Neuroscientist Sergio Canavero, from the Turin Advanced Neuromodulation Group, was hit with a barrage of criticism after publishing his initial research last year, in which he said head transplants could be carried out by severing the heads of two patients at the same time, then cooling and flushing out the ‘recipient’ head before attaching it to its new body with polymer glue.
Some critics at the time said head transplants were "Frankenstein science," while others asked how Canavero proposed to connect the donors' and recipients' spinal chords.
But Canavero now says it is possible to merge bone marrow, surgically cut with an ultra-sharp knife, when fusing one person’s head onto another person’s spine.
He wrote in the Frontier of Neurology journal this month that the operation would be made possible using special membrane-fusion substances called fusogens, which would be injected between the two stumps cut in the spinal chord.
He backed up his claims by pointing to experiments on rats at the University of Dusseldorf, adding that the animals had fully recovered use of their limbs after the procedure.
Canavero was not available for comment when contacted by The Local on Monday.
But his latest findings were dismissed by Dr Calum MacKellar from the Scottish Council of Human Bioethics.
“Changing the bone marrow has been done for years, especially with cancer patients,” MacKellar told The Local.
“But the biggest problem with this kind of transplant would be the nerves, and that’s still not possible.”
Head transplants on animals in the past have left them paralysed and they eventually died, MacKellar added.
“The Soviet Union did head transplants on monkeys and they died after a few weeks,” he said.
“They were paralysed from the head down; even though the heart was still pumping, the neurological function did not work. That is the biggest challenge.”
The ethical challenge is even greater, MacKellar said.
“The question of identity is complex…there needs to be a lot more research done,” he said.
“If it ever goes ahead it will take decades…neurologists today have a lot more urgent matters to contend with.”
MacKeller also said that face transplants today, which have been performed for about a decade, are still very rare and only happen in extreme cases.