Risk factors that may cause neurological complications are identified in the study.

"Obesity is at epidemic proportions in the United States," says principal investigator P. James B. Dyck, M.D. The National Institutes of Health (NIH) estimates that 64 percent of adult Americans are overweight or obese.

"As more people elect to have bariatric surgery for morbid obesity, it's important to monitor our experience with these surgeries and make them as safe as possible," said Dr. Dyck, associate professor of neurology at the Mayo Clinic College of Medicine in Rochester, Minnesota.

"We found that people were at risk for neurological complications (peripheral neuropathy, or PN) following bariatric surgery. Nutritional support before and after surgery seems to a key factor in determining whether people had PN complications," Dr. Dyck noted.

"Diseases of the peripheral nervous system, PN, can be focal -- like carpal tunnel syndrome which affects fingers and hands -- or more generalized, causing wide spread pain or weakness," Dr. Dyck said. "The peripheral nerves are the 'wires' that go throughout the body and conduct motor and sensory information."

In the study, the charts of 435 people who had one of two types of bariatric surgery approved for treatment of the morbidly obese by the NIH (gastric bypass and 'stomach stapling') were compared with the charts of 123 obese patients who had gall bladder surgery to determine whether bariatric surgery or abdominal surgery in general was associated with PN.

All patients were obese and were compared on indices including age, gender, rate of weight loss, degree of obesity (body mass index or BMI), time to reach maximum weight loss, and taking multivitamin and calcium supplements, to determine which factors were correlated with neurological complications.

"People who had had bariatric surgery were significantly more likely to have PN than the people in the control group," Dr. Dyck said. "The most common PNs were carpal tunnel syndrome and sensory neuropathy, but a small number had a more severe form of PN, which can lead to extreme pain and weakness, sometimes confining people to a wheelchair," he noted.

"The risk factors that we found correlated with PN included very rapid weight loss, not taking vitamins, and prolonged nausea and vomiting. Factors including age, gender, pre-surgery BMI and general health had no association," Dr. Dyck said. "A major risk factor correlated with PN after surgery was failure to attend a nutritional clinic. The evidence was very strong that PN complications were associated with malnutrition," he commented.

"Our study offers a clear message that PN after bariatric surgery is largely preventable and that a multidisciplinary approach to bariatric surgery that includes good follow-up and good nutritional counseling is the key to a successful outcome," Dr. Dyck concluded. "This gives people a good way to evaluate programs that offer bariatric surgery and assure a better outcome."