Alzheimer’s surgery may see changes

Ranging in age from their mid-teens to late 50s, the four Canadians died tragically after transplants of brain material gave them Creutzfeldt-Jakob disease (CJD), the human equivalent of mad cow disease.

Now, more than a decade later, their own brain tissue is being studied for answers to an unsettling question about another dreaded illness: Is it possible that Alzheimer’s disease — like CJD — could be transmitted from person to person?

New research, supported by the federal government, follows recent findings in the U.K. and Switzerland suggesting the protein “plaque” tied to Alzheimer’s can, in fact, be passed between human brains.

If so, that has real implications for surgery, especially since “misfolded” proteins — like the beta-amyloid implicated in Alzheimer’s — are not easily eradicated from hospital instruments, three Canadian researchers note in a recent commentary.

“If that (transmission) is shown in just one case … public-health thinking would need to rise to meet that challenge,” said Dr. Michael Coulthart, a Public Health Agency of Canada scientist. “It’s very important to get ahead as far as you can of something that may be an issue in even a few cases.”

Scientists stress a number of caveats: the evidence of Alzheimer’s transmissibility is far from definitive; even if that research is borne out, the circumstances in which transmission could happen would likely be rare; and the best way to curb the risk of dementia remains much simpler: eating a healthy diet and exercising.

Still, modern public health strives to predict possible threats — like HIV-tainted blood — before they overtake us, Coulthart said.

“You’re always looking for things that might be coming,” he said. “Precaution has become part of the basic name of the game in public health.”

Almost 750,000 Canadians have Alzheimer’s or other forms of dementia, a figure expected to double within 15 years.

It’s long been known that the “prion” proteins responsible for mad-cow and CJD can be transmitted, including through the eating of infected meat, being treated with contaminated brain tissue, or even through blood transfusions.

More recently, scientists have been able to inoculate animals with other types of “misfolded” proteins, including the beta-amyloid found in Alzheimer’s patients.

But the most striking science has emerged over the past five months.

First was a discovery in Britain involving eight, relatively young patients who contracted and died from CJD after they received growth hormone from the pituitary glands of dead people.

Scientists found that half of them also had Alzheimer’s-related amyloid plaque in their brains and blood vessels.

Then last month, Swiss researchers reported similar findings from seven people who had received grafts from cadavers of dura mater — the membrane that covers the brain and spinal cord — and developed CJD. Five of the brains showed pathological signs of Alzheimer’s, too.

The four Canadians whom Coulthart, director of CJD surveillance for the Public Health Agency, and his colleagues are studying are also believed to have acquired Creutzfeldt-Jakob from grafts of dura mater. They died from 1998 to 2003.

As part of the country’s CJD surveillance system, and with the consent of next of kin, samples of brain tissue from people with the disease are kept in a bank overseen by the federal agency.

Outside experts say the evidence that Alzheimer’s could be transmissible is plausible, though hardly conclusive. Even if the notion is proven valid, though, they question how important a factor it would turn out to be in the spread of dementia.

A number of issues appear to be at play in developing Alzheimer’s, not just the amyloid plaque and the tau proteins found in patients’ brains on autopsy, said Dr. Larry Chambers, scientific adviser to the Alzheimer’s Society of Canada. Other elements include cardio-vascular health, aging, environment and genetics, he said.

“It’s really complex, this business of trying to find the causal change that leads to dementia,” said Chambers, also a University of Ottawa professor.

It’s important to remember there is good evidence that eating a heart-healthy diet and exercising regularly is the best way to lower dementia risk — and prevent various other chronic diseases, too, said Dr. Paul Verhoeff, a psychiatrist and dementia expert at Toronto’s Baycrest Health Sciences.

Meanwhile, growth hormone is now synthetically made — not taken from humans — and dura mater grafts are no longer conducted.

“I wouldn’t become anxious about it,” Verhoeff said about the possibility that Alzheimer’s could be transmitted.