Jun 28 2013

Head Transplantion

Here’s a fun one to finish out my vacation week – I recently received the following question:

I recently listened to a podcast dedicated to an often forgotten Skeptic, H.P. Lovecraft. (www.hppodcraft.com). In listening to the episode devoted to “Herbert West: Re-animator”, they mentioned historical experiments where animal heads were transplanted to other bodies, and survived. This set off a ping on my SkepDAR, and I researched it further. (Read: Wikipedia)

I found reference to a journal article in Surgical Neurology International, in which the author claims to lay the ground-work for the first successful surgical transplant of a human head.

As a lay-person, it seems like a plausible medical intervention. That being said, I’d love to hear the SGU tackle both the plausibility of the procedure and the ramifications such a procedure could have on our society. Could this be the key to Bob’s immortality?

In a word, no. At least not anytime soon. The technical hurdles are still too great.

Surprisingly, however, there has been some experimentation in this direction. The most famous such experiment was performed by Dr. R.J. White, who in 1973 transplanted one monkey head onto the body of another monkey. The experiment was declared a “partial success,” because the resulting monkey survived for a few days.

In the 1950s Soviet surgeon┬áVladimir Demikhov conducted a series of experiments in which he attached the head and shoulders of one dog onto another, creating two-headed dogs. (Watch the video if you’re not sensitive to that sort of thing.) Apparently this was done to demonstrate the Soviet Union’s superior medical technology.

In 2002 Japanese scientists transplanted the heads of infant rats onto the thighs of adults. This was done to create an animal model to study the effects of ischemia (lack of oxygen) on the development of the brain.

None of these experiments, however, constitute a head transplant – or more accurately, in my opinion, a body transplant. I think it is more accurate to describe these procedures as grafting a head onto the body of another animal, which then serves as a life support system for the head.

These are not true transplants because the head is never functionally connected to the body. In the case of the monkey, for example, the spinal cord is severed and it never attaches to the host body. The monkey head received blood supply from the body it was attached to, but it was functionally still a completely isolated head. It could have been attached to a heart-lung machine for all it knew.

In a 2001 interview with BBC news, Professor Robert White who conducted the monkey experiment is quoted as saying:

“People are dying today who, if they had body transplants, in the spinal injury community would remain alive.”

Head transplant is not a treatment for a severed spinal cord, and probably never will be. If we could get the spinal cord from the transplanted head to connect to the spinal cord of the recipient body, then we would have the technology to repair damaged spinal cord in the first place. The severed spinal cord is the main problem with head transplants and will likely not be solved anytime soon.

Other technical aspects of the transplantation process are challenging but not insurmountable. Obviously there is a lot of anatomy to connect. The arteries would be a serious challenge. The brain would need to be cooled to a low temperature to prolong survival during the process, and there would need to be a way to keep blood circulating to the brain while all the main arteries are connected – two carotids and two vertebrals.

The alternative to a full head transplant is a brain transplant. I don’t think this would be any easier, however. You still have the problem of severing the spinal cord (probably just below the brainstem, from inside the skull). You also have all the cranial nerves to reattach. You would still need to attach the blood supply – two carotids still, but further up inside the skull, and perhaps the basilar artery (formed by the union of the two vertebrals).

It seems likely to me, however, that by the time we have the technology to successfully transplant either a brain or a whole head, we will by necessity have the technology to repair whatever it is that is wrong with the original body in the first place.

We have to postulate some very advanced medical technology, in my opinion, before you get to a scenario with any kind of head/brain transplant is useful. For example, I can imagine growing cloned bodies, but somehow keeping the brain from developing or just keeping it unconscious and not functional, then transplanting the brain of an old or dying person into a young fresh version of their body.

The limiting factor here is the brain itself – it ages too. So, once again, if we have the technology to keep the brain young and going, this might also provide the same technology to keep the rest of the body going. Perhaps, however, there will be a period of time when the lifespan of the brain will be significantly greater than the lifespan of the body, or when the body will be unavoidably decrepit, and a body transplant will be desirable.

I’m going to stick my neck out, however, and predict that such a procedure will not be developed in time to benefit anyone alive today over 40.

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