A 35-year-old construction worker presents with painful grouped vesicles on an erythematous base along the right T4 dermatome. He reports severe burning pain that preceded the rash by 3 days. Two weeks later he develops persistent shooting pain in the same distribution despite the rash resolving. What is the mechanism of this persistent pain?
- A Reactivation of herpes simplex virus in the trigeminal ganglion
- B Neuronal damage and sensitisation in the dorsal root ganglion causing peripheral and central sensitisation ✓
- C Autoimmune demyelination of peripheral nerve fibres
- D Secondary bacterial superinfection of nerve roots
Explanation
This presentation describes herpes zoster (shingles) with postherpetic neuralgia (PHN), defined as pain persisting beyond 3 months after rash healing. The mechanism involves VZV-induced inflammatory damage to dorsal root ganglion neurons, causing loss of large myelinated A-beta fibres that normally inhibit pain transmission, thereby unmasking peripheral and central sensitisation of C-fibre nociceptors (gate-control theory derangement). Age over 50, severe acute pain, and ophthalmic distribution are risk factors for PHN. Treatment includes tricyclic antidepressants, gabapentinoids, and lidocaine patches.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.