Can varicella-zoster reactivation cause persistent neuropathic pain after the rash resolves?

Varicella-zoster virus (VZV) establishes latency in dorsal-root and cranial sensory ganglia. When it reactivates as herpes zoster, the rash may heal while neural injury and pain signaling abnormalities persist, producing postherpetic neuralgia (PHN).

Clinical and pathological evidence

• VZV reactivation involves replication within sensory ganglia and spread along sensory axons. Pathological observations in PHN show sensory-neuron cell-body injury and severe loss of peripheral axons, consistent with direct viral injury together with inflammatory and immune-mediated damage.
• Persistent dermatomal neuropathic pain after zoster is clinically recognized as PHN, commonly defined as pain lasting at least 90 days after rash onset, although definitions differ.
• Age is a major clinical consideration: in a prospective community cohort of adults aged 50 years or older, 19.7% of incident zoster cases developed PHN. This is particularly relevant for an 83-year-old, in whom the outcome is clinically important.

Mechanistic explanation

• Residual injured nociceptors can develop altered ion-channel expression, reduced activation thresholds, and ectopic spontaneous firing. This provides a peripheral source of burning pain, electric-shock sensations, and touch-evoked pain (allodynia) after lesions resolve.
• Persistent abnormal afferent input can activate spinal microglia and promote impaired inhibitory signaling and NMDA-dependent central sensitization. These maladaptive spinal changes can sustain spontaneous pain and allodynia even after the acute rash is no longer present.

Interpretation

• The evidence strongly supports the biological sequence from sensory-ganglion VZV reactivation to peripheral sensory-neuron/axon injury and a credible pathway to persistent neuropathic pain.
• The exact relative contributions of direct viral cytotoxicity, host inflammation, peripheral hyperexcitability, and central sensitization vary between individuals and are not fully quantifiable from prospective human studies.

Bottom line

• VZV reactivation can injure sensory neurons and peripheral axons, and the resulting peripheral ectopic firing plus central sensitization can maintain PHN well beyond rash resolution.