A U.S. ad featuring an Ontario woman who spoke out against the Canadian health-care system may be exaggerating the severity of her condition, say medical experts.

Canadian experts say that had Shona Holmes's case been deemed an emergency, she would have received care in Canada within days. (CBC)

Shona Holmes has appeared in U.S. ads saying she had to go to the Mayo Clinic in Arizona to be treated for a rare type of cyst at the base of her brain — a Rathke's cleft cyst. She mortgaged her home and paid $100,000 to be treated there because getting care in Canada involved a six-month wait, she said. She is currently suing OHIP to recoup those costs.

Holmes, from Waterdown, Ont., said she would have died had she relied on the Canadian health-care system and waited to see a specialist.

But the director of the brain tumour research centre at the Montreal Neurological Institute says he thinks that claim is "an exaggeration."

Dr. Rolando Del Maestro says the lesion Holmes was diagnosed with is benign, and usually slow-growing. It typically does not require urgent attention, he said.

"If it's a real emergency in the sense that the patient's visual function is getting substantially worse, the patients would be brought in immediately and would be operated on the next day," he said.

In 2005, Holmes, complaining of headaches and vision loss, went to see a Canadian doctor and was put on a six-month waiting list to see specialist.

After trying unsuccessfully to expedite the process, she was diagnosed and treated at the Mayo Clinic. Holmes said U.S. doctors considered the cyst a tumour, and that it would cause death if not removed immediately.

But neurosurgeon Michael Schwartz of Toronto's Sunnybrook Hospital says he's never seen or heard of a death from a Rathke's cyst. He told CBC News symptoms can be alleviated if the cyst is drained or part of it removed to take pressure off the optic nerve. "Then the person's vision almost always improves.

"If somebody called me about a patient that was losing her vision or had a structural abnormality of the brain I would see them within days."

Opposition to Obama

The contentious advertisement is being run by a conservative lobby group, the Americans for Prosperity Foundation, opposed to U.S. President Barack Obama's plan to involve the government playing a role in reforming U.S. health care.

It warns that Washington wants to bring in Canadian-style health care that would cause "deadly" delays for people waiting for important medical procedures.

Holmes denies taking any money from Americans for Prosperity for her message. Her publicist, paid for by the lobby group, says she's now declining interviews.

But Holmes told CBC News in an earlier interview she believes Canadians are not speaking up about the problems in the health-care system. She said that every time she thinks about stopping her criticism of the system, she gets "another really sad phone call or desperate phone call of somebody who is tragically trying to get treatment in Canada and can't."

Americans for Prosperity says it has spent nearly $1.8 million US running the ad in Washington, D.C., and 11 states with key senators who are either writing health-care bills or wavering on the issue.

It is one of a handful of commercials that are expected to grow in number and criticism this summer as detailed health bills emerge from the U.S. Congress and dozens of interest groups, companies and labour unions tussle to influence legislators.

Through June 27, $31 million has been spent for roughly 47,000 TV ads on health care this year, says Evan Tracey, president of the Campaign Media Analysis Group, a firm that tracks issue advertising.

So far, Tracey said about $15 million has been spent on ads favouring the Democrats' push to revamp the health-care system and $4 million to oppose it. Another $12 million has gone to ads generally favouring better health care, nearly all of it from the Pharmaceutical Research and Manufacturers of America, representing drug makers, which hopes its market will expand if more people have insurance.

Tracey estimated that $250 million will ultimately be spent on the campaign this year.

With files from The Associated Press