A man who was pronounced "brain dead" lived to tell of it and is now recovering.
This speaks to the fact that it is difficult to determine from third person accounts of the brain--a fantastically complex organ--what a person's first person experience actually is. This young man heard the doctors pronounce him dead! The benefit of the doubt must always go to the living human being, no matter how damaged or compromised his or her body may be. The burden of proof must always be on those who would let the person die. "Thou Shalt Not Murder."
Moreover, consciousness is not exhausted by brain states; there is a mind or soul that is distinct from, but related to, the material states of the brain. This is supported by Scripture, science, and philosophy. For a paper on this topic, see my "Brains, Minds, and Persons."
For more details, see J.P. Moreland and Scott Rae, Body and Soul