Continued from Part 1 …
Here, we present Part Two of a three-part series on the feasibility of head transplant surgery, written by Dr. Christopher Winfree.
In Part 1, we gave an overview of the topic including recent news reports. Dr. Winfree then covered the technical problems associated with such a procedure. In part two he discusses the biggest obstacle of all: the physiological issues.
There are number of physiological limitations, which are not straightforward to solve.
The most problematic issue is the lack of intact vagus nerve function. The vagus nerves come directly out of the brain and bypass the spinal cord. They are important for maintaining autonomic homeostasis, digestion, blood pressure, heart rate, etc.
Without the vagus nerves, the human body quickly would expire. This is likely the reason the animal studies [mentioned in Part 1] were not associated with a long survival.
Surgeons could feasibly attach the recipient’s proximal vagus nerves [those in the head] to the distal donor’s vagus nerve stumps [those in the body]. But they would need time to grow to reach their targets in the organs.
The rate of regrowth of injured peripheral nerves [including the vagus nerves] is about one millimeter per day. This means it could take a year or more for the nerves to reach their targets.
With current critical care support technology, it is likely impossible to sufficiently support the human body without functional vagus nerves during the recovery period. In the future, this obstacle may be addressed with more advanced critical care systems.”
Head transplantation will likely not be a realistic option for patients until this physiological obstacle is better dealt with. This limitation is the most critical, even if all the other technical and ethical issues are addressed.
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