Postherpetic neuralgia

Overview

Postherpetic neuralgia (PHN) is pain that often follows resolution of acute herpes zoster and healing of the zoster rash. Herpes zoster is caused by reactivation of latent varicella zoster virus (human herpes virus 3) in people who have been rendered partially immune by a previous attack of chickenpox. Herpes zoster infects the sensory ganglia and their areas of innervation. It is characterised by pain in the distribution of the affected nerve, and crops of clustered vesicles over the area. Pain may occur days before rash onset, or no rash may appear (zoster sine herpete), making the diagnosis difficult. PHN is thought to arise following nerve damage caused by herpes zoster. PHN can be severe, accompanied by itching, and it follows the distribution of the original infection. All definitions of PHN are arbitrary and range from 1 month to 6 months after the rash. For clinical trials, neuralgia of 3 months or more has become the most common definition, because resolution of neuralgia after 3 months is slow. Thus, the number of people required for parallel and crossover trial designs is limited, and there is less risk of a period effect in a crossover trial.

Latest citations

Triaging herpes zoster ophthalmicus patients in the emergency department: do all patients require referral? (12 December 2013)

Thiamine, Cobalamin, Locally Injected Alone or Combination for Herpetic Itching: A Single-Center Randomized Controlled Trial. (12 December 2013)