I know that heart transplants are around but the same can’t be said for brains. Both are organs, however the brain is a delicate and complex one more the heart. Also there’s the issue of removing it literally kills the patient since the brain is connected to the spinal cord, optic nerve & etc.
Even if it was possible under the current technology we have, would there still be limitations? How will memory transfer work if giving an Alzheimer’s patient a new mind, implanting a new one replacing the diseased one. The brain is sensitive to drops in oxygen levels (it dies when low).
The brain is the command center for a person, without one: person is dead (literally), so there’s that dilemma. You need technology similar to a cardiopulmonary bypass but for the brain to retain essential functions and information, if you want to keep the patient alive during a mind transplant.
Let’s say you managed to implant a new mind: you now have the arduous task of reconnecting every single nerve (visible and microscopic) and restoring key functions (spinal cord integration), also taking into account if the patients immune system will accept or reject that.
There’s not a hard-coded wiring diagram of how the neurons from the brain connect to the rest of the body—everybody’s wired a bit differently, and the brain normally figures out how to work with what it’s got during development. So there’s no one-to-one way to connect the nerves from one person’s brain to those in another person’s body—and if it doesn’t get the signals it’s expecting, it will just seem like noise.
Besides which—if I remember correctly, you can’t generally reconnect severed nerves. Instead, the remaining portion of the nerve cell has to grow a new axon that retraces the route of the old one, and it can only trace the old path for a limited distance (like, if it’s close enough to receive chemical signals from the original site). But I’m not sure I’ve got all the details right on that.