The history, theory, and present status of brain transplantation

Many questions remain unanswered concerning fetal tissue transplantation: Which conditions result in maximal graft survival and function? Which patients are best suited for transplantation therapy? Why do some patients improve more than others? Is immunosuppression necessary when transplanting fetal tissues? Even though the science of neural transplantation is still in its infancy, the clinical use of CNS transplantation has been achieved on a worldwide scale. The many unanswered questions demand continued laboratory investigations and development of more clinically applicable animal models. Ongoing clinical trials will provide advancement of technique and generate more questions. The future is promising for CNS transplantation. As experience and knowledge accumulate, treatment of a greater variety of CNS diseases, including degenerative, traumatic, vascular, and developmental disorders, may find therapeutic options in the realms of brain transplantation. Key factors in transplantation which must be defined relate to donor tissue, transplant technique, and recipient status. Improvements in surgical techniques will advance the field, but the key issue remains how to increase cell survival and axonal extensions within the host brain.