ABSTRACT
A variety of global disorders of consciousness have been identified, including coma, persistent vegetative state (PVS), and minimally conscious state (MCS). Perhaps the most widely recognized disorder of consciousness is the coma, a state that occurs subsequent to brain injury. Comatose patients exhibit no evidence of wakefulness or arousal, no evidence of awareness, and no communication. Philosophers and scientists have elaborated more fine-grained concepts of consciousness. New noninvasive methods for imaging brain activity have the potential to revolutionize the diagnosis, care, and treatment of patients with disorders of consciousness. An enormous body of imaging studies in normal test subjects has identified signature patterns of brain activity associated with the performance of particular cognitive tasks. Diagnosis of states of consciousness, whether by bedside examination, or by measurement of brain activity, is made on the basis of objective, physically manifest phenomena. Consciousness is usually assessed by observation of and communication with another agent.
