Dr. Canavero says he believes recent animal studies have shown human head transplantation is "feasible."
Dr. Sergio Canavero, of the Turin Advanced Neuromodulation Group (TANG) in Italy, believes the revolutionary procedure - named HEAVEN-GEMINI - could save the lives of people with metastatic cancer or muscle-wasting disorders, such as muscular dystrophy.
Medical News Today first reported on Dr. Canavero's proposal in July 2013. Back then, he noted some challenges for human head transplantation: reconnecting the severed spinal cord, and preventing the immune system from rejecting the head.
In an editorial recently published in the journal Surgical Neurology International, Dr. Canavero says he believes these challenges can now be overcome, noting that recent animal studies have confirmed human head transplantation is "feasible."
The idea of head transplantation is not new. In 1970, US neurosurgeon Dr. Robert White transplanted a monkey's head onto another monkey's body. Though the animal was able to see, hear, taste and smell, it was left paralyzed because surgeons did not have the technology to fuse the monkey's spinal cord nerves to its head. It died 9 days following the procedure, after the animal's immune system rejected its head.
But in his editorial, Dr. Canavero points to a 2014 study in which German researchers successfully reconnected the severed spinal cords of rats, suggesting the same technique could be applied to humans.
In addition, the researcher believes modern drugs mean the possibility of immune rejection is not as challenging as it once was. William Matthews, chairman of the American Academy of Neurological and Orthopedic Surgeons (AANOS) told New Scientist magazine that the immune response to a head transplant should be manageable. "The system we have for preventing immune rejection and the principles behind it are well established," he added.
What will the HEAVEN-GEMINI procedure involve?
Both the recipient's head and the donor body will be placed in "hypothermia mode" for approximately 45 minutes, which is believed to eliminate any neurological damage that may be caused by lack of oxygen.
The head will be removed from the donor body using an "ultra-sharp blade" in order to limit damage to the spinal cord. "The key to SCF [spinal cord fusion] is a sharp severance of the cords themselves," Dr. Canavero explains, "with its attendant minimal damage to both the axons in the white matter and the neurons in the gray laminae. This is a key point."
The recipient's head will then be attached to the donor body. This is the most difficult part of the procedure, which will involve fusing the end of spinal cord in the body with that of the head. Dr. Canavero says chemicals called polyethylene glycol (PEG) or chitosan can be used to encourage SCF. Next, the muscles and the blood supply will be sutured.
In his original proposal, Dr. Canavero said the procedure is likely to take 36 hours to complete and require the skills of 100 surgeons.
Once the surgery is complete, the recipient will be kept in a coma for around 3-4 weeks to avoid neck movements and give the nerve connections time to fuse. During this time, the recipient's spinal cord would be subject to electrical stimulation via implanted electrodes, with the aim of enhancing the new nerve connections.
Dr. Canavero told New Scientist that once the recipient awakes, they will be able to move their whole body and their voice would sound the same. He believes that the patient will be able to walk within 1 year with the help of physical therapy.
The ethics 'is a real stumbling block'
It is not surprising that many researchers are skeptical about Dr. Canavero's proposal, claiming it is too far-fetched to work.
"This is such an overwhelming project, the possibility of it happening is very unlikely," Harry Goldsmith, a clinical professor of neurosurgery at the University of California-Davis told New Scientist. "I don't believe it will ever work, there are too many problems with the procedure. Trying to keep someone healthy in a coma for 4 weeks - it's not going to happen."
In addition, the procedure has raised many ethical concerns. In 2013, Dr. Canavero said there is a worry that, without sufficient regulation, the procedure may one day lead to wealthy, aging individuals securing the healthy bodies of young individuals on the black market, with "unscrupulous" surgeons carrying out the head transplantation.
Still, he believes the HEAVEN-GEMINI procedure has the potential to save lives, and he hopes his proposal at the AANOS Annual Conference will attract some support for the world's first human head transplantation - particularly from the US.
Dr. Canavero told New Scientist:
"The real stumbling block is the ethics. Should this surgery be done at all? There are obviously going to be many people who disagree with it.
If society doesn't want it, I won't do it. But if people don't want it in the US or Europe, that doesn't mean it won't be done somewhere else. I'm trying to go about this the right way, but before going to the moon, you want to make sure people will follow you."