Detecting Awareness in the Vegetative State

Abstract

The assessment of residual brain function in the vegetative state, is extremely difficult and depends frequently on subjective interpretations of observed spontaneous and volitional behaviors. For those patients who retain peripheral motor function, rigorous behavioral assessment supported by structural imaging and electrophysiology is usually sufficient to establish a patient's level of wakefulness and awareness. However, it is becoming increasingly apparent that, in some patients, damage to the peripheral motor system may prevent overt responses to command, even though the cognitive ability to perceive and understand such commands may remain intact. Advances in functional neuroimaging suggest a novel solution to this problem; in several recent cases, so‐called “activation” studies have been used to identify residual cognitive function and even conscious awareness in patients who are assumed to be vegetative, yet retain cognitive abilities that have evaded detection using standard clinical methods.

Source imaging of QEEG as a method to detect awareness in a person in vegetative state

“…While these responses could result from awareness, the authors note that such responses 'can go on in the absence of conscious awareness'. Owen et al [6] describe a VS patient who, when asked to visualize two different actions, displayed distinctly different fMRI changes, identical to those seen in normal controls complying with the same requests. They interpreted these results as demonstrating that the patient understood the question and complied with the request, i.e.…”

“…Neuroimaging has recently been the focus of much interest as a potential technique to detect awareness without relying on movement and speech. As recently reviewed, PET and fMRI studies have indicated that patients meeting clinical criteria for the VS may respond specifically to their names [5]. While these responses could result from awareness, the authors note that such responses 'can go on in the absence of conscious awareness'.…”

Theories and methods in the scientific study of consciousness

“…Similar arguments can be made for studies that have examined the brain-activity patterns of subjects in a persistent vegetative state (PVS). Recent studies have demonstrated that some patients in PVS, though apparently completely unresponsive to external stimuli, are able to perform visual imagery experiments as assessed by the patterns of brain activity they produce in functional magnetic resonance imaging studies (Owen & Coleman, 2008;Owen et al, 2006). These results have of course great consequences for the treatment of patients in PVS, but also for our understanding of awareness (see Charland-Verville, Vanhaudenhuyse, Laureys, & Gosseries, this volume).…”

Assessment and Intervention with Patients with Severe Disorders of Consciousness

“…Neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), can help identify potential abilities even in cases with minimal (or no apparent) responsiveness (Bodart et al 2013;Coleman and Pickard 2011;Harrison and Connolly 2013;Monti 2012;Owen 2013;Owen and Coleman 2008). Indeed, the use of those techniques has allowed researchers to reach important diagnostic conclusions (e.g., Blume et al 2015;Monti et al 2010;Owen et al 2006).…”

“…The Coma Recovery Scale-Revised (CRS-R) is considered to be the most dependable scale for identifying sensory and communication expressions or responses to objects that serve to determine the patient's level of functioning (Boly 2011;Bosco et al 2010;Bruno et al 2011;Doig and Lane-Brown 2012;Godbolt et al 2012;Kalmar and Giacino 2005;La Porta et al 2013;Schnakers et al 2009;Seel et al 2010;Shiel et al 2000). Problems with this scale (and similar scales) are likely to arise when patients do not possess the hand and head responses relevant for some of the scale items and/or are unable to comprehend verbal instructions (Bosco et al 2009;Di Perri et al 2016;Lancioni et al 2014a;Owen and Coleman 2008;SchmitterEdgecombe 2006).…”