Because the treatment is expensive and not available in the United States, worries arise about whether stem cell injections are an expensive racket, offering false hope to paralyzed people.

But the science to support stem cells' healing possibilities is sound. NeuroVita Clinic is the Moscow treatment facility where Clarksvillian Brittney Ham received stem cell injections. Dr. Andrey S. Bryukhovetskiy explains how stem cells work on the clinic's Web site, www.neurovita.ru, translated here into English:

"Stem cells are able to proliferate and give rise to the main cell components of all organs and tissues of a body. It is the immature cell which is able to self renew and to develop into specific cells of an organism. All cells of a human arise from the only cell that is formed at impregnation. When a human is adult, the stem cells are localized primarily in bone marrow and in small quantities in all organs and tissues to provide restoration of the damaged organs and tissues."

Stem cells, then, have the ability to become any part of the human body. Putting them in place to regrow nerves is the goal of injecting stem cells into the spinal cord. What degree of sensation or function Ham will regain below the break in her spinal cord is uncertain. However Ham said the improvements she saw from her first visit, in 2006, made her cry with joy.