So on a December day, Mitchell Kohler, 7, is lying on a bed at Primary, watching a Scooby-Doo movie while Swoboda delivers little electric shocks and measures them. He takes valproic acid to see if it will help his disease. The shocks, he says, "feel like a goose pecking at me. A mean goose."

Mitchell has type 3, meaning he has much less-severe SMA. He walks, but his mom, Kellie, who has made the trip with him from Boise, Idaho, says he's clumsy and sometimes just falls down. It is possible that sometime in the future he will lose the ability to walk, but for now he's an active little boy who loves taking gymnastics.

His SMA first showed up when he was a little over 2. He was "walking funny and couldn't get up right," Kellie Kohler says.

Colin and Taleah wait in the hallway because they're up next for the testing. Taleah has the most severe form, type 1. Colin is a type 2. Children with SMA have various numbers of copies of the SMN2 gene, which determines the degree of disability. The number ranges from 0-6, with more severe disease for those with fewer copies. Colin has 4.

Type 1 patients such as Taleah live abbreviated lives, felled prematurely by their fragility and complications. She has been extremely weak since she was 4 months old and is terribly susceptible to illness, especially respiratory problems. She is, at 3, a relatively old type 1 SMA child. As many as 90 percent die by age 2. Her mother, Swoboda notes, "takes exquisite care of her," but has still almost lost her several times.

Monica English shrugs at the praise. "When you are told your child has a terminal illness and no one can give you hope, you find your own way," she says.

Type 2 children live longer, but their lifespan is shortened. Someone with Type 3 can have a very normal lifespan. And there's some guesswork involved. Someone can be a "weak type 3 or a strong type 2," for instance, and it's hard to tell for sure, Swoboda says. She knows a man in his 30s who has six SMN2 copies and can run and is strong. But he has the double genetic deletion that is SMA.

Some families with kids who have SMA fly into Salt Lake from far away to participate in the yearlong study. For several months, testing and physical therapy establish a baseline. Then they're given one of the medications (they're being compared for effectiveness) for the rest of the year to see what it does.

Because Taleah has SMA, her baby brother was tested while still in the womb. He was enrolled in the study and given the study medication first when he was 3 days old, in hopes of preventing the disease's progression.

"We won't know for a couple of years if we've changed Colin's course," Swoboda says. "If we help him from birth, there's a better chance of catching it before his motor neurons drop."