Pain, nerve trunk inflammation, and neuronal injury are hallmarks of acute herpes zoster (AHZ). We hypothesize that the development of post-herpetic neuralgia (PHN) strongly depends on two factors: 1) the severity of the initial neural injury and 2) the ability to recover from the initial neural injury. To test this hypothesis, we will prospectively follow 150 patients at high risk for development of PHN. Evolution of pain and neural injury will be evaluated at 2-6 weeks, 6 weeks, 3 months, 6 months and at 2 years or longer after the onset of AHZ by multiple measures. Assessments at 2 years or longer will be compared to those collected during the first 6 months after HZ in order to test whether or not sensory function and cutaneous innervation continues to normalize beyond 6 months in subjects who recover from HZ without severe PHN.
Preliminary analysis of study data showed reduced innervation in HZ skin, mirror image skin and distant control skin in the acute phase of HZ that was not specific to the persistence of pain at 3 months. The innervation appeared to recover more fully by 6 months in distant control skin than in mirror-image skin and HZ skin, despite the fact that the subjects were continuing to experience a further reduction in their zoster-associated pain. This suggests that the symptoms of pain and sensory dysfunction are not due to a mere loss in overall innervation density. The proposed subsequent ≥ 2 year study visit and analysis will allow us to directly correlate pain resolution with resolution of sensory and innervation abnormalities.