Trigeminal neuralgia

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Diagnosis rests on a highly specific clinical pattern rather than a single test. The patient describes repeated, stereotyped bolts of pain within the trigeminal territory, commonly V2 or V3, precipitated by an otherwise harmless action. Each attack is brief, although volleys can recur over minutes and severe periods can dominate the day. A short refractory interval after a trigger may occur. Autonomic features can be mild, but striking ipsilateral tearing or agitation with longer attacks suggests a trigeminal autonomic cephalalgia instead.

Classification influences counselling. Classical trigeminal neuralgia requires neurovascular compression with nerve-root morphological change; idiopathic disease has no demonstrated cause; secondary disease is attributable to pathology such as multiple sclerosis plaque or a cerebellopontine-angle lesion. MRI is therefore more than a search for a touching vessel, because vessel contact is common in asymptomatic people. Imaging must be interpreted against the clinical phenotype and by teams experienced in high-resolution trigeminal sequences.

Treatment combines prompt relief with longitudinal planning. Carbamazepine can be transformative but has clinically important haematological, hepatic, dermatological, electrolyte and interaction risks. Dose selection follows BNF, renal or hepatic context and local prescribing responsibility. Remissions may permit cautious dose reduction; abrupt withdrawal risks rebound pain and, in susceptible people, seizures. When medicine is ineffective, not tolerated or unacceptable, referral should occur before repeated dental procedures or escalating sedatives cause avoidable harm.

Key points

Trigeminal neuralgia causes recurrent unilateral electric-shock, stabbing or shooting pain in one or more trigeminal divisions, most often maxillary or mandibular, lasting a fraction of a second to about two minutes.
Innocuous triggers such as light touch, talking, chewing, tooth brushing, shaving or a breeze are characteristic; patients may identify a small trigger zone and pause during attacks.
Classical disease is associated with neurovascular compression that produces morphological change of the trigeminal root; secondary disease arises from multiple sclerosis, tumour or another structural lesion.
A normal examination is usual in classical disease. Objective sensory loss, bilateral symptoms, prominent hearing change or another cranial-nerve sign increases concern for a secondary cause.
Persistent aching can coexist between paroxysms, but continuous pain without brief triggered shocks should prompt reconsideration of dental, temporomandibular, neuropathic or trigeminal-autonomic diagnoses.
MRI of the brain and trigeminal pathways is indicated through specialist pathways, especially in younger people, atypical presentations, sensory signs or when an intervention is being considered.
Carbamazepine is the standard initial medicine in UK guidance; introduce and titrate it deliberately, checking interactions, pregnancy potential, baseline blood count, liver tests, sodium and relevant ancestry-related genetic risk.
Oxcarbazepine is commonly used by specialists when carbamazepine is ineffective or poorly tolerated, but hyponatraemia and off-label or local formulary status require explicit review.
Opioids and ordinary analgesics rarely control the momentary discharges and can add harm; early expert help is preferable during severe flares that prevent oral intake.
Microvascular decompression offers durable relief when neurovascular compression is suitable and the person accepts craniotomy; ablative procedures and stereotactic radiosurgery trade different onset, recurrence and sensory-loss risks.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Classical neurovascular compression

An arterial or venous loop can compress the trigeminal root and produce morphological change at the brainstem entry zone.

Idiopathic trigeminal neuralgia

A typical syndrome may occur without demonstrable neurovascular compression or another structural cause on specialist imaging.

Secondary demyelinating disease

Multiple sclerosis can create a symptomatic plaque within trigeminal pathways, especially in younger people or bilateral disease.

Tumour and structural lesions

Cerebellopontine, skull-base and other lesions can compress or infiltrate the nerve and often add sensory or cranial-nerve abnormalities.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Focal root demyelination
Pulsatile compression or inflammatory disease strips myelin from adjacent trigeminal axons near the root entry zone.
2
Ephaptic cross-excitation
Ordinary touch signals abnormally activate neighbouring pain fibres across demyelinated segments, converting innocuous stimuli into electric shocks.
3
Paroxysmal brainstem discharge
Hyperexcitable trigeminal circuits generate brief, stereotyped discharges with an inhibitory refractory interval after each painful attack.
4
Central sensitisation
Repeated attacks can create persistent background ache and broaden triggers despite the continued paroxysmal core syndrome.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Paroxysmal quality

Brief unilateral electric, shooting or stabbing discharges begin and end abruptly, remaining within one or more divisions of the trigeminal nerve.

Harmless trigger

Speaking, chewing, brushing teeth, washing the face or a light breeze reliably precipitates attacks and may produce visible behavioural freezing.

Classical distribution

V2 and V3 are affected more often than V1; pain does not usually cross the midline, although separate bilateral disease can occur, particularly with multiple sclerosis.

Secondary warning pattern

Age under about 40, bilateral attacks, sensory deficit, deafness or other neurological signs make multiple sclerosis or a structural lesion more likely.

Severe flareRed flag

Repeated triggers can make swallowing, drinking and oral hygiene impossible, causing dehydration, weight loss and psychological crisis despite a normal examination.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Structured pain historyFirst step
Why
Test the syndrome against recognised diagnostic features and common mimics.
Interpretation and limitations
Record duration of each paroxysm, divisions involved, trigger zones, refractory interval, pain between attacks, autonomic symptoms and previous dental treatment.
02
Cranial-nerve and oral examination
Why
Identify sensory loss, another neuropathy or a local dental or mucosal source.
Interpretation and limitations
Map light touch and pinprick across V1 to V3, corneal responses where appropriate, muscles of mastication and other cranial nerves; objective asymmetry prompts secondary-cause evaluation.
03
MRI brain with trigeminal sequences
Why
Detect multiple sclerosis, mass lesions and surgically relevant neurovascular compression.
Interpretation and limitations
A vessel merely contacting the nerve is not sufficient for classical classification; root displacement, atrophy or indentation and phenotype concordance matter.
04
Baseline full blood count and liver tests
Why
Provide a safety baseline before carbamazepine and investigate later toxicity.
Interpretation and limitations
Pre-existing marrow or hepatic abnormality changes prescribing; fever, sore throat, mouth ulcers, bruising or jaundice during treatment requires urgent clinical and laboratory review.
05
Serum sodium, urea and electrolytes
Why
Establish electrolyte and renal context before sodium-channel-blocking treatment.
Interpretation and limitations
Older age, diuretics and oxcarbazepine increase hyponatraemia risk; confusion, falls or seizure during therapy should trigger an urgent sodium check.
06
HLA-B*1502 assessment where relevant
Why
Reduce severe cutaneous-reaction risk in susceptible ancestry groups before carbamazepine.
Interpretation and limitations
Follow BNF and MHRA ethnicity-specific advice; genetic testing does not replace counselling to stop and seek help for a new blistering or mucosal rash.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Dental or temporomandibular pain

Local tooth pathology, chewing tenderness and longer aching pain support dental or joint disease rather than brief cutaneous-triggered shocks.

Trigeminal autonomic cephalalgia

Prominent tearing, nasal symptoms, restlessness and syndrome-specific duration favour a TAC, though short attacks may overlap.

Post-herpetic or painful trigeminal neuropathy

Continuous burning, sensory loss and a zoster, trauma or procedure history support neuropathy rather than classical neuralgia.

Giant-cell arteritis or acute glaucoma

Jaw claudication, visual symptoms, scalp tenderness or a red painful eye indicate time-critical inflammatory or ocular disease.

Additional chapter-specific clues

Alternative facial pain

Hours of burning pain, dental thermal sensitivity, jaw-joint provocation, rash, marked cranial autonomic activation or temporal tenderness points away from straightforward trigeminal neuralgia.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Clinical diagnosisConfirm phenotype and exclude urgencyFirst stepA patient reports recurrent unilateral episodes of severe facial pain.

1Characterise each attack's quality, duration, distribution and triggers, then ask about rash, vision, dental symptoms, jaw pain, temporal tenderness and cranial autonomic features.
2EscalationExamine oral structures, temporomandibular joints, trigeminal sensation and the remaining cranial nerves, escalating infection, ocular disease, vasculitis or neurological deficit appropriately.
3Make a working clinical diagnosis when brief shock-like triggered attacks fit, but arrange imaging or specialist review rather than using medicine response as proof.

02Initial medicineIntroduce carbamazepine safelyThe syndrome is convincing and immediate symptom prevention is required.

1Review pregnancy possibility, blood count, liver function, sodium, interactions, driving and ancestry-related genetic precautions before selecting the BNF-consistent starting regimen.
2Start low and increase gradually according to pain, tolerability and local guidance, explaining that scheduled dosing prevents attacks whereas as-needed ordinary analgesia is usually ineffective.
3Provide written toxicity advice and early review, with urgent cessation and assessment for serious rash, mucosal lesions, marrow symptoms, jaundice or severe neurological adverse effects.

03Poor controlEscalate refractory or intolerant diseaseFirst lineEscalationAdequately titrated first-line therapy fails, toxicity occurs or nutrition is threatened.

1Check diagnosis, adherence, interactions and whether a continuous pain syndrome or dental pathology has been misclassified before simply increasing the dose.
2Seek neurology or specialist facial-pain advice about oxcarbazepine or other add-on options, making off-label status and laboratory monitoring clear.
3EscalationUse urgent hospital or specialist pathways when attacks prevent fluids, oral medicines or sleep, avoiding reflex opioid escalation that does not target the mechanism.

04Definitive procedureChoose a neurosurgical strategyDefinitivePain remains disabling or long-term medicine is ineffective, unsafe or unwanted.

1Obtain high-resolution imaging and discuss whether classical neurovascular compression makes microvascular decompression an anatomically appropriate option.
2Compare craniotomy and durable pain relief with radiosurgery or percutaneous lesioning, whose latency, recurrence, facial numbness, corneal injury and anaesthesia-dolorosa risks differ.
3Record the person's priorities and arrange long-term follow-up because recurrence, sensory change and medication reduction need active supervision after intervention.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

First-line preventive treatment for the characteristic paroxysms of trigeminal neuralgia.

Carbamazepine

A common oral introduction is 100 mg once or twice daily with gradual increments; use the current BNF regimen, lowest effective dose and individualised maximum rather than a fixed template.

Check interactions, blood count, liver function and sodium; counsel about dizziness, ataxia, teratogenicity, reduced hormonal-contraceptive effectiveness, blood dyscrasia and serious cutaneous reactions including ancestry-related HLA-B*1502 risk.

An alternative sodium-channel blocker when carbamazepine is poorly tolerated or ineffective.

Oxcarbazepine

Specialists often begin a low divided oral dose and titrate against attacks; exact use follows the local formulary because trigeminal-neuralgia prescribing may be off label.

Hyponatraemia can be prominent and cross-sensitivity with carbamazepine rash is possible; review sodium, renal context, interactions, pregnancy considerations and shared-care responsibility.

May be considered as specialist adjunctive therapy in refractory disease rather than routine first-line treatment.

Lamotrigine

Use only on specialist advice with the slow current BNF titration schedule, especially when interacting enzyme-inducing medicines alter exposure.

Rapid escalation increases serious rash risk; stop and assess rash or mucosal illness, review pregnancy and interactions, and do not use an accelerated schedule for an acute flare.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Malnutrition and dehydration

Fear of chewing, swallowing or facial contact can prevent eating, drinking, oral hygiene and medicine use during severe flares.

Chronic pain and depression

Unpredictable shocks and anticipatory fear impair sleep, work, mood and social contact and can create self-harm risk.

Medicine toxicity

Sodium-channel medicines can cause sedation, imbalance, hyponatraemia, blood or liver abnormalities and important interactions during treatment.

Procedure-related sensory injury

Ablative or surgical procedures may cause facial numbness, corneal injury, dysaesthesia, anaesthesia dolorosa, hearing or cranial complications.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Review attack frequency, trigger burden, eating and drinking, sleep and ability to perform oral care rather than recording pain intensity alone.
During titration assess drowsiness, diplopia, gait, falls and driving safety, especially in older people and those taking other sedating medicines.
Repeat full blood count, liver tests and sodium when clinically indicated and according to BNF or local shared-care policy; investigate toxicity symptoms immediately.
Reconcile every new medicine for enzyme-induction interactions, including anticoagulants, contraception, antiseizure treatment and immunosuppressants.
At remission, seek prescribing advice before slow reduction; abrupt changes can provoke recurrent severe pain and create avoidable adverse effects.
After a procedure document sensory examination, corneal symptoms, pain recurrence and medication plan, with rapid ophthalmic review if corneal sensation is compromised.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Triggering outweighs severity

Many disorders cause severe facial pain, but a harmless light stimulus reliably precipitating a seconds-long electric discharge is particularly discriminating.

Vessel contact is common

MRI contact alone does not establish classical disease; morphological nerve-root change and concordance with the painful side strengthen causal interpretation.

Young age shifts probability

Trigeminal neuralgia in a younger adult is unusual enough to intensify the search for multiple sclerosis or another secondary lesion.

Dental harm is preventable

Triggering by chewing can misdirect care toward extraction, but the absence of local dental findings and presence of cutaneous triggers should halt irreversible procedures.

Procedure choices are not equivalent

Microvascular decompression preserves nerve function but requires craniotomy, while destructive techniques avoid open surgery at the price of more sensory disturbance.

11Common pitfallsFrequent interpretation and management errors.

01
Calling any severe facial pain trigeminal neuralgia without documenting duration and triggers.
02
Using response to carbamazepine as the sole diagnostic test.
03
Ignoring sensory loss or bilateral disease that suggests secondary pathology.
04
Prescribing carbamazepine without interaction, pregnancy and laboratory review.
05
Escalating opioids for millisecond paroxysms instead of preventive treatment.
06
Allowing repeated irreversible dental treatment despite a neuropathic phenotype.
07
Waiting until repeated medicine toxicity before discussing procedural options.