Neurosurgeon Sergio Canavero announced in 2015 that he would soon be able to perform the world’s first human head transplant procedure. This means it would be possible to remove someone’s head and transplant it onto the neck and shoulders of another person. So far this has only been done on cadavers, not living people.
But let’s say you want to preserve the face you already have? Or are you tired of the body you’re in? Could it be possible to swap brains between bodies instead?
Emma Stone recently won her second Oscar for her performance in the brilliant surreal comedy Poor Things. In the film, Stone’s character, Bella Baxter, receives a brain transplant from her surviving unborn child after killing herself. The surgery was performed by experimental scientist Dr Godwin Baxter (played by Willem Dafoe).
Anyone who has watched the film will see Dr Baxter remove the brain from the back of the skull, removing it as easily as separating a pea from its pod.
For reasons I’ll explain later, this scene isn’t anatomically correct, but it does raise the question: How possible is it to perform a brain transplant? What are the practical aspects of perhaps the most challenging operation ever devised?
Challenge one: getting in, getting out
The living brain has a soft, white tissue and is protected from damage by the skull. Although it’s a tough nut to crack, bone will probably be the easiest structure to get through. Modern neurosurgical techniques use craniotomy saws to remove a piece of the skull and access the brain underneath.
It is worth noting that not all neurosurgical operations reach the brain in this way. The pea-sized pituitary gland is located at the base of the brain, just behind one of the sinuses at the back of the nasal cavity. In this case, it is logical to use the nose instead of the nose for pituitary surgery.
While the nose is not large enough to accommodate a new brain, it can certainly serve as a pathway for its removal, albeit in pieces. Ancient Egyptians, who thought the brain was unimportant, removed part of the brain from the nasal passages during the mummification process.
Once you pass the skull, you reach the part where the brain is swaddled; three protective membranes or meninges. First, wait, it’s hard. The second, aptly named arachnoid, resembles a spider web, while the third, the pia, is delicate and invisibly thin. It is these structures that become inflamed in meningitis.
These membranes provide stability and prevent the brain from blowing around. They also divide the inside of the skull into compartments. The first provides a protective cuff of fluid around the outside of the brain; Think of pickled cucumbers floating in a jar of vinegar. This fluid, known as cerebrospinal fluid (CSF), is made from filtered blood and is colorless.
The meninges also form channels between the brain and skull. These are the pathways through which both blood and CSF from the brain return to the heart.
Once the skull and meninges are opened, there will be enough window to remove the brain. This will be the simplest part of the operation.
Second challenge: connecting circuits
Now it’s time to put the new brain into action. This is where things get complicated.
The brain receives sensory information from all over the body and sends instructions to it, causing muscles to contract, the heart to beat, and glands to secrete hormones. Removing a brain requires cutting the 12 pairs of cranial nerves and spinal cord that emerge directly from it. Information enters and exits the brain through all these structures. Do you see the difficulty?
Nerves don’t just come back together. As soon as you cut them they usually begin to break down and die, but some are more resistant to damage than others. Research groups around the world are experimenting with how to stimulate the regrowth of nerve cells after damage to prevent neurological symptoms. The ideas that can be realized in this regard are very diverse, but include the use of chemicals or infusion of cells that stimulate neuronal recovery.
The researchers also suggested that a special biological adhesive could be used to reattach the two severed ends of a severed nerve or spinal cord.
Removing the old brain would also require cutting the arteries that supply blood. This will also cut off critical oxygen and nutrition, requiring reconnection.
Third challenge: after
The last and most uncertain period is the aftermath. And the list of speculations is endless. Will the subject regain consciousness? Will they be able to think? To move? Breath? How will the body react to the new brain?
Because the body’s normal response to unknown tissues is to reject them, most transplant surgeries require donors that match the recipients. The immune system believes that this new entity will cause harm, so it sends out a cavalcade of white blood cells and antibodies to attack and destroy it. Normally, brains are protected against this attack by another shield called the blood-brain barrier. If not properly reconstructed during surgery, the donor’s brain may be vulnerable to attack.
It is equally important to consider how the brain will react to its new home. In Poor Things, Bella Baxter’s brain and body are reportedly “not quite in sync.” But brains can learn to grow. So, just as babies acquire a range of thoughts, behaviors, skills and abilities during childhood development, a transplanted brain can do the same.
So brain transplantation currently remains the subject of science fiction and academy award-winning cinema. Feasibility according to basic anatomy and physiology makes the development of such a complex procedure infeasible. So will more time, tools, technology, expertise and of course money make this feasible? If Poor Things offers a glimpse into the ethics of brain swapping, then it’s a frightening thought.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Dan Baumgardt does not work for, consult, own shares in, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond his academic duties.