Conscious awareness in PVS and MCS

Abstract

Throughout the final month of Theresa Schiavo's life, her parents insisted she was in a minimally conscious state (MCS),1 not in a persistent vegetative state (PVS).2 Based on reliable expert medical testimony, Judge Greer ruled that Schiavo was in a PVS and beyond hope of significant improvement. Her postmortem examination revealed profound and widespread cortical, subcortical, and thalamic damage consistent with a PVS,3 but even these findings did not conclusively settle the dispute. How can neurologists prove that a brain-damaged patient utterly lacks conscious awareness and has no hope of meaningful recovery? There is a biologic limitation to what any person can know about the quantity and quality of another person's awareness. No one can directly experience the conscious life of another person, so our clinical knowledge is inferential. A neurologist can apply auditory, visual, somesthetic, noxious, or olfactory stimuli and on the basis of the quality of the patient's responses make a reasoned judgment as to that person's level of awareness. Although an experienced and skillful neurologist usually will be correct, there exists a possibility that, despite the absence of clinically apparent evidence of conscious awareness, the patient remains aware at a level that cannot be adequately assessed clinically.4 The difference between a severely brain-damaged person who retains awareness and one who does not is the essential difference …