Postherpetic Neuralgia

Abstract

Herpes zoster is a painful dermatomal, vesicular rash due to the reactivation of a latent varicella zoster (chicken pox) virus infection in cranial nerve or dorsal root ganglia. Lifetime incidence of herpes zoster is estimated to be 10–20 %. Risk is increased in immunocompromised individuals. Using a definition of postherpetic neuralgia as herpes zoster-associated pain lasting 30 or more days, rates reported are as high as 30 % in individuals younger than 40 years and up to 74 % in those above 60 years. The most commonly affected dermatomes are thoracic, cranial (especially trigeminal), lumbar, and cervical. Herpes zoster ophthalmicus may occur when the virus infects the ophthalmic branch of the trigeminal nerve in the upper face. The rash appears 1–4 days after a prodrome of fever, malaise, and dysesthesias. Vesicular eruption becomes pustular approximately 3 days after, followed by crusts forming by 7–10 days. Diagnosis is made on the basis of the typical dermatomally delineated rash. Pain and mild sensory loss follow the same dermatomal distribution.

Because of the intense pain experienced by these patients, herpetic neuralgia oftentimes presents for emergency treatment. The primary goal of therapy is to shorten the clinical course, provide analgesia, and reduce the risk of developing postherpetic neuralgia.

Acyclovir has not consistently shown reduction in the incidence or severity of postherpetic neuralgia, but it may be prescribed. Prednisone may reduce the acute pain and could potentially reduce the incidence of postherpetic neuralgia. However, prednisone should not be administered in immunocompromised individuals. Symptomatic/pain control medications include pregabalin, gabapentin, and carbamazepine.