Postherpetic Neuralgia Pathogenesis
Postherpetic neuralgia is caused by neuropathic pain resulting from injury to sensory pathways after herpes zoster (reactivation of varicella-zoster virus) in the affected dermatome.[1] The major pathological processes involve persistent inflammation and damage in the dorsal root ganglia and peripheral nerves, with downstream effects on spinal cord signal processing.[1][2]
Primary Etiologic Process After Herpes Zoster
Herpes zoster is characterized by inflammation of the dorsal root ganglia and neuritis during the acute phase.[2] Persistent neuronal injury follows, producing ongoing neuropathic pain in the distribution of the prior rash.[1][2]
Dorsal Root Ganglion and Peripheral Nerve Injury
Histopathologic findings in postherpetic neuralgia include myelin and axonal loss and dorsal horn atrophy in some cases.[1] Chronic inflammatory changes in relevant nervous tissue have been described in patients with postherpetic neuralgia.[3] Persistent inflammation in peripheral nerves can progress to demyelination and degeneration, with subsequent scarring of skin, peripheral nerves, and dorsal root ganglia.[4]
Central Sensitization From Peripheral Nerve Damage
Altered central nervous system signal processing contributes to pain persistence after the initial viral illness.[1] Pain is associated with injury-related changes that increase excitability of sensory pathways and amplify nociceptive signaling.[4]
Proposed Mechanistic Contributors
Inflammatory mediators have been implicated in promoting nociceptor ion-channel dysfunction and persistent pain signaling after zoster-associated nerve injury.[5]
Clinical Implication of the Mechanism
The clinical syndrome reflects neuropathic pain from damaged sensory pathways rather than ongoing active skin infection.[1][2]