you shouldn't put aborted baby cells/embryos/embryonic stem cells inside a person's brain. When you put fetal neural cells in a person's brain, those cells grow rapidly because they're programmed to grow a brain in 9 months. Also, there is also the probability that the body's immune system will reject the foreign body in it just like in kidney and other body organ transplants - the donated organ must be matched with the patient.
Using fetal cells have been used before to treat Parkinson's patients with a result of death to the patient. The cells grew teratomas containing skin, nails and bone.