Evaluation of peripheral nerve function using current perception threshold in the herpes zoster patients and the development of post-herpetic neuralgia

Background: We performed this study to evaluate peripheral nerve function in patients with herpes zoster (HZ) using current perception threshold (CPT) and to compare results between patients who developed post-herpetic neuralgia (PHN) and those who did not. Methods: With Institutional Review Board (IRB) approval and informed consent, 27 patients with HZ were enrolled in the study. At the first visit, all patients were examined clinically and neurophysiologically. CPTs were determined at stimulus frequencies of 2000, 250, and 5 Hz in the affected region and in the contralateral site. Patients were re-examined 6 months after the onset of their symptoms. Patients who still had pain were defined as PHN patients and the others as non-PHN patients. Results: CPT values in affected areas were significantly higher than those in unaffected areas. Thirteen patients were included in the PHN group, and 14 patients in the non-PHN group. Visual analogue scale (VAS) values at the first visit were significantly higher in the PHN group than in the non-PHN group. There were no differences in CPTs at 5 or 250 Hz, whereas CPTs at 2000 Hz for the PHN group were significantly higher in the affected region than those for the non-PHN group. Conclusion: CPT is a useful indicator in the assessment of sensory impairment in HZ patients. Our results suggest that, besides the intensity of pain, the impairment of peripheral nerve fiber function might be an important factor in the development of PHN.