Altered Cortical Complexity And Topological Properties Of Gray Matter Structural Covariance Networks In Minimal Hepatic Encephalopathy

Part 1 Reduced Cortical Complexity in Cirrhotic Patients with Minimal Hepatic Encephalopathy Background and Aims: Gray matter volume loss,regional cortical thinning,and local gyrification index alteration have been documented in minimal hepatic encephalopathy(MHE).Fractal dimensionality(FD),another morphological parameter,has been widely used to describe structural complexity alterations in neurological or psychiatric disease.Here,we intended to investigate FD alterations in MHE.Methods and Materials: We performed high-resolution structural magnetic resonance imaging on cirrhotic patients with MHE(n = 20)and healthy controls(n = 21).We evaluated their cognitive performance using the psychometric hepatic encephalopathy score(PHES).The regional FD value was calculated by computational anatomy toolbox(CAT12)and compared between groups.We further estimated the association between patients’ cognitive performance and FD values.Results: MHE patients presented significantly decreased FD values in the left precuneus,left supramarginal gyrus,right caudal anterior cingulate cortex,right isthmus cingulate cortex,right insula,bilateral pericalcarine cortex,and bilateral paracentral cortex compared to normal controls.In addition,the FD values in the right isthmus cingulate cortex and right insula were shown to be positively correlated with patients’ cognitive performance.Conclusion: Aberrant cortical complexity is an additional characteristic of MHE,and FD analysis may provide novel insight into the neurobiological basis of cognitive dysfunction in MHE.Part 2 Altered Topological Properties of Gray Matter Structural Covariance Networks in Minimal Hepatic EncephalopathyBackground and Aims: Liver cirrhosis commonly induces brain structural impairments that are associated with neurological complications(e.g.,minimal hepatic encephalopathy(MHE)),but the topological characteristics of the brain structural network are still less well understood in cirrhotic patients with MHE.This study aimed to investigate the topological alterations of brain structural covariance networks in MHE.Methods and Materials: This study included 22 healthy controls(HC)and 22 cirrhotic patients with MHE.We calculated the gray matter volume of 90 brain regions using an automated anatomical labeling(AAL)template,followed by construction of gray matter structural covariance networks by thresholding interregional structural correlation matrices as well as graph theoretical analysis.Results: MHE patients showed abnormal small-world properties of the brain structural covariance network,i.e.,decreased clustering coefficient and characteristic path length and lower small-worldness parameters,which indicated a tendency toward more random architecture.In addition,MHE patients lost hubs in the prefrontal and parietal regions,although they had new hubs in the temporal and occipital regions.Compared to HC,MHE patients had decreased regional degree/betweenness involving several regions,primarily the prefrontal and parietal lobes,motor region,insula and thalamus.In addition,the MHE group also showed increased degree/betweenness in the occipital lobe and hippocampus.Conclusion: These results suggest that MHE leads to altered coordination patterns of gray matter morphology and provide structural evidence supporting the idea that MHE is a neurological complication related to disrupted neural networks.