Individualized Thalamic Parcellation Reveals Alterations in Shape and Microstructure of Thalamic Nuclei in Patients with Disorder of Consciousness

Weihao Zheng; Xufei Tan; Tingting Liu; Xiaoxia Li; Jian Gao; Lirong Hong; Xiaotong Zhang; Zhiyong Zhao; Yamei Yu; Yi Zhang; Benyan Luo; Dan Wu

doi:10.1093/texcom/tgab024

Individualized Thalamic Parcellation Reveals Alterations in Shape and Microstructure of Thalamic Nuclei in Patients with Disorder of Consciousness

Cereb Cortex Commun. 2021 Apr 2;2(2):tgab024. doi: 10.1093/texcom/tgab024. eCollection 2021.

Authors

Weihao Zheng¹, Xufei Tan², Tingting Liu¹, Xiaoxia Li³, Jian Gao⁴, Lirong Hong⁴, Xiaotong Zhang⁵, Zhiyong Zhao¹, Yamei Yu³, Yi Zhang¹, Benyan Luo³, Dan Wu¹

Affiliations

¹ Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, 310027, P.R. China.
² Department of Clinical Medicine, School of Medicine, Zhejiang University City College, Hangzhou, 310015, P.R. China.
³ Department of Neurology and Brain Medical Centre, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, 310003, P.R. China.
⁴ Department of Rehabilitation, Hospital of Zhejiang Armed Police Corps, Hangzhou, 310051, P.R. China.
⁵ Interdisciplinary Institute of Neuroscience and Technology, Qiushi Academy for Advanced Studies, Zhejiang University, Hangzhou, 310029, P.R. China.

Abstract

The thalamus plays crucial roles in consciousness generation and information processing. Previous evidence suggests that disorder of consciousness (DOC) caused by severe brain injury, is potentially related to thalamic abnormalities. However, how the morphology and microstructure change in thalamic subfields and thalamocortical fiber pathways in patients with DOC, and the relationships between these changes and the consciousness status remain unclear. Here, we generated the individual-specific thalamic parcellation in 10 DOC patients and 10 healthy controls (HC) via a novel thalamic segmentation framework based on the fiber orientation distribution (FOD) derived from 7-Tesla diffusion MRI, and investigated the shape deformation of thalamic nuclei as well as the microstructural changes associated with thalamic nuclei and thalamocortical pathways in patients with DOC. Enlargement of dorsal posterior nucleus and atrophy of anterior nucleus in the right thalamus were observed in DOC cohort relative to the HCs, and the former was closely linked to the consciousness level of the patients. We also found significant reductions of fiber density, but not fiber bundle cross-section, within several thalamic nuclei and most of the thalamocortical fiber pathways, suggesting that loss of axons might take primary responsibility for the impaired thalamocortical connections in patients with DOC rather than the change in fiber-bundle morphology. Furthermore, the individual-specific thalamic parcellation achieved 80% accuracy in classifying patients at the minimally conscious state from the vegetative state, compared with ~60% accuracy based on group-level parcellations. Our findings provide the first evidence for the shape deformation of thalamic nuclei in DOC patients and the microstructural basis of the disrupted thalamocortical connections.

Keywords: disorder of consciousness; individualized thalamic parcellation; microstructural changes; nucleus deformation; thalamocortical connectivity.