Darrell Dexter's comments in favour of his province's participation in a trial came in response to the Manitoba health minister, who wrote a letter to her provincial, federal and territorial counterparts seeking support for so-called liberation therapy.

The treatment is based on a theory that narrowed neck veins cause blood-borne iron deposits to build up and damage brain cells, and that unblocking the veins will help people with MS.

The Cambridge, Mass., biotech company reported that the number of deaths among patients that have developed the infection--known as progressive multifocal leukoencephalopathy, or PML--remains at 12.

Sales of Tysabri are important to the future of both Elan and Biogen. The drug is considered a highly effective therapy for multiple sclerosis, but its growth has been slower than originally hoped due to concerns about the risk of PML that led to the drug's temporary withdrawal beginning in 2005.