Human Head Transplants – Fantasy to Fact?by Viatcheslav Wlassoff, PhD | March 26, 2015
When English author Mary Shelley penned Frankenstein in 1818, little did she know that her vision might come true, albeit in a slightly different way and as a boon to mankind. Shelley’s Victor Frankenstein created the Monster by sewing together body parts from human corpses. In a way, Frankenstein created Life. Doctors and surgeons today do nothing different; they save lives by transplanting organs, bones, skin, and nerves and veins. To date, they can transplant almost every major organ of the body, like the heart, liver, lungs, kidneys, pancreas, and intestine, but not the head. This may be about to change!
Italian neurosurgeon Dr. Sergio Canavero recently created quite a stir by his announcement that he will attempt the head transplant surgery within three years. He believes that modern medicine already has the means to do this procedure successfully.
Unsurprisingly, Cavanero’s announcement was met with harsh criticism. Mainstream media dutifully covered the potential moral and ethical problems associated with head transplantation. In this article, I’d like to analyse how much science is really behind the Dr. Cavanero’s thinking and whether such surgery can really be done at present time. This is an aspect of the problem which was mostly ignored by the reporters concerned with the ethics.
Although heads have not been transplanted in human beings, this procedure has been attempted in monkeys. In 1970, Robert White and his team transplanted the head of a monkey on to the body of another monkey. The removal of the head and the transplantation was carried out simultaneously. The monkey lived for 8 days, and there were no surgical complications. However, this experiment did not address the challenge of reconnecting the severed spinal cords to prevent paralysis. So no head transplantation experiment in monkeys or humans has been attempted since.
But Dr. Canavero says he has come up with a way to reconnect spinal cords in human beings during a head transplant.
Head Transplant in Humans: The Way Forward
Dr. Canavero has named his human head transplant project HEAVEN. A person who is possibly suffering from an incurable and debilitating medical condition but has a healthy and functioning head and brain will be the recipient. A person who has been declared brain-dead but still has a healthy body will be the donor. So after the procedure, the donor will receive a new head.
Dr. Canavero believes that inducing hypothermia during the transplantation procedure and using sharp severing instruments and specialized healing agents will help him overcome many of the challenges inherent in the procedure.
Human Head Transplant Challenge #1: Sustaining Life After the Head is Severed
The biggest challenge during the human head transplant procedure is to stabilize and keep alive the individual after his head is severed and blood flow stops. Research data show that human beings can be sustained without blood flow if the body is cooled to a temperature range of 12oC and 15oC. At these temperatures, the metabolic activity in the cerebral region drops to about 10 percent of what is normal. The data from cardiac surgery has revealed that producing profound hypothermia causes total cessation of circulation. These conditions can be safely sustained for about 45 minutes without causing any neurological damage to the individual.
Canavero believes 45 minutes is adequate time for the surgeons to reconnect the severed spinal cords.
Human Head Transplant Challenge #2: Preventing Cell Damage in the Spinal Cord Stumps
Dr. Canavero realizes that reattaching the severed spinal cords is not enough to merit a complex and costly head transplant procedure. The individual who has received the new head should be able to regain some of his earlier motor abilities. This implies that the heads should be severed with as little damage to the neuronal cells, so it is easy to restore the connections, and consequently, motor functionality.
According to clinical findings, there have been several instances where patients with sharp wounds to their spinal cords not only survived but also recovered from their initial stages of paralyses and regained their earlier range of motor functionality. On the other hand, one clinical study on the victim of a self-inflicted 0.38 caliber gunshot (with greater scar area) reveals that the patient did not recover from his state of paralysis.
Another study has found that axons have to be regenerated to restore neurological functionality in cases where the damaged nerve is separated by a gap. Axon generation is most effective when this gap is less than two centimeters in length.
So the challenge in human head transplantation is to minimize the scar area when severing the spinal cords. Dr. Canavero proposes using a specialized severance tool that will minimize the scar area and keep cell damage to a minimum. He has in mind the tools that will create the force of less than 10 N during transections. Incidentally, a typical spinal cord injury involves the force of around 26,000 N.
Dr. Canavero believes that an ultra-sharp nanoknife made from a layer of silicon nitride could be used to inflict a sharp cut.
Human Head Transplant Challenge #3: Healing, Regenerating Neurons, and Restoring Connections and Motor Functionality
The chances of restoring the donor’s earlier level of motor abilities increases greatly the faster the severed cords join and the damaged membranes are repaired. And the faster the healing process, the quicker the neural connections will be restored. Usually in healthy individuals, the body’s natural healing mechanisms swing into action when there is a cut or a wound. But to heal the spinal cord tissues in a case of head transplant, Dr. Canavero proposes using a compound called polyethylene glycol (PEG).
According to several research studies, PEG has the ability to heal wounds or reseal at the molecular level. In fact, scientists are already exploring avenues to establish PEG as an effective means of managing and/or treating spinal cord injury and restore or improve motor functionality in patients.
Dr. Canavero also intends to apply electrical stimulation at the point where the two severed ends of the cords fuse to accelerate healing. It has been established that electrical stimulation not only speeds up the axons and dendrons regeneration but can also trigger voluntary movements in individuals with chronic complete paralysis.
Human Head Transplant Challenge #4: Post-Transplant Complications
Organ rejection and poor or impaired blood flow to the transplanted organ are some common post-transplant complications. However, medicine has the means to diagnose these conditions and intervene effectively. For instance, the presence of a couple of serum protein biomarkers confirms acute rejection in renal transplant patients.
Color Flow Doppler (CFD) ultrasonography has been found to be an effective way to monitor blood flow after surgery. These monitoring and diagnostic methods may be implemented to detect post-transplant complications in people who have received a new head.
Every great scientific breakthrough sounds incredulous at first. The idea of a head transplant in humans may sound fantastic, dreadful or ridiculous, depending on your personal position, but I have no doubt that eventually it could be done.
Potential benefits for certain patients are obvious. If human head transplant is successful, paraplegics who have substantial amounts of spinal cord intact and people suffering from muscular dystrophy can dream of an independent and self-sufficient future where they are back to doing the things they love and are able to live more productive lives. Yet, there is also no doubt that the possibility of successful human head transplantation will create serious concerns in many quarters.
Angeli, C., Edgerton, V., Gerasimenko, Y., & Harkema, S. (2014). Altering spinal cord excitability enables voluntary movements after chronic complete paralysis in humans Brain, 137 (5), 1394-1409 DOI: 10.1093/brain/awu038
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