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. 2020 Dec 2;10(12):930.
doi: 10.3390/brainsci10120930.

Covert Cognition in Disorders of Consciousness: A Meta-Analysis

Caroline Schnakers  1 , Michaela Hirsch  2 , Enrique Noé  3 , Roberto Llorens  3   4 , Nicolas Lejeune  5 , Vigneswaran Veeramuthu  6 , Sabrina De Marco  7 , Athena Demertzi  5 , Catherine Duclos  8 , Ann-Marie Morrissey  9 , Camille Chatelle  5 , Anna Estraneo  10   11
Affiliations

Covert Cognition in Disorders of Consciousness: A Meta-Analysis

Caroline Schnakers et al. Brain Sci. .

Abstract

Covert cognition in patients with disorders of consciousness represents a real diagnostic conundrum for clinicians. In this meta-analysis, our main objective was to identify clinical and demographic variables that are more likely to be associated with responding to an active paradigm. Among 2018 citations found on PubMed, 60 observational studies were found relevant. Based on the QUADAS-2, 49 studies were considered. Data from 25 publications were extracted and included in the meta-analysis. Most of these studies used electrophysiology as well as counting tasks or mental imagery. According to our statistical analysis, patients clinically diagnosed as being in a vegetative state and in a minimally conscious state minus (MCS-) show similar likelihood in responding to active paradigm and responders are most likely suffering from a traumatic brain injury. In the future, multi-centric studies should be performed in order to increase sample size, with similar methodologies and include structural and functional neuroimaging in order to identify cerebral markers related to such a challenging diagnosis.

Keywords: cognitive motor dissociation; consciousness; covert cognition; minimally conscious state; severe brain injury; vegetative state.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
PRISMA Flow Diagram.
Figure 2
Figure 2
Impact of disorders of consciousness on the rate of responders: forest plots and publication bias (Funnel plots and Kendall’s tau). An observed outcome (and confidence interval) above 0 means MCS > VS (for Panel 1) or MCS− > VS (for Panel 2).
Figure 3
Figure 3
Impact of etiology on the rate of responders: forest plots and publication bias (Funnel plots and Kendall’s tau); Panel 1 illustrates the findings when considering traumatic brain injury (T) versus non-traumatic brain injury (NT) in VS and in MCS patients. Panel 2 illustrates the findings when considering traumatic brain injury (T) versus non-traumatic brain injury (NT) in VS and in MCS− patients. An observed outcome (and confidence interval) above 0 means T > NT (for both Panel 1 and 2).
See this image and copyright information in PMC

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