Human head transplantation (the head anastomosis venture project – HEAVEN) has been for a long time merely a neurosurgical and medical theoretical concept that did not enjoy much attention among the medical community. However, in recent times, there have been voices trying to revitalize this question. Italian neurosurgeon, Dr. Sergio Canavero, is one of the most prominent protagonists in this regard. The idea behind this concept is to help people who have severe physical disabilities (such as neuromuscular dystrophies or tetraplegia), but have an intact head and brain. There is a vast array of medical, ethical and physiological questions and obstacles that are ahead of this endeavor. Despite a lot of skepticism, Dr. Canavero has laid out a couple of transplantation protocols he believes can get the job done. In these protocols, he tried to answer and address every possible challenge that is expected to occur during this delicate and immensely complex procedure. The main purpose of this short article is to analyze the crucial components of his protocols and try to determine if they have any rational scientific relevance and ethical/medical justification.
Why do it?
Before you chop someone’s head off, you’d better have some good reasons, right? This is fundamental. In medicine, conditions are treated if the potential benefits of the treatment outweigh the potential risks. For each particular disease state, there has to be a justified medical indication and logical/rational foundation behind treatment. This is the sine qua non of every medical intervention. You have to bear in mind that anything you do has to lead, ultimatively, to a better quality of life. In that regard, I doubt that this procedure would accomplish that goal at the present moment and it principally acts as an academic exercise, albeit lethal one. I generally do not support doing things just for the sake of doing them, especially in medicine where such behavior can be costly and unethical. Sure, you can become hero of the day and act in a „told you so“ manner if things go your way, but what if they don’t?
Even if you theoretically manage to overcome the technical and technological barriers that are inherent to this procedure, the question still remains: will this person experience improved quality of life? Dr. Canavero’s logic is that people who suffer from severe and/or progressive neurological conditions, e.g. muscular dystrophy or quadriplegia, could potentially benefit from this procedure. How? Well, if your peripheral nervous system does not work but you do have preserved cognitive functions (brain and brain stem), then you would be able to theoretically join healthy brain with healthy body of a deceased donor. The idea is that this body would be donated by those people who were clinically confirmed as brain-dead due to, for example, severe head trauma, but still had a fully functional body to offer. On the other hand, the „recipient“ of the body would give an informed consent that he/she is willing to undergo a body transplantation procedure, regardless of a high risk that this procedure could end in death. In popular jargon – „people who have nothing to lose“ are the group of people that are targeted as candidates for this procedure in Dr. Canavero’s opinion.
Dr. Canavero laid out 2 operative protocols that provide a theoretical framework for this type of experiment. One of them is called HEAVEN1 and addresses head-to-body anastomosis, while the other is named GEMINI2 and features a spine fusion protocol. The physiological obstacles that Dr. Canavero needs to overcome in order to succeed in this endeavour are tremendous, but I will try to briefly tackle the 4 major ones.
- Brain perfusion problems – in only a few minutes post-decapitation, it is expected that neurons will be exposed to a hypoperfusive state, ultimately resulting in brain tissue death.
- Fusion of two ends of the spinal tract – this has never been done before in humans.
- Reparation and regeneration of neuronal connections and spinal tracts/projections within the CNS and the restoration of the motor and sensory functionality.
- Post-transplantation complications – this includes potential tissue transplant rejection reactions that are immunologically mediated.
Should we do it?
At this point, we just do not know enough about the proposed procedures. Some of them have been performed on animal models and some were done only in a Petri dish. Results obtained through animal experiments and in-vitro molecular models might not correlate (and most commonly they don’t) with human physiology. In the early 1970s, American neurosurgeon Robert Joseph White performed the first monkey head transplantation onto a body of another monkey3. The recipient monkey lived for 8 days, and there were no surgical complications encountered. However, the monkey was quadriplegic since the surgical protocol did not address the problem of spinal fusion4. This resulted in a monkey who was completely paralyzed from the neck down, but who could still eat and follow objects with its eyes since the cranial nerves, brain stem and other brain structures were intact and perfused by the circulatory system of the donor’s body. Moreover, it was reported that the transplanted head could hear sounds and smell/taste food. However, immunologic reactions in the form of graft rejection ensued and the monkey died from them.
In this regard, Canavero’s protocol is essentially just a „compilation“ of biotech solutions for a wide spectrum of problems in medicine. Successful translation of any of these theoretical concepts into the clinical arena would be a giant leap in medicine. However, strictly lege artis, there is no strong evidence that these techniques will be successfull at all. Patients undergoing this procedure could be left in much more catastrophic and miserable conditions than those endured prior the procedure. Transplantation of a human head onto a new human body should not be perceived merely as transplanting a flower from one pot to another. We do not know how the brain would interact with the new neurochemical and biochemical milleu of the body that it just received. How would the brain integrate and process new signals arriving from the newly discovered periphery? How would the brain process perception and information coming from these new muscles and other body structures? These problems were emphasized in a recent letter written by Dr. Cartolovni and Dr. Spagnolo, published in the Surgical Neurology International journal. In this letter, the authors argue that Canavero’s perception of the human body functional framework is strictly mechanistic, and largely disregards the importance of body self-cognition, which plays a real part in the formation of human self.
Additionally, they state that head transplant procedures raise significant social and ethical problems in terms of organ donation. A leading medical ethicist, Dr. Arthur Caplan from NYU’s Langone Medical Center, states that the implications of this procedure are far-reaching and extremely dangerous from the ethical and medical standpoint. Similarly, Dr. Jerry Silver from Case Western University states that he perceives human transplants as a barbaric method at this point in time. Moreover, he said that he does not expect such procedures to be successfully performed for at least the next hundred years.
In my opinon, we are not ready for this type of procedure, at least in light of the most recent evidence-based medicine. Even if the tremendous technical difficulties could be surpassed, it still remains a question how the brain (center) would integrate with the periphery. At this point, I assume that the brain would be overwhelmed with the amount of input that it would receive from the periphery, ultimately leading the transplant recipient to derangement, pain and insanity. The prospects of this experiment are simply grim and unfavorable, with our present knowledge and, therefore, I would advocate for its halt.
- Canavero S. HEAVEN: The head anastomosis venture Project outline for the first human head transplantation with spinal linkage (GEMINI). Surg Neurol Int. 2013;4(2):S335-42.
- Canavero S. The „Gemini“ spinal cord fusion protocol: Reloaded. Surg Neurol Int. 2015;6:18.
- White RJ, Wolin LR, Massopust LC Jr, Taslitz N, Verdura J. Primate cephalic transplantation: Neurogenic separation, vascular association. Transplant Proc. 1971;3:602-4.
- White RJ. Hypothermia preservation and transplantation of brain. Resuscitation. 1975;4:197-210.
- Čartolovni A, Spagnolo AG. Ethical considerations regarding head transplantation. Surg Neurol Int. 2015;6:103.
Floating head, neck redone by TaylorHerring