Shingles, a common name for herpes zoster, results from reactivation of the virus that causes chicken pox within sensory nerve roots of the back and spine. According to the National Institutes of Health, the name "shingles" comes from the Latin word "cingulum," which means belt or girdle and connotes the virus' preference for the back and trunk. Shingles produces a skin rash, as well as back pain that may be permanent for some people.
Reactivation of the varicella-zoster virus inflames the sensory nerves, resulting in pain that seems to radiate from the back to the front of the chest. According to University of Alabama Medical School professor Richard J. Whitely, in some people, inflammation appears to sensitize nerves, so that pain sensations continue even after inflammation has resolved, a condition doctors call postherpetic neuralgia.
Back pain due to shingles usually begins two to three days before the appearance of a one-sided, blistering skin rash. The rash usually lasts seven to 10 days, but occasionally lasts two to four weeks. Back pain usually subsides as the rash starts to improve, except in people who develop postherpetic neuralgia.
According to the National Institutes of Health, 25 percent of people develop shingles, usually after the age of 40. Shingles rarely recurs, except in people with immune system problems, such as AIDS or bone marrow transplant recipients. About half of people who develop shingles also develop postherpetic neuralgia.
Back pain due to shingles usually begins as superficial, mild burning, tingling or itching. When the rash appears, pain usually becomes worse and may be severe. Pain seems to come from the skin and the touch of clothing or even a breeze may be sufficient to trigger shooting pains that interfere with activities. For people with postherpetic neuralgia, pain does not subside when the rash goes away.
The skin rash caused by shingles is characterized by redness and blister-like eruptions confined to a single side of the body. Although shingles itself is not life-threatening, patients with postherpetic neuralgic often suffer from depression, sleeplessness, weight loss and disability.
Antiviral drugs such acyclovir, valacyclovir and famcyclovir can reduce the duration and severity of acute shingles. Doctors treat postherpetic neuralgia with a variety of drugs, including steroids, antidepressants, anticonvulsants, narcotics and topical agents. Steroids quell lingering inflammation within the nerve roots. Antidepressants and anticonvulsants modify the transmission of pain signals. Narcotics send pleasure signals that cancel out pain signals. Topical agents usually involve delayed release of local anesthetics, such as lidocaine, that stop all signal transmission from the treated nerves, including perception of temperature and touch, as well as pain.
In May 2006 the U.S. Food and Drug Administration approved a varicella-zoster virus vaccine, Zostavax, for people 60 and older who have already had chicken pox. In the 2008 Shingles Prevention Study, a joint venture between Merck Pharmaceutical, the U.S. Department of Veterans Affairs and the National Institute of Allergy and Infectious Diseases, researchers reported that the vaccine reduced the risk of getting shingles by half in treated patients and, among patients who still developed the disease, the vaccine reduced the risk of developing postherpetic neuralgia by two-thirds.