We’ve come a long way in organ transplants. The first successful one was a kidney transplant in 1954, while the first lung was successfully transplanted in 1983. Nowadays, transplanted kidneys, hearts, pancreases, livers and lungs are seen as something quite normal. Other transplants however, are anything but…
In recent years, there has been a lot of controversy surrounding a type of transplant that has never yet been done: the head transplant. Given that we are essentially our brains, it is actually more accurate to refer to this as a full-body transplant, in that the recipient’s head is attached to the donor’s body.
The debate regarding head transplants was sparked after Dr Sergio Canavero, an Italian neurosurgeon, announced in 2015 that he would perform the first head transplant in 2017. The person who has volunteered to undergo this operation is Valery Spiridonov, a Russian 31-year-old man who suffers from Werdnig-Hoffmann disease, a genetic muscle-wasting disorder that has confined him to a wheel chair for much of his life. Dr Canavero explains that after a year of physiotherapy, following the operation, the patient will be able to walk.
Despite Canavero’s enthusiasm, many neurosurgeons and scientists have serious doubts about the feasibility of head transplants. The main problem is that no one has ever successfully reconnected the nerves of the spinal cord. If we knew how to reconnect these nerves, people with spinal injuries could be operated on and walk again. Alas, this is not the case.
However, Canavero states that the difference with spinal-cord injury is that there is gross damage to the nerves, making them hard to reconnect. He intends to use an ultra-sharp blade to cleanly cut the nerves. Canavero believes that severed nerves cut in this way can be fused together using a type of plastic called polyethylene glycol that acts as glue, in combination with electrical stimulation at the point of fusion, which promotes regeneration of neurons. The main caveat with this theory is that it’s just a theory, having never been successfully achieved in animals.
In 1970, the head of a monkey was transplanted onto the body of another monkey. Although the monkey was able to see, hear, smell and eat, it couldn’t move its body, because spinal-cord fusion had not been developed yet –the monkey died a few days later. More recently, during 2013 and 2014, head transplants have been repeatedly performed in mice, without managing to achieve survival of more than one day. However, Canavero, who claims to be morally opposed to animal experimentation, thinks we don’t need more animal data, since human anatomy differs from monkeys or mice.
Even if the patient did survive this operation and the spinal cords were successfully fused together, it is still unclear whether they would walk again, since the complex network of neural connections differs from one person to another. If a head transplant guarantees survival, but no movement, it could be an option for patients with terminal conditions, who would benefit from a new healthy body, even if that meant becoming tetraplegic.
Besides the lack of scientific evidence for the feasibility of the procedure, other issues raised by Canavero’s critics are ethical concerns. Aside from the philosophical questions about the personal identity of the resultant individual, we should also ask ourselves whether we want to use one body to potentially save one person’s life, instead of using that one body to donate a heart, lungs, liver and kidneys to save many lives. We have certainly come a long way in the field of transplantation, and with ambitions such as Canavero’s in the pipelines for the very near future, what is already interesting to see is just how far we can and should push the transplant boundary.
Ren, X.-P., Song, Y., Ye, Y.-J., Li, P.-W., Han, K.-C., Shen, Z.-L., Shan, J.-G., Luther, K. and Yang, B.-F. (2014), Allogeneic Head and Body Reconstruction: Mouse Model. CNS Neuroscience & Therapeutics, 20: 1056–1060. doi: 10.1111/cns.12341.
Canavero S. HEAVEN: The head anastomosis venture Project outline for the first human head transplantation with spinal linkage (GEMINI). Surgical Neurology International. 2013;4(Suppl 1):S335-S342. doi:10.4103/2152-7806.113444.