Postherpetic neuralgia

Postherpetic neuralgia (PHN) is neuropathic pain that occurs due to damage to a peripheral nerve caused by the reactivation of the varicella zoster virus (herpes zoster, also known as shingles). PHN is defined as pain in a dermatomal distribution that lasts for at least 90 days after an outbreak of herpes zoster.^[1] Several types of pain may occur with PHN including continuous burning pain, episodes of severe shooting or electric-like pain, and a heightened sensitivity to gentle touch which would not otherwise cause pain or to painful stimuli.^[2] Abnormal sensations and itching may also occur.^[2]

Postherpetic neuralgia is the most common long-term complication of herpes zoster, and occurs in approximately 20% of patients with shingles.^[2] Risk factors for PHN include older age, severe prodrome or rash, severe acute zoster pain, ophthalmic involvement, immunosuppression, and chronic conditions such as diabetes mellitus and lupus.^[1] The pain from postherpetic neuralgia can be very severe and debilitating. There is no treatment which modifies the course of the disease and management primarily aims to control symptoms.^[2] Affected individuals often experience a decrease in their quality of life.^[2]

Shingles vaccination is the only way for adults to be protected against both shingles and postherpetic neuralgia, with the vaccine Shingrix providing 90% protection from postherpetic neuralgia.^[3] The chickenpox vaccine is approved for infants to prevent chickenpox, which also protects against PHN from a herpes zoster infection.^[4]