Bariatric Surgery Puts Patients at Risk for Peripheral Neuropathies

Patients who undergo bariatric surgery (BS) expect to lose weight, notnerve function. According to a new study, however, these patients are athigher risk for peripheral neuropathy (PN).

Malnutrition may be the main cause, according to principal investigator P.James B. Dyck, MD, associate professor of neurology at the Mayo Clinic Collegeof Medicine in Rochester, Minn. At the 23rd Annual Science ReportersConference, held October 6 in Washington, D.C., and sponsored by the AmericanMedical Association, Dyck discussed how lack of nutritional counseling andsupplementation, coupled with gastrointestinal (GI) complications, contributedto post-surgical starvation.

In the retrospective study, reported in the October 2004 issue ofNeurology, researchers reviewed the medical records of 435 patientswho had undergone one of four types of gastric bypasssurgery.¹Laparoscopic procedures were excluded. All patients were seen at the MayoClinic between January 1985 and December 2001. Many of the patients had theirsurgeries elsewhere and were referred to Mayo after complicationsdeveloped.

The control group comprised 300 patients, all of whom were obese and hadundergone cholecystectomy.

Of the BS patients, 71 (16%) developed PN postoperatively. Neuropathieswere focal (involving one nerve) or generalized, and ranged from mild tosevere. Some patients ended up in wheelchairs.

Of the control group, four patients (3%) developed PN after surgery.

“People who attended [Mayo's] nutrition clinic before and after[surgery] and who were well-followed had less peripheral neuropathy,”Dyck says. “Patients need close nutritional and vitamin supplementationbefore and after surgery.”

WEIGHT LOSS: TOO MUCH, TOO FAST?

Patients who developed PN after surgery lost an average of 43 kg andreached their maximum weight loss at 8 months. Patients who did not develop PNlost an average 33 kg and took an average of 19 months to plateau. Patientswith PN had a lower postoperative body mass index (BMI) than patientswithout.

The study revealed that GI complications added to the problem.“People were [already] taking in fewer calories, vitamins, andnutrients,” Dyck says. “With prolonged nausea, vomiting, diarrhea,and dumping, these people are set up for malnutrition.” Patients with PNhad reduced levels of serum albumin and transferrin. Thiamine levels were notroutinely checked.

SURGICAL PERSPECTIVE

“It's clear that [PN] is related to a vitamin B1 (thiamine)deficiency in patients who get into excessive vomiting or aren't taking theirvitamins as they should,” says Harvey J. Sugerman, MD, president of theAmerican Society for Bariatric Surgery.

“We make a very big point both before and after surgery of patientstaking vitamins,” Sugerman says. “We tell them on the first visit,when we discuss risk. We discuss it in [classes] that all patients must takeimmediately before surgery. The issue is also addressedpostoperatively.”

Sugerman, who retired recently, says excess weight loss was never an issuein his practice. “These patients don't reach their ideal body weight.They lose about two-thirds of their excess weight. If a patient has a problemwith nausea and vomiting, that would be associated with[malnutrition] risk.”

Sugerman agrees with Dyck's emphasis on the importance of a broadmultidisciplinary approach in the care of BS patients.

A VARIETY OF NEUROPATHIES

The researchers found three patterns of post-BS neuropathies:

Mononeuropathy: Carpal tunnel syndrome was the most commonmononeuropathy after BS. Of the 39 patients who developed a single neuropathy,31 had carpal tunnel syndrome. Seventeen had bilateral mononeuropathies, allcarpal tunnel except for one case of bilateral neuropathies at the elbows.Sugerman says one explanation for carpal tunnel syndrome after BS is thatpatients “lose fat pads around their wrists where the nerves comein.”

Sensory predominant polyneuropathy (SPN): Twenty-seven patients werediagnosed with SPN. Symptoms include prickly numbness, usually in the feet andhands. Sixteen had aching, stabbing, or burning pain; 12 had autonomicsymptoms including lightheadedness, urinary incontinence, and impotence.Eighteen patients had reduced deep tendon reflexes. The mean was 21 on theNeuropathy Impairment Score (NIS), a measure of loss of strength, reflex, andsensation.

Radiculoplexus neuropathy: This was found in five patients. It has asudden onset and causes numbness and weakness. Three of the patients hadlumbosacral radiculoplexus neuropathy (lower limb syndrome) and two hadcervical radiculoplexus neuropathy (upper limb syndrome). The mean NIS was 35.None of the patients in the control group developed radiculoplexusneuropathy.

DIABETES IMPLICATIONS

Glycated hemoglobin (A1C) level was not associated with PN development inBS patients. Although type 2 diabetes was not found to be a risk factor for PNoverall, Dyck says subgroup analysis showed that it was a contributing factorfor mononeuropathy. He notes that anyone who has diabetes will have issueswith healing, but adds that BS can help these patients.

TAKING A TEAM APPROACH

BS is effective for many morbidly obese patients, and the number of theseprocedures is on the rise. Based on weight, “some 20 to 25 millionAmericans would be candidates for bariatric surgery,” Dyck says.Although the study didn't address treatment, “the obvious thing is tomeet nutritional needs,” Dyck says. “When you do this, you're onthe way to treating neuropathy.”

Study patients who had undergone surgery at the Mayo Clinic had a lowerincidence of PN, which was attributed to close pre- and postoperativemonitoring by a health care team.

“I would tell patients to choose a program with a multidisciplinaryapproach, not just choose a surgeon,” Dyck says. ▪

A Pound of Prevention

Harvey J. Sugerman, MD, president of the American Society for BariatricSurgery, recommends:

1. All obesity surgery patients should get multivitamins with B vitamins,vitamin C, and calcium.

2. Gastric bypass patients, especially menstruating females, should getsupplemental iron, calcium, and high-dose vitamin B12.

3. Patients getting the duodenal switch procedure should get all the abovesupplements plus water- and fat-soluble vitamins. Duodenal switch limits foodintake and absorption of calories and nutrients by the body. Patients loseboth fat and fat-soluble vitamins during the procedure.

4. Problems with nausea and vomiting should be addressed before malnutritionbegins.

For instance, laparoscopic adjustable gastric band patients can have theirbands loosened, and gastric bypass patients can have their narrowed outletdilated using endoscopy.