The transplantation of fetal stem cells into human brains received Food and Drug Administration approval in October. The intended recipients are six children who have Batten disease, a rare, degenerative genetic disorder that's always fatal. The procedure, which has successfully treated Batten disease in mice, could open the door to treatment of many other neural disorders.

Because of a defective gene, children with Batten disease lack an enzyme needed to remove cellular waste, which then accumulates in the brain and causes blindness, paralysis, and death. The researchers hope that immature brain cells injected into the brains of children with this disorder will mature into normal brain cells that produce the missing enzyme. Although mature brain cells have been transplanted into patients to treat Parkinson's disease and stroke, this will be the first transplantation involving immature brain cells.

Approval from an internal Stanford University review board was pending as we went to press. The fetal stem cells will originate from surgical and spontaneous abortions, raising ethical concerns about the procedure for some.