Jul 02 2013

Follow Up on Head Transplants

I recently wrote about the implausibility of performing whole head or brain transplants.  By coincidence (I think, unless this paper triggered the question to which I was responding) a recent paper proposes how to successfully complete a human head transplant.

Italian neurosurgeon Sergio Canavero writes:

“The greatest technical hurdle to [a head transplant] is of course the reconnection of the donor’s (D)’s and recipients (R)’s spinal cords. It is my contention that the technology only now exists for such linkage…. [S]everal up to now hopeless medical connections might benefit from such a procedure.”

To recap my prior post – prior surgeons have attached the head of a monkey or dog onto the body of another. I argued that these were not really transplants but grafts, as the body was providing blood to the severed head, but there was no functional connection. The primary hurdle to achieving any kind of functional connection is the spinal cord.

Canavero is arguing that with existing technology we can make a clean sharp cut of the donor and recipient spinal cords and this will allow them to connect together, providing functional control of the severed head to the donor body (what he calls a cephalosomatic linkage).  He adds that a plastic like polyethylene glycol can be used to “glue” the two spinal cord ends together and encourage their regeneration.

We are making some progress in getting spinal cords to regenerate, but I think Canavero is vastly overstating where we currently are. For example he cites a recent rat study in which partial function was restored. In this study, however, only bladder function was partially restored, not motor function.

Spinal cord regeneration research is exciting. Researchers have identified the likely reasons for why peripheral nerves regenerate and spinal cords do not. This at least suggests possible treatment strategies. It may be possible to eventually get damaged spinal cord to regenerate to the point of functional recovery. This research, however, is progressing with baby steps. Eventually these baby steps will likely add up to a viable treatment, but that is still years away.

Canavero’s point that a clean surgical cut will repair more easily than traumatic damage seems valid. But it is not clear, and in fact is pure speculation, that this difference will be sufficient to restore meaningful function.

Also, transplanting a head introduces another variable – that of acceptance vs rejection of a graft from another person. Transplant rejection is an issue, and it is not clear if this will interfere with spinal cord regeneration.

I still maintain that once we know how to coax a spinal cord to regenerate in order to connect two severed ends, it will likely be easier to repair an existing spinal cord than to transplant a head onto a new body. Still, there are some conditions, like muscular dystrophy, where the spinal cord is not the problem (the muscles are) and therefore a head/body transplant would offer a possible solution.

If Canavero wishes to support his speculation, the next step would be doing full head transplants in rats or larger animals to demonstrate his principle. I, of course, would be interested to see the results.

23 responses so far

23 thoughts on “Follow Up on Head Transplants”

  1. Bill says:

    The first thing this makes me wonder is: isn’t it more of a body transplant?

    The second thing is: even assuming this eventually worked out, how easy would it really be to find dead but otherwise healthy donor bodies?

  2. JamieGeek says:

    What if you could clone yourself and then transplant your “old” head onto your more youthful body. Just keep doing that every 20-30 years… Perhaps the youthful body would keep the head from looking too aged (may look really creepy with a 90 year old head on a 20 year old body! LOL).

  3. rcmcghee says:

    Would it be possible to transplant both the head and the spinal cord?

  4. Bruce Woodward says:

    Bill, it can probably be either, it depends on how you state it in a sentence.

    As for donors, if it were eventually something that was possible I would think it could be part of a organ donation scheme. I would consider donating my body if I were ever in a brain dead/vegetative state for something like this and there would probably be others willing to do it too.

    I guess it is not really a question we will know the answer to until the technology is available and it is viable, if it ever will be.

    This whole thing takes me down a very familiar rabbit hole, if we were able to transplant a head, could we then transplant a nose, or an eye or an ear or inner ear? What about transplanting the actual brain itself? If we got to a stage where we understood the brain well enough could we then transplant parts of our brains?

  5. Marshall says:

    JamieGeek, the brain ages as well. In some unsucessful brain aging cases like Alzheimer’s disease and Parkinson’s, the brain is the bottleneck, and its rapid decline with aging is the cause of death.

    Here’s a more interesting question–what if we were to successfully transplant a human brain onto, say, a gorilla body? Would our larger motor cortex allow for the dexterity that nonhuman primates lack, yet allow us to take advantage of their greater strength?

  6. DOYLE says:

    What if you transplanted head stacked upon head to create a human totem pole.

  7. pdeboer says:

    @DOYLE sequel to Human Centipede 2, Human Totem Pole!

  8. DOYLE says:

    Human pez dispenser with four part harmony.

  9. I used to do spinal cord injury research and I can state that it is very, very difficult to repair a damaged cord. Contusion (bruising) injuries are simpler than transection injuries, but even these are complex beasts. A former colleague is now in charge of a project using stem cells to “plug” holes, e.g as in syringomyelia which tends to degenerate to a bad end. Such holes could, in principle, be arrested with a suitable graft. But just getting the right number of cells so that the graft grows to fill the hole and no more, let alone stimulating the graft to join two ends of a fiber that has likely degenerated via Wallerian and retrograde processes (depending on the end) so that it functions at all, let alone well, seems to be a distant target. As you say, Steven, I think it’s pure speculation that a transected cord could be repaired in any meaningful way.

    What irks me about these sorts of proposals is that it sets the bar too high. We don’t need to reconnect a fully transected cord to be able to claim success. If you are a syringomyelia patient and a graft can preserve lower limb function, or perhaps save your life for an extended time, then stabilization can be the very definition of success. I would prefer that Canavero set his sights lower, and not waste a bunch of animals proving that cord repair of the sort he envisions is way beyond our present capabilities. I would use an analogy such as the Wright brothers attempting to do a moon landing by 1910, but even that doesn’t seem to quite do the obstacles justice.

  10. evhantheinfidel says:

    There is a forum I’m a member of that is mostly dedicated to science fiction, but that also tackles some futuristic science issues. The contrast between pure science fiction fans and scientists (who may still be fans of fiction, but still know what they’re talking about) is stark!

  11. Bill Openthalt says:

    @ practiCal fMRI
    How sure are we that there is full conformance between the wiring and signalling conventions in different humans? In other words, does it even make sense to “connect” nerves based on their spatial alignments, or do we need to know more about the “programming” of the two systems to connect them?

  12. Hi Bill,

    You raise one of a litany of complexities. The firing patterns of neurons are immensely complex, and presumably for very good, perhaps subtle, reasons. So understanding which white matter tracts to connect to which other ones, let alone all the interactions between gray matter at every level of the spinal cord, is unimaginably complicated. Given that these processes change all the time and we can’t measure anything instantaneously, I’m not even sure if it makes sense in principle to try to connect everything “properly.” Functionally – in a manner consistent with some sort of persistent biological function – may be achievable, but they probably wouldn’t end up looking like the sort of connections that we would want, e.g. to transplant a head, come around from the anesthesia and go home to recover like we might from a less complicated surgery. It’s hard enough to reconnect ligaments and bones and make them work reasonably well, and these systems are as rocks to space rockets compared to nervous tissue.



  13. DOYLE says:

    What is the dna in the resident body retained a archival memory of its experience,so that when the second head was grafted it created multiple persona.which would have narrative control.

  14. DOYLE says:

    My bad,should begin with what if

  15. Waydude says:

    I love how we are seriously considering this.

  16. BillyJoe7 says:

    Hmmm…I thought we were doing the opposite.

  17. Nitpicking says:

    I think that rather than actually reconnecting the spinal cord, it would be much easier to put a layer of adaptive electronics between. Connect each transected neuron (on each side of the break) to an electronic circuit and have a small processor pack transmit the signals bidirectionally. We know that sort of electrode-neuron connection works because we already use them.

  18. BillyJoe7 says:

    …are you serious (:

  19. Bill Openthalt says:

    @ DOYLE
    Hehe – imagine a female head on a male body or vice-versa. That would put a new spin on the “bearded woman” schtick.

  20. Billzbub says:

    @Nitpicking and @Bill Openthalt

    I like that idea because it would allow a computer to translate the head and body interfaces in the event that they don’t speak the exact same language. As I think Bill Openthalt pointed out above, the signal interface of one person may not match that of another person, and having electronics between them may be the only way to have a meaningful interface.

    It may be easier just to create a robotic body.

  21. jre says:

    I think it was Douglas Hofstadter who observed that, in a brain transplant, you always want to be the donor.

    The late Iain M. Banks wrote in Use of Weapons of a space mercenary who fell into the hands of a primitive band who decided to behead him as a sacrifice. He experienced the whole falling into the basket thing (gives a whole new spin on the “Oh Shit Moment”) before the Culture scooped him up and grew him a new body. Even advanced as the Culture is (or will be), they do let on that after a minute or two more in the basket, they couldn’t have saved him. Always remember: seconds count when your head is in the basket!

  22. Mlema says:

    “If Canavero wishes to support his speculation, the next step would be doing full head transplants in rats or larger animals to demonstrate his principle. I, of course, would be interested to see the results.”

    I thought we were all in agreement that at this point in time head transplants are science fiction. If some guy was in his basement lopping off heads and switching up the bodies, regardless of how long the results stay alive, he would find himself in a psychiatric hospital/prison PDQ. But a white coat and a lab makes this science? I don’t think “interested to see the results” is the proper skeptic’s take on this guys “research”.

    Science fiction is fun. Sadism? Not so much.

  23. heyfred3000 says:

    Even though I think we’re talking about mostly motor and nociceptive function, I’m guessing we wait on a molecular film sensor medium that encircles the proximal cord and triangulates infinitely within the plane, then coordinating either with some programmed stimulus or some unimaginably complex brain mapping EEG information, providing low-level targeting stimulation through the distal neurons to allow the proximal cord to have a timely target and perform like regenerating peripheral nerves. In other words, DO hold your breath……your new head probably won’t be able to stimulate your diaphragm to inhale any time soon.

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