CLEVELAND, Ohio (February 5, 2014)--Injecting a little anesthetic near a nerve bundle in the neck cut troublesome hot flashes significantly, shows a new randomized, controlled trial published online today in Menopause, the journal of The North American Menopause Society (NAMS). The technique could give women who cannot or prefer not to take hormones or other medications an effective treatment alternative.

In this study from two Chicago medical schools, Northwestern University and the University of Illinois at Chicago, 40 women who had moderate to severe hot flashes got either a stellate ganglion block--an injection of tiny amounts of anesthetic near a nerve bundle in the neck--or an injection of plain saline solution. Both groups of women kept diaries of the frequency and severity of their hot flashes from two weeks before the injection until six months afterward. In addition, for 24 hours at the start of the study and three months after the injection, the women wore skin conductance monitors, which measured hot flashes objectively and also let the women record when they felt a hot flash.

On average, the women had 10 hot flashes a day, rating two-thirds of them moderate or severe. (Hot flashes lasting up to 15 minutes with symptoms such as perspiration, clammy skin, dry mouth, tense muscles, and rapid heartbeat were considered "moderate." Hot flashes lasting up to 20 minutes with symptoms such as "raging furnace" warmth, weakness, feeling faint, extreme perspiration, and heart irregularities were considered "severe.")

Four to six months after the injection, the total number of hot flashes wasn't significantly different between the real- and sham-treated groups, but the number of moderate to severe hot flashes was cut in half for women who got the real nerve block (52%) compared with just 4% for the women who got the sham injection. What's more, the intensity of the hot flashes dropped 38% for the women who got the real nerve block, compared with just 8% for those who got the sham injection.

"A few small studies suggested that this treatment had potential, but this is the first study to show that this hot flash treatment really is better than placebo. The nerve blocks could prove very helpful for women with a history of breast cancer, as well as for women who prefer not to use hormones or other drugs for hot flashes," says NAMS Executive Director Margery Gass, MD.

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The study, "Effects of stellate ganglion block on vasomotor symptoms: findings from a randomized controlled clinical trial in postmenopausal women," was supported by the Department of Obstetrics and Gynecology, Northwestern University and grants from the National Institute of Child Health and Human Development and the National Institutes of Health Office of Research on Women's Health and will be published in the August 2014 print edition of Menopause.