication side effects from various drugs 2, 4

Other Conditions

• Scarlet fever and Kawasaki disease 2

Diagnostic Workup

Clinical Assessment

• Document onset timing, duration, character, and location specificity of pain, with particular attention to whether symptoms started after dental procedures or medical illness 2, 4
• Thorough oral examination to identify any mucosal lesions, candidiasis, or traumatic factors—the mucosa should appear completely normal in primary BMS 1, 2, 4
• Medication review to identify potential pharmacological causes 2, 4

Essential Laboratory Tests

The American College of Physicians recommends the following blood work: 4

• Complete blood count (CBC) with differential to identify anemia 2, 4
• Iron studies (ferritin, serum iron, TIBC) as iron deficiency frequently presents with burning tongue 2, 4
• Vitamin B12 levels as deficiency is a well-established cause 2, 4
• Fasting glucose and HbA1c to evaluate for diabetes 4
• Thyroid function tests (TSH, free T4) 4
• Vitamin D 25(OH) levels 4

Specialized Testing

• Qualitative sensory testing may be considered if neuropathic etiology is suspected 2
• Tongue biopsy should be considered if mucosal abnormalities are present, diagnosis is uncertain, or there is unilateral pain, ulceration, or non-healing lesions to rule out malignancy 2, 4

Psychological Associations

Anxiety disorder, hypochondriasis, conversion disorder, and especially depression are frequently associated with BMS, particularly in middle-aged to elderly women with these psychiatric histories. 7, 6 However, it remains unclear whether psychological findings are the consequence of chronic pain or its cause. 7 Patients with BMS have a relatively high percentage of past and/or present psychiatric or psychological treatment. 7 After excluding organic factors, depression should be strongly considered in elderly patients with predominant mouth complaints. 7

Subjective oral dryness, age, medication use, taste disturbances, illness, depression, and anxiety are all factors significantly associated with BMS. 6

Clinical Pitfalls

• Inadequate reassurance and failing to emphasize that the condition won't worsen is a critical error that increases patient anxiety 1
• Treatment failures are common in BMS management, and patients should be informed about the chronic nature of the condition 1
• The condition may persist for months to years, with most patients experiencing gradual onset 3, 7
• BMS should be viewed as a marker of illness and/or distress, and its complex etiology demands specialist treatment 6