Structural changes in brains of patients with disorders of consciousness treated with deep brain stimulation

Abstract

Disorders of consciousness (DOC) are one of the major consequences after anoxic or traumatic brain injury. So far, several studies have described the regaining of consciousness in DOC patients using deep brain stimulation (DBS). However, these studies often lack detailed data on the structural and functional cerebral changes after such treatment. The aim of this study was to conduct a volumetric analysis of specific cortical and subcortical structures to determine the impact of DBS after functional recovery of DOC patients. Five DOC patients underwent unilateral DBS electrode implantation into the centromedian parafascicular complex of the thalamic intralaminar nuclei. Consciousness recovery was confirmed using the Rappaport Disability Rating and the Coma/Near Coma scale. Brain MRI volumetric measurements were done prior to the procedure, then approximately a year after, and finally 7 years after the implementation of the electrode. The volumetric analysis included changes in regional cortical volumes and thickness, as well as in subcortical structures. Limbic cortices (parahippocampal and cingulate gyrus) and paralimbic cortices (insula) regions showed a significant volume increase and presented a trend of regional cortical thickness increase 1 and 7 years after DBS. The volumes of related subcortical structures, namely the caudate, the hippocampus as well as the amygdala, were significantly increased 1 and 7 years after DBS, while the putamen and nucleus accumbens presented with volume increase. Volume increase after DBS could be a result of direct DBS effects, or a result of functional recovery. Our findings are in accordance with the results of very few human studies connecting DBS and brain volume increase. Which mechanisms are behind the observed brain changes and whether structural changes are caused by consciousness recovery or DBS in patients with DOC is still a matter of debate.

Figure 1

Initial structural MRI scans of included patients showing an absence of any large brain lesion (patients 1–5, from left to right).

Figure 2

Volumetric analysis was conducted using the CIVET pipeline measuring regional cortical volume and thickness for parietal, occipital, frontal, temporal lobes, isthmus of the cingulate gyrus, parahippocampal, and cingulate gyrus and insula (a), and volBrain software, for subcortical structures segmentation (b). Single-subject volumetric analysis is presented.

Figure 3

Regional cortical volumetric analysis in three measuring points (prior to DBS, 1 year after DBS, and 7 years after DBS). The regional cortical volumetric analysis revealed significant volume increase in right parahippocampal gyrus, left cingulate gyrus, and left insula, while the trend of volume increase was presented in left parahippocampal gyrus volume, right cingulate gyrus volume, and right insula volume. Vertical bars, standard deviation.

Figure 4

Subcortical structures volumetric analysis in three measuring points (prior to DBS, 1 year after DBS, and 7 years after DBS). Significant volume increase of caudate, hippocampus, and amygdala were presented, while putamen and accumbens volumes presented a trend of volume increase during three measuring points. Both globus pallidus and thalamus volume decreased over time. Vertical bars, standard deviation.