In a woman over 50 presenting with brief electric‑shock facial pain triggered by light touch, how should trigeminal neuralgia be diagnosed and managed (including imaging, first‑line medication, alternative drugs, and surgical options)?

Trigeminal Neuralgia: Diagnosis and Management

Diagnosis

In a woman over 50 with brief electric-shock facial pain triggered by light touch, the diagnosis of trigeminal neuralgia is made clinically based on the characteristic pain pattern: unilateral, paroxysmal attacks lasting seconds to minutes with mandatory refractory periods between attacks, sharp shooting quality, and trigger zone sensitivity. 1, 2

Key Diagnostic Features

• Pain characteristics: Sharp, shooting, electric shock-like pain in V2 and/or V3 distribution (most common), lasting 2 seconds to minutes with pain-free intervals between attacks 1, 3
• Triggers: Light touch, washing, cold wind, eating, brushing teeth—seemingly innocuous stimuli that precipitate attacks 1, 2
• Refractory period: Mandatory pain-free intervals between attacks; if the patient can trigger attacks repeatedly without pain-free intervals, consider alternative diagnoses 3
• Examination: Typically normal between attacks; the presence of sensory deficits requires urgent imaging to rule out secondary causes 3

Critical Differential Diagnoses in Women Over 50

• Giant cell arteritis: Continuous dull aching temporal/jaw pain aggravated by chewing, with scalp tenderness, elevated ESR, visual disturbances, fever, and absent temporal pulse—requires immediate high-dose corticosteroids to prevent vision loss 1, 4
• Trigeminal autonomic cephalgias (SUNCT/SUNA): Up to 200 attacks daily with no refractory period, accompanied by tearing, conjunctival injection, rhinorrhea, and facial redness 1, 3
• Post-herpetic neuralgia: Continuous burning pain at the site of previous herpes zoster with allodynia and hyperalgesia 1, 3
• Glossopharyngeal neuralgia: Deep ear and back of tongue pain triggered by swallowing, not V2/V3 distribution 3

Common pitfall: Continuous pain suggests Type 2 trigeminal neuralgia, post-traumatic neuropathy, or alternative diagnoses—not classical trigeminal neuralgia. 3

Imaging

MRI with contrast is mandatory for all patients with suspected trigeminal neuralgia to distinguish classical TN (neurovascular compression), secondary TN (MS, tumor), and idiopathic TN, and to guide treatment decisions. 3, 2, 5

• Imaging protocol: High-resolution thin-cut sequences through the trigeminal nerve course with 3D heavily T2-weighted sequences combined with MRA to characterize vascular compression 3
• Include pituitary fossa views if SUNCT/SUNA is suspected 3
• Imaging congruence: 83-100% correlation with surgical findings for neurovascular compression 3

First-Line Medical Management

Start carbamazepine 200 mg at bedtime, then gradually increase by 200 mg every 7 days to a target dose of 400-1200 mg daily divided into 2-3 doses, taken routinely on a scheduled basis—not as-needed. 6, 2

• Evidence: Level A evidence from four placebo-controlled trials showing 70% of patients achieve partial or complete pain relief with continuous therapy 6
• Mechanism: Modulation of voltage-gated sodium channels, decreasing neuronal activity in demyelinated trigeminal nerve fibers 7
• Critical point: Carbamazepine must be taken daily on schedule to maintain therapeutic plasma concentrations and prevent attacks, not as-needed during pain episodes 6

Alternative Medications

Oxcarbazepine is equally effective as carbamazepine with fewer side effects and is the preferred alternative first-line agent. 3, 6, 5

Second-Line Options (when carbamazepine/oxcarbazepine fail or are not tolerated):

• Lamotrigine: Particularly effective for SUNCT/SUNA if misdiagnosed 1, 5
• Gabapentin combined with ropivacaine: Second-line option 3
• Pregabalin: Alternative anticonvulsant 3, 5
• Baclofen: Can be used alone or as add-on therapy 3, 5
• Botulinum toxin type A: Emerging option for add-on therapy 5

These medications also require continuous scheduled administration, not as-needed dosing. 6

Surgical Options

Microvascular decompression (MVD) is the first-line surgical treatment for patients with neurovascular compression on MRI who are medically refractory or cannot tolerate medications, offering 70% pain freedom at 10 years. 5, 8, 9

Surgical Algorithm:

• MVD indications: Classical TN with neurovascular compression on MRI, patients without major comorbidities, desire for non-destructive procedure 5, 8
• MVD outcomes: 70% pain-free at 10 years, but carries 0.2-0.4% mortality risk and 2-4% risk of ipsilateral hearing loss 9

Neuroablative Procedures (for patients too frail for MVD or without neurovascular contact):

• Radiofrequency thermocoagulation: Recommended in elderly patients or those with major comorbidities, 50% pain-free at 4 years 8, 9
• Retrogasserian glycerol injection: Alternative percutaneous procedure 8
• Balloon compression: Alternative percutaneous procedure 8
• Stereotactic radiosurgery: Pain relief typically within 1 month but can take up to 6 months 3, 8

All ablative procedures result in sensory loss as a trade-off for pain relief. 9

Treatment Algorithm

1. Confirm diagnosis clinically with characteristic paroxysmal pain pattern and triggers 1, 2
2. Obtain MRI with contrast to classify TN type and rule out secondary causes 3, 2
3. Start carbamazepine or oxcarbazepine with scheduled daily dosing, titrating to effect 6, 2
4. If inadequate response or intolerance, add second-line medications (lamotrigine, gabapentin, pregabalin, baclofen) 3, 5
5. Refer for neurosurgical evaluation early if medical management fails—75% achieve initial control with pharmacotherapy, but many eventually require surgery 2, 9
6. Choose MVD if neurovascular compression present and patient is surgical candidate 5, 8
7. Choose radiofrequency or other ablative procedure if no neurovascular contact, patient too frail for MVD, or patient preference 5, 8