Trigeminal Neuralgia (โรคปวดเส้นประสาทไตรเจมินัล)

• ICD10:
  • G50.0 Trigeminal neuralgia
  • G50.1 Atypical facial pain
  • G50.8 Other disorders of trigeminal nerve
  • G50.9 Trigeminal disorder, unspecified
• ICD11:
  • 8A84 Trigeminal neuralgia
  • 8A84.0 Classical trigeminal neuralgia
  • 8A84.1 Secondary trigeminal neuralgia
  • 8A84.Y Other specified trigeminal neuralgia

Overview

Trigeminal Neuralgia (TN) is a chronic pain disorder that affects the fifth cranial nerve (trigeminal nerve), responsible for sensation in the face and motor functions such as biting and chewing. It presents as recurrent, paroxysmal episodes of intense, electric shock-like pain lasting from a fraction of a second to two minutes. Episodes may occur in clusters, separated by pain-free intervals.

The condition can be classified into two main types: Classical TN, caused by vascular compression at the nerve root entry zone, and Secondary TN, associated with underlying structural or demyelinating lesions (e.g., multiple sclerosis, tumours). Patients often experience severe psychological distress and impaired quality of life due to the unpredictability and intensity of pain.

Management involves both pharmacologic and surgical options, with antiepileptic agents as first-line therapy and microvascular decompression as the preferred surgical treatment when indicated.

Epidemiology

Trigeminal neuralgia has an annual incidence of approximately 4–13 cases per 100,000 people. It is more prevalent in females (female-to-male ratio of about 2:1) and most commonly affects individuals aged over 50 years. The right side of the face is more commonly affected than the left, and bilateral involvement is rare (<2%).

Primary (classical) TN accounts for about 80–90% of cases, whereas secondary TN, due to structural or demyelinating lesions, represents 10–20%. Among younger patients (<40 years), multiple sclerosis should always be considered as a possible cause.

Genetic predisposition is rare, but vascular risk factors such as hypertension and atherosclerosis have been associated with increased likelihood of neurovascular compression. Patients frequently report a progressive course, where initial paroxysmal attacks may evolve into more constant or lingering pain phases over time.

Pathophysiology

Clinical Presentation

Trigeminal Neuralgia (TN) is characterised by brief, recurrent episodes of severe, unilateral, stabbing, or electric shock-like facial pain. The pain typically affects the distribution of one or more branches of the trigeminal nerve — most often the maxillary (V2) and mandibular (V3) divisions — and never crosses the midline. Each episode lasts from a fraction of a second to two minutes, with pain-free intervals between attacks. The pain may occur spontaneously or be triggered by innocuous stimuli such as touching the face, talking, eating, or exposure to cold wind.

Patients frequently identify trigger zones — small, highly sensitive areas on the face or inside the mouth where light stimulation immediately provokes pain. These stimuli activate cross-talk between sensory fibres, leading to an abnormal response of sharp, electric-like pain. As the disease progresses, attacks may become more frequent and can evolve into a background of persistent dull pain between paroxysms.

During attacks, patients often freeze or grimace, a reaction known as “tic douloureux”. Many avoid touching the affected area or chewing on that side. Autonomic features such as tearing, facial flushing, or conjunctival redness may occur transiently during attacks, but they are milder than in cluster headache. Between attacks, neurological examination is typically normal in classical TN.

Physical examination plays an essential role in ruling out secondary TN due to demyelination, tumour, or structural compression. Abnormal findings such as sensory loss, reduced corneal reflex, or exaggerated jaw jerk reflex suggest central nervous system involvement and warrant neuroimaging. In contrast, classical TN presents with a normal neurological examination, preserved corneal reflex, and absence of sensory deficits.

Sign & Symptom	Pathogenesis / Mechanism	Frequency	Specificity
Electric shock-like facial pain	Ectopic discharges in demyelinated trigeminal fibres	++++	++++
Trigger zones (face/oral mucosa)	Cross-activation between Aβ and nociceptive fibres	++++	++++
Pain provoked by talking, chewing, or touching face	Abnormal ephaptic transmission within sensory fibres	++++	+++
“Tic douloureux” (pain grimace)	Facial muscle contraction response to severe paroxysmal pain	+++	+++
Absent corneal reflex (rule out)	Demyelination or brainstem lesion involving V1	+	++++ (suggests secondary TN)
Abnormal jaw jerk reflex (rule out)	Pyramidal tract involvement in central lesion	+	++++ (indicates central pathology)
Sensory loss or hypoesthesia (rule out)	Trigeminal root compression or demyelinating plaque	+	++++ (secondary TN)

In summary, TN presents as paroxysmal, unilateral, lancinating pain confined to trigeminal distribution, often triggered by minimal stimulation. Normal examination supports classical TN, whereas sensory deficits or abnormal reflexes indicate a secondary cause requiring further investigation.

Investigation

The diagnosis of Trigeminal Neuralgia (TN) is mainly clinical, but investigations are essential to confirm neurovascular compression and exclude secondary causes such as multiple sclerosis or tumours. High-resolution MRI with MR angiography (MRA) is the preferred imaging modality to visualise vascular compression at the trigeminal root entry zone. Neurophysiologic testing and a thorough neurological examination further support diagnosis.

Diagnosis Criteria (Dx)

According to ICHD-3 (International Classification of Headache Disorders, 3rd edition), the diagnostic criteria for Trigeminal Neuralgia are:

• Recurrent paroxysms of unilateral facial pain in the distribution of one or more divisions of the trigeminal nerve, with no radiation beyond.
• Pain has at least three of the following characteristics:
  • Recurring in paroxysms lasting from a fraction of a second to two minutes.
  • Severe intensity.
  • Electric shock-like, shooting, stabbing, or sharp in quality.
  • Precipitated by innocuous stimuli to the affected side (trigger zones).
• No clinically evident neurological deficit.
• Not better accounted for by another diagnosis.

Differential Diagnosis (DDx)

Disease	Distinguishing Features	Diagnostic Clues
Atypical Facial Pain	Constant, dull, poorly localised pain without trigger zones.	No paroxysmal attacks; unresponsive to carbamazepine.
Cluster Headache	Severe orbital pain with autonomic symptoms (tearing, rhinorrhoea).	Longer attacks (15–180 min), male predominance.
Postherpetic Neuralgia	History of herpes zoster infection, persistent burning pain.	Presence of skin lesions or scarring in trigeminal distribution.
Dental Pain / Sinusitis	Local tenderness, swelling, prolonged dull pain.	Confirmed by dental or sinus imaging; no trigger zones.
Multiple Sclerosis-related TN	Occurs in younger patients; bilateral in some cases.	Brain MRI shows demyelinating plaques at trigeminal root entry zone.

Treatment

The management of Trigeminal Neuralgia (TN) aims to relieve paroxysmal facial pain, prevent recurrence, and improve quality of life. Treatment is typically initiated with pharmacological therapy, and surgical intervention is reserved for drug-resistant or intolerant cases. A multidisciplinary approach, combining medical management, psychological support, and patient education, is essential.

First-line therapy involves the use of sodium channel-blocking anticonvulsants, primarily carbamazepine and oxcarbazepine. Carbamazepine remains the gold standard and provides effective pain control in 70–80% of patients. Oxcarbazepine is better tolerated, with fewer drug interactions. When first-line agents fail or are not tolerated, adjunctive options include lamotrigine, baclofen, and gabapentin.

In refractory cases, microvascular decompression (MVD) offers the highest long-term success rate by relieving vascular compression at the trigeminal root. Other interventional options include percutaneous rhizotomy (radiofrequency, glycerol, or balloon compression) and stereotactic radiosurgery (Gamma Knife). These techniques are particularly useful for patients unable to undergo open surgery. Adjunctive therapies such as physiotherapy and cognitive behavioural therapy (CBT) may support chronic pain adaptation. Early diagnosis and individualised treatment planning remain crucial for optimal outcomes.

Pharmacology

Pharmacologic therapy is the cornerstone of trigeminal neuralgia management. Drugs act by stabilising neuronal membranes and reducing ectopic impulse generation in the trigeminal root entry zone. The table below summarises the major drug classes, mechanisms, and clinical considerations.

Drug Class	Example	Mechanism of Action	Clinical Notes
Sodium Channel Blocker	Carbamazepine	Inhibits voltage-gated sodium channels, reducing neuronal hyperexcitability	First-line drug; start at 100 mg BID; monitor CBC and LFT for toxicity
Sodium Channel Blocker	Oxcarbazepine	Similar mechanism; fewer hepatic enzyme interactions	Alternative for patients intolerant to carbamazepine
GABA Agonist	Baclofen	Activates GABAB receptors, inhibiting synaptic transmission	Useful as adjunct in partial responders; may cause sedation
Calcium Channel Modulator	Gabapentin / Pregabalin	Reduces excitatory neurotransmitter release via α2-δ subunit binding	Effective for chronic or atypical TN; well tolerated
Sodium Channel Modulator	Lamotrigine	Inhibits presynaptic glutamate release and stabilises neuronal membranes	Second-line; requires gradual titration to avoid rash

Therapeutic drug monitoring is essential with carbamazepine to prevent hyponatraemia, bone marrow suppression, or hepatic enzyme induction. Combining low doses of two antiepileptic agents can enhance efficacy with reduced side effects. In elderly patients or those with comorbidities, cautious dose titration and regular lab monitoring are mandatory. Pain recurrence after prolonged remission may respond to reintroduction of the previous effective dose.

Guideline

International guidelines, including the European Federation of Neurological Societies (EFNS) and the American Academy of Neurology (AAN), recommend a stepwise approach to TN management. The following summarises evidence-based practice for both pharmacologic and surgical care.

Step 1: Initial Medical Management

• Carbamazepine (100–1200 mg/day) or Oxcarbazepine (300–1800 mg/day) is the first-line treatment.
• If partial response: add Baclofen or Lamotrigine.
• Monitor for side effects: dizziness, hyponatraemia, hepatic dysfunction.

Step 2: Alternative or Adjunctive Therapy

• Gabapentin or Pregabalin may be used for refractory or continuous pain.
• Short courses of corticosteroids may help acute flares but are not for long-term use.
• Pain management referral for chronic or psychosomatic overlay.

Step 3: Interventional and Surgical Management

• Microvascular Decompression (MVD): Relieves vascular compression; long-term relief in 80–90% of patients.
• Percutaneous Rhizotomy: Radiofrequency, glycerol, or balloon compression for high-risk surgical patients.
• Gamma Knife Radiosurgery: Non-invasive, effective within weeks; suitable for elderly or poor surgical candidates.

Step 4: Long-term Management

• Gradual dose tapering after ≥6 months pain-free.
• Psychological and physical therapy for chronic pain adaptation.
• Regular follow-up for side effect surveillance and recurrence monitoring.

Example Doctor’s Orders

Disclaimer: Example for educational purposes only, not for direct patient advice.

Prognosis

With appropriate treatment, most patients achieve significant pain relief. Approximately 70–80% respond to carbamazepine or oxcarbazepine during initial therapy. However, spontaneous remissions and relapses are common, and up to 30% of patients develop medication intolerance or refractory pain. Long-term outcomes are best in those undergoing microvascular decompression (MVD), where over 80% achieve sustained remission for more than five years.

Predictors of poor prognosis include bilateral symptoms, sensory deficits, and underlying multiple sclerosis. Patients with secondary TN have higher recurrence rates and require multimodal management. Psychological distress, anxiety, and sleep disturbance often accompany chronic TN, necessitating supportive care. Early diagnosis and adherence to therapy improve quality of life and reduce recurrence.

Prevention

• Identify and avoid known trigger activities such as cold exposure, shaving, or vigorous brushing.
• Manage vascular risk factors (e.g., hypertension, atherosclerosis) to reduce neurovascular conflict.
• Regular dental and ENT evaluations to exclude secondary causes.
• Maintain compliance with pharmacotherapy and follow-up imaging when indicated.

Conclusion

Quiz (USMLE OSCE)

Frequently Asked Questions (FAQ)

Why is carbamazepine considered the first-line therapy?

It effectively suppresses paroxysmal discharges by stabilising sodium channels and has the most robust clinical evidence for efficacy.

Can trigeminal neuralgia be cured permanently?

Classical TN due to vascular compression may be cured by microvascular decompression, while secondary TN requires long-term control of the underlying cause.

Is surgery safe for elderly patients?

Yes, minimally invasive options like Gamma Knife radiosurgery are safe and effective for older or medically unfit patients.

What differentiates TN from atypical facial pain?

TN has sharp, brief, trigger-induced pain, whereas atypical facial pain is constant, dull, and lacks trigger zones.

Can stress or cold weather trigger attacks?

Yes, both physical and emotional stressors, including cold exposure, can precipitate episodes in susceptible individuals.