## Clinical Diagnosis: Trigeminal Neuralgia (TN) **Key Point:** This is a classic presentation of trigeminal neuralgia (tic douloureux): - Unilateral, lancinating pain in V2/V3 distribution - Triggered by light touch (shaving) - Brief duration (seconds to minutes) - Complete remission between episodes - Normal neurological exam and normal MRI exclude secondary causes ## Management Algorithm for Trigeminal Neuralgia ```mermaid flowchart TD A[Confirmed TN diagnosis]:::outcome --> B{Secondary cause?}:::decision B -->|Yes: MRI shows tumor/MS/vascular lesion| C[Treat underlying cause]:::action B -->|No: MRI normal| D[First-line medical therapy]:::action D --> E[Carbamazepine 100-200 mg BD]:::action E --> F{Pain controlled?}:::decision F -->|Yes| G[Continue maintenance]:::outcome F -->|No| H[Add/switch: oxcarbazepine, baclofen, pregabalin]:::action H --> I{Refractory after 2-3 drugs?}:::decision I -->|Yes| J[Consider surgical intervention]:::action J --> K[Microvascular decompression or ablative procedure]:::action ``` **High-Yield:** Carbamazepine is the gold-standard first-line agent for TN, with 70–80% initial response rate [cite:Harrison 21e Ch 379]. **Clinical Pearl:** The key to diagnosis is the **trigger** (light touch, eating, talking) and **complete remission** between attacks — this distinguishes TN from other facial pain syndromes. ## Why Carbamazepine First? | Aspect | Rationale | |--------|----------| | **Mechanism** | Blocks voltage-gated Na^+^ channels; stabilizes neuronal membranes | | **Efficacy** | 70–80% response in idiopathic TN | | **Timing** | Immediate initiation; effect seen within days | | **Cost** | Inexpensive, widely available in India | | **Evidence** | Level 1 evidence; standard of care | **Tip:** Start low (100 mg BD), titrate slowly to avoid side effects (dizziness, ataxia, hyponatremia). Monitor CBC and LFTs baseline and at 1–2 weeks. 
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