US Federal regulators have approved what would be the first transplant of fetal stem cells into human brains, a procedure that if successful could open the door to treating a host of neural disorders. The transplant recipients will be children who suffer from a rare, fatal genetic disorder. The Food and Drug Administration said that doctors at Stanford University Medical Center can begin the testing on six children afflicted with Batten disease, a degenerative malady that renders its young victims blind, speechless and paralyzed before it kills them.