Vegetative State: Difficulty in Identifying Consciousness and Predicting Outcome

Abstract

Article consists of literature review, authors experience of the application of neurovisualization and neurophysiological research methods to predict the recovery of consciousness in patients in vegetative state (VS). According to the literature data PET with FDG has higher sensitivity in the detection of signs of consciousness, then functional MRI (fMRI). The method fMRI allows assessing the functional activity of the brain in a state of rest and in response to stimulation with different modalities ― visual, auditory, etc (with the application of active and passive paradigm). A higher specificity in the detection of signs of consciousness have the methodology of fMRI with the active paradigm, at the same time, the absence of signs of consciousness according to the fMRI can not be charged as a basis for the conclusion of a poor prognosis in a particular patient. Neurophysiological tests (EEG, TMS, EP, etc) are more readily available and quite effective. Based on the literature analysis, the authors comes to the conclusion that neurovisualization and neurophysiological tests used in the prediction of the outcome of VS reflects the residual functional activity of different brain areas, in a context of diffuse brain damage, and the recovery of consciousness is usually combined with the restoring of the functional activity off the thalamocortical tracts, which activity, indirectly, is evaluated using these methods. In the authors' opinions, the main disadvantage in the interpretation of the is the lack of a common pathophysiological concept of the organization of brain functions in VS patients. The authors offer for the discussion their concept of stable pathological states of the brain, which is based on the works of Russian pathophysiologists.