Human Head Transplants

I've gone for a slightly controversial topic for my first post on this blog; the claims of Italian neuroscientist, Dr. Sergio Canavero, that human head transplants are now possible.

Canavero's Claims

Canavero claims to have developed a procedure which will allow the transplantation of a head onto a donor body (that of a brain-dead patient), to be used in cases such as tetraplegia or muscular dystrophies, where the brain functions normally but the body has limited or no movement. 

Canavero references the work of David White in 1970, whereby the head of a Rhesus monkey was transplanted onto the body of another monkey. However, since the technology did not at the time exist to re-connect the spinal cord, the head was not able to integrate with its new body, and the line of research was not really pursued.

Canavero believes that it is now possible to re-attach the spinal cord from the head, to the severed spinal cord in the new body; he suggests that the head (and brain, obviously) could be removed and transplanted onto a healthy donor body. His technique would involve inducing hypothermia by cooling both host and donor to between 12 and 15 °C (55 - 59°F), before the host head is removed from its body at the same time as the head is severed from the donor body. The induction of hypothermia reduces the metabolic rate of the brain to around 10% its usual rate, allowing it to survive without blood flow for around an hour; thus, the surgical team have an hour to re-connect the donor body.

Canavero believes that through severing the spinal cord with an ultra-sharp blade, it will be possible to fuse the spinal cord of the head with the of the donor body, using the inorganic polymer polyethylene glycol (PEG), which has shown huge potential for the fusing of axons, with minimal damage.

My Thoughts

I wouldn't like to say whether Canavero's technique is technically possible - I doubt it, but then again the human nervous system is an amazing thing and we learn unexpected things about it almost daily, so anything is possible. What concerns me about Canavero's work is the ethical aspects of it; this is discussed by Jerry Silver, who worked with White in the 1970 experiment referenced by Canavero. He disputes Canavero's claims that, "The monkey lived 8 days, and was, by all measures, normal, having suffered no complications." Silver recalls that when the head woke up following the surgery, it would show facial expressions suggesting pain, confusion and anxiety, and would not live very long. Obviously, surgical techniques have improved tremendously in the last 43 years, but even so I feel like this should be approached with significantly more caution that Canavero is showing.

Canavero himself admits that he has not (in his paper) considered the ethical aspects of his procedure, but his recommendation that practice surgeries be carried out on brain-dead patients strikes me as somewhat disturbing, particularly given recent evidence that patients who appear brain-dead may not actually be so. Furthermore, he suggests that the procedure may find applicability in muscular dystrophies, which are "a source of huge suffering, with no cure at hand." However, recent work has reported a promising new drug which may prevent or delay the onset of symptoms; thus there are much more practical and far less ethically-dubious treatment options open for muscular dystrophy, rendering this research a little superfluous - in my opinion.

I completely agree that it would be a fascinating area of research and a massive accomplishment if it were to be possible to successfully transplant a human head onto another body, but research should not be carried out for the sake of research, with no purpose in mind. For this reason, I agree with Silver that "this should never happen."

If you're interested, you can access Canavero's full paper here, and this article gives a good summary in layman's terms.

References:
Canavero, S. (2013). HEAVEN: The Head Anastomosis Venture for the first human head transplantation with spinal linkage (GEMINI). Surgical Neurology International, doi: 10/4103/2152-7806.113444
White, R. J., Wolin, L. R., Massopust, L. C., Taslitz, N., & Verdura, J. (1971). Primate cephalic transplantation: Neurogenic separation, vascular association. Transplantation Proceedings, 3, 602 - 604.