A 52-year-old man from Delhi presents to the neurology clinic with a 3-month history of severe, lancinating pain in the right V2 distribution (maxilla and upper teeth). The pain is triggered by chewing, touching the face, and cold wind. Intraoral examination reveals no dental pathology. MRI brain with contrast is normal. Which is the most appropriate next step in management?

Explanation

## Clinical Diagnosis **Key Point:** The clinical presentation is pathognomonic for trigeminal neuralgia (TN)—unilateral, lancinating pain in a single trigeminal division (V2 here) triggered by light touch or eating, with normal imaging. ## Management Algorithm ```mermaid flowchart TD A[Suspected Trigeminal Neuralgia]:::outcome --> B{MRI normal?}:::decision B -->|Yes| C[Classic TN - Medical Management]:::action B -->|No| D[Secondary TN - Investigate cause]:::action C --> E[First-line: Carbamazepine]:::action E --> F[Titrate to therapeutic dose<br/>400-1200 mg/day]:::action D --> G[MRA/CTA for vascular<br/>compression or tumor]:::action F --> H{Response?}:::decision H -->|Good| I[Continue maintenance]:::outcome H -->|Poor| J[Add oxcarbazepine or<br/>baclofen]:::action J --> K[Consider surgical options:<br/>MVD, GKRS, RFN]:::action ``` ## First-Line Pharmacotherapy | Drug | Mechanism | Starting Dose | Target Dose | Advantages | |------|-----------|---------------|-------------|------------| | **Carbamazepine** | Sodium channel blocker | 100 mg BD | 400–1200 mg/day | Gold standard; 70–80% response | | Oxcarbazepine | Sodium channel blocker | 150 mg BD | 600–1800 mg/day | Better tolerability; fewer DDI | | Baclofen | GABA~B~ agonist | 5 mg TDS | 40–80 mg/day | Adjunct; monotherapy less effective | | Pregabalin | Calcium channel modulator | 75 mg BD | 300–600 mg/day | Second-line; useful in refractory cases | **High-Yield:** Carbamazepine is the **gold standard first-line agent** for classic trigeminal neuralgia. Efficacy is 70–80% in early disease. Always check baseline CBC and LFTs before starting (risk of aplastic anemia, hepatotoxicity). **Clinical Pearl:** The diagnosis of classic TN is **clinical**. Normal MRI rules out secondary causes (MS, tumor, vascular compression). Imaging is not needed to start medical therapy in classic cases. **Warning:** Do NOT order further imaging (CTA, MRA) in a patient with classic TN and normal MRI—this delays treatment and increases cost. Imaging is reserved for atypical features, bilateral pain, or young age (<40 years). ## Why Carbamazepine Now? 1. **Diagnostic confirmation:** Response to carbamazepine is itself diagnostic of TN. 2. **Evidence-based:** International Headache Society and neurology guidelines recommend carbamazepine as first-line. 3. **Timing:** No contraindication evident in the stem; initiate immediately. 4. **Dose titration:** Start low (100 mg BD) to minimize side effects (dizziness, diplopia, ataxia); increase by 100 mg every 3–5 days. [cite:Harrison 21e Ch 380]