Reductions of Thalamic Volume and Regional Shape Changes in the Vegetative and the Minimally Conscious States

Abstract

The thalamus is known to play a key role in arousal regulation and support of human consciousness. Neuropathological studies have identified thalamic damage as one of the most common abnormalities present in the brains of patients who were in a vegetative state (VS) or a minimally-conscious state (MCS) state at the time of their deaths. Nonetheless, no in vivo studies of thalamic abnormalities in these patients have been conducted. Using high-resolution T1-weighted magnetic resonance images and a novel approach to shape analysis, we investigated thalamic global and regional changes in a sample of patients in a VS or an MCS. Group comparisons and correlations with clinical variables were performed for the total thalamic volume and for each surface vertex. Total thalamic volume was significantly lower in patients than in healthy volunteers. Shape analysis revealed significant bilateral regional atrophy in the dorso-medial body in patients compared to controls; this atrophy was more widespread in VS than in MCS patients. Lower thalamic volume was significantly correlated with worse Disability Rating Scale scores. Shape analysis suggested that the dorso-medial nucleus and the internal medullar lamina were the main regions responsible for this correlation. Our findings suggest that MCS and VS patients present different patterns of regional thalamic abnormalities, and that these differences partially explain their clinical profile.

A Voxel-Based Analysis of FDG-PET in Traumatic Brain Injury: Regional Metabolism and Relationship between the Thalamus and Cortical Areas

“…[8,11,22,[26][27] Recent studies have focused on thalamic metabolism in TBI patients, including our previous results [12], and they support the contribution of the latter two listed mechanisms due to the functional or anatomical disconnection between the cerebral cortex and the deeper brain regions. [11,22,[28][29] Metabolic data from other brain structures that were analyzed in this study supports deafferentation as a basic mechanism that may explain the thalamic hypometabolism detected in our patients.…”

Sleep in the Unresponsive Wakefulness Syndrome and Minimally Conscious State

“…This would be in line with brain imaging studies showing not only the correlation between the extent of thalamus damage and the behavioral disability and outcome in DOC, but also the restoration of the thalamocortical connectivity during recovery of consciousness. [30][31][32][33] Otherwise, REMS is sensitive to cortical injury, so the amount of this stage may be related to the severity of the cortical injury and behavioral impairment in brain-injured patients, but our results don't support this hypothesis.…”

Thalamic and extrathalamic mechanisms of consciousness after severe brain injury

“…patients (which parallel a previous small sample study 8 ) might not just be a consequence of low power. (No vertices appeared significant in the reverse of any of the above comparisons; eg, in no region did patients exhibit expansion as compared to healthy volunteers, or positive correlations with any of the continuous variables.…”

“…3-5 Consequently, although our understanding of DOC is continuously increasing, 6,7 little is known about the connection between behaviorally defined clinical entities and the underlying brain damage, [8][9][10] or the degree to which standard behavior-based clinical assessments (eg, JFK View this article online at wileyonlinelibrary.com.…”

“…2 Although information concerning the nature and extent of a patient's brain damage is generally taken into consideration during clinical assessments, current differential diagnosis procedures rely exclusively-as per international guidelines-on behavioral presentation. [3][4][5] Consequently, although our understanding of DOC is continuously increasing, 6,7 little is known about the connection between behaviorally defined clinical entities and the underlying brain damage, [8][9][10] or the degree to which standard behavior-based clinical assessments (eg, JFK Coma Recovery Scale-Revised [CRS-R] 4 ) systematically reflect, or index, specific aspects of neural pathology.…”