Science Questions

Is a brain transplant possible?

Tue, 15th Oct 2013

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Roshan asked:

Is a brain transplant going to be possible in the near future?


We posed this question to the brain panel.

Katie -   So in fact, the idea of transplanting brains did have some media attention earlier this year. An Italian neuroscientist wrote an article which had quite a lot of discussion suggesting that a brain transplant could theoretically be achieved by transplanting the whole human head onto a donor body.  He proposed a method for reconnecting the severed spinal cords.  

In this paper, he referred to the work in 1970s of Dr. White and he transplanted a rhesus monkey head onto the body of another rhesus monkey.  The monkey was apparently able to see and smile and taste, and in Dr. Whiteís words, Ďbiteí and he did this with the idea that eventually, human head could be transplanted onto a donor body.  It might help people who had healthy brains but some degenerative illness of the body.  So, while the animal awoke, it was reported to live for a very short time.  It didnít really have any use of the body because they werenít able to reconnect the spinal cords.

Hannah -   And has that study been replicated since the 1970s?

Katie -   Well, no.  It hasnít been replicated.  Of course, the ethics of doing a research programme like that now would be very questionable.  It just wouldnít be allowed.

Bill -   The easiest part would probably be connecting up the blood supplies, but connecting up the broken nerves is a real problem especially in this central nervous system, the spinal cord.  However, you can transplant brains in embryos.  You can transplant an embryonic frog brain from one frog to another.  You can transplant embryonic chick brain to a quail.  Lots of brain transplants are possible.  Itís when you get to the mammals that it becomes particularly challenging because the nerves donít regenerate so well and they donít cross cuts.  So, when you cut a nerve cell axon and you want that cut nerve then to be able to regenerate its axon and make connections with the appropriate targets, it has a really hard time doing that in a mammal.


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Peripheral nerves do regenerate, but slowly.  I believe they will generally follow the routes of existing nerves.

Central nerves (currently) don't regenerate, but there is a lot of research in spinal cord regeneration.

If doing a "brain transplant", one would likely choose to take the brain (or head), as well as the spinal cord and as much of the nerves as possible after they exit out of the spine. 

It would be a complex surgery as the spine provides armor for the spinal cord, also flexibility for body movements, so it couldn't easily be opened and reclosed.  Perhaps one could use some kind of a Laparoscopic procedure, but spaces are tight. CliffordK, Fri, 25th Oct 2013

I'm not sure even peripheral nerves regenerate if you destroy the cell body. Axons can. cheryl j, Fri, 25th Oct 2013

Peripheral ganglia may not regenerate, but the axons and dendrites should be able to, and should be able to reconnect with existing nerve cells and muscles (with some relearning).

There are, of course, ethics involved in such a transplant.  But, there is the occasional hypoxic brain death injuries that otherwise leaves much of the body intact with a non-functional brain.  And, of course, conditions that might leave the brain and spine healthy and intact, but with a poorly functioning body.

Still, it wouldn't be something to be taken lightly.

Unless we can improve our anti-rejection methods, immune system compatibility would be a major issue.  The worst thing would be the rejection of one's own brain.  Perhaps if one had time and a very close match, one could do a bone marrow transplant first, followed by the Central Nervous System transplant. CliffordK, Sat, 26th Oct 2013

Is this a brain transplant, or an "everything else" transplant?
If Joe needs a new liver and Jack dies in a car crash Jack's liver can be transplanted into Joe (assuming he's lucky).
But if Joe needs a new brain and Jack dies in a car crash and they move Jacks brain into Joe's body then wait for him to wake up.
When they ask this individual his name he will say he is Jack- but in a new body.
From Jack's point of view, he has had a body transplant (And Joe is no longer with us) Bored chemist, Sat, 26th Oct 2013

Good Point...
As long as it is between Jack and Joe.

On the other hand, it would become much more complicated with Jack and Jill.

If there is  not also a gonad transplant, then the parenthood of future children would also be ambiguous. CliffordK, Sat, 26th Oct 2013

With nerve cells and the spinal cord, would this be possible if stem cell research could come up with a way to regenerate them? carrie7654, Thu, 21st Nov 2013

Good question.  Christopher Reeve was a big proponent of stem cell research with respect to treating a severed spinal cord, although eventually he succumbed to complications from his injuries. 

There may be two issues.

Regeneration of axons (& dendrites).
Regeneration of whole nerve cells.

The spinal cord may be considered as an extension of the brain stem.  Severed axons in the CNS (brain and spinal cord) are inhibited from regrowing.  Are the cells actually also killed? 

For a brain transplant, the trick would be to replace the brain and spinal cord together if possible, and thus only be limited by peripheral nerve regeneration. 

If the spinal cord is severed, perhaps one could remove the growth inhibiting factors, and slowly regrow the spinal cord, although it may take years for axon regrowth from the neck to the toes.  Getting the proper, or even close connections would still be difficult.

If there are neurons that have died, then stem cell research might help.

Perhaps another option would be to create an artificial ganglion.  So, rather than regrowing the neurons and axons in situ, one could grow replacement nerves in the laboratory, then convince the body to make new connections near the severed point in the nerves to the new ganglia.
CliffordK, Sun, 24th Nov 2013

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