Thermal Quantitative Sensory Testing in Zoster-related Pain

OBJECTIVES: Thermal detection abnormalities in herpes zoster (HZ) and postherpetic neuralgia (PHN) remain incompletely characterized. We compared pathologic-site cold and warm detection threshold abnormalities between HZ and PHN, assessed within-patient asymmetry between pathologic and contralateral sites, and explored associations between baseline quantitative sensory testing (QST) features and approximately 3 months clinical outcomes in HZ. METHODS: This retrospective observational study (January 2023-July 2025) compared HZ and PHN cross-sectionally and explored clinical status in the HZ subgroup approximately 3 months after rash onset. Thermal QST was performed at pathologic and contralateral sites using site-appropriate references. Paired pathologic-contralateral and between-group comparisons used Wilcoxon signed-rank, Mann-Whitney U, and exact tests, with Holm correction applied post hoc. RESULTS: Sixty-two participants were included (HZ, n=27; PHN, n=35). Pathologic-site warm detection threshold (WDT-P) abnormalities were more frequent in PHN than HZ (68.6% vs. 40.7%; P=0.028), but lost significance after Holm correction (adjusted P=0.057) or sex adjustment. Pathologic-contralateral differences were robust for cold detection threshold (CDT; r=0.658) and WDT (r=0.549), remaining significant after Holm correction. In the HZ subgroup, differences in age and WDT-P abnormality according to clinical status approximately 3 months after rash onset did not remain significant after multiplicity correction. DISCUSSION: Pathologic-contralateral thermal asymmetry was the most consistent finding across HZ and PHN, supporting segmental thermal sensory dysfunction across pain stages. Between-group WDT-P differences and HZ clinical-status findings warrant prospective evaluation but do not establish stage-specific or prognostic effects.