Sergio Canavero will propose the launch of his new project to transplant a human head in June, at the annual conference of the American Academy of Neurological and Orthopaedic Surgeons, AANOS. The project, if successful, will be used to help people with severe nerve damage and degenerative muscle diseases. The world’s first head transplant was performed on a monkey by a team led by Robert White, at the University School of Medicine in California in 1970. No attempt was made to join the spinal cord, so the monkey was paralysed from the neck down. The monkey survived for nine days, breathing without assistance, before the donor body’s immune system rejected the head.
Canavero’s proposed procedure involves joining the spinal cords after the two bodies have been cooled. The cooling is essential to prolong the time before irreparable cell degradation occurs. The neck tissues are dissected and major blood vessels linked up by tubes to prevent brain death and blood loss. Then both spinal cords are cut, decapitating both bodies before the patient’s head and donor’s body are moved together. The tricky part, if it weren’t tricky enough already, is joining the spinal cords.
If the neck cord is broken during everyday life the victim dies very quickly. The brain can no longer control the diaphragm, resulting in lung collapse and suffocation. However, the heart will continue to beat as it produces its own electrical impulses for control—hence why defibrillation is needed to restart a heart regardless of brain activity. Lung collapse will be avoided by machine assisted respiration in the procedure. The two spines then need to connect so the patient’s brain has control of bodily function when awakened.
As yet, no successful spinal cord join has occurred in any procedure. Canavero believes that the chemical polyethylene glycol will change this. The chemical encourages the fat in a cell’s membrane to connect to all neighbouring cells. When applied correctly, it will join the cords together and avoid joining to the bone itself. This method isn’t used in existing spinally damaged patients as it would fuse all cells together and cause harm.
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Muscles and arteries will then be sutured before the patient is put into a month-long coma for monitoring and healing to occur. Implanted electrodes will stimulate the spine for this period so the new nerve connections are strengthened. To prevent the rejection of the head, drugs already used in organ transplants will be administered. Canavero predicts the patients should be able to talk upon waking and walk within a year.
Obtaining ethics approval rests upon the spiritual dilemma of where a human’s sentience comes from. Patricia Scripko, a neurologist and bioethicist in California, sees no issue. “I believe what is specifically human is held within the higher cortex [of the brain]” she says. “In this case you’re not altering the cortex.” She does acknowledge that many cultures and belief systems see the soul as occupying the entire body, and many are already opposed to organ transplants. Quite simply, the world may not be ready for this. William Mathews, chairman of AANOS, agrees. “I embrace the concept of spinal fusion… but I disagree with Canavero on the timing. He thinks it’s ready, I think it’s far in the future.”
Regardless of the conference’s outcome Canavero is content to wait. “If society doesn’t want it, I won’t do it. But if people don’t want it in the US or Europe that doesn’t mean it won’t be done somewhere else” he said. Several people have already volunteered for the procedure.