I should add that I didn't answer the latter half of your question. So I will do it now.

You can't replace the brain like you can replace the heart cause once nerves are severed, they become dead or at least damaged leading to dysfunctions such as peripheral neuropathy, whose main symptoms are numbness (nerves lose efficiency), and pricking needles sensation (the nerves tell the brain they're in pain.) Nerve cells are the cells which act as wires, transferring what your muscles sense to the brain and from brain transferring orders about what to do to your muscles.

Now I am no surgeon, but from what I know, the brain is different from the heart. Before going into that, I should add that every foreign material is rejected by the body, even a foreign heart. Doctors have to give the patient immunsuppressants to avoid the heart getting rejected by the body, i.e., preventing killing of the donor heart once it is transplanted into the receiver's body.


Heart and kidneys are much more simple to transplant surgically and there are proper medications that help body acknowledge, "Hey, this new guy (organ) is an ally, not a threat" but unfortunately as the brain is infinitely more complex than a simple pump or a filter, we do not know enough about it to make a successful transplant. And I doubt a person can be revived by brain transplant, as the nature of the question seems. It is the unfortunate fact of matter, that no matter how much we progress, we'll never be able to properly do a brain transplant. In my opinion, that's actually the best, or we'll have zombies.

I myself wanted to do research on the nervous system, its pathology and its therapeutics, its anatomy and its physiology because I myself suffer from various brain conditions and I know how it's like to suffer. My parents are also neuropsychologically ill, and my uncle who is my childhood hero, recently went through a brain surgery and he'll never fully recover. He can drive and hold a job, but his personality has changed and even his driving his limitations. I wish I could help, but my doctors told me I too am just another victim of helplessness and despair.