by Neurosurgeon Sergio Canavero announced in 2015 that he may soon be able to perform the world’s first human skull transplant procedure. This would mean that one person’s head could be removed, and it could be attached to another person’s neck and shoulders. So far, this is only done on cadavers and not on living people.
But you probably want to keep the face you already have? Or tired of the body you live in? Would it ever be possible to transfer brains between bodies instead?
Emma Stone recently won her second Oscar for her performance in the surreal comedy Poor Things. In the film, Stone’s character, Bella Baxter, receives a brain transplant from her surviving unborn child after killing herself. Experimental scientist Dr. Godwin Baxter (played by Willem Dafoe) performs the surgery.
Anyone who has watched the film, Dr. Baxter will see the brain from the back of the skull, and it is as easy to shell as peas from a pod.
For reasons I will explain later, this view is not anatomically correct, but it begs the question – how feasible is it to perform a brain transplant? What are the practical aspects of perhaps the most challenging operation ever conceived?
Challenge one: get in, get out
The living brain has a soft set blancmange texture, and is protected from harm by the skull. Despite being a tough nut to crack, the bone is probably the easiest structure to negotiate. Modern neurosurgical techniques use a craniotomy saw to remove a patch of skull, and gain access to the brain underneath.
It is worth noting that not all neurosurgical operations reach the brain in this way. The pea-sized pituitary gland sits at the base of the brain, just behind one of the sinuses at the back of the nasal cavity. In this case, it makes sense to use the nose instead for pituitary surgery.
Although the nose wouldn’t be big enough to fit a new brain through, it could certainly serve as a way to remove a head – albeit in pieces. During the mummification process the ancient Egyptians, who considered the brain unimportant, removed pieces of it through the nasal passages.
After the skull, you reach the swaddling of the brain – through protective membranes, or meninges. The first, the dura, is tough. The second, the aptly named arachnoid, is like a spider’s web, while the pia, the third, is delicate and invisibly thin. It is these structures that become inflamed in meningitis.
These membranes provide stability and prevent the brain from sloshing around. They also separate the insides of the skull into compartments. The former provides a protective fluid cuff around the outside of the brain – think of a jellyfish swimming in a jar of vinegar. It is called cerebrospinal fluid (CSF), and is made from filtered blood and is colorless.
The meninges also make passages between brain and skull. These are the channels by which both blood and CSF are returned from the head to the heart.
On opening up the skull and meninges, much of the window will be removed from the brain. This is the simplest part of the operation.
Challenge two: connecting the circuits
Now it’s time to get the new brain in. This is where things get complicated.
The brain receives sensory information from all over the body and sends instructions back to it, making muscles contract, the heart beat and glands secrete hormones. To remove a brain it is necessary to cut through the 12 pairs of cranial nerves that come directly from it, and the spinal cord. Information passes in and out of the brain through all these structures. See the difficulty?
Nerves don’t just go together again. As soon as you cut them, they will usually begin to wilt and die, although some are more resilient to damage than others. Research groups around the world are experimenting with how to promote the regrowth of nerve cells after damage to avoid neurological symptoms. There are many ideas that could be achieved in this regard but they include the use of chemicals or grafting into cells that stimulate neuronal recovery.
Researchers have also suggested that a special biological glue could be used to glue two severed nerve or spinal cord ends back together.
To remove the old brain it will also be necessary to cut the arteries that supply blood. This will have cut off critical oxygen and nutrition, which will also require mating.
Challenge three: the aftermath
It is the last period, more uncertain than the consequence. And the list of speculations is endless. Will the subject regain consciousness? Will they be able to think? Move? Breathe? How does the body react to the new brain?
Most transplant surgeries require matching donors with recipients, since the body’s normal reaction to unknown tissues is to reject them. The immune system sends a cavalcade of white blood cells and antibodies to attack and destroy, certain that this new presence means harm. Brains are normally protected from this attack by another shield, called the blood-brain barrier. If not properly reconstructed during the operation, the donor’s brain could be open to attack.
It is equally important to consider how the brain will cope with its new home. In Poor Things, it was reported that Bella Baxter’s brain and body were “not completely in sync”. But brains can be learned to grow. So, just as children acquire an arsenal of thoughts, behaviors, skills and abilities during their childhood, a transplanted brain could do the same.
Thus, brain transplantation remains the subject of science fiction and academy award-winning cinema. Feasibility based on basic anatomy and physiology makes it unlikely that such a complex procedure will develop. But will more time, tools, technologies, expertise and, of course, money ever be viable? If Poor Things sheds light on the ethics of brain swapping, that’s a scary thought.
This article from The Conversation is republished under a Creative Commons license. Read the original article.
Dan Baumgardt does not work for, consult with, own shares in, or receive funding from any company or organization that would benefit from this article this, and has not disclosed any relevant connections beyond their academic appointment.
