Although an Italian neurosurgeon recently boasted that he plans to conduct a human head transplant within two years, experts say this proposal is scientifically and ethically absurd.

The idea behind the operation is that it could theoretically extend the life of a person whose body is gravely damaged or diseased by putting his or her head onto the body of a deceased donor. The surgeon said he plans to achieve this feat by joining the spinal cords of the severed head and new body. However, some experts aren't convinced.

"I don't think it's possible," said Dr. Eduardo Rodriguez, a professor of reconstructive plastic surgery at NYU Langone Medical Center in New York City, who performed the world's most complete facial transplant in 2012.

Even today, after decades of research on spinal-cord injuries, there are still very limited options for treating people with these injuries, he said. In other words, because researchers have not found a way to rejoin two parts of an injured person's spinal cord, it's difficult to think that they could join two spinal cords from two different people.

A heady procedure

The unorthodox idea is the brainchild of Dr. Sergio Canavero, a functional neurosurgeon at the Turin Advanced Neuromodulation Group in Italy.

The first step of Canavero's proposed procedure would be to sever the spinal cords of both a recipient (who has a diseased body but an otherwise healthy head and brain) and a donor (who would likely be a brain-dead person, with an otherwise healthy body). He would then fuse the recipient head and donor body together, essentially giving the head a new body to control and inhabit.

In an interview with Live Science, Canavero described the procedure in an almost blasé way. "Once I attach a new body, I fully expect the head and body to adapt to each other," he said. He even went so far as to compare head transplants to sending humans to space. "If America doesn't [attempt the procedure], China will," he said.

Canavero fancifully calls the procedure the "head anastomosis venture," which he abbreviates as "HEAVEN."

Both decapitations would be done under hypothermic conditions (i.e., with the body temperatures lowered), in order to preserve the tissue during the time when it is not connected to a circulatory system, he said. The nerves would be electrically stimulated after the operation, to help the person recover, he added.

Canavero said he has dreamed of doing a head transplant since he was 15, when he read a newspaper article about Dr. Robert White, an American surgeon who transplanted the head of one monkey onto another monkey's body in 1970. After the operation, the monkey was paralyzed from the neck down but was able to hear, smell, taste and move its eyes. The animal died nine days later because its immune system rejected the "foreign" head.

In the 1950s, a Soviet scientist named Vladimir Demikhov conducted a similar experiment with dogs, except instead of severing both animals' heads, he surgically attached the head of one animal onto the other so that it had two heads. And Japanese scientists have done the same with rats.

To be clear, there have been no known attempts to perform a head transplant in humans.

Scientifically unsound

Canavero claims his technique could succeed where attempts to heal the spinal cords of people with injuries have failed because his procedure involves making a sharp, clean cut through both spinal cords, instead of the types of blunt blows that people undergo in accidents or other injuries. He demonstrated his notion in a 2014 TEDx talk he gave in Cyprus by holding up two bananas and neatly slicing through one with a knife while letting the other drop to the ground, where it squished under its own weight.

Canavero said he could join two people's spinal cords using a compound called polyethylene glycol (PEG), which has been shown to help heal spinal-cord injuries in some animals.

But Rodriguez told Live Science,"We're not to the point where we can replace a head and have a functioning central nervous system."

Rodriguez and his colleagues performed the world's most comprehensive face transplant in 2012, on a man named Richard Norris, who had suffered a gunshot wound that left him disfigured. Although that transplant was a success and Norris did regain some function of his facial nerves and muscles, "it's not perfect," Rodriguez said.

Then, there's the issue of immune system rejection — in which the immune system sees the new body part as foreign and attacks it — which is always a risk in organ transplants. Although medications that suppress the immune system work fairly well, transplant recipients' bodies may still reject organs, Rodriguez said. "I can't even entertain the possibility [of a head transplant] — it's a little too much science fiction right now," he said.

Ethically 'ludicrous'

Even if a head transplant were medically possible, it poses major ethical issues, some experts say.

"I think it's ludicrously stupid," said Arthur Caplan, a bioethicist, also at NYU. "You'd probably be charged with homicide if you chop somebody's head off before they're dead," he added.[7 Absolutely Evil Medical Experiments] A person's body is also very important to his or her personal identity, Caplan said. "The idea behind this [transplant] is to preserve you, but if the only way you could do it is to transform your body, you haven't really saved yourself — you've become someone else," he told Live Science.

Caplan said he thinks it's much more likely that scientists will one day be able to replace the body of a person who has serious injuries with an artificial body, such as an exoskeleton. "We'll probably see a head on a robot before we see it on [another] body," he said.

But Canavero remains undeterred. As with any controversial idea throughout history, "you will meet with a lot of resistance from certain quarters," he said.