05/10/2012 11:58 am ET Updated Jul 10, 2012

Experimental Multiple Sclerosis Treatment Could Be Dangerous And Even Deadly: FDA

* At least 2 dead, one paralyzed from procedure

* Controversy about link between MS and blood vessel changes (Adds further FDA comment; recasts 1st paragraph)

By Anna Yukhananov

WASHINGTON, May 10 (Reuters) - U.S. drug regulators are warning people with multiple sclerosis that an experimental treatment that props open internal veins in the neck and chest can cause death or serious injury.

The Food and Drug Administration on Thursday said at least two people had died from the procedure, which uses stents or balloon angioplasties to widen veins that connect the brain and spinal cord to the heart. One person was permanently paralyzed, and others had bleeding in the brain, suffered strokes, blood clots or other side effects.

It is unknown how many people received the treatment and how many had problems, as stents and angioplasties are not approved for this use by the FDA, the agency said. Stents are steel mesh coils that can keep arteries open, while balloon angioplasties use a balloon at the tip of a catheter to open blocked blood vessels.

The FDA could not immediately identify the stent models being used in such treatments.

The FDA announcement relates to a controversy that has developed in the multiple sclerosis (MS) community about the causes of the chronic, progressive disorder of the brain and spinal cord.

The disease, which affects about 2.5 million people worldwide and has no cure, attacks the central nervous system and can lead to numbness, paralysis and loss of vision. Drugs that treat the condition, from companies like Biogen Idec Inc and Sanofi SA, can often only prevent relapses or slow its progression.

The underlying cause of MS is unknown. Some researchers believe that although it is typically thought of as a disorder of the immune system, it may actually be caused by blood vessel changes. Their theory is that veins bringing blood from the brain and spine back to the heart sometimes become too narrow, making blood leak back into the brain tissue. They say that could trigger inflammation, eventually causing the balance and muscle problems seen in MS.

Other scientists have not been able to show a link between MS and compromised blood flow, which is called chronic cerebrospinal venous insufficiency, or CCSVI, or prove the condition exists at all.

Meanwhile, MS patients seek new treatments, prompting patient advocacy and research groups to invest in more research studying the link between multiple sclerosis and CCSVI.

"Our position is that the evidence is simply insufficient to determine whether there's a link," said Dr. William Maisel, deputy director and chief scientist of the FDA's devices division. "We want patients to be aware this treatment (with stents or balloon angioplasty) is unproven, that there are significant risks associated with the treatment, (and) the benefits are uncertain."

The FDA said people who want to try the experimental treatment should first discuss the risks with their doctor, or should try the treatment while participating in clinical trials. (Reporting by Anna Yukhananov; Editing by Michele Gershberg, Maureen Bavdek and John Wallace)