Global functional connectivity reveals highly significant differences between the vegetative and the minimally conscious state

Abstract

A major challenge in the diagnosis of disorders of consciousness is the differential diagnosis between the vegetative state (VS) and the minimally conscious state (MCS). Clinically, VS is defined by complete unawareness, whereas MCS is defined by the presence of inconsistent but clearly discernible behavioural signs of consciousness. In healthy individuals, pain cries have been reported to elicit functional activation within the pain matrix of the brain, which may be interpreted as empathic reaction. In this study, pain cries were presented to six VS patients, six MCS patients, and 17 age-matched healthy controls. Conventional task-related functional magnetic resonance imaging (fMRI) showed no significant differences in functional activation between the VS and MCS groups. In contrast to this negative finding, the application of a novel data-driven technique for the analysis of the brain's global functional connectivity yielded a positive result. The weighted global connectivity (WGC) was significantly greater in the MCS group compared to the VS group (p < 0.05, family-wise error corrected). Using areas of significant WGC differences as 'seed regions' in a secondary connectivity analysis revealed extended functional networks in both MCS and healthy groups, whereas no such long-range functional connections were observed in the VS group. These results demonstrate the potential of functional connectivity MRI (fcMRI) as a clinical tool for differential diagnosis in disorders of consciousness.

Pain issues in disorders of consciousness

“…ACC and insula) in 30% of patients in a VS/UWS in response to noxious stimulation as well as pain cries [27,28] (Figure 1). The last study, nevertheless, also showed, in parallel to previous findings, that the connectivity within the whole pain network was significantly decreased as compared to patients in a MCS [29]. Even though this suggests an altered perception in patients in a VS/UWS, the activation of the affective pain network might denote the presence of residual pain perception Figure 1.…”

Functional connectivity in disorders of consciousness: methodological aspects and clinical relevance

“…They showed extended functional networks in both MCS and healthy subjects, whereas no such functional connections were observed in VS. These results demonstrate the potential of functional connectivity MRI as a clinical tool for differential diagnosis in disorders of consciousness (Kotchoubey et al 2013). …”

Finding a way in: A review and practical evaluation of fMRI and EEG for detection and assessment in disorders of consciousness

“…This finding lends further support to the notion that isolated cognitive processes may be preserved in VS, but that deficient connectivity is at the heart of decreased consciousness. Kotchoubey et al (2013) studied global functional connectivity under emotional load in 6 VS and 6 MCS patients who listened to recorded human pain cries compared to non-emotional vocalizations. While they observed no significant stimulusrelated activation in either group in a typical GLM analysis, a whole brain functional connectivity analysis revealed stronger connectivity in the MCS than in VS patients, in emotion-related networks similar to those observed in healthy controls.…”