Is the world ready to experience the first human head transplantation?
An Italian neurosurgeon Sergio Canavero who made the biggest claim of performing first ever human head transplant in 2017 recently developed a bicephalic model of head transplantation to fix a mouse head to the body of a rat.
Given the fact that the double-headed rat survived only approximately 36 hours, Canavero says that the primary goal of this experiment is to provide scientific evidence justifying his biggest claim.
The whole story started two years ago in Annapolis, Maryland where Canavero presented his idea of human head transplantation and related surgical procedure to the American Academy of Neurological and Orthopedic Surgeons.
In his presentation, he claimed that despite being a risky surgery, there is 90% chance of success. The surgery, as he mentioned, may cost up to $15 million.
Valery Spiridonov, a Russian computer scientist suffering from spinal muscular atrophy, voluntarily agrees to undergo the first head transplant surgery.
As a proof of concept, Canavero along with his collaborator, Xiaoping Ren from the Harbin Medical University in China, have performed a series of experiments that involve splitting the spinal cord of a dog and allow it for fusion under hypothermia, a low temperature condition ranging from 12 – 15 °C.
However, the procedure adopted in these experiments to fuse spinal cord has raised many questions.
“These papers do not support moving forward in humans,” says Jerry Silver, a neuroscientist at Case Western Reserve University in Ohio.
HUMAN HEAD TRANSPLANTATION – MAJOR OBSTACLES
Although sounds exciting, this improbable idea still needs to cross many hurdles to be in the horizon. Many ethical and technical questions need to be answered before even reaching the first step of the milestone.
Latest rat experiment conducted by the surgeons were only able to show the benefits of continuous blood supply from a third rat in keeping the head alive until it is attached again to the recipient’s body.
“Keeping organs alive and intact during the transplant procedure is a very important part of transplants,” says Dean Burnett, a neuroscientist at Cardiff University. “Any approach or data that can help improve this process would be of value.”
“The current experiment seems to be purely to show that severed heads ‘can’ be kept alive and attached to another body, but that doesn’t tell us much beyond the fact that it’s physically possible to do this,” Burnett said.
THE TIME WINDOW
After decapitation, hypothermic head of the recipient must be attached to the donor’s body and reconnected to the donor’s circulatory system within just 60 minutes. A head kept longer than 60 minutes can suffer potential brain damage.
Organ transplantation in general suffers from a major obstacle of immune rejection. Upon receiving an organ from a donor, body’s immune system treats it as a foreign substance, which is immunologically termed as antigen. These antigens trigger a cascade of immunological reactions, which are ultimately aimed to attack and reject the foreign body.
Since a head is a complex structure holding many important organs such as eyes, nose, ears, and most importantly brain, implanting a foreign head can increase the rate of rejection substantially.
RE-ESTABLISHING BRAIN-SPINAL CORD CONNECTION
According to Canavero, the biggest hurdle to perform successful human head transplantation is to precisely connect and reestablish the brain-spinal cord axis. This is crucial to regain full brain-motor activity.
In this case, neuron regeneration ability of central nervous system should be well enough to effectively connect millions of connections between brain and spinal cord.
“In the spinal cord there are millions of highly complex connections,” Burnett said. “Reattaching severed spinal cords is currently beyond us; attaching two that have never been connected before should be significantly more difficult. There’s nothing in this questionable research that challenges this situation.”
It might be very tough psychologically to inhabit someone else’s body.
According to Canavero’s proposed protocol, Spiridonov is undergoing virtual reality training to be prepared for possible psychological stresses. Post-transplantation, he will undergo psychometric evaluation to ensure minimal stress that might associate with this hypothetical procedure.
Nevertheless, Canavero and his collaborator need to come up with concrete animal experiments before even planning to execute head transplantation in humans.
Since it is nearly impossible to have U.S. approval for this surgery, atleast in the present scenario, Canavero has other countries in mind where it can be a legitimate process.