Talk at AAAS Evaluates New Imaging Technology's Usefulness in Understanding "Persistent Vegetative" and "Minimally Conscious" States
Feb 15, 2002
The latest research in the conditions known as "persistent vegetative state" and "minimally conscious state" will be presented by Dr. Nicholas Schiff, Assistant Professor of Neurology and Neuroscience at Weill Cornell Medical College, at the meeting in Boston today of the American Association for the Advancement of Science (AAAS).
Displaying images of brain functions obtained with the most advanced technology, Dr. Schiff will discuss the problems and dilemmas posed by persons who—whether through stroke, brain injury, cardiac arrest, or other trauma to the central nervous system—show some signs of consciousness but cannot fully communicate and respond.
Dr. Schiff notes that the National Institutes of Health have identified "epidemic levels" of traumatic brain injury in today's United States population—about 2% live with some consequence of such injury. He will discuss differences that exist in a continuum of at least four states:
- brain dead (the heart is still beating and the lungs still breathe, but there is no activity in the brain);
- coma (the eyes are closed, and the person is unarousable and unresponsive);
- persistent vegetative state—PVS (the eyes alternate between open and closed, and the person may grimace, make noises, move a limb or two, even cry, but the person shows no evidence of awareness of self or the environment); and
- minimally conscious state—MCS (the person demonstrates inconsistent but definite evidence of some awareness of self and the environment, but is unable to communicate).
Persons in such diminished states pose serious interpretive dilemmas for their doctors and families. Are they aware? If so, to what degree? Can they suffer? If they are suffering, how bad is it? Is their condition irreversible, or might they recover?
As is well known, with the persistent vegetative state (PVS), several critical court decisions have affirmed the right to cut off life support. But as understanding of states beyond PVS develops further, new questions have arisen. There have been instances in which patients in a minimally conscious state (MCS) have fluctuated from conditions that do not support any hope of future interaction to a communicative state.
Dr. Schiff is interested in these questions, and others: Why are these persons in their conditions? Can modern technology detect signs of consciousness or, at least, activity in their brains? Can something be done to bring some of them back to health?
Dr. Schiff and his colleagues have studied severely brain-injured persons through several techniques of imaging: magnetic resonance imaging (MRI), positron emission tomography (PET scans), and electroencephalography (EEG). In collaboration with Dr. Joy Hirsch of Memorial Sloan-Kettering Cancer Center, they have recently performed functional MRIs of patients in minimally conscious states, and he will present some of these images at his talk.
Persistent vegetative state is characterized by overwhelming brain injury, Dr. Schiff says the latest research shows. The brain has only fragments of circuits, and these lead to only fragments of behavior. Some persons in a minimally conscious state, by contrast, have widely preserved brain activity, although they are severely dysfunctional.
Dr. Schiff says that, for now, tools like functional MRIs are not for routine clinical use. They are only for research, trying to answer the basic questions that will have to be answered before we can address larger issues of trying to bring severely brain-injured persons back to health.