New Nerve Block for Obesity Treatment

A new implantable medical device, developed by Mayo Clinic researchers, shows promise as a less invasive alternative to existing bariatric surgery, according to findings published in the July 2008 issue of the journal Surgery.

A six-month trial in Australia, Mexico and Norway, looked at 31 obese participants who received the vagal nerve blocking device, also called VBLOC vagal blocking therapy. The patients lost an average of nearly 15 percent of their excess weight. A quarter of the participants lost more than 25 percent, and three patients lost more than 30 percent.

Pacemaker for the Stomach

VBLOC therapy is similar to a heart pacemaker, but instead of stimulating a normal, regular heartbeat, it uses high-frequency electricity to block the nerve impulses between the brain, stomach and pancreas.

A pacemaker monitors the heart continuously to regulate its beating. But in VBLOC, the patient flips a switch to activate the VBLOC device when the system is worn during the daytime hours so that the blocking signal can influence how the stomach functions and food is digested following a meal.

The lead wires are implanted in the abdomen laparoscopically, with electrodes attached to the vagal nerves and the neuroregulator, a pacemaker-sized device, is implanted just under the skin.

Reversible and Safer

While gastric bypass involves removing portions of the digestive tract and rerouting the flow of food and, therefore, is not reversible, the VBLOC delivery system can be removed if desired, and previous studies in animals have indicated that it does not damage or permanently affect the vagal nerves.

With VBLOC, there is no distortion of digestive system anatomy as is the case with both gastric bypass and gastric banding, and to date there have been no significant issues related to food intolerance, nausea or vomiting as is common with both bypass and banding.

More Research to Come

A follow-up double-blinded study, which will involve up to 300 patients at multiple medical centers including a limited number from the Mayo Clinic, will be important for gauging the device’s true effectiveness.

      “In an open label study such as the one being published this month, there is always potential for the device to ‘work’ because patients believe it will,” explains Michael Camilleri, M.D., Mayo Clinic gastroenterologist.

“In the next study, which has already begun, all patients will have the device implanted, but one-third will not have it turned on during the first year of the study, so that after meals, it won’t be blocking the nerve signals; this is called ‘sham’ treatment. Neither the patients nor their doctors will know whether the blocking signals are going through or not. This “pivotal” study will tell us whether a placebo effect is responsible for some of the weight loss.

“After the pivotal study is completed, those who had the ‘sham’ treatment will have their devices turned on so they can experience the benefits,” Dr. Camilleri says. “And unlike the first study, participants also will have access to behavioral counseling and dietary modifications, which will lead to a more realistic comparison of the magnitude of weight loss through vagal blockade as compared with bariatric surgery. The findings published this month are promising, but the next study will tell us whether VBLOC therapy is a viable alternative to gastric bypass or gastric banding, and for which patients.”