In clinical trials, the new drug, BG-12, has been shown to lower the number of nerve cell attacks with fewer side effects. It is expected to cost about $50,000 a year, the same as other similar drugs. NBC's Robert Bazell reports. http://vitals.nbcnews.com/_news/2012/09/19/13967277-new-ms-drug-may-help-manage-one-of-the-biggest-mysteries-

Multiple sclerosis is a horrible disease afflicting an estimated 400,000 Americans. There is no cure and little understanding of the cause, even though the patterns of MS leave many tantalizing clues.

An experimental drug called BG-12 helps reduce the number of “flare-ups" in the disease, researchers reported on Wednesday -- much like the nine other drugs already approved to treat MS.

MS occurs because the immune system – mostly disease-fighting T-cells – destroy the myelin sheath, the coating on the outside of brain and spinal nerve cells. This doesn’t happen continually, but in separate attacks or flare-ups, often a year or more apart. No part of the brain or spinal cord seems resistant. Although people with MS can appear very healthy, these autoimmune attacks often inflict severe damage.

Lorie Osco was diagnosed with multiple sclerosis 15 years ago.  She has not had any side effects since she began taking it.

“MS can affect vision, movement, strength, sensation, bowel, bladder, sexual function, mood, cognition," says Dr. Robert Fox, a neurologist at the Cleveland Clinic who headed the BG-12 study. "Everything the brain does can be impaired from MS.”

Like most autoimmune diseases, it's possible MS is set off by a viral infection. After the infection, the immune system starts to mistake neurons for virus or infected cells and destroys them. The evidence for a viral role comes from studies done in the Orkney, Shetland and Faroe Islands off Scotland. All these islands share similar geography and ethnic makeup. Prior to 1943, the Orkneys and Shetlands had a high incidence of MS, and the Faroe Islands almost none. Then it evened out. The best guess is that the movement of British troops spread a virus.

Dr. Robert Fox, a neurologist at the Cleveland Clinic who headed the BG-12 study, says the drug is not a cure for MS, but it is well tolerated and helps decrease new lesions.      

Despite this and similar other areas that became infected at a certain time, scientists have yet to identify the virus.

There also strong evidence for genetic susceptibility. Much of that comes from the incidence of MS among various ethnic groups. Caucasians have the highest incidence. Some ethic groups have almost no MS. These include the Inuit of Canada, Yakuts of Russia, the Hutterites, a religious group in Montana, Hungarian Romani, Norwegian Lapps, Australian Aborigines and New Zealand Maoris.

Many populations in Africa almost never suffer MS, but when they migrate to Europe or the U.S. their rates go up. Many Asian populations have almost no MS, and for them migration does not seem to increase susceptibility. In general, MS seems to occur far more often in cooler climates than closer to the equator. Also like many autoimmune diseases, hormones seem to play a role. MS occurs about three times as often in women as men — especially for cases diagnosed for people in their 20s, 30s, and 40s.

Scientists have focused on each of these clues. But none has so far yielded the cause or a cure for the disease. And although people with MS have near-average life expectancies, until there are better medications, they will likely end up in a wheelchair with many other disabilities.