Gastric bypass and stomach-stapling patients should recognize risk of nerve injury post-surgery

October 14, 2004

ROCHESTER, Minn. -- Mayo Clinic researchers have found a significant number of patients who undergo "stomach stapling" or gastric bypass surgery for weight reduction develop peripheral neuropathy, damage to any of the body's nerves outside of the brain and spinal cord. The development of nerve damage is associated with malnutrition, and so the researchers contend may be largely preventable with proper nutritional care.

"Surgeons who do weight-reduction surgery and the general public and should be aware that nerve damage is a frequent consequence of the surgery," says P. James (Jim) Dyck, M.D., Mayo Clinic neurologist and lead investigator in this study, which will be presented at the American Medical Association Science Reporters Conference on Oct. 14 and published in the Oct. 26 issue of the journal Neurology. "I'm not saying that people shouldn't have this surgery, but I am saying that there are real potential complications and that good follow-up care is necessary."

The Mayo Clinic investigators found that 16 percent of weight-reduction surgery patients they studied developed a peripheral neuropathy: nerve problems ranging from minor tingling or numbness in the feet to severe pain and weakness confining patients to wheelchairs.

"It's surprising how many of these patients developed peripheral neuropathy," says Dr. Dyck. "Sixteen percent is a large number. But patients who were part of nutritional programs before and after their weight loss surgery generally didn't develop these neuropathies, so we believe the nerve damage is largely preventable."

Dr. Dyck and colleagues identified risk factors in weight-reduction surgery patients who later developed nerve problems: 1) they lost weight at a much faster pace, 2) they received less nutritional supplementation, 3) they experienced prolonged nausea and vomiting, and 4) they failed to attend nutritional clinics.

"The evidence is very strong that nerve complications are associated with malnutrition," says Dr. Dyck.

Some forms of malnutrition are well recognized to cause peripheral neuropathy, such as thiamine deficiency in the disease beriberi. Rather than the surgery being a direct cause of neuropathy, the associated rapid weight loss and prolonged nausea and vomiting can lead to malnutrition and neuropathy.

An important key to preventing peripheral neuropathy is to seek a robust program with presurgical and postsurgical care by a multidisciplinary team of specialists who can oversee the patient's nutritional status. "Don't just choose a surgeon, choose a program," says Dr. Dyck. "Patients in our study who were not part of programs were more likely to end up with nerve problems. This is a life-changing operation. It's like having transplant surgery -- you need long-term follow-up."

Michael Sarr, M.D., a Mayo Clinic weight-reduction surgeon who participated in this study, adds, "It's a risky operation, but it's a calculated risk in that morbid obesity is life threatening. Obesity can cause sleep apnea, diabetes untreatable by insulin, excess fatty substances in the blood, and coronary artery disease. Weight-reduction surgery shouldn't be taken lightly, but it has tremendous benefit to select patients."

Dr. Dyck and colleagues embarked on this study due to a pattern they observed in the peripheral neuropathy clinic. "We'd seen patients with nerve problems in our clinic who'd had weight-reduction surgery," he says. "We saw the association, and we wanted to test it in a scientific way."

The investigators searched the charts of 435 patients who had undergone either Roux-en-Y gastric bypass or vertical banded gastroplasty, also known as "stomach stapling," at Mayo Clinic or other medical institutions to determine who later developed peripheral neuropathy. Three nerve disorders were identified in the study patients: 1) sensory predominant neuropathy, marked by pain and/or sensory loss, usually in the feet, 2) mononeuropathy, involving individual nerves, as in carpal tunnel syndrome, and 3) radiculoplexus neuropathy, marked by weakness, sensory loss and/or pain in a patchy, multifocal way. Radiculoplexus neuropathy can have the most serious consequences of the three, including confining a patient to a wheelchair.

To ensure that peripheral neuropathy was not linked to just any abdominal operation, the team also identified a control group of 123 obese patients who had undergone open gallbladder removal, another abdominal surgery. Only 3 percent of the control group developed a peripheral neuropathy.

"This is highly statistically significant," says Dr. Dyck. "We believe that the peripheral neuropathy relates specifically to the weight-reduction surgery and not just any type of abdominal surgery."

Dr. Dyck and colleagues have not yet studied whether these nerve problems are reversible. "We don't know what the long-term outcomes will be for these patients," he says. "Nerves can regrow, and there are people who have improved."

According to Dr. Dyck, this is the largest and most systematic identifying patterns of neuropathy in weight-reduction surgery patients. It also is the first to use a control group to look for an association between weight-loss surgery and nerve problems, and the first to identify risk factors for developing peripheral neuropathy.
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