What's difference between severe brain damage ond brain dead?

Brain activity. Brain death occurs when there is complete cessation of brain activity. It is determined by a flat (no activity) eeg, absence of blood flow to the brain, and other signs on examination. People with severe brain damage have some degree of brain activity, usually not enough to regain consciousness.
Brain Death. . Brain death is complete loss of all brain function. Clinical examination and confirmatory brain blood flow studies are usually how the diagnosis is made . Severe brain damage is not complete function loss with preservation of blood flow to at least some brain tissue.