Natural history of pain following herpes zoster.

In a longitudinal observational study of 94 patients (39 M:55 F, mean age 69) at elevated risk for developing post herpetic neuralgia (PHN), the natural history of pain during the first 6 months after herpes zoster (HZ) rash onset was determined. Pain severity and impact were rated using pain-VAS, SF-MPQ, and MPI. Applying a definition of PHN of average daily pain >0/100 on the pain VAS during the last 48 h, 30 subjects had PHN at 6 months. These 30 subjects reported more pain and a higher SF-MPQ score (p<0.01) at study inclusion than the 64 subjects whose pain completely resolved by 6 months. At 6 months, mean daily pain in the PHN group was 11/100 (95% CI 5,16) and only nine of these subjects were still taking prescription medication for HZ pain. The rate of recovery (pain severity over time) was the same in the PHN and no-pain groups. At study inclusion, the SF-MPQ and MPI scores in our PHN group were similar to historical controls with chronic severe PHN enrolled in clinical trials, but by 6 months the scores in our PHN subjects were significantly lower than historic controls. Only two subjects met the more stringent criteria for 'clinically meaningful' PHN at 6 months (> or = 30/100 on the pain VAS). Defining PHN as average daily pain >0/100 at 6 months after rash onset appears to substantially overestimate the number of HZ patients negatively impacted by ongoing pain and disability.