You may have seen the recent social media buzz about head transplant surgery. In a February, 2015 New Scientist cover story, Italian neurosurgeon Sergio Canavero said the successful transplantation of one person’s head onto another person’s body could be feasible within two years.
Despite what you might think from the slew of horror movies made in the 60’s and 70’s, the procedure is quite complex. There are technical and physiological obstacles as well a variety of ethical dilemmas. Many of these are decades away from a solution–if not longer.
Dr. Winfree addresses much of this in the BuzzFeed article but says that is just the tip of the iceberg. Here, we present Part One of a three-part series written by Dr. Winfree to further explain these issues.
In brief, the concept consists of taking the body of one the donor and attaching it to the severed head of a recipient. The body donor is presumably a brain dead individual who has donated an organ to an organ sharing network. The recipient presumably has a body that is becoming rapidly nonfunctional from some pathological process. And, assuming appropriate immunological compatibility, their head would be attached to the donor body using an incision at the level of the neck.
This technique has been performed in animals with only limited success. The surviving primate lived roughly a week before expiring. The concept is an intriguing one. However, it would be met with a series of limitations.
The technical challenges confronting head transplantation in humans are substantial, but I do not think that they are insurmountable.
Removing an organ from the body and preparing it for transplantation has been worked out fairly adequately for most organs. A head, however, is a lot more complicated.
The brain typically will not survive being starved of oxygen for more than few minutes–up to an hour if kept sufficiently cold. Although therapeutic hypothermia can prolong the time that the brain can survive without blood flow, there are significant side effects with its administration. Coagulopathies and wound infections can be devastating in the setting of prolonged, deep hypothermia. Further advances in this field, however, might adequately address these limitations.
The surgical techniques used to sever the recipient donor head and donor body will undoubtedly require refinements as the protocol matures with experience.
Transection and reattachment of blood vessels during solid organ transplantation often traps air bubbles in the bloodstream. These are typically flushed out using back-pressure and other techniques–a fairly straightforward process when the organs are small. Avoiding emboli [blood clots] and strokes while backflushing a human head may be problematic.
Perhaps novel vascular bypass techniques can address these issues. Perhaps the recipient’s head could be put on bypass, using blood from the donor body. To perfuse the brain during the lengthy re-anastomosis [re-attachment] process, thus minimizing the need for prolonged hypothermia.
There are number of potential solutions here, and I think with advancing technology and expertise with performing the procedure these are all surmountable.
Perhaps the biggest unsolved technical obstacle is reattaching the spinal cord. This is, essentially, the Holy Grail for spinal cord injury researchers. The technology does not currently exist to accomplish this in a way that permits recovery of function. That is not to say that this will not be solved in the future, but this may take decades.
Not only is there the physical attachment of the spinal cord, but the nerves have to grow and reestablish their pathways despite the presence of the nerve cells’ unwillingness to grow in the central nervous system.
Even if the nerve cells did want to grow, they would encounter a nonpermissive substrate. Further, cells would hit a substantial glial scar, no matter how finely a surgeon could sever the spinal cord–with whatever instrument was available. With time and additional research devoted to these issues, I suspect that these are surmountable obstacles.
Of note, leaving the spinal cord severed would not necessarily doom the procedure to failure. A person could conceivably be okay with living without spinal cord function, as long as they had a body to support their brain. There are lots of examples of high cervical spinal cord injury patients who live comparatively normal lives, albeit as a quadriplegic. So, again I do not think that would doom this procedure to failure.
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