The notion of transferring a human brain from one skull to another exists firmly in the realm of science fiction, not current medical possibility. A true human brain transplant involves surgically removing the entire brain and placing it into a donor body. This procedure has never been successfully attempted in a living person and remains unequivocally impossible with today’s technology. The operation would require the complete severing and subsequent perfect re-establishment of every connection between the brain and the spinal cord, a feat far beyond the capabilities of modern neurosurgery.
The Biological Impossibility
The primary barrier to performing a brain transplant lies in the intricate complexity of the central nervous system (CNS). The brain must be completely separated from the spinal cord, which houses the vast communication network connecting the brain to the rest of the body. This separation causes irreversible injury because the adult mammalian CNS possesses a remarkably low intrinsic capacity for regeneration.
The main obstacle is the inability to perfectly fuse the millions of severed axons of the spinal cord. These axons are the projections of nerve cells that transmit electrical signals, and their precise re-connection is necessary for the brain to control movement and receive sensory input. The injury environment within the CNS actively inhibits regrowth due to the presence of inhibitory factors like NogoA and Chondroitin Sulfate Proteoglycans (CSPGs) that are released after trauma.
Furthermore, severing the spinal cord triggers the formation of a glial scar, which acts as both a physical and chemical barrier to axonal regrowth. Even if surgeons could overcome these inhibitory factors, they would still need to perfectly align and fuse the millions of individual axons to their corresponding partners on the donor spinal cord. The current state of neurosurgery lacks any technique capable of achieving this level of microscopic specificity and functional restoration across a complete transection.
The brain’s reliance on a continuous supply of oxygen and nutrients presents another significant technical challenge. Any interruption of blood flow, even for a few minutes, results in rapid, widespread cell death. Maintaining the brain’s viability during the transfer process requires profound hypothermia and specialized perfusion techniques to slow metabolism and minimize ischemic damage. Even with these protective measures, the sheer volume of neural connections and the delicate structure of the brainstem make the procedure biologically unfeasible.
The Distinction Between Brain and Head Transplants
The public often confuses a true brain transplant—the transfer of only the neural tissue—with a head transplant, technically known as cephalosomatic anastomosis. A head transplant involves moving the entire head, including the brain, spinal cord stub, and all associated vascular and muscular tissues, onto a donor body. This distinction is important because the head transplant, though still considered impossible to achieve with functional success, represents a slightly less complex connection point than a true brain transplant.
In a head transplant, the primary surgical connection involves fusing the two ends of the spinal cord and rejoining the major blood vessels, trachea, and esophagus in the neck. The brain itself remains within the skull and is not internally manipulated or separated from the brainstem. This focus on the neck connection point is why controversial proposals for human transplantation, such as those put forth by Italian neurosurgeon Sergio Canavero, have centered on the head transplant model.
Canavero proposed using polyethylene glycol (PEG) to attempt to promote the fusion of the severed spinal cord stumps. The procedure would require cooling the head and donor body to a hypothermic state to extend the time available for the operation. While Canavero and his colleagues have reported performing controversial rehearsals on cadavers, no living human has ever undergone a successful head transplant with recovery of motor or sensory function below the neck. The underlying biological problem of re-fusing a completely severed spinal cord remains unsolved.
Identity and Ethical Considerations
Assuming a future medical breakthrough could overcome the biological hurdles, a brain transplant would raise profound questions concerning personhood and identity. Since the brain is considered the seat of consciousness, memory, and self-identity, a brain transplant would result in the recipient’s mind inhabiting a new body. The philosophical question of “who is who” becomes central, as the person receiving the new body would still possess their original identity, memories, and personality.
The ethical implications of consent and moral status are equally complex. The recipient would be giving consent for a procedure that carries an extremely high risk of death or a state of consciousness entirely detached from the body. Furthermore, the donor body, taken from a brain-dead individual, would need to be healthy and maintained on life support, raising moral questions about the utilization of the body as a mere biological vessel.
Even if the procedure were technically successful, the psychological toll on the recipient would be immense. The brain would suddenly be receiving sensory input from an entirely new physical structure, including a different nervous system, new limbs, and a foreign chemical environment. Bioethicists have noted the potential for severe psychological distress or even psychosis as the brain struggles to map its established sense of self onto an unfamiliar physical reality.