Are human head transplants on the horizon?

The past few posts I’ve written have been on the brain and neurology. I’m sure that some of the posts have sounded almost like science fiction rather than science:

Some amazing information, and true. And, even though they may sound far-fetched, most of us probably realized that, with current research techniques, they are possible. We will surely build on this research in the future. Whether those future outcomes are great (brain repair using cloned neural tissue) or horrific (motor or mind control) remains to be seen. However, when I read a paper describing this next research proposal – head transplants – I thought it was pure science fantasy.

Injury to neural tissue is difficult to repair. Nerves can be fragile things. We’ve seen people who have had traumatic injuries, or neurologic diseases, of the spinal cord who have been paralyzed. An example of the former is the late Christopher Reeve, who sustained spinal cord damage as the result of a fall. The latter is exemplified by Stephen Hawking, who has Amyotophic Lateral Sclerosis (ALS, Lou Gehrig’s disease). Both were almost completely paralyzed as a result.

Heads via Shutterstock

Heads via Shutterstock

What happens when neurological tissue is damaged? Many things that are far beyond the scope of this article. But, briefly, a few of the mechanisms are: immediate damage to the neurons, that can be deadly to them either immediately or over time, swelling, decreased blood supply, bleeding into the damaged tissue, release of neurotransmitters, damage from free radicals and scarring. All of those make repair very difficult.

Treatment includes stabilizing the area to prevent additional movement, surgery to decompress the area, remove debris and blood from the area and other treatments. Speed is of the essence, some studies show better outcomes when the area is treated quickly after the injury.

Experiments have shown that if the spinal cord is severed surgically (i.e., very precisely and cleanly) it can be reunited and the cells are able to regenerate better, to a degree. Additional research has focused on preventing scarring and enhancing the neurons’ ability to repair themselves.

Some of the early spinal cord work was done in the 1970s and 1980s. But the techniques available didn’t produce very good results in experimental animals. However, there have been some major changes since then.

Reapproximating the cut areas of the cord precisely, using microsurgical and other techniques, and the use of medications and chemicals, have started to produce impressive results. So much so that a neurosurgeon did a paper on the possibility of human head transplantation.

Sounds like science fiction. But so were kidney transplants until the 1950s. So was most heart surgery till the heart-lung bypass pump was developed.

Animal head transplants have been done for over 40+ years

Many people do not realize that animal head transplants have been done for over 40 years. Sometimes the donor head is connected to the recipient’s body. Other times the recipient’s head is removed and the donor head implanted. The first produces a two-headed animal.  Reportedly, a number of two-headed dogs were produced. Both heads could breathe and eat. But the dogs died in less than a month because of rejection issues with the transplanted head.

Similar experiments were done in monkeys, but the monkey’s own head was removed and the donor head attached, producing a one-headed animal. Again, these animals only lived a short time, but the heads did function. One of the transplanted monkey’s heads even tried to bite the researchers.

These experimental animals were sacrificed after a few days. If not, the animals would have probably died from rejection. Remember, though, that much more is now known about tissue compatibility matching, the phenomenon of rejection and snit-rejection drugs, than was available in the 1970s and 1980s.

The author of this article is neurosurgeon Sergio Canavero. He’s written in detail about just how the surgery would need to be carried out, and the details behind preparation of the patients, surgical teams, operating rooms, technology and other factors. The paper has been published in a peer-reviewed journal and is available, online, for free. It’s worth reading, however it is really technical and detailed at times.

I am an MD, but I’m not a neurosurgeon, much less a surgeon. But I think that his article is very well thought out and the planning seems good. We may not ever know if it would work until it is attempted.

Aside from the technical issues, which are many, it raises a number of other interesting and difficult questions.

Is it even ethical to attempt a human head transplant?

The cost of a surgical procedure like this would be millions of dollars (after the construction of special operating rooms, obtaining necessary equipment, training surgeons and staff, etc.). Would it ever be worth is to spend that much money to save one life? If “yes,” who would qualify? How would we prioritize?

Would this lead to black market surgery for those who could afford it to have a chance at quasi-immortality? A black market in “recipient” bodies who are procured because of histocompatibility to the oncoming head transplant?

Does the chimera produced have the identity of the “body,” the identity of the “head,” both, or is it an entirely new person?

Does its new family consist of both of the previous beings’ families? If it has children, are they legally part of the biologic parent (i.e., from his reproductive cells) or the cerebral parent (who directed the procreative act), both, or is it the child of a new person?  (Genetically, they’d be the children of the body-parent, not the head-parent. But what about legally?)

I don’t know the answers. Perhaps they aren’t answerable, no transplant like this has ever been attempted.

What do you think about these issues? Are there even other problems that must be addressed?


Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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