Can persistent nerve injury after shingles drive central sensitization and ongoing pain?

Shingles can leave persistent sensory-nerve and dorsal-root-ganglion injury even after cutaneous lesions resolve. This provides a biologically and clinically supported explanation for postherpetic neuralgia (PHN), although persistent pain has more than one mechanism.

Clinical and sensory evidence

• Human PHN phenotypes are consistent with enhanced central pain processing. In one 42-person cohort, mechanical sensitization occurred in 73.8% and temporal summation or hypersensitivity beyond the affected dermatome in 38.1%.
• Dynamic mechanical/brush allodynia—pain from ordinarily non-painful touch—was reported in 64% in one quantitative sensory-testing study and mechanical allodynia in 78% in another. These findings support dorsal-horn hyperexcitability, though they are indirect rather than direct spinal measurements.
• A longitudinal cohort of 20 people followed for approximately 32 months identified a subgroup with preserved C-fiber function but increasing mechanical pain sensitivity, a pattern compatible with central sensitization.

Mechanistic basis

• Varicella-zoster virus–related injury can cause loss of epidermal nociceptive endings and sensory axons, while injured C-fibers and dorsal-root-ganglion neurons may develop ectopic spontaneous activity.
• Sustained abnormal afferent input can increase glutamatergic/NMDA-receptor signaling in the spinal dorsal horn, promoting temporal summation, prolonged depolarization, spontaneous firing, receptive-field expansion, and reduced inhibitory control.
• In this sensitized state, innocuous Aβ mechanoreceptor input may be interpreted as painful, explaining dynamic mechanical allodynia.

Clinical implications

• Persistent pain after rash resolution can therefore reflect both ongoing peripheral pathology (ectopic activity or deafferentation) and spinal amplification; central sensitization is not necessarily the only or universal driver.
• For an 83-year-old man with ongoing pain, allodynia, temporal summation, sensory loss, and pain distribution can help identify the dominant phenotype.

Bottom line

• Persistent nerve injury after shingles can plausibly drive spinal central sensitization and help maintain PHN after the rash resolves, with moderate clinical and mechanistic support.