Altered long- and short-range functional connectivity in the patients with end-stage renal disease: a resting-state functional MRI study

To investigate alterations of functional connectivity density (FCD) in patients with end-stage renal disease (ESRD) by using resting-state functional magnetic resonance imaging (rs-fMRI). Medical research ethics committee approval from Jinling hospital and written informed consent from each subject were obtained. Forty six patients with ESRD, consisting of 21 patients minimal nephrotic encephalopathy (MNE) and 25 non-nephro-encephalopathy (non-NE), as well as 23 healthy controls underwent rs-fMRI. Neuropsychological tests were performed in all subjects, while laboratory tests were performed in ESRD patients. A voxel-wise whole brain functional connectivity analysis was used to generate long- and short-range FCD maps. The maps among MNE, non-NE, and healthy controls groups were compared by using one-way analysis of variance tests. A multiple regression analysis was performed to evaluate the correlations between FCD and the variables of neuropsychological or laboratory tests. Compared with healthy controls, non-NE showed decreased long-range FCD mainly in parietal lobe. Moreover, MNE showed further decreased long-range FCD in bilateral middle prefrontal cortex (MPFC), anterior cingulate cortex (ACC) and right superior frontal gyrus. Meanwhile, non-NE showed decreased short-range FCD mainly in frontal cortex, and further reduction in bilateral ACC and right superior parietal gyrus in MNE. In addition, patients with ESRD mainly exhibited increased long-range FCD in left temporal lobe and caudate; and increased short-range FCD in bilateral orbitofrontal cortex and temporal gyri (P < 0.05, AlphaSim corrected). The number connection test type A score, serum creatinine, urea, and dialysis duration showed negative correlation with FCD in some brain regions, while the digital symbol test scores positively correlated with short-range FCD in left inferior parietal lobule (all P < 0.05, AlphaSim corrected). The prominent long- and short-range FCD reduction was found mainly in default mode network (DMN) and bilateral frontal and parietal lobes, while the progressively decreased long- and short-range FCD in ACC/MPFC and the long-range FCD in left superior frontal gyrus from non-NE to MNE was associated with cognition dysfunction in ESRD patients.

Brain Default Mode Network Changes after Renal Transplantation: A Diffusion-Tensor Imaging and Resting-State Functional MR Imaging Study

PURPOSE

To investigate structural and functional alterations of the default mode network (DMN) in the brain after renal transplantation in patients with end-stage renal disease by using diffusion-tensor imaging and resting-state functional MR imaging.

MATERIALS AND METHODS

This prospective study was approved by the local medical research ethics committee, and written informed consent was obtained. Twenty-one patients with end-stage renal disease (15 men, six women; mean age ± standard deviation, 32 years ± 9.5) who were scheduled to undergo renal transplantation and 21 healthy control subjects (15 men, six women; mean age, 31 years ± 6.5) were included. Diffusion-tensor imaging and resting-state functional MR imaging were performed in all subjects. Patients were imaged both before and 1 month after renal transplantation. Structural (mean diffusivity, fractional anisotropy, path length, and number of tracts derived from diffusion-tensor imaging tractography) and functional (temporal correlation coefficient derived from resting-state functional MR imaging) connectivity of the DMN were quantitatively compared with two-sample t tests or paired t tests. Intergroup correlation analysis was performed to compare structural or functional indexes and results of neuropsychological or blood biochemistry tests.

RESULTS

Mean diffusivity was decreased in the fiber bundles connecting the posterior cingulate cortex and the precuneus to the bilateral inferior parietal lobules in patients after renal transplantation compared with that in patients before transplantation (P < .05). Temporal correlation coefficients for patients after renal transplantation nearly reached the levels of those for control subjects (all, P > .05). The change in mean diffusivity of the fiber bundles connecting the posterior cingulate cortex and the precuneus to the right inferior parietal lobule positively correlated with the change in hematocrit levels (r = 0.522, P = .015), the change in temporal correlation coefficients between the posterior cingulate cortex or precuneus and left or right inferior parietal lobules correlated with changes in number connection test type A scores (r = -0.549, P = .010) and digit symbol test scores (r = 0.533, P = .013).

CONCLUSION

Functional connectivity changes in the DMN, which were associated with improved hematocrit levels and cognitive function, may recover earlier than structural connectivity changes do 1 month after renal transplantation.

Abnormal degree centrality in neurologically asymptomatic patients with end-stage renal disease: A resting-state fMRI study

OBJECTIVE

End-stage renal disease (ESRD), characterized by multi-organ dysfunction, has been shown to co-occur with abnormal brain function. Previous resting-state fMRI studies suggested that regional brain spontaneous activity and functional connectivity within the default mode network are abnormal in ESRD patients. The current study aimed to depict intrinsic dysconnectivity pattern of whole-brain functional networks in voxel level in neurologically asymptomatic patients with ESRD.

METHODS

fMRI datasets were acquired from 22 ESRD patients (without clinical neurological disease) and 29 healthy control (HC) subjects. We investigated the degree centrality for a given element in a network to reveal the changes of functional connectivity throughout the huge human functional network. In the brain regions showing a difference between the HC and ESRD groups, we further conducted receptive operation characteristic (ROC) analyses to confirm the accuracy, sensitivity and specificity of our results.

RESULTS

ESRD patients showed decreased functional connectivity in the left inferior parietal and left precuneus within the brain network; both regions are important components of the default-mode network (DMN). In contrast, patients showed increased connectivity in depression-related regions including bilateral inferior frontal gyrus and right superior temporal gyrus. These regions showed an acceptable accuracy (0.68-0.75), sensitivity (0.64-0.70) and high specificity (0.82-0.96) in distinguishing between the two groups.

CONCLUSIONS

Our findings reveal abnormal intrinsic dysconnectivity pattern of whole-brain functional networks in ESRD patients.

SIGNIFICANCE

Our results could lead to a better understanding of the intrinsic dysconnectivity patterns of default-mode network-related regions in ESRD patients from the whole brain network perspective.

Abnormal Intrinsic Brain Activity Patterns in Patients with End-Stage Renal Disease Undergoing Peritoneal Dialysis: A Resting-State Functional MR Imaging Study

PURPOSE

To analyze the spontaneous brain activity patterns in patients with end-stage renal disease (ESRD) undergoing peritoneal dialysis (PD) by using resting-state functional magnetic resonance (MR) imaging with an amplitude of low-frequency fluctuations (ALFF) algorithm.

MATERIALS AND METHODS

This study received institutional review board approval, and all subjects gave informed consent. Forty-four patients with ESRD, 24 of whom were undergoing PD (PD group; eight women; mean age, 34 years ± 8) and 20 who were not undergoing PD or hemodialysis (nondialysis group; six women; mean age, 37 years ± 9) and 24 healthy control subjects (eight women; mean age, 32 years ± 9 years) were included. All subjects underwent neuropsychologic tests, and patients with ESRD underwent laboratory testing. ALFF values were compared among the three groups. The relationship between ALFF values and clinical markers was investigated by using multiple regression analysis.

RESULTS

Patients in both the PD and nondialysis groups showed lower ALFF values in default mode network regions than did healthy control subjects (P < .01, false discovery rate corrected). Patients in the PD group showed lower ALFF values than did those in the nondialysis group in the left superior parietal lobe (1.51 ± 0.21 vs 2.01 ± 0.40), left inferior parietal lobe (0.99 ± 0.16 vs 1.13 ± 0.22) and left precuneus (1.45 ± 0.39 vs 1.77 ± 0.41) (P < .01, corrected with simulation software). In patients in the PD group, neuropsychologic test scores correlated with ALFF values of the middle temporal gyrus and the parietal and occipital lobe, serum urea and creatinine levels negatively correlated with ALFF in some default mode network regions, and hemoglobin positively correlated with ALFF in the bilateral precuneus, precentral, and supplementary motor areas (P < .01 corrected).

CONCLUSION

Patients with ESRD who were undergoing PD showed more severe spontaneous brain activity abnormalities that correlate with cognitive impairments than did patients who were not undergoing dialysis. Elevated serum urea, creatinine, and lowered hemoglobin levels affect spontaneous brain activity in patients with ESRD.

Multimodality MRI Findings in Patients with End-Stage Renal Disease

Patients with end-stage renal disease (ESRD) suffer from a number of complex neurological complications including vascular damage and cognitive dysfunction. It is of great significance to detect the neurological complications and improve the prognosis of ESRD patients. Many new noninvasive MRI techniques have been steadily used for the diagnosis of occult central nervous system complications in ESRD patients. This gives an opportunity to understand the pathophysiological mechanisms of these neurological disorders. This paper is a review that presents the MRI findings of occult brain damage in ESRD patients, outlines the applications of advanced MRI techniques, and introduces a brief perspective in this study field.

Aberrant functional connectome in neurologically asymptomatic patients with end-stage renal disease

Purpose

This study aimed to investigate the topological organization of intrinsic functional brain networks in patients with end-stage renal disease (ESRD).

Materials and Methods

Resting-state functional MRI data were collected from 22 patients with ESRD (16 men, 18–61 years) and 29age- and gender-matched healthy controls (HCs, 19 men, 32–61 years). Whole-brain functional networks were obtained by calculating the interregional correlation of low-frequency fluctuations in spontaneous brain activity among 1,024 parcels that cover the entire cerebrum. Weighted graph-based models were then employed to topologically characterize these networks at different global, modular and nodal levels.

Results

Compared to HCs, the patients exhibited significant disruption in parallel information processing over the whole networks (P< 0.05). The disruption was present in all the functional modules (default mode, executive control, sensorimotor and visual networks) although decreased functional connectivity was observed only within the default mode network. Regional analysis showed that the disease disproportionately weakened nodal efficiency of the default mode components and tended to preferentially affect central or hub-like regions. Intriguingly, the network abnormalities correlated with biochemical hemoglobin and serum calcium levels in the patients. Finally, the functional changes were substantively unchanged after correcting for gray matter atrophy in the patients.

Conclusion

Our findings provide evidence for the disconnection nature of ESRD’s brain and therefore have important implications for understanding the neuropathologic substrate of the disease from disrupted network organization perspective.

Diffuse interstitial brain edema in patients with end-stage renal disease undergoing hemodialysis: a tract-based spatial statistics study

To investigate white matter (WM) alterations and their correlation with cognition function in end-stage renal disease (ESRD) patients undergoing hemodialysis (HD) using diffusion tensor imaging (DTI) with tract-based spatial statistics (TBSS) approach. This prospective HIPAA-complaint study was approved by our institutional review board. Eighty HD ESRD patients and 80 sex- and age-matched healthy controls were included. Neuropsychological (NP) tests and laboratory tests, including serum creatinine and urea, were performed. DTI data were processed to obtain fractional anisotropy (FA) and mean diffusivity (MD) maps with TBSS. FA and MD difference between the 2 groups were compared. We also explored the associations of FA values in WM regions of lower FA with ages, NP tests, disease, and dialysis durations, serum creatinine and urea levels of ESRD patients. Compared with controls, HD ESRD patients had lower FA value in the corpus callosum, bilateral corona radiate, posterior thalamic radiation, left superior longitudinal fasciculus, and right cingulum (P<0.05, FWE corrected). Almost all WM regions had increased MD in HD ESRD patients compared with controls (P<0.05, FWE corrected). In some regions with lower FA, FA values showed moderate correlations with ages, NP tests, and serum urea levels. There was no correlation between FA values and HD durations, disease durations, and serum creatinine levels of ESRD patients (all P>0.05). Diffuse interstitial brain edema and moderate WM integrity disruption occurring in HD ESRD patients, which correlated with cognitive dysfunction, and serum urea levels might be a risk factor for these WM changes.