The study that gave Molson this chance was impressive in its scope and its execution — conducted at multiple hospitals by hematologists and neurologists in Canada and lasting nearly 20 years, from conception to publication. It built on decades of basic research about MS, stem cells, and the immune system, including years of experience using the treatment in patients with blood and bone marrow cancers like leukemia and lymphoma.

Other scientists have already seen promising results in MS patients using similar treatment protocols, but none have managed what Atkins’s team has: to completely halt the disease’s attack on the brain —no relapses, no new MRI lesions in all surviving patients — and for such a long follow-up period.

Several researchers who were not involved with the experiment — and who typically are reserved about novel treatments — told Vox they were excited and hopeful for the treatment’s potential to benefit others with the disease.

“I think this is going to be the new standard of care for progressive MS,” said Rudnicki.

“It’s exciting — an important proof of principle,” said Jeffrey Gelfand, a neurologist specializing in MS at the University of California San Francisco.

Tim Caulfield, a University of Alberta professor who has been tracking stem cell research, noted the difference between this robust finding and the unfounded claims in stem cell clinics around the world: “This is a fascinating development … [and] a good example of the difference between the real clinical research and what is being marketed by the clinics providing unproven therapies — you can’t simply ‘inject’ stem cells and expect significant results.”

Still, there are major caveats to consider. This study was small and lacked a comparison or control arm. Similar, larger studies are needed to confirm the results, and it’s not clear what will happen to patients like Molson in the much longer term.

Ottawa Hospital hematologist Harry Atkins, the researcher who led the study, pointed out that only about 5 percent of MS patients would be eligible for this treatment: again, the minority who have an aggressive form of MS that’s not responding to any treatment.

 Javier Zarracina/Vox

And not everyone in the study had results like Molson’s. Of the 24 patients, 70 percent saw the progression of their disease halt or reverse, but the other 30 percent continued to worsen.

That minority who didn’t respond, the researchers think, had MS that was already too far along by the time of their treatment. “At early stages, once the immune system quiets down, the brain can partially heal itself, so the disability tends to get better,” Atkins explained. “But as time goes on, the brain can’t repair itself.”

One patient died, which puts the potential for death from this procedure at around 4 percent, and severe infections after stem cell treatments — the kind Molson picked up, or worse — are also common.

Since there are other MS medications that are much less toxic and can help some patients, doctors only recommend considering this therapy as a last resort. (Theoretically, the treatment could be done in most blood and marrow transplant centers associated with major hospitals, Atkins said, but there are only a few that perform the procedure. Interested patients can contact the MS Society for more information.)

There’s also the cost: Atkins put it at about $50,000 to $65,000 per patient — and that’s if nothing goes wrong.

And there are questions about the very long-term effects. It’s not clear what the next 10, 20, or 50 years look like for patients like Molson.

“We know in the long term survivors from groups that have their transplants for cancer and they’re cured and they live a long time,” Atkins said, “that they have a higher incidence of the general population of other diseases [such as heart disease and cancers].”

Already, Atkins and his team have been working on other applications for this stem cell procedure. They managed to reverse “stiff-person syndrome” — a rare neurological disease that causes the muscles in the body contract to the point of complete immobilization — in one patient. And there’s talk of applying the treatment tomyasthenia gravis, another incurable autoimmune disease.

Cures in medicine are extremely rare. Atkins thinks it’s still too early to label this treatment a cure for MS. “We have only followed our patients for up to 13 years, so it’s hard to say what the next 10 to 20 will bring. You’d want to know that before you’d call this a cure.”

For now, though, Atkins will use the word miracle. “It still appears like a miracle to me to see patients recover, and get back to the things that they were supposed to do in life,” he said. “It is very rewarding to see and it wasn’t what we expected, and we are overjoyed about it to know this treatment can help people in that way.”