Researchers at the University of Calgary have documented serious health complications in multiple sclerosis patients who travelled outside of Canada to undergo a controversial treatment for their disease.

Many MS patients have travelled overseas to find clinics willing to provide the treatment invented by Italian physician Paolo Zamboni, which uses balloon angioplasty to open up blocked veins in the necks of those who suffer from the disease.

The new study followed five patients who had the vein opening therapy and were treated in Calgary hospitals in October and November last year after complications from their surgeries.

The lead author of the paper, Dr. Jodie Burton, admits that it is difficult to draw conclusions since there were only five patients involved and it's not known how many Canadians went to locations like the United States, Mexico, India, and Poland to have the procedure done.

But she says the seriousness of the complications should serve as a — quote — "cautionary tale" to anyone considering having the procedure done.

Burton says patients shouldn't be afraid to let their doctors know they had the treatment and physicians need to know what to watch for as a result.

In June, the federal government announced it will hold early-stage clinical trials into the treatment.