Editing Head transplant (section)

==Medical challenges==
There are three main technical challenges. As with any [[organ transplant]], managing the immune response to avoid [[transplant rejection]] is necessary. Also, the brain is highly dependent on [[perfusion|continuous flow of blood]] to provide oxygen and nutrients and remove waste products, with damage setting in quickly at normal temperatures when [[ischemia|blood flow is cut off]]. Finally, managing the [[nervous system]]s in both the body and the head is essential, in several ways. The [[autonomic nervous system]] controls essential functions like breathing and the heart beating and is governed largely by the [[brain stem]]; if the recipient body's head is removed this can no longer function. Additionally each [[nerve]] coming out of the head via the spinal cord needs to be [[Epineurial repair|connected]] to the putatively corresponding nerve in the recipient body's spinal cord in order for the brain to control movement and receive sensory information. Finally, the risk of systematic [[neuropathic pain]] is high and {{as of|2017|lc=y}} had largely been unaddressed in research.<ref name=Lamba2017rev/>

Of these challenges, dealing with blood supply and transplant rejection have been addressed in the field of transplant medicine generally, making transplantation of several types of organs fairly routine;<ref name=Lamba2017rev/> however, {{as of|2017|lc=y}} in a field as common as [[liver transplantation]] around a quarter of organs are rejected within the first year and overall mortality is still much higher than the general population.<ref>{{cite journal|last1=Muduma|first1=G|last2=Saunders|first2=R|last3=Odeyemi|first3=I|last4=Pollock|first4=RF|title=Systematic Review and Meta-Analysis of Tacrolimus versus Ciclosporin as Primary Immunosuppression After Liver Transplant.|journal=PLOS ONE|date=2016|volume=11|issue=11|pages=e0160421|doi=10.1371/journal.pone.0160421|pmid=27812112|pmc=5094765|bibcode=2016PLoSO..1160421M|doi-access=free}}</ref> The challenge of grafting the nervous system remained in early stages of research {{as of|2017|lc=y}}.<ref name=Lamba2017rev/><ref name=Furr2017rev/>