의과대학/박사Objective
The human brain is a complex network of interlinked regions and composed of the structural (or backbone) network and dynamic functional networks. Studies revealed that the abnormal brain network has associated with the emergence of brain diseases. Delirium is one of brain diseases, and its etiologies are multifactorial. To identify risk factors of delirium, this study aimed to investigate neural substrates of delirium using complex network analysis and investigate phenotypic subgroups of delirium using topology-based data analysis
Materials and Methods
A total of fifty-eight hip fracture patients were recruited in this study. Structural and functional neuroimaging data from all participants were acquired before hip fracture surgery. Among the participants, only thirty-two patients were scanned for postoperative MRI data acquisition. Neural substrates in preoperative delirium, and functional connectivity re-organization during an episode of delirium were studied using a framework of complex network analysis. In topological data analysis, cognitive impairment, personality scales such as neuroticism and conscientiousness, and delirium rating scale were considered to identify phenotypic subgroups of delirium.
Results
Among fifty-eight patients, twenty-five patients were identified as delirium after hip fracture surgery. In the study of neural substrates of delirium, the significant increase of characteristic path length in structural network was observed in preoperative delirium (P<0.05). Also, increased structural path length densities connecting frontal to subcortical and visual sensory regions were played a pivotal role in characterizing delirious patients (corrected P<0.05). Furthermore, functional connectivity density between the prefrontal cortex and audiovisual sensory areas were significantly increased in preoperative delirium (corrected P<0.05). Interestingly, functional connectivity density between the visual cortex and the frontal and auditory areas were strongly suppressed in during-delirum patients (P<0.05). Finally, topology-based data analysis identified three subgroups of delirium in dimensions of cognitive function and personality.
Conclusion
This study investigated neuroimaging-based neural risk factors for delirium. The increased path length of structural network in preoperative delirium implies that there existed disruptions of the connection weights such as a fractional anisotropy and the number of streamlines in the backbone network. The significantly suppressed functional connectivity from the visual cortex to the auditory cortex and frontal regions may play a pivotal role in characterizing the delirious phenomena such as dysfunction in perception, a deficit in sustaining the conscious mental state, and hallucination. Lastly, topological data analysis suggests that neural substrates of delirium could be different for phenotypic subgroups of delirium.ope
