Postherpetic neuralgia

Postherpetic neuralgia (PHN) is a chronic neuropathic pain syndrome defined as pain persisting more than 3 months after the resolution of herpes zoster-associated rash. It is often characterized as spontaneous aching or burning with paroxysmal shooting pains in the affected dermatome and may be accompanied by allodynia or hyperalgesia. There is an increased incidence of PHN in elderly patients, patients with ophthalmic herpes zoster, and immunocompromised patients. PHN may result from dorsal horn destruction, although pathophysiologic changes in more proximal central structures and distal peripheral structures have been described. Based on randomized, controlled studies, the most effective medical therapies include gabapentin, topical lidocaine, tricyclic antidepressants, and oral opioid analgesics. Surgical interventions for refractory cases including intrathecal drug administration, central ablative procedures, and central electrical stimulation continue to meet with limited success.