A 52-year-old man from Delhi presents to the neurology clinic with a 3-month history of severe, lancinating pain in the right cheek and upper jaw. The pain is triggered by touching his face, chewing, or exposure to cold wind, and lasts 15–30 seconds per episode. He has tried topical analgesics without relief. Neurological examination reveals normal facial sensation and motor function. MRI brain with contrast is normal. Which is the most likely diagnosis?

Explanation

## Diagnosis: Trigeminal Neuralgia (Tic Douloureux) **Key Point:** Trigeminal neuralgia is a chronic neuropathic pain disorder affecting the trigeminal nerve (CN V), characterized by sudden, severe, stabbing pain in the distribution of one or more divisions of the trigeminal nerve. ### Clinical Features Supporting This Diagnosis | Feature | Trigeminal Neuralgia | Differential Diagnosis | |---------|----------------------|------------------------| | **Pain character** | Lancinating, electric, stabbing | TMJ: dull ache; sinusitis: pressure | | **Duration** | 15 sec – 2 min per episode | TMJ: prolonged; sinusitis: constant | | **Triggers** | Touch, chewing, cold, wind | TMJ: jaw movement; sinusitis: none specific | | **Sensory exam** | Normal | TMJ: normal; sinusitis: normal | | **Imaging** | Often normal (classic); may show vascular compression | TMJ: normal; sinusitis: sinus opacification | | **Distribution** | V2 (maxillary) or V3 (mandibular) | Glossopharyngeal: posterior pharynx | **High-Yield:** Classic presentation includes: 1. Unilateral lancinating pain in CN V distribution (most common: V2 or V3) 2. Trigger zones (perioral, nasolabial area) 3. Brief duration (seconds to <2 minutes) 4. Normal neurological exam 5. Normal imaging (excludes secondary causes) **Clinical Pearl:** The patient's pain is triggered by light touch and chewing — hallmark features of trigeminal neuralgia. The normal sensory exam and imaging rule out secondary causes (tumor, demyelination, vascular malformation). **Mnemonic: LANCINATING** — Light touch triggers, Acute onset, Neuropathic character, Cheek/chin distribution, Ipsilateral, Neuralgia (CN V), Abrupt cessation, Trigger zones, Intense pain, Normal exam, Glossopharyngeal excluded, Anatomically V2/V3. ### Pathophysiology Trigeminal neuralgia results from: - Demyelination of the trigeminal nerve root (most common) - Vascular compression (neurovascular conflict) — typically superior cerebellar artery or vertebral artery compressing the nerve at the root entry zone - Ectopic firing in damaged nerve fibers - Central sensitization in brainstem trigeminal nuclei ### Management Approach ```mermaid flowchart TD A[Trigeminal Neuralgia Suspected]:::outcome --> B[Confirm diagnosis clinically]:::action B --> C[First-line: Carbamazepine or Oxcarbazepine]:::action C --> D{Response?}:::decision D -->|Good| E[Continue; monitor levels]:::action D -->|Poor/Intolerant| F[Add/switch: Baclofen, Gabapentin, Pregabalin]:::action F --> G{Refractory?}:::decision G -->|Yes| H[Surgical intervention: MVD, gamma knife, percutaneous rhizotomy]:::urgent G -->|No| E ``` **First-line pharmacotherapy:** Carbamazepine (400–1200 mg/day) or oxcarbazepine (600–1800 mg/day) — both block sodium channels and reduce ectopic firing. [cite:Harrison 21e Ch 379]