How Human Head Transplants Could Work

Dr. Sergio Canavero discusses his hopes to perform the world's first head transplant on Russian Valery Spiridonov at a meeting of the American Academy of Neurological and Orthopaedic Surgeons in Annapolis, Maryland, on June 12, 2015.
Dr. Sergio Canavero discusses his hopes to perform the world's first head transplant on Russian Valery Spiridonov at a meeting of the American Academy of Neurological and Orthopaedic Surgeons in Annapolis, Maryland, on June 12, 2015.
© Jay Mallin/ZUMA Press/Corbis

In 2009, Cincinnati Bengals wide-receiver Chris Henry was involved in a tragic automobile accident. The accident left him with such grave injuries that he was pronounced brain-dead at the hospital. As Henry was not signed up to be an organ donor, his mother, Carolyn Henry Glaspy, found herself with the choice of what to do with his organs. Glaspy consented to donate her son's lungs, liver, kidneys and pancreas to four different strangers. Her decision saved the lives of several people desperately clinging to life on the transplant list. She even met them after the operations to see how her son lived on through the organ recipients [source: Donate Life North Carolina].

This story, and the many other similar ones out there, is simultaneously heartbreaking and heartwarming. How would the emotions change if the conversation wasn't about organ transplants but rather an entire body transplant? What if surgeons were able to place the head of someone with an intact brain onto the body of someone brain-dead like Chris Henry? Would Henry's mother have made the same choice, knowing her son's body was still walking the planet but with another brain controlling it? How would the recipient feel with a totally different body? Would this new person be good at football?

Furthermore, if we're going so far as to swap heads on bodies, where would we stop? What if they attached a woman's head or a child's head? How would this type of operation even work?

Stick with us as we explore the medical and ethical aspects of how human head transplants could work.

Giving and Receiving: Organ Transplants in a Nutshell

Visually challenged youth in India hold posters during a campaign to create awareness about eye donation in Kolkata on Aug. 27, 2014.
Visually challenged youth in India hold posters during a campaign to create awareness about eye donation in Kolkata on Aug. 27, 2014.
Dibyangshu Sarkar/AFP/Getty Images

Often when you get your driver's license, you have the opportunity to sign up as a potential organ donor. How does the rest of the organ donation story play out? Let's look at it from the two opposite points of view: the recipient of the organ and the donor.

To become eligible to receive an organ (or a few organs) from a donor, patients must be in such poor health that one of their organs is on the verge of failure. Kidney failure, heart disease and lung disease are all conditions where a patient could benefit from a transplant.

Many people don't realize, however, that transplants go beyond organs like heart, lungs and kidneys and include tissue donation as well. For example, people who are severely burned may receive skin transplants; some conditions that cause blindness can be corrected with a cornea transplant and doctors even have performed transplants with tendons, bone and cartilage.

Once a patient meets the criteria to receive an organ, he or she gets placed on a waiting list. In the United States, this database is maintained by the United Network for Organ Sharing (UNOS). UNOS is responsible for matching organ recipients with donors as they become available. Once on the list, the patient waits for the call, which may take months to several years, depending on the organ [source: Gift of Life Donor Program]. Sometimes it doesn't come in time.

People can sign up to be organ donors anytime by registering through UNOS or at the Department of Motor Vehicles when obtaining a driver's license. If an incident occurs where a person suffers irreversible loss of all brain function and is declared brain-dead, thereby making their organs eligible for donation, the family still must consent to the donation. From there, the process moves quickly to make the match to a recipient and get the operation going.

That's the general process for a regular organ transplant. But we're not talking about a regular one; we're talking about transplanting a head. First of all, this procedure would obviously not work for a living donor. Transplants involving living donors happen in situations where a living person can donate an organ (namely kidney or liver) to another without dying. You clearly cannot donate your head without dying. In theory, a head transplant could occur between living donors if they swapped heads; however, this would be a very costly elective surgery (if even ever approved), as there is no medical condition where trading heads would be suggested as a form of treatment. So what we're looking at in the case of a head transplant is a situation where you have someone with a condition that leaves the mind intact but devastates the body.

Perhaps it's better to think of it as a body transplant, as the transplant recipient is really keeping his or her own head but receiving a new body. Technically, you are moving the head on to a new body, but that's only because the head is smaller and easier to move than an entire body.

Could this ever happen? Keep reading to learn more about the experiments that have paved the way toward bringing this operation closer to reality.

From Monsters to Mice: A History of Head Transplants

A two-headed dog created by Soviet scientist Dr. Vladimir Demikhov in a transplanting experiment is fed by unidentified laboratory assistants on April 15, 1959.
A two-headed dog created by Soviet scientist Dr. Vladimir Demikhov in a transplanting experiment is fed by unidentified laboratory assistants on April 15, 1959.
© Bettmann/Corbis

The idea of pulling together a human from parts of other humans is nothing new. Perhaps the most famous example in literature is the imaginings of Mary Shelley in her novel "Frankenstein" (1818). As you probably remember, in this tale a scientist named Frankenstein assembles a monster from different parts of graveyard corpses and gives it life in the laboratory. Outside the pages of fiction, scientists have experimented quite a bit with assemblages of animals. Let's look at a few examples involving head transplants.

In 1954, Russian doctor Vladimir Demikhov performed a series of experimental operations creating two-headed dogs. He successfully grafted the head and forelegs of one dog onto the neck of another. Amazingly, both heads could see, hear, smell and swallow. The longest any one of his experimental animals lived was 29 days. By modern standards, such an experiment seems cruel and unnecessary; however, Demikhov was motivated by his sincere interest in saving human lives. He hoped to gather all he learned from the dog experiments and apply it to human transplants.

At the time, only bone, blood vessels and corneas had been successfully transplanted in humans. Transplants on larger organs like kidneys were attempted, but the organs were always rejected. Demikhov and his team had their sights set on creating a tissue bank with a storehouse of organs to be used any time someone was in need of a transplant.

Fast-forward to 1970 in the United States where head transplant experiments were attempted with rhesus monkeys. Dr. Robert White in Cleveland was able to perform a head transplant where the monkey survived neurologically intact for 36 hours, although it could not move. After nine days, the head was rejected by the monkey's immune system, and the animal died. The largest obstacle cited by the transplant team was the inability to connect the spinal cord.

Since then, experiments have continued in China with mice, and some progress has been made in the understanding of spinal cord connection. And while nothing has been tried yet with humans, an Italian surgeon and member of a think tank devoted to the advancement of brain stimulation named Sergio Canavero is convinced he has a method to transplant a human head that will work and is gearing up to try it out.

The Plan: Cut Off Head. Reattach to New Body.

Just as with a regular old organ transplant, the first step for a head transplant is identifying someone in need. In this case, the "organ" recipient is keeping his or her own head, which is getting transplanted onto a body. While there may be numerous people in the world with illnesses that destroy the body but leave the mind intact (like progressive muscular dystrophies), there's only one guy so far who has come forward willing to try this risky operation (in December 2017): Valery Spiridonov, a 30-year-old Russian with a rare genetic disease that gradually wastes away his muscles.

That's half the equation handled. You still need a donor, but that's not something that can be planned in advance. The donor will have to be matched to Spiridonov (or any other future candidate for the surgery) for height, build and immunotype, and the donor will have to be screened for disorders. Once the donor is in place, there has to be a plan to carry out the operation.

Lucky for Spiridonov, Dr. Canavero has already thought this through. First order of business: an operating room big enough for two surgeries at once. You can't have someone running through the streets to a hospital across town carrying a head in a bucket of ice. The highest chance of success is for the reconnection to occur as quickly as possible (within an hour) [source: Canavero]. There would have to be teams of doctors, nurses and other support staff to cover all different specialties within medicine: neurosurgery, vascular surgery, orthopedics for spine fusion, plastic surgery and many more.

Once the surgery teams are in place, both the recipient and the donor would be prepped as they might for a regular surgery — intubated, ventilated via tracheotomy (remember — heads will be chopped off; ventilation through the mouth won't be very helpful) and given antibiotics. The next and very crucial step is cool. Literally. You'd have to cool the bodies to about 50 degrees F (10 degrees C) [source: Canavero]. Low temperatures like this lead to low blood flow, which provides protective effects on the brain, blunting a lot of biological processes that lead to neural cell death.

With the recipient first lying down and later seated and the donor seated to facilitate the surgical procedures, deep incisions would be made at each neck, exposing arteries, jugular veins and the spine. All muscles in both patients would be color-coded with markers to facilitate later linkage. The spinal cords would get the final cut, leaving some slack for fusion to the new body. Very quickly, the "good" head would be moved to the "good" body and the spinal cord stumps fused within 1-2 minutes. Speed here is key. While bleeding out isn't so much a danger (vessels in the neck would be clamped), the brain desperately needs oxygen and glucose that it can only get if it is attached to the body via the spinal cord. Cooling the patients will help buy the surgeons a little bit of time, but they will still have to work very quickly if they want any hope of the transplant working [source: Canavero].

You might recall the spinal cord fusion being the challenging step with the monkeys in the 1970s. Canavero proposes using a polyethylene glycol (PEG) glue to fuse them. PEG is a widely used plastic with a range of applications in products like toothpaste, skin cream and various medications. PEG has been shown to immediately repair cell membranes damaged by mechanical injury, so Canavero believes it to be a strong candidate to reconnect the spinal cord [source: Borgens]. The spine also would need stabilization, which could be achieved with the help of wires, screws, rods and clamps.

After the surgeon reattaches the cord, he'd quickly sew together the carotid arteries and then reconnect the trachea, esophagus and nerves. The muscles that were marked would be joined, and then everything would get stitched up by a plastic surgeon.

The patient would require sedation in the intensive care unit of the hospital for a minimum of three days, but for the first attempt at the surgery, Canavero will likely induce a coma lasting three to four weeks, just to play it safe. The surgeon expects that, once awake, the patient should be able to talk and feel their face, but they'd require at least a year of physiotherapy before they could fully move their body [source: Canavero].

Thirty-six hours of surgery, years of therapy and $11-13 million later, done [source: Hamblin]! Seems pretty easy, no?

© 2015 HowStuffWorks, a division of Infospace LLC

The Biggest Challenges for Head Transplanters and Transplantees

As all experiments thus far have shown, the biggest challenge with this surgery will be reconnecting the spinal cord. But that's just the largest hurdle in the operating room. A host of potential post-op problems need to be addressed, too.

If everything goes smoothly during the surgery (and that's a big "if"), the first concern after the operation will be head rejection. You don't want the body fighting against the head, so regular blood samples and biopsies will have to be performed to confirm no antidonor antibodies have been formed.

There's also the chance that the surgery will largely work and the head will get attached and accepted by the new body, but there will be smaller issues that didn't go so well during the surgery. For example, some nerves associated with the vocal cords loop down from the brain, down the neck and back up again. Reconnecting them may pose a larger challenge to the surgeons, and speech may be affected. The esophagus might not be totally leak-proof after reattachment, leading to potential complications with digestion.

Perhaps the biggest deal of all will be the psychological impact on the recipient of the new body. Unlike many other organ transplants, a full body transplant will always be visible to the recipient — a constant reminder that their body is not their own. Patients who have received hand transplants are an excellent comparison point, as they have an ever-present visible reminder of the transplant. These transplant recipients have had to figure out how to mourn the loss of their hand and come to terms with their sense of self and body image. And that's just for a hand. Imagine the degree to which an entire new body will affect the psychology of a patient. Even if someone is medically determined to be a suitable candidate for the surgery, a psychiatric evaluation will be a necessity to make certain they can handle their new life with a new body.

The Ethics of Head Swaps

Canavero has a plan and a patient ready to give this crazy procedure a try in December 2017, but will he be allowed? He has stated that if the surgery is not approved in the European Union or the former Soviet Union, he will carry out the procedure in China. Given the newness and experimental nature of the surgery, there aren't really systems in place right now to approve or disprove of it. Presumably in the United States, head transplants would require approval by the institutional review board of the institution where the surgery might take place, the transplant community, the neurosurgery academy and the ethics board.

From the medical perspective, Canavero has presented a seemingly solid case; however the ethics board would have their work cut out for them. In 2013, Case Western Reserve University neurologist Jerry Silver who witnessed monkey head transplant told CBS News, "I remember that the head would wake up, the facial expressions looked like terrible pain and confusion and anxiety in the animal. The head will stay alive, but not very long. It was just awful ... This is bad science, this should never happen."

Who is Silver to say whether or not this type of operation should be done? But really, who is anyone to say? Who gets to determine if this is an ethical procedure? Finding answers to the ethical questions that arise from this surgery may be even more difficult than figuring out how to successfully carry out the operation. If this surgery were to work, where would we stop?

  • Could people pay money to electively swap heads for no medical reason at all?
  • Is it OK to create any type of person you want, mashing together parts from a bunch of individuals?
  • Would you be the same person if you had a different body? Where is "the person" located anyway — in the body or brain?
  • Could the surgery be used to help people change their gender?
  • The newly bodied person would carry the mind of the recipient, but if they were to reproduce, the offspring would carry the genetic inheritance of the donor. Is that OK?

If and when we do figure out how human head transplants could work, we'll have to do some deep thinking as a society to find out if we even want to go to these extremes, and what implications such medical breakthroughs would have on our world.

Author's Note: How Human Head Transplants Could Work

More than any other article I've written for HowStuffWorks, this one has really gotten me thinking. The idea of this surgery seemed so outlandish to me. As I did my research and learned that a doctor is ready to actually make an attempt at executing it, I couldn't stop thinking of all the potential implications of what would happen if it were successful. Would society ever allow such a thing to occur? And if we did, what rules would be drawn up to dictate what would be OK?

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Sources

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