Covert Cognition in Disorders of Consciousness: A Meta-Analysis

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.

Risk factors for 2‐year mortality in patients with prolonged disorders of consciousness: An international multicentre study

“…Only a few studies on DoC have collected multimodal clinical and neurophysiological findings in a multicentre longitudinal design [17]. Third, as this study was based on clinical diagnosis and did not have a complete neuroimaging workup, we could not search for signs of covert cognition [49] and analyse mortality in patients showing such signs. Fourth, the multicentre design of the present study made it possible to reduce the sampling biases and idiosyncrasies of single-centre studies, but we could not analyse our data stratified for country, as samples were too small to be representative.…”

Sleep and Circadian Disturbance in Disorders of Consciousness: Current Methods and the Way towards Clinical Implementation

“…Interestingly, all patients (n=4) that showed command following in an active functional magnetic resonance imaging (fMRI) task had preserved spindling activity during sleep. As active paradigms have been suggested to aid the diagnosis 49 , sleep spindles might be an interesting marker to take into consideration.…”

Empowering the voiceless. Disorders of consciousness, neuroimaging and supported decision-making

“…Monti and colleagues in their study found that 10% of the patients that appeared to be vegetative showed signs of awareness and were able to conduct mental imagery tasks in an fMRI scanner ( 9 ). Later, it was argued that 14–17% of patients suffering from PDoC showed brain activity that might account for consciousness when participating in these studies ( 10 , 11 ). Another study demonstrated that also EEG could be used to uncover awareness in patients suffering from VS (which is of significant interest considering the practical and financial advantages of EEG as compared to fMRI) ( 12 ).…”