10.4 Orofacial Pain & Neuropathic Disorders
Key Takeaways
- Trigeminal neuralgia is paroxysmal, unilateral, brief (seconds) lancinating electric-shock pain in the V2/V3 distribution with trigger zones; first-line treatment is carbamazepine, refractory cases go to microvascular decompression or gamma knife
- Burning mouth syndrome is bilateral continuous burning of the tongue with no clinical signs, typically in post-menopausal women and associated with anxiety and depression; best-evidenced treatments are topical clonazepam, alpha-lipoic acid, and cognitive behavioural therapy
- Glossopharyngeal neuralgia mimics trigeminal neuralgia but affects the posterior tongue and throat and is triggered by swallowing; management is the same — carbamazepine first-line
- Post-herpetic neuralgia follows shingles in the V1 distribution and is prevented by early antiviral treatment and the shingles vaccine; myofascial pain/TMD pain is musculoskeletal and differs in quality from neuropathic pain
- Distinguishing odontogenic from non-odontogenic pain is the critical first step: odontogenic pain is provoked by hot/cold/chewing and localised to a tooth, whereas neuropathic pain is spontaneous, paroxysmal or continuous, and not provoked by dental stimuli
Trigeminal Neuralgia (TN)
Trigeminal neuralgia is the classic neuropathic facial pain. The International Headache Society defines it as unilateral, paroxysmal, brief (a few seconds to two minutes), electric-shock or lancinating pain in the distribution of one or more divisions of the trigeminal nerve, typically V2 and V3 (V1 less often).
Diagnostic features
- Paroxysmal — sudden onset, rapid cessation, seconds in duration
- Unilateral and follows a single division (does not cross the midline)
- Trigger zones — light touch to the cheek, lip, or gum (washing, shaving, eating, cold wind) provokes pain
- Refractory period after each paroxysm
- No neurological deficit between attacks (if deficit present, suspect multiple sclerosis or a space-occupying lesion — image with MRI)
Pathophysiology and management
Most classic TN is caused by neurovascular compression of the trigeminal nerve root at the cerebellopontine angle, typically by the superior cerebellar artery loop. MRI excludes secondary causes (MS, tumour, acoustic neuroma).
| Step | Treatment |
|---|---|
| First-line | Carbamazepine (start low, titrate to response; ~70% respond) |
| Second-line drugs | Oxcarbazepine, gabapentin, pregabalin, baclofen |
| Refractory / intolerant | Microvascular decompression (posterior fossa, moves the artery off the nerve) or gamma knife stereotactic radiosurgery |
Burning, continuous pain alongside paroxysmal attacks suggests TN with concomitant continuous pain, which is harder to treat.
Glossopharyngeal Neuralgia
Same paroxysmal quality as TN but in the posterior tongue, throat, and ear, triggered by swallowing or coughing. Diagnosis is clinical plus MRI to exclude a cerebellopontine angle lesion. Carbamazepine is first-line; refractory cases go to microvascular decompression of CN IX.
Burning Mouth Syndrome (BMS)
Burning mouth syndrome is a persistent intraoral burning sensation — typically bilateral, on the anterior tongue — with no identifiable local or systemic cause and no clinical signs. It overwhelmingly affects post-menopausal women and is strongly associated with anxiety, depression, and sleep disturbance.
Diagnosis of exclusion
Exclude secondary causes first:
- Candidiasis, dry mouth, allergic contact stomatitis (dental materials, toothpaste)
- Iron, vitamin B12, folate deficiency
- Diabetes, thyroid disease
- Tongue thrusting habit
Only when these are excluded is the diagnosis primary BMS.
Management (best evidence per Cochrane)
The overall quality of evidence is very low, but the interventions with the most consistent support are:
- Reassurance and patient education — many cases improve spontaneously over months to years
- Topical clonazepam — 1 mg tablet held in the mouth for three minutes then spat out, three times daily (best short- and long-term trial evidence)
- Alpha-lipoic acid 600 mg daily for 2-4 months
- Cognitive behavioural therapy (CBT) — long-term benefit demonstrated
- Low-level laser therapy, capsaicin rinse, and gabapentin are alternatives
Note: No dedicated NHS Clinical Knowledge Summaries (CKS) topic exists for BMS. UK oral medicine practice follows Cochrane and specialist unit algorithms.
Atypical Facial Pain (Persistent Idiopathic Facial Pain)
- Continuous, poorly localised, deep facial pain that does not follow an anatomical nerve distribution
- Often described in dramatic terms; commonly associated with anxiety and depression
- All investigations (imaging, dental) are normal
- Management: tricyclic antidepressants (amitriptyline, nortriptyline) at low dose, plus psychological support; analgesics are typically unhelpful and should not be escalated
Post-Herpetic Neuralgia (PHN)
Post-herpetic neuralgia is persistent neuropathic pain in the dermatome affected by herpes zoster (shingles), lasting more than three months after the rash. In the face it follows the V1 (ophthalmic) division.
- Risk rises sharply with age (over 60 is the major risk factor)
- Prevented by early antiviral treatment of shingles (aciclovir, valaciclovir within 72 hours of rash) and by the shingles vaccine (Shingrix in the UK, offered at 65-70 years)
- Management: first-line gabapentin, pregabalin, or amitriptyline; topical lidocaine patches for focal pain
Myofascial Pain & Temporomandibular Disorder (TMD) Pain
Myofascial pain and TMD are musculoskeletal pains of the muscles of mastication and the temporomandibular joint, not neuropathic. Features:
- Dull, aching, variable pain over the pre-auricular area and masseter
- Worse with chewing, clenching, stress; morning stiffness if nocturnal bruxism
- Limited mouth opening, joint clicking or crepitus
- Management: patient education and self-management (soft diet, jaw exercises, warm compresses), occlusal splint (soft bite guard) for bruxism, analgesia, physiotherapy; reserve surgery for proven internal derangement refractory to conservative care
Odontogenic vs Non-Odontogenic Pain — The First Question
| Feature | Odontogenic | Non-odontogenic (neuropathic / musculoskeletal) |
|---|---|---|
| Trigger | Hot, cold, sweet, chewing | Light touch, swallowing, stress, spontaneous |
| Localisation | To a specific tooth | Diffuse, crosses midline, follows nerve or muscle |
| Quality | Throbbing, aching | Lancinating, electric, burning, dull deep ache |
| Duration | Hours-days, relieved by treatment | Seconds (TN), or continuous weeks-months |
| Dental tests | Vitality, percussion positive | All dental tests negative |
Misattributing TN or BMS to a tooth leads to needless extrations and endodontic treatment. Always test the suspected tooth with vitality and percussion, and consider non-odontogenic pain when dental tests are negative and the pain quality is neuropathic.
A 58-year-old woman describes 20-second episodes of electric-shock pain in her right cheek and lower jaw, triggered by washing her face, with no neurological deficit between attacks. What is the first-line pharmacological treatment?
A 62-year-old post-menopausal woman has bilateral continuous burning of the anterior tongue for four months. Examination, full blood count, ferritin, B12, folate, HbA1c, and oral swab are all normal. What is the most appropriate initial management?
A 72-year-old man developed severe, continuous burning pain across his right forehead and scalp three months after an episode of shingles affecting the same area. The pain is not relieved by paracetamol. What is the most appropriate first-line drug?
A 35-year-old reports a dull, aching pain over his left pre-auricular area and masseter that is worse on chewing and on waking, with limited mouth opening and a joint click. Hot and cold tests on all teeth are negative. What is the most likely diagnosis and first-line management?