A quadriplegic since she was 14, Jessica Grimm learned long ago how to work around her body's limitations.

She lives alone, uses a computer, has a job, even drives a car. But the Arlington student must rely on a coterie of assistants to help her dress, cook and get through each day.

Now 27, Grimm is eager for more independence. So much so that she traveled to Costa Rica last month for a controversial stem cell treatment that's unavailable in this country.

Grimm and her family raised about $20,000 to cover her trip to the Institute for Cellular Medicine, where doctors injected her with adult stem cells.

"I was actually able to take a few steps on my own before I left, which I've never done," she said. "My mom was crying. Then my physical therapist started crying."

The feat thrilled Grimm, who previously had some mobility in her legs and hand. But she still has no idea whether the treatment actually succeeded.

Doctors told her it could take months to see results. And it's possible that the real credit for her footsteps should go not to the cell injections, but to the strenuous physical therapy she did in Costa Rica.

"I don't know if it was the physical therapy or the stem cells. But it definitely showed me I need to get back into physical therapy," Grimm said. "If I can build more muscle, there's no telling."

That kind of ambiguity troubles some U.S. researchers, who worry about a rise in "stem cell tourism" as foreign clinics promote treatments for multiple sclerosis, Alzheimer's disease and a host of other illnesses. They contend that doctors from Ukraine to Mexico are pitching risky procedures on the Internet to vulnerable patients, with no science to back up their claims.

It's unclear how many people are traveling abroad for stem cell therapy or even how many clinics offer the treatments. But one biotech company, which boasts 24 hospitals in China, claims to have treated more than 3,000 patients at its facilities alone.