Can injured sensory fibers after shingles develop spontaneous ectopic firing and abnormal excitability that sustain post-herpetic neuralgia?

After herpes zoster, persistent pain can reflect injury across sensory ganglia, roots, and peripheral axons. In severe post-herpetic neuralgia (PHN), human pathology demonstrates ganglion-cell, axonal, and myelin loss, supporting a neuropathic basis for ongoing symptoms.

Peripheral excitability and pain generation

• Sensory-fiber injury after shingles is supported by human and pathological evidence. Damage to peripheral axons and dorsal-root-ganglion neurons provides a biologically credible substrate for altered nociceptor function.
• Ectopic spontaneous firing and hyperexcitability are plausible contributors to PHN. Inflammatory mediators and nerve injury can lower nociceptor activation thresholds, enabling spontaneous or exaggerated discharges from injured axons or sensory-neuron cell bodies. This could generate continuing peripheral nociceptive input and help explain burning pain, touch-evoked pain (allodynia), and hypersensitivity.
• However, direct recordings demonstrating ectopic firing or measured abnormal excitability specifically in people with PHN are not available. Thus, these phenomena are mechanistically well-grounded but not directly proven as the dominant driver in individual patients.

Central mechanisms and clinical heterogeneity

• Central sensitization is also supported as a contributor. Continuing peripheral input may induce plasticity in central pain pathways, amplifying pain signaling and reducing inhibitory control.
• PHN is heterogeneous: fiber loss/deafferentation can coexist with pain, and a small biopsy study associated fiber loss with allodynia but not clearly with spontaneous pain or overall pain intensity. Peripheral hyperexcitability therefore cannot account for every sensory phenotype.

Bottom line

• The claim is broadly credible: shingles-related sensory injury is established, and resultant ectopic firing and abnormal excitability are plausible mechanisms sustaining PHN. In an 83-year-old with persistent post-zoster pain, these peripheral mechanisms may be relevant, but pain likely reflects a combination of peripheral nerve injury and central sensitization rather than one mechanism alone.