■ Evidence from functional neuroimaging studies on resting state suggests that there are two distinct anticorrelated cortical systems that mediate conscious awareness: an “extrinsic” system that encompasses lateral fronto-parietal areas and has been linked with processes of external input (external awareness), and an “intrinsic” system which encompasses mainly medial brain areas and..

Some patients awaken from their coma but only show reflex motor activity. This condition of wakeful (eyes open) unawareness is called the vegetative state. In 2002, a new clinical entity coined ‘‘minimally conscious state’’ defined patients who show more than reflex responsiveness but remain unable to communicate their thoughts and feelings. Emergence from the minimally conscious state is defined by functional recovery of verbal or nonverbal communication.1 Our empirical medical definitions aim to propose clearcut borders separating disorders of consciousness such (...) as coma, vegetative state and minimally conscious state but clinical reality shows that these boundaries can often be fuzzy (fig 1). Recent clinical, electrophysiological and neuroimaging studies are shedding light on these challenging limits of consciousness encountered following severe acute brain damage. At the patient’s bedside, it is very challenging to differentiate reflex or automatic motor behaviour from movements indicating signs of consciousness, and hence some minimally conscious patients might be misdiagnosed as being vegetative. For some motor responses (eg, blinking to visual threat, brief fixation, normal flexion response to pain, etc) it remains unclear whether they truly are voluntary or willed because we lack convincing scientific evidence. We also lack consensus on how to practically assess some of these behavioural responses. For example, there is no agreement on what stimulus to employ in the assessment of visual pursuit movements— often one of the first clinical signs heralding the transition from the vegetative to the minimally conscious state. Vanhaudenhuyse and colleagues2 recently studied visual pursuit in 51 post-comatose patients comparing eye tracking of a moving object, person or mirror. It was shown that more.. (shrink)

Following coma, some patients will recover wakefulness without signs of consciousness (only showing reflex movements, i.e., the vegetative state) or may show non-reflex movements but remain without functional communication (i.e., the minimally conscious state). Currently, there remains a high rate of misdiagnosis of the vegetative state (Schnakers et. al. BMC Neurol, 9:35, 8) and the clinical and electrophysiological markers of outcome from the vegetative and minimally conscious states remain unsatisfactory. This should incite clinicians to use multimodal assessment to detect objective (...) signs of consciousness and validate para-clinical prognostic markers in these challenging patients. This review will focus on advanced magnetic resonance imaging (MRI) techniques such as magnetic resonance spectroscopy, diffusion tensor imaging, and functional MRI (fMRI studies in both “activation” and “resting state” conditions) that were recently introduced in the assessment of patients with.. (shrink)