Study sheds light on endometriosis pain

Jun 10 2005

Women with endometriosis often have several types of chronic pain conditions because their abnormal growths develop a nerve supply that communicates with the brain, new research suggests.

Florida State University Professor of Neuroscience Karen Berkley was the lead researcher in a study that shows that endometrial cysts become supplied by sympathetic and sensory nerves that could contribute to both the different types of pain associated with endometriosis and the body's ability to maintain the disease. The new nerves likely sprout from those that supply the blood vessels that grow along with and nourish the cysts, Berkley said.

Berkley, Andrea Rapkin of the University of California at Los Angeles and Raymond Papka of Northeastern Ohio Universities College of Medicine drew the conclusion after research on human tissue replicated results Berkley and her colleagues found last year on rats with surgically induced endometriosis. Their findings will be published in the June 10 issue of the journal Science.

"It's been a mystery - clinically - why there is such a co-occurrence between endometriosis and other painful conditions we wouldn't think would be related: irritable bowel syndrome, interstitial cystitis and even migraines," Berkley said. "It may happen in part because this new nerve supply comes into the central nervous system and interacts with information coming from other organs, such as the colon and bladder, that the brain may interpret as pain."

The types of nerves that develop in the cysts, the agents that activate them, the sites in the central nervous system where the nerves deliver information and how the information is modulated by estrogen all influence how the disease will manifest itself, the researchers suggest.

The variability of the nerve supply of the cysts in different individuals may help explain why symptoms and severity of pain vary so greatly in women who have endometriosis, a disease that may affect up to 50 percent of women in their reproductive years, according to Berkley.

Endometriosis is thought to occur when cells from the lining of the uterus escape into the pelvic cavity during menstruation and attach themselves to the outside of the uterus, ovaries or other organs in the abdomen. The cells can develop into growths or cysts that impact fertility and may cause severe menstrual cramps and other pelvic pains.

Berkley said she and her colleagues hope their findings may lead to new treatments for endometriosis. Currently the disease is treated with hormone therapy or surgery.