Trigeminal neuralgia: diagnosis, management, and the AU general practice role

Trigeminal neuralgia (TN) is one of the most severe pain syndromes encountered in general practice. The characteristic paroxysmal, electric-shock facial pain — triggered by acts as ordinary as eating, speaking, or a gentle face-wash — is distinctive once encountered but is frequently misattributed to dental, sinusoidal, or migrainous pathology, delaying diagnosis by an average of several years. The Australian burden is not negligible: estimated prevalence is approximately 15–20 per 100,000, with a female predominance and peak incidence in the sixth and seventh decades. The GP’s role encompasses accurate diagnosis using ICHD-3 criteria, mandatory brain MRI at first presentation, first-line pharmacotherapy with PBS-subsidised carbamazepine, safety monitoring, and co-management with neurology and neurosurgery when medications fail.

A. Core clinical assessment

ICHD-3 diagnostic criteria for trigeminal neuralgia

The International Headache Society’s third edition criteria (ICHD-3) define trigeminal neuralgia as:

1. Paroxysmal attacks of unilateral facial pain
2. Located in one or more divisions of the trigeminal nerve — V1 (ophthalmic), V2 (maxillary), V3 (mandibular)
3. Duration of one second to two minutes per paroxysm
4. Severe intensity; electric-shock, shooting, or stabbing quality
5. Precipitated by innocuous stimuli (eating, speaking, touching the face, dental hygiene, cold air)
6. Not better accounted for by another ICHD-3 diagnosis

The ICHD-3 classification distinguishes: Classical TN (caused by neurovascular compression, confirmed on MRI), Secondary TN (due to an identifiable neurological disease such as MS, tumour, or arteriovenous malformation), and Idiopathic TN (meeting criteria but with no MRI abnormality and no neurological disease).

History — key discriminating features

A neurological deficit on examination (altered sensation in the trigeminal territory) is a red flag for secondary TN. Document: which divisions are affected (V2 and V3 are most common in classical TN; V1-only or all three divisions raises concern for secondary pathology), whether there is background aching between paroxysms (TN type 2 or alternative diagnosis), whether onset was before age 40 (bilateral onset or young onset raises suspicion for MS), and whether the patient has a known history of MS or other neurological disease.

Enquire explicitly about suicide ideation at every consultation. The pain burden in inadequately controlled TN is exceptional; the label “suicide disease” reflects historical case series, not hyperbole.

Physical examination

In classical TN, neurological examination is normal between paroxysms. A careful sensory examination of V1, V2, and V3 distributions is essential: light touch, pinprick, and corneal reflex (V1). Any objective sensory deficit — reduced light touch, altered pinprick, reduced corneal reflex — points to secondary TN or an alternative cranial neuropathy, requiring urgent neurological review. Assess for signs of MS (limb spasticity, cerebellar signs, optic atrophy).

Examine the oral cavity to assess dental, mucosal, or salivary gland pathology; chronic orofacial pain from dental sources is a common alternative diagnosis that may coexist with TN.

Mandatory MRI at every new diagnosis

The EAN 2019 guidelines and Cruccu NEJM 2020 review both state that MRI is mandatory for every new diagnosis of trigeminal neuralgia. A normal neurological examination does not exclude secondary TN. The recommended protocol is high-resolution 3T MRI with:

• 3D time-of-flight MR angiography (3D-TOF MRA) to demonstrate neurovascular contact with the trigeminal root entry zone
• 3D-FIESTA or CISS sequences (constructive interference in steady state) for detailed nerve anatomy

MRI serves three purposes: identify neurovascular compression (supporting classical TN and surgical candidacy), exclude secondary causes (MS plaques at root entry zone, vestibular schwannoma, meningioma, epidermoid cyst), and assess surgical anatomy pre-operatively.

B. Evidence appraisal — pharmacological management

Carbamazepine — first-line with NNT ~1.7

The Cochrane review by Wiffen et al. (2014) found that carbamazepine produces at least 50% pain relief in 58–63% of patients versus 26–29% with placebo, yielding an NNT of approximately 1.7 — one of the most effective NNTs in neuropathic pain pharmacology. It is PBS-listed as a general benefit for trigeminal neuralgia, meaning GPs can prescribe without Authority Required.

Practical carbamazepine prescribing:

• Start 100–200 mg twice daily; increase every 3–7 days based on response and tolerability
• Typical effective dose: 400–800 mg/day in divided doses; maximum 1,200 mg/day
• CYP3A4 auto-induction: the drug accelerates its own metabolism at 2–4 weeks, often requiring dose escalation to maintain effect — counsel patients on this in advance
• Common early adverse effects: dizziness, unsteadiness, diplopia, nausea (improve with slow titration and consistent timing with food)
• Monitor at baseline and periodically: serum sodium (SIADH-related hyponatraemia, particularly in older adults), full blood count (rare aplastic anaemia, leucopenia), liver function, serum carbamazepine level when toxicity or non-response is suspected

HLA-B*1502 testing before initiation — critical for at-risk ancestry

Carbamazepine carries a risk of Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) in carriers of the HLA-B*1502 allele. This allele is prevalent in Han Chinese, Thai, Filipino, Vietnamese, Malaysian, Cambodian, and Indian populations at frequencies of 2–8%, versus under 0.1% in European populations. Testing is available via pathology and results typically take 3–5 business days. If positive:

• Carbamazepine is contraindicated
• Oxcarbazepine carries intermediate cross-reactivity risk — use with caution and discuss with neurology
• Alternative agents (lamotrigine, baclofen, gabapentin) should be considered as bridging therapy while urgent neurology referral is arranged

Oxcarbazepine — no PBS listing for trigeminal neuralgia

Oxcarbazepine is often considered a second-line alternative to carbamazepine; the EAN 2019 guideline rates it as level A evidence. However, it is NOT PBS-listed for trigeminal neuralgia in Australia. Private script cost is approximately $30–50/month, which is affordable for most patients but should be discussed. It has a somewhat better tolerability profile than carbamazepine and does not induce its own metabolism. It is off-label for TN in Australia; document the indication.

Second-line and adjunctive agents

When carbamazepine is ineffective, not tolerated, or contraindicated, options include (largely off-label for TN):

• Lamotrigine: evidence in TN as add-on to carbamazepine; titration over 6–8 weeks required
• Baclofen: moderate evidence; useful adjunct; can reduce attack frequency
• Gabapentin and pregabalin: used empirically but limited TN-specific evidence; useful when patients have coexisting neuropathic pain syndromes

Polypharmacy increases toxicity risk and drug interaction burden; neurological review before adding a second agent is advisable.

C. Acute severe attacks and procedural options

Managing a pain crisis in general practice

Patients presenting in an acute pain crisis require compassionate, rapid response. Oral carbamazepine at existing doses may not abort an acute attack. Practical measures:

• Intravenous lidocaine infusion (in monitored settings, evidence limited but used in specialist pain units)
• Intranasal lidocaine topically to the nasal mucosa can provide brief relief in attacks involving V2
• Ketamine at subanesthetic doses — limited evidence, specialist setting only
• In-room needle-based infraorbital or mental nerve blocks by practitioners trained in procedural analgesia

Most acute crises require same-day emergency department or specialist pain unit support rather than management in general practice.

Surgical options — when to discuss

Barker et al. (NEJM 1996) reported that microvascular decompression (MVD) achieves pain freedom in approximately 70% of patients at 10 years — the highest durability of any TN treatment. MVD requires posterior fossa craniotomy and is appropriate only for:

• Patients with neurovascular compression confirmed on high-resolution MRI
• Medically fit for general anaesthesia
• Failure of adequate pharmacological trials

Stereotactic radiosurgery (Gamma Knife/CyberKnife): minimally invasive, no general anaesthesia; pain relief typically begins 4–12 weeks post-treatment; lower long-term durability (~50% pain-free at 5 years); median time to recurrence shorter than MVD. Suitable for older or medically frail patients.

Percutaneous procedures (glycerol rhizotomy, balloon compression, radiofrequency thermocoagulation): immediate relief, day-procedure; most cause predictable sensory loss in the treated division; high recurrence rates (50% by 5 years); used when MVD is declined or contraindicated.

The GP’s role is to discuss these options, provide information resources (see TNA Australia), and facilitate neurosurgical referral.

D. Australian health system operations

PBS prescribing access

Carbamazepine (PBS item 1080M and brand equivalents) is unrestricted for trigeminal neuralgia — no Authority Required. Oxcarbazepine has no PBS listing for TN and is private. Gabapentin and pregabalin are PBS-listed for neuropathic pain (Authority Required for most indications); when used for TN, document the indication and note the off-label status.

MBS items relevant to TN care

• MBS item 2715 — GP Mental Health Care Plan: recommended at diagnosis to support psychological wellbeing and formally refer to psychological therapy, given the impact of pain on mental health
• MBS long consultation items (23, 36) appropriate for complex medication titration and monitoring visits
• MBS item 110 — specialist neurological consultation; item 116 for follow-up
• MBS item 56001 or equivalent — brain MRI with gadolinium; should be ordered at first diagnosis
• Neurosurgical MBS items for MVD and percutaneous procedures: require specialist ordering

Specialist referral and co-management

Neurological assessment is strongly recommended when: diagnosis is uncertain, MRI suggests secondary TN, first-line pharmacotherapy has failed or is not tolerated, or surgical candidacy is being considered. Neurosurgical referral is appropriate when MRI confirms neurovascular compression in a medically fit patient with inadequately controlled pain. Pain management specialist input is useful in refractory cases where multimodal pharmacotherapy is needed.

NDIS and chronic pain disability support

Severe refractory TN can cause significant functional impairment and social isolation. Where activities of daily living are substantially impaired, NDIS eligibility is worth exploring. The GP can provide a supporting report documenting functional impact and treatment history. Allied health (clinical psychology, occupational therapy) can be coordinated via the GP Management Plan (MBS item 721).

E. Special populations

Trigeminal neuralgia in multiple sclerosis

Secondary TN from a demyelinating plaque at the trigeminal root entry zone occurs in 1–2% of MS patients, and 2–4% of TN patients have MS as the underlying aetiology. TN in MS tends to occur at a younger age (often before 40) and is more frequently bilateral than classical TN. Carbamazepine remains the first-line medication; however, response may be less robust. Early neurology referral is essential to optimise both TN management and disease-modifying therapy for MS.

Older adults

Older patients are at highest risk for carbamazepine-related hyponatraemia, which can present as confusion, falls, or seizure. Serum sodium monitoring is particularly important in those on diuretics, ACE inhibitors, or SSRIs (all of which may also cause SIADH). Start at the lowest effective dose and titrate slowly. If surgery is being considered, the relative risk of MVD versus stereotactic radiosurgery needs to be weighed against comorbidities.

Women of childbearing age

Carbamazepine is a Category D teratogen (neural tube defects, craniofacial malformations; it also induces failure of combined oral contraceptives by CYP3A4 induction). If a woman with TN is considering pregnancy, discussion with neurology about medication options (some prefer oxcarbazepine, though it also induces CYP450) and folic acid supplementation (high-dose 5 mg/day pre-conception and in first trimester) is essential. Document the medication discussion and contraceptive counselling.

Patients with dental pain as a differential

TN confined to V2 or V3 is frequently attributed to dental pathology; patients may undergo multiple extractions before TN is diagnosed. Once TN is diagnosed, maintain a collaborative relationship with the patient’s dentist — dental work can trigger attacks and patients may require behavioural strategies (numbing with ice, modified brushing technique) during flares. Local anaesthetic applied to the trigger zone before dental procedures may be useful.

When to escalate

Refer urgently (same day / next day) for:

• Sensory deficit on examination — secondary TN must be excluded promptly (neurology or emergency department)
• Rapid-onset bilateral pain — suspect secondary cause (MS, posterior fossa lesion)
• Suicidal ideation with plan or intent — crisis-level mental health assessment
• Acute pain crisis uncontrollable in general practice — emergency department for procedural analgesia

Refer semi-urgently (within 4 weeks) to neurology for:

• Uncertainty about diagnosis (features atypical for classical TN)
• First-line carbamazepine failed or not tolerated
• Considering oxcarbazepine, lamotrigine, or combination therapy
• Onset under age 40 or bilateral presentation

Refer to neurosurgery for:

• Medically fit patients with MRI-confirmed neurovascular compression whose pain is inadequately controlled on pharmacotherapy

If you or a patient is in distress: Lifeline 13 11 14 (24/7) · Beyond Blue 1300 22 4636 · 13YARN 13 92 76 (First Nations crisis support) · Emergency 000.

What this article is and is not

This article provides educational information to support Australian GPs in the diagnosis and management of trigeminal neuralgia. It is a clinical summary for practitioners, not a patient self-diagnosis or self-management guide. All medication decisions — including initiation, dose adjustment, and switching — must be individualised by the treating clinician in the context of the patient’s complete medical history. Surgical and procedural options require specialist assessment. When this article references pain severity or psychological risk, those statements are clinical descriptions to guide clinicians, not representations about any individual patient’s prognosis.

---

Sources cited