Neurosurgeon to perform first head transplant: Could it
actually work?
John Murphy, MDLinx, 09/22/2016
Italian neurosurgeon Sergio Canavero, MD, made headlines in
June 2015 when he announced his plan to perform the first human head transplant
in 2017. Now, in the September 19, 2016 issue of Surgical Neurology
International, Dr. Canavero and colleagues backed up that audacious plan with a
series of proof-of-principle papers that detail their extraordinary surgical
procedure—which they described as “the defining event of the 21st century.”
Not surprisingly, the scientific and medical communities
have reacted to Dr. Canavero’s head transplant procedure with curiosity,
skepticism, and outright scorn.
“Brain transplantation is not ready for prime time,” wrote
Arthur Caplan, PhD, Head of the Division of Bioethics at New York University
Langone Medical Center in New York, NY, in an editorial in Forbes. “To attempt
to move a brain to a new body given what is known about the medicine and
science involved, one would have to be out of one’s mind.”
“My answer to Dr. Caplan,” Dr. Canavero said in an interview
with Motherboard.com, “is he doesn’t know what he’s talking about. The nutty
guy is him, not me.”
Dr. Canavero, who heads the Turin Advanced Neuromodulation
Group, in Turin, Italy, acknowledges that others view head transplantation as
impossible; but he gives the procedure a 90% chance of success. Plus, he
already has his first patient: Valery Spiridonov, 31-year-old Russian man who
has Werdnig-Hoffmann disease, a rare but severe form of spinal muscular
atrophy.
The procedure (dubbed cephalosomatic anastomosis) is more
like a body transplant than a head transplant, literally speaking. Dr. Canavero
will essentially remove Spiridonov’s deteriorating body from his head, and
replace it with a brain-dead but healthy donor body. It’s expected to be a
36-hour, $15 to $20 million procedure involving at least 150 health care
professionals, including doctors, nurses, technicians, psychologists, and
virtual reality engineers.
Here’s how they plan to do it:
• Freeze the brain: First, both the recipient and the donor
are anesthetized and intubated, and their heads are locked into place. Both
patients are given immunosuppressants throughout the procedure. The recipient’s
head is then cooled to 10° C (50° F) to halt electrocortical activity,
rendering him temporarily brain-dead. (“As close to death as possible,” Dr.
Canavero described.) The spinal cords in both patients are cooled as well.
• Sever the neck: To prevent coagulation, the recipient’s
head is drained of blood and then flushed with lactated Ringer’s solution. The
surgical teams then cut deep incisions around each patient’s neck (at the C5/6
level) and all of the anatomic structures are carefully separated to expose the
carotid and vertebral arteries, jugular veins, and spine. Next, vascular
surgeons loop silastic cannulas around the carotid arteries and jugular veins,
and clamp the vessels at the tips to stop blood flow and prevent air emboli
when the head is removed.
• Cut the spinal cord: Of all the steps in this lengthy
procedure, this one may be the most critical. Here, the surgeons use a diamond
nanoblade to “clean-cut” the spinal cords of both patients simultaneously.
Unlike accidental spinal cord injury, which causes widespread damage to the
spinal cord, the ultra-sharp severing used in this procedure allows the spinal
cord to be reconnected with minimal damage and eventual recovery, Dr. Canavero
wrote.
• Fuse the spinal cord: Immediately after decapitation, the recipient’s
head is wheeled to the donor body, where the surgeons quickly join the stumps
of the spinal cords. Now comes the other critical step: the severed myelinated
axons are fused together with a specially-designed polyethylene glycol (PEG)
polymer that reseals the cellular membranes of neurons. The “secret
ingredients” in this particular PEG are graphene nanoribbons, developed by Rice
University scientists, which first act as a conduit and then as a scaffold upon
which the neuronal fibers can grow. Electrical stimulation is applied to the
fusion point of the spinal cord to accelerate the regeneration of neural
connections. In order to reinforce the link, the surgeons attach a few loose
sutures around the joined spinal cord.
• Reconnect the rest: To restore circulation, the vascular
surgeons remove the silastic cannulas one by one and suture the arteries and
veins of the head to those of the new body. After the dura is sutured and
clamped watertight, then the trachea, esophagus, vagus and phrenic nerves are
reconnected and all the muscles are rejoined. Plastic surgeons suture the skin
for optimum cosmetic results.
The recipient is taken to the ICU and kept in an induced
coma for three to four weeks. Immunosuppression is continued and the patient is
regularly screened for any sign of anti-donor antibodies. After coming out of
the coma, Dr. Canavero foresees the recipient will need both physical therapy
and psychological counseling; but he expects the patient will be able to walk
again within 6 months of the surgery.
Could it actually work?
Dr. Canavero’s colleagues have already shown in mice and in
a dog that sensorimotor function can be recovered after severing and
re-attaching the spinal cord. His collaborator Xiaoping Ren, MD, of Harbin
Medical University in China, performed a head transplant in a monkey in the
past year. Still, “the proof of the pudding rests in human studies,” wrote Drs.
Canavero and Ren. They hope to perform the first human head transplant on
Spiridonov in December 2017.
But the skeptics are many, and they too have science and
medicine to back up their positions.
“This is such an overwhelming project, the possibility of it
happening is very unlikely,” Harry S. Goldsmith, MD, Clinical Professor of
Neurosurgery at the University of California, Davis, said in a 2015 article in
New Scientist. “I don’t believe it will ever work, there are too many problems
with the procedure.”
Richard Borgens, PhD, Director of the Center for Paralysis
Research at Purdue University in West Lafayette, Indiana, told New Scientist,
“There is no evidence that the connectivity of cord and brain would lead to
useful sentient or motor function following head transplantation.”
“In my opinion, this procedure has no feasibility at all,”
Lorenzo Pinessi, MD, Director of the Neurology Clinic at Italy’s University of
Turin, told Newsweek. “It is demented.”
For Spiridonov, who faces a mortal disease, the idea isn’t
demented at all—just the opposite. “Removing all the sick parts but the head
would do a great job in my case,” he told The Atlantic. “I couldn’t see any
other way to treat myself.”
Dr. Canavero outlined the ideas behind head transplantation
in this September 2015 TEDx talk.
http://www.mdlinx.com/neurology/article/623
