For the last week, an Italian neurosurgeon has been executing a full-blown media offensive, talking up his plan to stitch one person's head to another person's body. If the powers-that-be would just get over their ethical queasiness, Sergio Canavero of the Turin Advanced Neuromodulation Group says he could accomplish the feat by 2017.
But full-body transplants aren't so crazy. In fact, it might surprise you that there was a successful operation as far back as 1818. Well, successful if you ignore that the transplantee freaked out and murdered his doctor's family. Oh wait. That was Frankenstein. I take it back, full body transplants are totally crazy.
What the hell, going to the moon was crazy too, right? And a maybe-crazy-but-what-the-hell moonshot is exactly how Canavero sees his plan to help patients with severe physical impairments. "Why did the US and the Soviet Union just vie for being the first to space? Because it is about measuring dicks. We want to demonstrate as a country, to say: I am the best," he says. Canavero's latest paper glosses over questions of ethics and practicality and tackles the trickiest aspect of the head-swapping procedure: The spinal splice.
Canavero's plan focuses on sewing two people together by their spinal cords. (Hooking up the rest of the utilities---blood vessels, airways, blood vessels---is incredibly difficult, but trifling in comparison.) Step one is to sever the cords with a special, ultra-thin blade. Canavero rightly notes most cases of spinal trauma are well, traumatic: Snapping your neck on a skateboard ramp is bound to leave the spinal cord in an untidy condition. Those nerve cells scar, and scarring would impede their regeneration (if cells in the central nervous system could regenerate—we’ll get to that in a sec). A clean wound, on the other hand, heals cleanly. Canavero likens those million sharply severed neurons to spaghetti. "Italians adore spaghetti, I love spaghetti, and spaghetti is what is called for here," he says.
The job of fusing those spaghetti-like spinal sections together falls to a substance called polyethylene glycol. This stuff has actually been pretty good at repairing the motor functions in rats with spinal trauma---though even the kindest critic will point out that successful rat experiments are a far cry from proving that the stuff will repair human spines. Still, Canavero is raring to go. "I have enough animal data," he says. "Give me a brain dead organ donor." Say someone is in a traumatic car accident, and doctors say that he cannot be saved. In the time between when the person's family says it's OK to pull the plug and the moment the doctors actually do so, Canavero asks for three to four hours. "I sever the spinal cord, add polyethylene glycol, and start measuring electrophysiological responses," he says.
After surgery (and during it, one hopes), Canavero will keep the patient in a coma. He estimates it will take about at least two weeks for the first axons to begin lacing themselves together, at which point the patient can be revived. Throughout the coma and for some time after, Canavero will bathe the spinal splice with a mild electrical current. This is not a free Frankenstein joke from the good doctor: It's actually a method that's seen surprisingly promising results healing real human patients with spinal trauma. Canavero is confident that this will keep the muscle cells operational. Combined with physical therapy, Canavero estimates his as-yet-unchosen patient (any volunteers?) will be back on her (new) feet in about a year.
In case this wasn't entirely clear: Canavero's plan is insane. Like, James Bond villain insane. And it's not just because his plan fits together like a Voltron of bad science (which it does). It's kind of a bummer, actually, because his plan could maybe work, if he was given free rein to cut and sew living peoples' heads to dead peoples' bodies until he got it right. But besides ethics, there's an unfortunate fact of biology standing in his way: The central nervous system in higher vertebrates---like humans---does not regenerate. "He's insane. You can't put a head on somebody else!" says Binhai Zhang, a neurosurgeon at UC San Diego. The reason why goes down to your DNA. "The genes in a mature mammalian central nervous system that control regeneration are repressed," says Michael Beattie, a professor of neurosurgery at UC San Francisco. They’ll stay that way, no matter how much you treat the spinal cord with polyethylene glycol and electrical currents. (Although, hey, who wants to work on un-repressing those genes?)
Nobody knows for sure why the cells in your brain and spine aren't wired for regrowth. After all, your peripheral nervous system---the circuitry for every other part of your body---conducts electrical impulses in exactly the same way, but its genes can code for self-repair. Beattie says this may have to do the fact the spine and brain contain the circuitry coded for movement, not just for conducting signals. Spinal cells must knit themselves together in super-complex configurations in order to command the motor functions you've learned over a lifetime. "Once the connections are made, you don't want the wrong connections getting created," he says.
The only reliable way to induce spinal cell regrowth in higher order vertebrates is with stem cell therapy. Last year scientists showed pluripotent stem cells could regrow damaged spinal cords—but only in rats. Mark Tuszynski studies stem cells in spinal injury at UC San Diego, and he says even with this advance the research community is years away from attempting such treatments on humans. "It’s not at the stage yet where there can be meaningful advances in clinical trials," he says. Plus stem cells will need help, in the form of drugs that knock down natural regeneration inhibitors that your body creates (because cancer), and still more drugs to keep your body from creating scar tissue around the wound. (Though in fairness, that's the idea behind Canavero's super-thin knife.) All of this research remains years away from clinical application.
And this slow, careful tempo---"do no harm" being a hallmark of western medicine---is what drives Canavero's bold assertion that he will have a successful head transplant in 24 months. "There are all these people who tell you: 'Who is this guy who can do this in two years?' When you go public with something like this, you have to have two balls like this. There are people who are not so strong-balled and will just get crushed by the critics. But I love the critics. This is a feat of theoretical neuroscience and the evidence is there and it’s going to work." In case you need clarification, his main argument there is 'Haters gonna hate.'
To Canavero, the process of making sure a treatment is ethical, safe, effective is equivalent to foot-dragging. Canavero says he is done experimenting. He believes that his head swapping procedure is, theoretically at least, ready for prime time. "Two years isn't to make any more experiments," he says. "I need two years to coordinate 150 people working for 36 hours taking turns and everything has to be perfect." This is time to practice, which means cadavers, cadavers, and more cadavers.
But none of Canavero's science is proven, which means many in the neurosurgical community are not impressed with Canavero. After all, there are millions of people on this planet who are paralyzed from back injuries, and his ideas can seem insulting to scientists working on proven medical solutions. "He's basically saying he can solve the problem of how to transplant a central nervous system," says Zhang. Canavero's ideas are controversial, but apparently not so distasteful that he is being outright ignored by western medicine. In June he will be the keynote speaker at the American Academy of Neurological and Orthopaedic Surgeons's annual meeting in Annapolis, MD. Nick Rebel, the organization's executive director, says the Academy is aware of the controversy surrounding head transplants, but says what they are really interested in hearing about are Canavero's ideas on spinal fusion. "The possibilities for treating people who are paraplegics, quadriplegics is really what’s of interest," he says.
But to doctors like Zhang, Canavero's science is fantastical, his ethics are nonexistent, and his ideas should not be taken seriously. Zhang believes that rather than acting like a responsible investigator for medical research, Canavero is acting like the hero of a fictional plot. And in fact, that's where Zhang thinks Canavero's talents would be best served. "This is science fiction," he says. "He can write a novel about this and sell it on Amazon and maybe that's the best course of action for him."
In fact, Canavero has written a book (marketed as nonfiction) which is available on Amazon. "Head Transplantation and the Quest for Immortality," he says. "Everyone who buys the book will help bankroll this operation. This is crowdfunding major medical endeavor."