A controversial new project to perform the world's first human head transplant by 2017 will be launched later this year, amid a storm of ethical issues and questions over the actual science involved.

First proposed two years ago by neuroscientist Sergio Canavero from the Turin Advanced Neuromodulation Group in Italy, the idea came about in considering how to improve things for people who have experienced severe muscle and nerve damage because of cancer. The biggest challenges involved, such as connecting the severed spinal cord of the transplanted head to the recipient's spinal cord, and figuring out how to introduce such a huge part without the body rejecting it, will be sorted over the next two years, Canavero predicts.

This month, he outlined the transplant technique he intends to follow in the journal Surgical Neurology International, and will announce his plan to get the project rolling at the annual conference of the American Academy of Neurological and Orthopaedic Surgeons (AANOS) in US in June, inviting other researchers to join him.

It's been almost five decades since the first 'successful' head transplant. And this experiment sure was a grisly one. In 1970, the head of one monkey was placed onto the body of another at the Case Western Reserve University School of Medicine in the US. While scientists weren't able to fuse the spinal cords, which means the monkey recipient couldn't move its new head, it was able to achieve assisted breathing, but it died in a mere nine days following the procedure. 

But Canavero thinks we've got the technology and expertise to do a whole lot better than that now. He described the process to Helen Thomson at New Scientist, and it's equal parts nuts and kinda genius. It starts with cooling both the body and head right down so the cells won't die when deprived of oxgyen through the process. Next, the neck is severed and all the crucial blood vessels are hooked up to tubes while the spinal cord on both the head and the body are severed.

"The recipient's head is then moved onto the donor body and the two ends of the spinal cord – which resemble two densely packed bundles of spaghetti – are fused together," says Thomson. "To achieve this, Canavero intends to flush the area with a chemical called polyethylene glycol, and follow up with several hours of injections of the same stuff. Just like hot water makes dry spaghetti stick together, polyethylene glycol encourages the fat in cell membranes to mesh."

Canavero told Thomson the final step would be to stitch up the muscles and blood supply, and to induce a three- or four-week coma to let the body heal itself while embedded electrodes stimulate the spinal cord to strengthen the new nerve connections. 

The recipient won't be able to get up and walk around soon after the surgery, he says, telling New Scientist that the damage to the spinal cord would take about 12 months to heal fully. The recipient would retain their old voice, he adds. 

Sounds simple, but is that really all there is to it? Not even a little bit, because we don't even know if the plan to use polyethylene glycol to fuse the spinal cords is even going to work, in which case Canavero will be forced to use one of his other options. "There is no evidence that the connectivity of cord and brain would lead to useful sentient or motor function following head transplantation," Richard Borgens, director of the Centre for Paralysis Research at Purdue University in the US, told Thomson. 

And then there's the whole 'how do you get the body to stop automatically rejecting the head?' issue. I'll let Helen Thomson explain that one over at New Scientist, because it's a doozy. Suffice it to say, this could be something that humans will have to prepare themselves for, if not in two years' time, perhaps within the next decade or five. We just have to figure out how to not end up like this in the process:

Source: New Scientist