A Johns Hopkins expert examines definitions of brain death vs. other states of lost consciousness.
A look at some of the differences between states of consciousness and brain death:
Brain death: These patients are no longer alive. There has been an irreversible cessation of all activity in both the brain and the brain stem. Reflexes that go through the spinal cord may persist even in a brain-dead state.
Coma: These patients are alive, but in a state of eyes-closed, depressed consciousness from which they cannot be aroused. Coma is distinguished from brain death by the presence of brain stem responses, spontaneous breathing or non-purposeful motor responses. Coma has three possible outcomes: progression to brain death, recovery of consciousness, or evolution to a state of chronically depressed consciousness, such as a vegetative state or minimally conscious state.
Vegetative state: Patients in vegetative states are alive but also have severely impaired consciousness, although their eyes may open spontaneously. The eye opening may give the impression of consciousness, but there is no awareness of the environment. These patients do not acknowledge the examiner; they do not attend or track objects that are presented to them; their movements are non-purposeful; they do not speak.
Minimally conscious state: These patients are also alive, with a severe alteration in consciousness, with intermittent, but inconsistent, behaviors suggesting awareness. Contrary to patients in coma or a vegetative state, minimally conscious patients may occasionally have purposeful movements, and they may track motions with their eyes or speak.
Source: Robert Stevens, associate professor of neuroscience and critical care at Johns Hopkins University School of Medicine.
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