Altered resting-state functional networks in patients with hemodialysis: a graph-theoretical based study

Multilayer network analysis in patients with end-stage kidney disease

This study aimed to investigate alterations in a multilayer network combining structural and functional layers in patients with end-stage kidney disease (ESKD) compared with healthy controls. In all, 38 ESKD patients and 43 healthy participants were prospectively enrolled. They exhibited normal brain magnetic resonance imaging (MRI) without any structural lesions. All participants, both ESRD patients and healthy controls, underwent T1-weighted imaging, diffusion tensor imaging (DTI), and resting-state functional MRI (rs-fMRI) using the same three-tesla MRI scanner. A structural connectivity matrix was generated using the DTI and DSI programs, and a functional connectivity matrix was created using the rs-fMRI and SPM programs in the CONN toolbox. Multilayer network analysis was conducted based on structural and functional connectivity matrices using BRAPH. Significant differences were observed at the global level in the multilayer network between patients with ESKD and healthy controls. The weighted multiplex participation was lower in patients with ESKD than in healthy controls (0.6454 vs. 0.7212, adjusted p = 0.049). However, other multilayer network measures did not differ. The weighted multiplex participation in the right subcentral gyrus, right opercular part of the inferior frontal gyrus, right occipitotemporal medial lingual gyrus, and right postcentral gyrus in patients with ESKD was lower than that in the corresponding regions in healthy controls (0.6704 vs. 0.8562, 0.8593 vs. 0.9388, 0.7778 vs. 0.8849, and 0.6825 vs. 0.8112; adjusted p < 0.05, respectively).This study demonstrated that the multilayer network combining structural and functional layers in patients with ESKD was different from that in healthy controls. The specific differences in weighted multiplex participation suggest potential disruptions in the integrated communication between different brain regions in these patients.

Reduced functional connectivity induced by longitudinal alterations of structure and perfusion may be associated with cognitive impairment in patients on maintenance hemodialysis

Hemodialysis (HD) leads to cognitive impairment; however, the pathophysiology of maintenance HD remains unclear. This study aimed to investigate the longitudinal alterations in gray matter volume (GMV) and cerebral blood flow (CBF) in patients on HD at follow-up compared with baseline, examine the alterations in functional connectivity (FC) by defining co-changed brain regions as seed points, and investigate the correlation between the co-changed brain regions and neuropsychological test scores. Twenty-seven patients with HD and 30 healthy controls were enrolled in this study. All participants underwent high-resolution T1-weighted imaging, arterial spin labeling, and functional MR imaging to measure GMV, CBF, and FC. The patients on HD were assessed at baseline and 3 years subsequently. The right and left medial superior frontal gyrus (SFGmed.L) exhibited significantly lower GMV and CBF in patients on HD at follow-up compared with baseline and lower FC between the SFGmed.L and left middle temporal gyrus (MTG.L). FC between the SFGmed.L and MTG.L was positively correlated with neuropsychological test scores in the HD group at follow-up. Reduced GMV and CBF may result in decreased FC between the SFGmed.L and MTG.L, which may be associated with cognitive impairment in patients on maintenance HD. Our findings provide unique insights into the pathological mechanisms of patients on maintenance HD with cognitive impairment.

Abnormal Functional Attributes of Central Executive Network in Patients with Mild Cognitive Impairment Associated with End-Stage Renal Disease

RATIONALE AND OBJECTIVES

To assess changes in the central executive network (CEN) of patients with mild cognitive impairment (MCI) associated with end-stage renal disease (ESRD).

METHODS

A total of 121 patients with ESRD and 66 healthy controls (HCs) were enrolled. Patients were divided into an MCI group (n = 67) and a cognitively unimpaired group (n = 54). All participants underwent resting-state functional magnetic resonance imaging and were evaluated using the Montreal Cognitive Assessment (MoCA). The functional attributes of the CEN were calculated using three methods of functional connectivity (FC) analysis. Relationships among imaging features, cognitive scale scores, and clinical data were assessed, and a model was constructed to diagnose MCI in patients with ESRD.

RESULTS

The comparison of the three groups showed that there were significant differences in the FC values of five connection pairs within the CEN, and the CEN demonstrated significant differences in connectivity to ten brain regions. In patients with MCI associated with ESRD, the information transmission efficiency of the CEN was reduced, which demonstrates the characteristics of a random network to some extent. Significant correlations were observed among imaging parameters, cognitive scale scores, and clinical data. The diagnostic model constructed based on these results demonstrated excellent discrimination and calibration.

CONCLUSION

Alterations in the function of the CEN provide relevant bases for revealing the neuropathological mechanism of MCI in patients with ESRD. The diagnostic model developed in this study may help to establish more reliable imaging markers for detecting early cognitive impairment in this patient population.

Functional disruptions of the brain network in low back pain: a graph-theoretical study

PURPOSE

The aim of this study was to investigate alterations in the topological organization of whole-brain functional networks in patients with chronic low back pain (CLBP) and characterize the relationship of these alterations with pain characteristics.

METHODS

Thirty-three CLBP patients and 34 matched healthy controls (HCs) underwent fMRI scans. A graph-theoretical approach was applied to identify brain network changes in patients suffering from chronic low back pain given its nonspecific etiology and complexity. Graph theory-based analysis was used to construct functional connectivity matrices and extract the features of small-world networks of the brain in both groups. Then, the whole-brain functional connectivity differences were characterized by network-based statistics (NBS) analysis, and the relationship between the altered brain features and clinical measures was explored.

RESULTS

At the global level, patients with CLBP showed significantly decreased gamma, sigma, global efficiency, and local efficiency and increased lambda and shortest path length compared with HCs. At the regional level, there were deficits in nodal efficiency within the default mode network and salience network. NBS analysis demonstrated that decreased functional connectivity was present in the CLBP patients, mainly in the frontolimbic circuit and temporal regions. Furthermore, aspects of topological dysfunctions in CLBP were correlated with pain severity.

CONCLUSION

This study highlighted the aberrant topological organization of functional brain networks in CLBP, which may shed light on the pathophysiology of CLBP and support the development of pain management approaches.

Dysfunctional Coupling of Cerebral Blood Flow and Susceptibility Value in the Bilateral Hippocampus is Associated with Cognitive Decline in Nondialysis Patients with CKD

SIGNIFICANCE STATEMENT

Patients with end stage CKD often develop cognitive decline, but whether this is related to the underlying disease or to hemodialysis remains unclear. We performed three-dimensional pseudocontinuous arterial spin labeling and quantitative susceptibility mapping prospectively in 40 patients with stage 1-4 CKD, 47 nondialysis patients with stage 5 CKD, and 44 healthy controls. Our magnetic resonance imaging data demonstrate that changes in cerebral blood flow-susceptibility coupling might underlie this cognitive decline, perhaps in the hippocampus and thalamus. These results suggest that magnetic resonance imaging parameters are potential biomarkers of cognitive decline in patients with CKD. Moreover, our findings may lead to discovery of novel therapeutic targets to prevent cognitive decline in patients with CKD.

BACKGROUND

Cerebral blood flow (CBF) and susceptibility values reflect vascular and iron metabolism, providing mechanistic insights into conditions of health and disease. Nondialysis patients with CKD show a cognitive decline, but the pathophysiological mechanisms underlying this remain unclear.

METHODS

Three-dimensional pseudocontinuous arterial spin labeling and quantitative susceptibility mapping were prospectively performed in 40 patients with stage 1-4 CKD (CKD 1-4), 47 nondialysis patients with stage 5 CKD (CKD 5ND), and 44 healthy controls (HCs). Voxel-based global and regional analyses of CBF, susceptibility values, and vascular-susceptibility coupling were performed. Furthermore, the association between clinical performance and cerebral perfusion and iron deposition was analyzed.

RESULTS

For CBF, patients with CKD 5ND had higher normalized CBF in the hippocampus and thalamus than HCs. Patients with CKD 5ND had higher normalized CBF in the hippocampus and thalamus than those with CKD 1-4. The susceptibility values in the hippocampus and thalamus were lower in patients with CKD 5ND than in HCs. Patients with CKD 5ND had higher susceptibility value in the caudate nucleus than those with CKD 1-4. More importantly, patients with CKD 5ND had lower CBF-susceptibility coupling than HCs. In addition, CBF and susceptibility values were significantly associated with clinical performance.

CONCLUSIONS

Our findings demonstrate a new neuropathological mechanism in patients with CKD, which leads to regional changes in CBF-susceptibility coupling. These changes are related to cognitive decline, providing potential imaging markers for assessing clinical disability and cognitive decline in these patients.

Altered Resting-State Functional Networks in Nondialysis Patients with Stage 5 Chronic Kidney Disease: A Graph-Theoretical Analysis

This study aimed to investigate the topological characteristics of the resting-state functional network and the underlying pathological mechanism in nondialysis patients with stage 5 chronic kidney disease (CKD5 ND). Eighty-five subjects (21 patients with CKD5 ND, 32 patients with CKD on maintenance hemodialysis (HD), and 32 healthy controls (HCs)) underwent laboratory examinations, neuropsychological tests, and brain magnetic resonance imaging. The topological characteristics of networks were compared with a graph-theoretical approach, and correlations between neuropsychological scores and network properties were analyzed. All participants exhibited networks with small-world attributes, and global topological attributes were impaired in both groups of patients with CKD 5 (ND and HD) compared with HCs (p < 0.05); these impairments were more severe in the CKD5 ND group than in the HD group (p < 0.05). Compared with the HC group, the degree centrality of the CKD5 ND group decreased mainly in the basal ganglia and increased in the bilateral orbitofrontal gyrus, bilateral precuneus, and right cuneus. Correlation analysis showed that the degree of small-worldness, normalized clustering coefficients, and Montreal Cognitive Assessment (MoCA) scores were positively correlated and that characteristic path length was negatively correlated with these variables in patients with CKD5 ND. The nodal efficiency of the bilateral putamen (r = 0.53, p < 0.001 and r = 0.47, p < 0.001), left thalamus (r = 0.37, p < 0.001), and right caudate nucleus (r = 0.28, p = 0.01) was positively correlated with MoCA scores. In conclusion, all CKD5 ND patients exhibited changes in functional network topological properties and were closely associated with mild cognitive impairment. More interestingly, the topological property changes in CKD5 ND patients were dominated by basal ganglia areas, which may be more helpful to understand and possibly reveal the underlying pathological mechanisms of cognitive impairment in CKD5 ND.

Aberrant brain gray matter and functional networks topology in end stage renal disease patients undergoing maintenance hemodialysis with cognitive impairment

Purpose

To characterize the topological properties of gray matter (GM) and functional networks in end-stage renal disease (ESRD) patients undergoing maintenance hemodialysis to provide insights into the underlying mechanisms of cognitive impairment.

Materials and methods

In total, 45 patients and 37 healthy controls were prospectively enrolled in this study. All subjects completed resting-state functional magnetic resonance imaging (rs-fMRI) and diffusion kurtosis imaging (DKI) examinations and a Montreal cognitive assessment scale (MoCA) test. Differences in the properties of GM and functional networks were analyzed, and the relationship between brain properties and MoCA scores was assessed. Cognitive function was predicted based on functional networks by applying the least squares support vector regression machine (LSSVRM) and the whale optimization algorithm (WOA).

Results

We observed disrupted topological organizations of both functional and GM networks in ESRD patients, as indicated by significantly decreased global measures. Specifically, ESRD patients had impaired nodal efficiency and degree centrality, predominantly within the default mode network, limbic system, frontal lobe, temporal lobe, and occipital lobe. Interestingly, the involved regions were distributed laterally. Furthermore, the MoCA scores significantly correlated with decreased standardized clustering coefficient (γ), standardized characteristic path length (λ), and nodal efficiency of the right insula and the right superior temporal gyrus. Finally, optimized LSSVRM could predict the cognitive scores of ESRD patients with great accuracy.

Conclusion

Disruption of brain networks may account for the progression of cognitive dysfunction in ESRD patients. Implementation of prediction models based on neuroimaging metrics may provide more objective information to promote early diagnosis and intervention.

Subthalamic and pallidal stimulation in Parkinson's disease induce distinct brain topological reconstruction

The subthalamic nucleus (STN) and globus pallidus internus (GPi) are the two most common and effective target brain areas for deep brain stimulation (DBS) treatment of advanced Parkinson's disease. Although DBS has been shown to restore functional neural circuits of this disorder, the changes in topological organization associated with active DBS of each target remain unknown. To investigate this, we acquired resting-state functional magnetic resonance imaging (fMRI) data from 34 medication-free patients with Parkinson's disease that had DBS electrodes implanted in either the subthalamic nucleus or internal globus pallidus (n = 17 each), in both ON and OFF DBS states. Sixteen age-matched healthy individuals were used as a control group. We evaluated the regional information processing capacity and transmission efficiency of brain networks with and without stimulation, and recorded how stimulation restructured the brain network topology of patients with Parkinson's disease. For both targets, the variation of local efficiency in motor brain regions was significantly correlated (p < 0.05) with improvement rate of the Uniform Parkinson's Disease Rating Scale-III scores, with comparable improvements in motor function for the two targets. However, non-motor brain regions showed changes in topological organization during active stimulation that were target-specific. Namely, targeting the STN decreased the information transmission of association, limbic and paralimbic regions, including the inferior frontal gyrus angle, insula, temporal pole, superior occipital gyri, and posterior cingulate, as evidenced by the simultaneous decrease of clustering coefficient and local efficiency. GPi-DBS had a similar effect on the caudate and lenticular nuclei, but enhanced information transmission in the cingulate gyrus. These effects were not present in the DBS-OFF state for GPi-DBS, but persisted for STN-DBS. Our results demonstrate that DBS to the STN and GPi induce distinct brain network topology reconstruction patterns, providing innovative theoretical evidence for deciphering the mechanism through which DBS affects disparate targets in the human brain.

Regional cerebral gray matter atrophy is associated with cognitive impairment in hemodialysis patients: a cross-sectional and longitudinal voxel-based morphological MRI study

This study aimed to explore gray matter volume (GMV) changes in patients undergoing hemodialysis and assess the clinical risk factors associated with GMV changes and the relationship between GMV changes and neuropsychologic test results. Eighty-eight hemodialysis patients and 76 healthy controls (HCs) were recruited in this study. Fifty patients underwent follow-up examinations (follow-up duration: 1.75 ± 0.55 years), including magnetic resonance imaging, blood biochemical, and neuropsychologic testing. Changes in GMV between the patients and HCs were assessed. Longitudinal GMV changes were also explored in the patients. The clinical risk factors associated with longitudinal GMV changes and the correlations between longitudinal GMV changes and neuropsychologic test results were analyzed in the patients. Patients undergoing hemodialysis had diffusely decreased GMV compared with HCs (with age, sex, and total intracranial volume [TIV] as covariates, P<0.001, voxel-wise threshold false discovery rate [FDR] corrected). Compared with patients at baseline, regional decreased GMV were found in patients at follow-up (with age and TIV as covariates, P<0.05, voxel-wise threshold FDR corrected). Increased serum urea concentrations, parathyroid hormone levels, and hemodialysis duration were independent risk factors for decreased GMV in patients undergoing hemodialysis (all P<0.05, FDR corrected). Patients undergoing hemodialysis had lower mini-mental state examination (MMSE) (27[26, 29]) and Montreal cognitive assessment (MoCA) (22[19.5, 24.0]) scores than those of the HCs (30[29, 30] and 28[26.9, 29]) (all P<0.05). The MMSE scores of the patients at follow-up (26[25, 28.5]) were lower than those of patients at baseline (28[25, 29.5]) (P=0.02). The decreased left caudate volumes were positively correlated with reduced MMSE scores in hemodialysis patients (r_s=0.437, P=0.033). Patients undergoing hemodialysis had noticeable GM atrophy over time, related to cognitive impairments.

Altered resting-state functional networks in patients with premenstrual syndrome: a graph-theoretical based study

Premenstrual syndrome (PMS) is a menstrual cycle-related disorder. Previous studies have indicated alterations of brain functional connectivity in PMS patients. However, little is known about the overall organization of brain network in PMS patients. Functional magnetic resonance imaging data deriving from 20 PMS patients and 21 healthy controls (HCs). Pearson correlation between mean time-series was used to estimate connectivity matrix between each paired regions of interest, and the connectivity matrix for each participant was then binarized. Graph theory analysis was applied to assess each participant's global and local topological properties of brain functional network. Correlation analysis was performed to evaluate relationships between the daily rating of severity of problems (DRSP) and abnormal network properties. PMS patients had lower small-worldness values than HCs. PMS-related alterations of nodal properties were mainly found in the posterior cingulate cortex, precuneus and angular gyrus. The PMS-related abnormal connectivity components were mainly associated with the thalamus, putamen and middle cingulate cortex. In the PMS group, the DRSP score were negatively correlated with the area under the curves of nodal local efficiency in the posterior cingulate cortex. Our study suggests that the graph-theory method may be one potential tool to detect disruptions of brain connections and may provide important evidence for understanding the PMS from the disrupted network organization perspective.

Abnormal brain functional networks in end-stage renal disease patients with cognitive impairment

INTRODUCTION

Cognitive impairment (CI) is common in patients with end-stage renal disease (ESRD). Neuroimaging studies have demonstrated structural and functional brain alterations underlying CI in patients with ESRD. However, the patterns of change in whole-brain functional networks in ESRD patients with CI remain poorly understood.

METHODS

We enrolled 66 patients with ESRD (36 patients with CI and 30 patients without CI) and 48 healthy control subjects (HCs). We calculated the topological properties using a graph theoretical analysis. An analysis of covariance (ANCOVA) was used to compare network metrics among the three groups. Moreover, we analyzed the relationships between altered network measures and clinical variables in ESRD patients with CI.

RESULTS

Compared with HCs, both patient groups showed lower local efficiency and small-worldness. ESRD patients had decreased nodal centralities in the default mode regions and right amygdala. Comparison of the two patient groups showed significantly decreased global (small-worldness) and nodal (nodal centralities in the default mode regions) properties in the CI group. Altered nodal centralities in the bilateral medial part of the superior frontal gyrus, left posterior cingulate gyrus, and right precuneus were associated with cognitive performance in the CI group.

CONCLUSION

Disrupted brain functional networks were demonstrated in patients with ESRD, which were more severe in those with CI. Moreover, impaired nodal centralities in the default mode regions might underlie CI in patients with ESRD.

Brain Structural Network Compensation Is Associated With Cognitive Impairment and Alzheimer's Disease Pathology

BACKGROUND

Structural network alterations in Alzheimer's disease (AD) are related to worse cognitive impairment. The aim of this study was to quantify the alterations in gray matter associated with impaired cognition and their pathological biomarkers in AD-spectrum patients.

METHODS

We extracted gray matter networks from 3D-T1 magnetic resonance imaging scans, and a graph theory analysis was used to explore alterations in the network metrics in 34 healthy controls, 70 mild cognitive impairment (MCI) patients, and 40 AD patients. Spearman correlation analysis was computed to investigate the relationships among network properties, neuropsychological performance, and cerebrospinal fluid pathological biomarkers (i.e., Aβ, t-tau, and p-tau) in these subjects.

RESULTS

AD-spectrum individuals demonstrated higher nodal properties and edge properties associated with impaired memory function, and lower amyloid-β or higher tau levels than the controls. Furthermore, these compensations at the brain regional level in AD-spectrum patients were mainly in the medial temporal lobe; however, the compensation at the whole-brain network level gradually extended from the frontal lobe to become widely distributed throughout the cortex with the progression of AD.

CONCLUSION

The findings provide insight into the alterations in the gray matter network related to impaired cognition and pathological biomarkers in the progression of AD. The possibility of compensation was detected in the structural networks in AD-spectrum patients; the compensatory patterns at regional and whole-brain levels were different and the clinical significance was highlighted.

Brain functional network alterations caused by a strong desire to void in healthy adults: a graph theory analysis study

PURPOSE

This resting-state functional magnetic resonance imaging (fMRI) study determined the functional connectivity (FC) changes and topologic property alterations of the brain functional network provoked by a strong desire to void in healthy adults using a graph theory analysis (GTA).

MATERIALS AND METHODS

Thirty-four healthy, right-handed subjects filled their bladders by drinking water. The subjects were scanned under an empty bladder and a strong desire to void states. The Pearson's correlation coefficients were calculated among 90 brain regions in the automated anatomical labeling (AAL) atlas to construct the brain functional network. A paired t test (P < .05, after false discovery rate [FDR] correction) was used to detect significant differences in the FC, topologic properties (small-world parameters [gamma, sigma], C_p, L_p, E_glob, E_loc, and E_nodal) between the two states in all subjects.

RESULTS

Both the two states showed small-world network properties. The clustering coefficient (C_p) and local efficiency (E_loc) in the whole brain network decreased, while the FC within the default mode network (DMN) increased during the strong desire to void compared with the empty bladder state. Moreover, an increased nodal efficiency (E_nodal) was detected in the basal ganglia (BG), DMN, sensorimotor-related network (SMN), and visual network (VN).

CONCLUSION

We detected FC changes and topologic property alterations in brain functional networks caused by a strong desire to void in healthy and suggest that the micturition control may be a process dominated by DMN and coordinated by multiple sub-networks (such as, BG, SMN, and VN), which could serve as a baseline for understanding the pathologic process underlying bladder dysfunction and be useful to improve targeted therapy in the future.