Dissociation of Vegetative and Minimally Conscious Patients Based on Brain Operational Architectonics

Abstract

Discrimination between patients in vegetative (VS) and minimally conscious state (MCS) is currently based upon the behavioral gold standard. Behavioral assessment remains equivocal and difficult to interpret as evidence for the presence or absence of consciousness, resulting in possible clinical misdiagnosis in such patients. Application of an operational architectonics (OA) strategy to electroencephalogram (EEG) analysis reveals that absence of consciousness in patients in VS is paralleled by significant impairment in overall EEG operational architecture compared to patients in MCS: neuronal assemblies become smaller, their life span shortened, and they became highly unstable and functionally disconnected (desynchronized). However, in a previous study, patients with different brain damage etiologies were intermixed. Therefore, the goal of the present study was to investigate whether the application of OA methodology to EEG could reliably dissociate patients in VS and MCS independent of brain damage etiology. We conclude that the observed EEG OA structure impairment in patients in VS and partial preservation in patients in MCS is a marker of consciousness/unconsciousness rather than physiological damage. Results of this study may have neuroscientific, clinical, and ethical implications.

Complexity of Multi-Dimensional Spontaneous EEG Decreases during Propofol Induced General Anaesthesia

“…Other theory-based indices that could be explored in conjunction with the complexity measures described here include ‘causal density’ [ 13 ] and various versions of integrated information (as measured by the quantity ‘phi’ [ 14 ]), integration measures based on long-range functional connectivity such as weighted symbolic mutual information [ 54 ], integration measures based on microstate properties across channels of spontaneous EEG activity, as recently applied to classify disorders of consciousness patients by Fingelkurts et al [ 7 ], and global graph-theoretic measures such as ‘efficiency’ of connectivity graphs [ 55 ]. Moreover, the computation of the LZc and ACE measures based on a simplification of the continuous EEG to a binary signal necessarily discards some information content from the signals analyzed.…”

“…The idea that the level and range of consciousness relates in some way to dynamical complexity of brain activity is becoming increasingly prominent [ 1 – 7 ]. A common way to conceptualize dynamical complexity in this setting is as simultaneous differentiation (subsets of the system being dynamically distinct) and integration (the system as a whole exhibiting coherence), and this idea draws from what is taken to be a fundamental property of conscious experience, namely that each conscious scene is composed of many different parts and is different from every other conscious scene (differentiation), yet each conscious scene is experienced as a coherent whole (integration) [ 2 – 5 ].…”

Measuring Consciousness in Severely Damaged Brains

“…Coherence and cross-approximate entropy EEG studies confirmed stronger frontoparietal connectivity in MCS patients as compared with VS/UWS patients (Figure 2i) (Lehembre et al 2012, Wu et al 2011. The organization of oscillatory brain connectivity in interacting modules is also preserved in MCS patients as compared with VS/UWS patients (Fingelkurts et al 2013), especially in the DMN (Fingelkurts et al 2012a). Overall, functional connectivity studies suggest a link between preserved cerebral functional interactions and higher consciousness level (e.g., arousal and/or cognitive functions) in MCS patients as compared with VS/UWS patients.…”

Toward Improving Diagnostic Strategies in Chronic Disorders of Consciousness: An Overview on the (Re-)Emergent Role of Neurophysiology

“…Table 1 shows the different assessments we reviewed with their main outcomes concerning significant MCS/UWS differentiation at group and individual level (i.e., disclosing patients with fLIS among those with UWS and MCS vs. UWS). Whether the clinical assessment remains fundamental and irreplaceable, the combinations of behavioral and electrophysiological/neuroimaging procedures represents an important, cautionary condition to reduce misdiagnosis [153][154][155][156][157][158][159]. Further electrophysiological studies are however required to confirm the values of basic and advanced neurophysiologic paradigms in DoC diagnosis, given that the moderate evidence concerning the possibility distinguishing MCS from UWS is in favor of a spared EEG reactivity, the presence of LEPs components, EPs features, and the PCI threshold [160].…”