Trigeminal neuralgia (TN) is a chronic neuropathic pain condition characterized by sudden, brief episodes of severe, electric shock–like, lancinating unilateral facial pain in one or more trigeminal nerve distributions, triggered by innocuous stimuli. [1-2] It is classified as classic (neurovascular compression, ~75%), secondary (~15%, due to MS or tumor), or idiopathic (~10%). [1] Average age of onset is 50–60 years, with higher prevalence in women and increasing incidence with age. [2]
1. History
- Character of pain: Electric shock–like, shooting, stabbing, sharp — paroxysms lasting a fraction of a second to 2 minutes (usually seconds) [1][3]
- Location: Unilateral, most commonly V2 (maxillary) or V3 (mandibular); right side more common than left [1]
- Triggers: Light touch to face, talking, chewing, brushing teeth, shaving, wind/breeze across trigger zone. Trigger zones are small, discrete areas — nearly pathognomonic for TN [2][4]
- Frequency: Attacks may recur hundreds of times per day; episodes cluster over weeks to months with pain-free intervals lasting months to years [2]
- Refractory period: Some patients note a brief period after a paroxysm during which additional pain cannot be triggered [4]
- Concomitant continuous pain: A subset has mild-to-moderate background aching/throbbing between paroxysms [2-3]
- Important negatives: No numbness (suggests neuropathy), no persistent burning, no bilateral simultaneous pain, no pain outside trigeminal territory [4]
2. Alarm Features
- Bilateral pain — raises concern for MS, systemic disease, or non-neurologic cranial pathology [1]
- Sensory loss/numbness in the trigeminal distribution — suggests secondary TN (tumor, MS, neuropathy) [2-3]
- Other neurologic deficits (weakness, ataxia, visual changes) — concerning for intracranial mass or demyelinating disease [1-2]
- Young age at onset (<40 years) — higher suspicion for MS-related TN [1]
- First division (V1) involvement alone — less typical; consider alternative diagnoses [5]
- Progressive pain with no remission periods — consider malignancy or infiltrative process [1]
- Severe exacerbation with inability to eat/drink — risk of dehydration and malnutrition; may require hospitalization [3]
3. Medications
First-line:
- Carbamazepine — drug of choice; start 200 mg BID, titrate by 200 mg/day every few days to max 1,200 mg/day; NNT ~2 for meaningful pain relief; ~75% initial response rate [1-2][5]
- Oxcarbazepine — alternative first-line, 300–1,800 mg/day in divided doses; potentially fewer side effects; high cross-reactivity risk if allergic to carbamazepine [1-2][6]
Second-line / adjunctive:
- European Journal of Neurology[6]
Acute exacerbation (ED):
- IV fosphenytoin or IV lidocaine — limited evidence but clinical experience supports efficacy; requires monitored setting [3][7]
- Opioids are ineffective in safe doses and should be avoided [3]
- NSAIDs are generally ineffective for neuralgic pain [7]
- Lidocaine injection into trigger zones may provide short-term relief [3]
Contraindications/cautions for carbamazepine:
- Cardiac conduction abnormalities (AV block) [1]
- Hepatic porphyria [8]
- HLA-B</em>15:02 screening required before initiation in patients of Southeast Asian, South Asian, or other at-risk ancestry — risk of fatal SJS/TEN. HLA-A</em>31:01 also associated with hypersensitivity in European, Korean, and Japanese populations [9-10]
- Side effects: dizziness, diplopia, ataxia, hyponatremia, elevated transaminases, Stevens-Johnson syndrome, aplastic anemia (rare), osteoporosis with long-term use [1-2]
- Significant drug-drug interactions (CYP3A4 inducer) — affects oral contraceptives, warfarin, many other medications [1]
- Carbamazepine may have a 50% failure rate over 5–10 years [2]
4. Diet
- During severe exacerbations, eating and drinking can trigger attacks, leading to dehydration and malnutrition — a key reason for hospitalization [3]
- Soft, room-temperature foods may reduce trigger stimulation during flares
- No specific long-term dietary modifications are evidence-based for TN
- Patients on carbamazepine should be counseled about adequate hydration given hyponatremia risk [8]
5. Review of Systems
- Neurologic: Visual changes, diplopia, limb weakness/numbness, gait instability (screen for MS) [1]
- Ophthalmologic: Eye redness, tearing (autonomic phenomena can occur during flares) [2]
- Dental: Prior dental procedures, tooth pain, jaw pain (>80% of TN patients initially seek dental evaluation) [2]
- ENT: Ear pain, hearing changes, nasal congestion, sinus symptoms
- Psychiatric: Depression, anxiety, suicidal ideation — TN profoundly impacts quality of life [2][11]
- Constitutional: Weight loss from inability to eat during exacerbations
6. Collateral History and Family History
- Family history of TN: 1–2% of patients may have a familial link; rare variants in voltage-gated ion channel genes have been identified [1-2]
- History of MS in patient or family — TN prevalence is 2–5% in MS patients (20-fold increased risk vs. general population) [1][12]
- Collateral from dentist: Prior dental evaluations, procedures, or extractions for presumed dental pain (common misdiagnosis)
- Social context: Functional impairment, inability to work, social withdrawal due to fear of triggering pain
7. Risk Factors
- Age >50 years — incidence increases with age [2]
- Female sex — higher prevalence [1-2]
- Multiple sclerosis — strongest disease association (OR 8.9 in one population study) [1][13]
- Hypertension — associated with higher TN incidence [2]
- Other neurovascular compression disorders (glossopharyngeal neuralgia, hemifacial spasm) [13]
- Systemic lupus erythematosus — emerging association (OR 2.84) [13]
- Hyperlipidemia and complex diabetes — associated in population-level data [13]
8. Differential Diagnosis
9. Past Medical History
- Multiple sclerosis — most important associated condition [1]
- Prior dental procedures — may have caused post-traumatic trigeminal neuropathy mimicking TN [1]
- Facial trauma or maxillofacial surgery [1]
- Hypertension — associated with TN and relevant to neurovascular compression [2]
- Previous TN episodes — natural history includes remissions and relapses; prior medication trials and responses
- Autoimmune conditions (SLE, scleroderma) — can cause trigeminal neuropathy [1][13]
10. Physical Exam
- Between attacks, exam is typically normal — this is characteristic of TN [2]
- Focused cranial nerve exam: Test all three trigeminal divisions for light touch, pinprick, and temperature; test corneal reflex; assess masseter/temporalis strength
- Trigger zone testing: Light touch to perioral/perinasal area may reproduce pain (be cautious — can provoke severe paroxysm)
- Facial sensation: Any numbness or hypoesthesia is a red flag for secondary TN [2-3]
- Other cranial nerves: Assess hearing (CN VIII — relevant for cerebellopontine angle pathology), facial symmetry (CN VII)
- Fundoscopic exam if concern for intracranial pathology
- Vital signs: Generally normal; tachycardia/hypertension may be present during acute pain crisis
- Oral exam: Rule out dental pathology, mucosal lesions
11. Lab Studies
- Blood tests are not recommended to diagnose TN [2]
- Pre-carbamazepine labs: CBC (risk of aplastic anemia/agranulocytosis), CMP (hepatic function, sodium baseline), HLA-B</em>15:02 in at-risk populations [9-10]
- Monitoring on carbamazepine: Periodic CBC, hepatic function, sodium levels [8]
- If secondary TN suspected: ESR/CRP (giant cell arteritis), ANA (autoimmune), consider LP if MS suspected
- Serum drug levels of carbamazepine are not routinely needed for efficacy monitoring (unlike epilepsy) [3]
12. Imaging
- Brain MRI with and without contrast is recommended for all patients with suspected TN to rule out MS, tumor, cerebral aneurysm, and AVM [2][6]
- 3D time-of-flight MRA identifies neurovascular compression with 95% sensitivity, 77% specificity [2]
- High-resolution sequences (3D CISS, 3D FIESTA, 3D FLASH) improve visualization of neurovascular conflict; 3.0T preferred over 1.5T [3][6][16]
- MRI findings in classic TN: neurovascular contact with morphological changes (displacement, indentation, atrophy) of the trigeminal nerve root [3]
- Demonstration of neurovascular contact should NOT confirm the diagnosis — it facilitates surgical decision-making [3]
- If MRI is contraindicated: CT with contrast to rule out tumors [6]
- Imaging is unnecessary to confirm the clinical diagnosis when presentation is classic, but is needed to exclude secondary causes [6]
The following figure outlines the AAFP's recommended diagnostic and treatment algorithm:
13. Special Tests
- Electrophysiologic trigeminal nerve reflex testing: Distinguishes classic from secondary TN with sensitivity 96%, specificity 93% (LR+ 14, LR− 0.04); useful when MRI is contraindicated or atypical features are present [2][17]
- Quantitative sensory testing (QST): Can detect subclinical sensory abnormalities; primarily a research tool [3]
- Diffusion tensor imaging (DTI): Emerging modality showing microstructural changes in the trigeminal nerve; not yet standard clinical practice [3][16]
14. ECG
- Pre-treatment ECG is recommended before starting carbamazepine — contraindicated in patients with AV block or other cardiac conduction abnormalities [1][8]
- Carbamazepine has mild anticholinergic activity and sodium-channel blocking properties that can worsen conduction defects [8]
- ECG is not part of the diagnostic workup for TN itself
15. Assessment
Clinical summary: TN is a clinical diagnosis based on ICHD-3 criteria — recurrent unilateral paroxysmal facial pain in trigeminal distribution, lasting <2 minutes, electric shock–like quality, triggered by innocuous stimuli. [1][3] Triggered paroxysmal pain is reported by 91–99% of patients and may be pathognomonic. [1]
Classification:
- Classic TN: Neurovascular compression with morphological nerve changes on MRI (~75%)
- Secondary TN: MS, tumor, AVM (~15%) — younger patients, more likely to have sensory loss and bilateral pain [1]
- Idiopathic TN: No identifiable cause (~10%) [1]
Subclassification: Purely paroxysmal vs. with concomitant continuous pain [3]
Complications: Depression, anxiety, weight loss, dehydration, social isolation, medication side effects, suicidality [2][11]
16. Treatment Plan
Initial stabilization (ED):
- Avoid opioids — ineffective and associated with need for additional drugs in 72% of cases [3][7]
- IV fosphenytoin achieved satisfactory relief in 64% of ED cases in one series [7]
- IV lidocaine — effective per clinical experience; requires monitored setting [3]
- Lidocaine injection into trigger zones for short-term relief [3]
- IV fluids if dehydrated from inability to eat/drink [3]
Outpatient pharmacotherapy:
- Carbamazepine 200 mg BID, titrate by 200 mg/day every several days to effect (max 1,200 mg/day) [1-2]
- If intolerant: oxcarbazepine 300–1,800 mg/day [1][6]
- Patients should be encouraged to self-adjust doses based on pain severity and side effects, as remission periods occur [3][6]
- Second-line add-on: lamotrigine, gabapentin, pregabalin, baclofen, botulinum toxin type A [6]
Surgical options (for medically refractory TN):
- Microvascular decompression (MVD) — first-line surgery for classic TN; 62–89% pain-free at 3–11 years; mortality 0.3%. A 5-year prospective study showed 59% of MVD patients were pain-free without medication vs. 19% with medical management alone [1][3][18]
- Percutaneous procedures (radiofrequency thermocoagulation, balloon compression, glycerol injection) — ablative; preferred when MRI shows no neurovascular contact [3]
- Gamma knife radiosurgery — non-invasive but destructive; 30–66% pain-free at 4–11 years [3]
The following figure illustrates the microvascular decompression procedure:
17. Disposition
Admission criteria:
- Severe exacerbation with inability to eat or drink (dehydration risk) [3]
- Need for IV fosphenytoin or lidocaine infusion (requires monitored setting) [3]
- Acute titration of antiepileptic drugs in refractory cases [3]
- New neurologic deficits suggesting secondary cause requiring urgent workup
Discharge criteria:
- Pain adequately controlled with oral medications
- Able to tolerate oral intake
- Outpatient follow-up arranged
- MRI ordered or scheduled
Specialist consultation triggers:
- Neurology: All new diagnoses (for confirmation, MRI interpretation, and classification) [6]
- Neurosurgery: Refractory to ≥2 adequate medication trials, intolerable side effects, or patient preference for surgical evaluation [3][6]
- Dentistry/oral surgery: If dental pathology cannot be excluded
- Ophthalmology: If V1 involvement with corneal reflex concerns
18. Follow Up / Return Precautions
Follow-up timing:
- Within 1–2 weeks of starting carbamazepine to assess response, side effects, and check labs (CBC, CMP, sodium) [2][8]
- MRI brain with and without contrast should be obtained in all patients [2]
- After several symptom-free months, consider a gradual drug-free trial (taper slowly over days) [2][6]
Return precautions — advise patients to seek immediate care for:
- Skin rash (risk of SJS/TEN — stop carbamazepine immediately) [9-10]
- Inability to eat or drink due to pain
- New numbness, weakness, vision changes, or other neurologic symptoms
- Dizziness, unsteadiness, or confusion (medication toxicity)
- Fever, sore throat, mouth ulcers (signs of agranulocytosis)
Patient counseling:
- TN is a chronic condition with natural remissions and relapses [2-3]
- Medication doses can be self-adjusted within prescribed range based on pain severity [3][6]
- 80% of patients initially seek dental care — reassure that this is a neurologic condition [2]
- Psychological support should be offered given the significant impact on quality of life [6]
- Expected recovery: ~75% achieve initial pain control with medication; carbamazepine efficacy may wane over years, and surgical options exist for refractory cases [2]
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