RALEIGH, N.C. - Doctors warn that a few obesity surgery patients have developed a serious neurological condition, with symptoms of confusion and poor coordination, linked to a lack of vitamin B1.

Wernicke encephalopathy, which is caused by a thiamine deficiency, is normally associated with severe alcoholism or chronic malnutrition. However, researchers say it can also occur within a few months of obesity surgery if patients stop taking prescribed vitamin supplements or if they vomit frequently, preventing vitamins from being absorbed.

Patients who show symptoms "need to seek help immediately and get injections of thiamine as early as possible," said study author Sonal Singh, an instructor in internal medicine at Wake Forest University School of Medicine. "For doctors, the message is that they should keep this in their minds when they see these patients."

Singh said cases of Wernicke encephalopathy may increase as the number of bariatric surgeries performed in the United States continues to grow. About 170,000 obesity surgeries were done in 2005, up from 120,000 the year before and 16,000 in 1992.

Philip Schauer, the president of the American Society for Bariatric Surgery, said that while Wernicke encephalopathy isn't unique to obesity surgery or a common outcome after such procedures, he agrees it's something doctors should watch for.

"A mild degree of nausea after surgery and rare, episodic vomiting is really common in the first several days and weeks after surgery. If it's an isolated thing, one or two episodes and that's it, it's not a problem," said Schauer, who is also director of bariatric surgery at the Cleveland Clinic in Ohio.

More severe symptoms should be addressed immediately, he said.

"The surgeon and the health care team ... must be aware of somebody having very severe nausea and vomiting," Schauer said. "That person, if they're calling from home, should be brought in to see the doctor or to the emergency room."

Singh and co-author Abhay Kumar of the University of Iowa searched obesity surgery case histories, dating back to the 1980s, locating 32 cases of Wernicke encephalopathy. They looked at symptoms and risk factors.

Their findings are published in the this week's issue of the journal Neurology. The researchers called for more study to determine how often the condition affects bariatric patients and to determine the best treatment for it.

The study found that cases occurred from four to 12 weeks after the surgery, though one occurred 18 months later. Twenty-seven victims were female, but that may be because 75 percent of the surgeries involved women.

The patients suffered from confusion, a lack of coordination and rapid rhythmic eye movement, classic symptoms of Wernicke encephalopathy. Several also had problems with weakness, seizures, deafness and limb numbness.

Most recovered completely after getting thiamine intravenously, though a few continued to have problems with memory, coordination and vision.