A jolt of electricity is delivered to a body with bolts attaching its head to its neck. It's a scene straight out of a horror movie, but it is eerily close to Italian neurosurgeon Sergio Canavero and Chinese surgeon Xiaoping Ren's plan to transplant a human head — down to the neck bolts and electricity.
Canavero and Ren recently performed a trial run on two cadavers, prompting outrage from the medical community, which has declared human head transplantation "fake news." An examination by a team of independent scientists published this month, however, suggests that, while fantastical seeming, the scientific and medical advancements necessary for human head transplantation are rapidly approaching plausibility. Nevertheless, major ethical and moral hurdles remain.
Canavero has been talking up his plan for human head transplantation in TED talks and the media for decades, despite producing little in the way of scientific evidence, going so far as to announce in 2015 that he would perform surgery on a human volunteer — a young man with Werdnig-Hoffman disease, a degenerative disease where the muscles waste away — by 2017. The volunteer backed out, and the surgery still hasn't been done on a living human, but Canavero maintains that it is "imminent." Together he and Ren devised a procedure for head transplantation, which they performed in a handful of animal studies on mice, rats and a dog, all of whom shockingly survived the surgery and even regained some motor function.
Without more animal testing, performing such a surgery on humans would be highly unethical, and Canavero's reputation as a sensationalist among medical professionals is well earned. But as transplant surgery reaches new heights — last month a wounded veteran received the first successful penis transplant — combined with advances in biology and computer science, human head transplantation may not be as far-fetched as once thought.
Still, surgical, immunological, psychological and ethical hurdles remain.
While it sounds outrageous, keeping a detached human head alive is not the main stumbling block, and may even currently be possible. The unconscious head would be kept at a very cold temperature (50 degrees Fahrenheit) to mitigate against brain damage, and be hooked up to two pumps — one supplying continuous blood flow and the other oxygen.
An adhesive called polyethylene glycol will be used to connect the volunteer's head with the spinal cord of the donor's body. The plan is to induce the volunteer into a coma for a month while blood and new nerve networks rebuild in hopes that the body doesn't reject the head — an inherent type of risk in all transplant procedures. In addition to the spine, the head will also have to be reconnected to airways, the esophagus and blood vessels.
The major barrier is fusing the spinal cord of the head to that of the donor body. If not successful, the body would be paralyzed, a medical problem that still has yet to be solved. This is not the obstacle it once was, however.
In December, Canavero and Ren published a study in which they severed the spinal cords of 12 dogs. They then applied polyethylene glycol to the incision of seven dogs and also delivered electrical stimulation. Over the next two months the dogs in the treatment group regained some motor function, while those in the control group did not. In earlier animal studies, Ren performed the complete head transplantation with spinal fusion technique on mice and rats, as well as a dog, all of whom also regained some motor function, although it was jerky and not completely normal.
"We have shown that with this technique, spinal perfusion is possible," Ren said (Canavero did not respond to multiple requests for comment). Ren acknowledges that the project is "controversial," but insists it is necessary to save people with "working brains whose bodies have died," including those with neuromuscular degenerative diseases, end-stage cancer and multiple organ failure.
That said, his focus right now is patients with spinal cord injuries and paralysis due to accidents or other causes. "These patients don't currently have good strategies, their mortality is very very high. So I try to translate this technique to benefit these patients," Ren said. "That is my main strategy in the future."
One of the essential keys to the technique is to use a very sharp, special blade to make as precise a cut as possible. Most spinal cord injury patients, however, have extremely frayed cord endings due to the traumatic nature of the injury, so the procedure will not work for them. What's more, polyethylene glycol is toxic to humans, according to Mark Hardy, an expert on immunosuppresion and a pioneering transplant surgeon at Columbia University, who co-authored the paper examining the scientific grounding of head transplantation. Ren's work in animals is "pretty good science," but it is not translatable to humans, Hardy said.
That said, "there are other ways" of potentially succesfully reattaching the spinal cord, Hardy said. He believes it may be possible "sometime in the next 10 to 12 years."
Stem cells are one avenue. In 2014 a Polish man who was stabbed repeatedly in the neck and had been paraplegic for four years had stem cells taken from his nose seeded at his spinal cord junction. With intense rehabilitation he can now stand and take a few steps. Electrostimulation, like Ren and Canavero are using, has also shown promise in spawning nerve regeneration, though both techniques have had only limited applicability so far.
In addition, Hardy said we may be able to bypass it with computers. "In the future, computers can replace some of these neural connections," he said. Currently, many people who receive artificial limbs also receive neural implants enabling them to move the limb just by thinking about it, as the electrostimulation in the brain triggered by the thought is picked up by the neural implant, which relays the signal to a computer and causes the limb to move. "This sounds totally fantastic and unreal, but it is happening," Hardy said.
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