Surgery that helps an obese patient lose weight can also reduce the body's ability to properly absorb certain nutrients, in particular vitamin B1. And that deficiency can lead to permanent brain damage if left untreated, researchers say.

In a review of the medical literature, researchers at the Wake Forest University School of Medicine found 32 cases of bariatric surgery patients who developed symptoms of Wernicke encephalopathy, a condition marked by memory loss and confusion, an inability to co-ordinate movements, and rapid-eye movement.

'We found that these people also had other symptoms, like hearing loss, convulsions and tingling and numbness of the arms and legs.'—Study author Dr. Sonal Singh on newly described symptoms of vitamin B1 deficiency

Wernicke's is caused by a deficiency in vitamin B1, also called thiamine, and these classic symptoms are usually seen in alcoholics, said lead author Dr. Sonal Singh, an internal medicine specialist at Wake Forest University in Winston-Salem, N.C.

"But interesting to our study, we found that these people also had other symptoms, like hearing loss, convulsions and tingling, and numbness of the arms and legs — symptoms that have not been previously described with Wernicke's," Singh said in an interview.

That made the researchers wonder if these bariatric surgery patients were suffering from more than just a B1 deficiency and may have been experiencing a deficit of other critical nutrients or had developed immunological problems.

Strangely, almost half of the patients with the neurological symptoms showed no brain lesions when given an MRI scan, said Singh, whose study will be released Tuesday in the journal Neurology.

Prompt treatment important

Of the 32 patients — who had one of four weight-loss surgeries, including gastric bypass and gastric banding — 13 made a full recovery. Eighteen others were left with various levels of dysfunction and one patient, a 33-year-old woman, died.

Most had experienced vomiting prior to onset of the neurological symptoms, said Singh, noting that patients ranged in age from 23 to 55, and 27 of the 32 were women. (In the United States, 75 per cent of bariatric surgery patients are women, he said.)

The vomiting could have been caused by any of several factors, including:

• The anatomical changes created by the surgery.
• Blockages caused by swelling around the surgical area.
• Ulcerations or other erosions of the stomach developed following the operation.

"When people who have had weight-loss surgery start experiencing any of these symptoms, they need to see a doctor right away," stressed Singh.

Check for vitamin deficiency

"Doctors should consider vitamin B1 deficiency and Wernicke encephalopathy when they see patients with these types of neurological complications after weight-loss surgery. If treated promptly, the outlook is usually good."

The average point at which patients began exhibiting Wernicke's symptoms was four to 12 weeks after surgery, though one patient developed problems two weeks after the operation and another 18 months later.

Wernicke's is a rare complication that can occur with any operation, but after bariatric surgery, there may be a blockage in the outlet of the new stomach that can cause vomiting, said Dr. Nicolas Christou, director of the bariatric surgery program at the McGill University Health Centre.

"If then people aren't able to keep down their food, and more importantly their vitamin supplements, then it's quite possible that they can become vitamin deficient and develop this particular complication."

It is important to keep people hydrated, give intravenous multivitamins and follow patients for six months after the surgery, said Christou, who was not involved in the study.

Singh said his study could not determine how common Wernicke's encephalopathy is among people who have surgery to help them lose weight, and he said studies that follow patients are needed to establish how often it occurs.

While some doctors prescribe thiamine supplementation after bariatric surgery as a matter of course, Singh believes national standards should be set for physicians to follow.

"This is an emerging risk which is going to become more important in the future as more people get surgery," he said.