Electrophysiological findings in peripheral fibres of subjects with and without post-herpetic neuralgia.

The peripheral nervous system was studied using classical electrophysiological methods in 23 subjects with post-herpetic neuralgia (PHN), and compared with the same parameters in 64 herpes zoster (HZ) patients without PHN. The findings indicated sensory axonopathy, the severity of which varied in different patients. Ten percent of all cases showed segmental paresis corresponding to dermatomes affected by HZ. In another 17% of patients axonal motor damage was only detectable by EMG as denervation. No statistically significant difference was found between the two groups in the mean percentage differences of the electrophysiological data for peripheral sensory fibres with respect to mean control values, or between sides affected by HZ and healthy sides. Hence HZ is associated with sensory axonopathy, the severity of which is similar, on the whole, in the groups with and without PHN and stable in time. This suggests that damage to peripheral large-diameter sensory fibres is not the cause of PHN.