Chapter 40

Acute herpes zoster, commonly called shingles, is an acute infectious viral disease that primarily affects the posterior spinal root ganglia of the spinal nerves. A single posterior spinal root ganglion or a small number of adjacent ones may be affected, usually on the same side. The corresponding ganglia of the cranial nerves also may be involved similarly. The causative virus, varicella-zoster, belongs to a DNA group of viruses that is host specific. The same virus produces chickenpox or varicella in children and young people.

### Etiology

Herpes zoster most frequently occurs in adults who previously have had chickenpox. It is thought that the virus remains dormant in the dorsal root ganglia until, many years later, it is reactivated and produces herpes zoster. The decrease in immunity that permits the reactivation may be caused by infection or malignancy, or it may occur in the iatrogenically immunosuppressed patient. The impact of stress on varicella-zoster virus has not been well studied, but major depression has been associated with markedly decreased varicella-zoster virus–specific cellular immunity.1 Patients experiencing stress during a zoster episode are more likely to have more severe pain, increasing their risk of postherpetic neuralgia.2 Patients with herpes zoster occasionally relate a history of recent contact with the virus exogenously; but it is rare, if ever, that an infection so develops. The incidence of herpes zoster does not increase during seasonal chickenpox epidemics.

It is thought that, after the virus multiplies in the dorsal root ganglion, it is transported along the sensory nerves to the nerve endings, where the lesions are formed. In the immunocompetent patient, the disease is confined to a local distribution because there is a rapid mobilization of defense mechanisms.

Although the posterior root ganglia of the spinal and cranial nerves are involved most commonly, any part of the central nervous system can be affected. For example, the anterior motor horn may be involved, or the patient may have myelitis or encephalomyelitis. In rare cases, only the sympathetic ganglia are affected, resulting in a syndrome resembling reflex sympathetic dystrophy.

The location of the herpes zoster infection may be determined by the site of a primary inflammatory disease, malignancy, or trauma. Patients with neoplasms, especially lymphomas, are more susceptible to herpes zoster. This high incidence may be the result of recent radiation of affected nodes, advanced disease, and possible splenectomy. Other associated diseases include meningitis, spinal cord tumors, anterior poliomyelitis, syringomyelia, tabes dorsalis, intoxication from arsenicals or carbon monoxide, and malignant neoplasms such as breast, lung, or gastrointestinal tumors.

### Incidence

Estimates of the incidence of herpes zoster in the U.S. population indicate an approximate 64% increase in the general population over the past 30 years, to approximately 215 cases per 100,000 person years.3 Men are affected more frequently than women. African Americans 65 years of age or older are significantly less likely ...

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