Cerebral magnetic resonance T2 high intensities in end-stage renal disease

Altered functional connectivity density in the brains of hemodialysis end-stage renal disease patients: An in vivo resting-state functional MRI study

Background

End-stage renal disease (ESRD) patients usually suffer from a high prevalence of central nervous system abnormalities, including cognitive impairment and emotional disorders, which severely influence their quality of life. There have been many neuroimaging research developments in ESRD patients with brain function abnormalities; however, the dysfunction of the salience network (SN) of them has received little attention. The purpose of this study was to investigate the changes of global functional connectivity density (gFCD) in brains of ESRD patients undergoing hemodialysis using resting-state functional magnetic resonance imaging (re-fMRI).

Methods

re-fMRI data were collected from 30 ESRD patients undergoing hemodialysis (14 men, 38.33±7.44 years old) and 30 matched healthy controls (13 men, 39.17±5.7 years old). Neuropsychological tests including the Montreal Cognitive Assessment (MoCA) and Beck Depression Inventory (BDI) were used to evaluate the neurocognitive and psychiatric conditions of the subjects. Blood biochemistry tests, including hemoglobin level, serum albumin level, blood urea level, serum phosphate, serum calcium, and parathyroid hormone level, and dialysis-related indicators, including blood pressure fluctuations in dialysis, single-pool Kt/V(spKt/V), and ultrafiltration volume of dialysis were obtained from the ESRD patients. A two-sample t-test was used to examine the group differences in gFCD between ESRD patients and healthy controls after controlling for age, gender and education.

Results

Compared with healthy controls, ESRD patients exhibited a significantly increased gFCD in the salience network, including the bilateral insula, and dorsal anterior cingulated cortex (dACC), and there was no significant correlation between gFCD and the structural mean grey matter volume in patients for every cluster in the brain regions showing significant different gFCD between the two groups. Furthermore, there were significant negative correlations between the degree of connectivity in the right insula and spKt/V.

Conclusion

Our findings revealed abnormal intrinsic dysconnectivity pattern of salience network-related regions in ESRD patients from the whole brain network perspective. The negative correlation between the right insula and spKt/V suggested that increased fractional removal of urea may reduce the pathological activity in the insula.

Kidney–brain axis inflammatory cross-talk: from bench to bedside

Epidemiologic data suggest that individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing neuropsychiatric disorders, cognitive impairment, and dementia. This risk is generally explained by the high prevalence of both symptomatic and subclinical ischemic cerebrovascular lesions. However, other potential mechanisms, including cytokine/chemokine release, production of reactive oxygen species (ROS), circulating and local formation of trophic factors and of renin–angiotensin system (RAS) molecules, could also be involved, especially in the absence of obvious cerebrovascular disease. In this review, we discuss experimental and clinical evidence for the role of these mechanisms in kidney–brain cross-talk. In addition, we hypothesize potential pathways for the interactions between kidney and brain and their pathophysiological role in neuropsychiatric and cognitive changes found in patients with CKD. Understanding the pathophysiologic interactions between renal impairment and brain function is important in order to minimize the risk for future cognitive impairment and to develop new strategies for innovative pharmacological treatment.

Cognitive Decline and Its Risk Factors in Prevalent Hemodialysis Patients

BACKGROUND

Cognitive impairment is common in patients treated with hemodialysis. The trajectory of cognitive function and risk factors for cognitive decline remain uncertain in this population.

STUDY DESIGN

Longitudinal cohort.

SETTING & PARTICIPANTS

314 prevalent hemodialysis patients.

PREDICTORS

Age, sex, race, education level, hemodialysis vintage, cause of end-stage renal disease, and baseline history of cardiovascular disease.

OUTCOMES

Cognitive function as determined by a comprehensive neurocognitive battery, administered at baseline and yearly when possible. Individual cognitive test results were reduced into 2 domain scores using principal components analysis, representing memory and executive function, which were used as our coprimary outcomes and by definition have a mean of zero and SD of 1.

RESULTS

Mean age was 63 years; 54% were men, 22% were black, and 90% had at least a high school education. During a median follow-up of 2.1 (IQR, 0.9-4.2) years, 196 had at least 1 follow-up test, 156 died, and 43 received a kidney transplant. Linear mixed models and joint models, which accounted for competing risks from death, dropout, or kidney transplantation, showed nearly identical results. The joint model demonstrated a decline in executive function (-0.09 [95% CI, -0.13 to -0.05] SD per year), whereas memory improved slightly (0.05 [95% CI, 0.02 to 0.08] SD per year). A significant yearly decline was also seen in the Mini-Mental State Examination score (median change, -0.41; 95% CI, -0.57 to -0.25). Older age was the only significant risk factor for steeper executive function decline (-0.04 [95% CI, -0.06 to -0.02] SD steeper annual decline for each 10 years of age).

LIMITATIONS

Prevalent hemodialysis patients only, limited follow-up testing due to high mortality rate, and exclusion of participants with severe cognitive deficits or dementia.

CONCLUSIONS

Prevalent hemodialysis patients demonstrate significant cognitive decline, particularly within tests of executive function. Older age was the only statistically significant risk factor for steeper cognitive decline, which may have important clinical consequences for patient management and education. Future studies should evaluate strategies to maintain or improve cognitive function.

Regional homogeneity changes in hemodialysis patients with end stage renal disease: in vivo resting-state functional MRI study

OBJECTIVE

To prospectively investigate and detect early cerebral regional homogeneity (ReHo) changes in neurologically asymptomatic patients with end stage renal disease (ESRD) using in vivo resting-state functional MR imaging (Rs-fMRI).

METHODS

We enrolled 20 patients (15 men, 5 women; meanage, 37.1 years; range, 19-49 years) with ESRD and 20 healthy controls (15 men, 5 women; mean age, 38.3 years; range, 28-49 years). The mean duration of hemodialysis for the patient group was 10.7±6.4 monthes. There was no significant sex or age difference between the ESRD and control groups. Rs-fMRI was performed using a gradient-echo echo-planar imaging sequence. ReHo was calculated using software (DPARSF). Voxel-based analysis of the ReHo maps between ESRD and control groups was performed with a two-samples t test. Statistical maps were set at P value less than 0.05 and were corrected for multiple comparisons. The Mini-Mental State Examination (MMSE) was administered to all participants at imaging.

RESULTS

ReHo values were increased in the bilateral superior temporal gyrus and left medial frontal gyrus in the ERSD group compared with controls, but a significantly decreased ReHo value was found in the right middle temporal gyrus. There was no significant correlation between ReHo values and the duration of hemodialysis in the ESRD group. Both the patients and control subjects had normal MMSE scores (≥28).

CONCLUSIONS

Our finding revealed that abnormal brain activity was distributed mainly in the memory and cognition related cotices in patients with ESRD. The abnormal spontaneous neuronal activity in those areas provide information on the neural mechanisms underlying cognitive impairment in patients with ESRD, and demonstrate that Rs-fMRI with ReHo analysis is a useful non-invasive imaging tool for the detection of early cerebral ReHo changes in hemodialysis patients with ESRD.

Factors associated with cerebral white matter hyperintensities in haemodialysis patients

AIM

Cerebral white matter hyperintensities (WMHs), comprising periventricular hyperintensity (PVH) and deep and subcortical white matter hyperintensity (DSWMH) on magnetic resonance imaging (MRI), have been reported to be markers of ischaemic cerebral small-vessel disease and risk factors for future stroke, cognitive impairment and dementia in the general population. However, there have been only a few reports describing WMHs in haemodialysis (HD) patients and these previous studies have been relatively small population studies with little investigation on prevalence and risk factors according to the regional subtypes of WMHs.

METHODS

Cranial MRI was performed on 179 HD patients and 58 healthy control subjects and we investigated the prevalence of WMHs (PVH and/or DSWMH) and the clinical factors associated with the presence of WMHs.

RESULTS

The prevalence of WMHs was significantly higher in the HD patients than in the healthy subjects. In the HD patients, multiple logistic regression analysis showed that independent and significant factors associated with the presence of PVH were age, female gender and systolic blood pressure and those associated with the presence of DSWMH were age, female gender, systolic blood pressure and body mass index.

CONCLUSIONS

These findings indicated a high prevalence of WMHs in HD patients. Older age, female gender and high blood pressure were strong factors associated with the presence of both PVH and DSWMH. Moreover, excess body weight was a significant factor associated with the presence of DSWMH only, indicating that there may be differences in risk factors according to the subtype of WMHs.

Anatomic brain disease in hemodialysis patients: a cross-sectional study

BACKGROUND

Although dialysis patients are at high risk of stroke and have a high burden of cognitive impairment, there are few reports of anatomic brain findings in the hemodialysis population. Using magnetic resonance imaging of the brain, we compared the prevalence of brain abnormalities in hemodialysis patients with that in a control population without known kidney disease.

STUDY DESIGN

Cross-sectional cohort.

SETTING & PARTICIPANTS

45 maintenance hemodialysis patients and 67 controls without reported kidney disease, both without history of known stroke.

PREDICTOR

The primary predictor was dialysis status. Covariates included demographics (age, race, and sex), vascular risk factors (diabetes and hypertension), and cardiovascular disease (coronary artery disease and congestive heart failure).

OUTCOMES

Magnetic resonance imaging of the brain features, including severity of white matter disease and cerebral atrophy (sulcal prominence and ventricular atrophy), hippocampal size, and small-/large-vessel infarcts.

MEASUREMENTS

Semiquantitative scale (0-9 for white matter disease and cerebral atrophy, 0-3 for hippocampal size) and infarct prevalence.

RESULTS

Mean ages of hemodialysis patients and controls were 55 ± 17 (SD) and 53 ± 13 years, respectively. In comparison to controls, hemodialysis patients had more severe white matter disease (1.6 vs 0.7) and cerebral atrophy (sulcal prominence, 2.3 vs 0.6; ventricular enlargement, 2.3 vs 0.9; hippocampal size, 1.3 vs 1.0), with all P < 0.001. In multivariable analyses, hemodialysis status was associated independently with worse white matter disease and atrophy grades. Hemodialysis patients also had a higher prevalence of small- (17.8%) and large- (7.8%) vessel infarcts than controls (combined, 22% vs 0%; P < 0.001).

LIMITATIONS

The dialysis cohort likely is healthier than the overall US hemodialysis population, partly limiting generalizability.

CONCLUSIONS

Hemodialysis patients have more white matter disease and cerebral atrophy compared with controls without known kidney disease. Hemodialysis patients also have a high prevalence of unrecognized infarcts.

Neurologic manifestations of acute and chronic renal disease

Acute and chronic renal disease is prevalent in hospitalized and ambulatory patient populations. Most patients with acute or chronic renal disease exhibit some degree of neurologic dysfunction affecting the CNS, peripheral nervous system, or both. Neurologic manifestations may be a direct consequence of the uremic state or a consequence of renal replacement therapy. Early recognition of common central and peripheral nervous system dysfunction as it relates to renal disease may provide opportunities for therapeutic intervention and improved outcomes. This review will summarize the most frequently encountered manifestations of acute and chronic renal disease, organized with respect to their occurrence as a direct consequence of advanced renal dysfunction or renal replacement therapy.

Cardiovascular disease and cognitive function in maintenance hemodialysis patients

BACKGROUND

Cardiovascular disease (CVD) and cognitive impairment are common in dialysis patients. Given the proposed role of microvascular disease on cognitive function, particularly cognitive domains that incorporate executive functions, we hypothesized that prevalent systemic CVD would be associated with worse cognitive performance in hemodialysis patients.

DESIGN

Cross-sectional cohort.

SETTING & PARTICIPANTS

200 maintenance hemodialysis patients without prior stroke from 5 Boston-area hemodialysis units.

PREDICTOR

CVD, defined as history of coronary disease or peripheral vascular disease.

OUTCOME

Performance on a detailed neurocognitive battery. Primary analyses quantified cognitive performance using principal components analysis to reduce cognitive tests to a processing speed/executive function domain and a memory domain. Multivariable linear regression models adjusted for age, sex, education, race, and other clinical and demographic characteristics.

RESULTS

Mean age of participants was 62 ± 18 (standard deviation) years and 75 (38%) had CVD. Individuals with CVD were older and more likely to be men, have diabetes, and be current or former smokers. In adjusted models, individuals with CVD performed 0.50 standard deviation worse (P < 0.001) on tests assessing processing speed/executive function, whereas there was no difference in performance on tests of memory. Similar results were seen assessing individual tests, with performance on the Block Design, Digit Symbol Coding, and Trail Making Tests A and B significantly associated with CVD in age-, sex-, education-, and race-adjusted analyses and approaching significance in fully adjusted models.

LIMITATIONS

CVD ascertainment dependent on patient recall and dialysis unit documentation. No brain imaging.

CONCLUSIONS

The presence of CVD is associated with worse cognitive performance on tests of processing speed and executive functioning in hemodialysis patients and identifies a high-risk population for greater difficulty with complex tasks.

[Cognitive impairment and chronic kidney disease: which links?]

Ageing of the population leads to an increase of cognitive disorders and chronic renal failure incidence. Compared to the general population, prevalence of cognitive impairment is more important in renal failure patients, especially in dialyzed patients. No direct link has been established between renal failure and cognitive impairment. The care of older and older patients and the high frequency of vascular risk factors, in particular hypertension and diabetes, partially explain the prevalence of vascular dementia and Alzheimer disease in this population. Other factors as the anemia, phosphocalcic metabolism disorders facilitate the cognitive impairment. The present work reviews the links existing between chronic renal failure and cognitive impairment.

Depression and cognitive function in maintenance hemodialysis patients

BACKGROUND

Both depression and cognitive impairment are common in hemodialysis patients, are associated with adverse clinical outcomes, and place an increased burden on health care resources.

STUDY DESIGN

Cross-sectional cohort.

SETTING & PARTICIPANTS

241 maintenance hemodialysis patients in the Boston, MA, area.

PREDICTOR

Depressive symptoms, defined as a Center for Epidemiological Studies Depression Scale (CES-D) score ≥16.

OUTCOME

Performance on a detailed neurocognitive battery.

RESULTS

Mean age was 63.8 years, 49.0% were women, 21.6% were African American, and median dialysis therapy duration was 13.8 months. There were 57 (23.7%) participants with significant depressive symptoms. In multivariable analysis adjusting for age, sex, education, and other comorbid conditions, participants with and without depressive symptoms performed similarly on the Mini-Mental State Examination (P = 0.4) and tests of memory. However, participants with greater depressive symptoms performed significantly worse on tests assessing processing speed, attention, and executive function, including Trail Making Test B (P = 0.02) and Digit-Symbol Coding (P = 0.01). Defining depression using a CES-D score ≥18 did not substantially change results.

LIMITATIONS

Cross-sectional design, absence of brain imaging.

CONCLUSIONS

Hemodialysis patients with a greater burden of depressive symptoms perform worse on tests of cognition related to processing speed and executive function. Further research is needed to assess the effects of treating depressive symptoms on cognitive performance in dialysis patients.

Neurological complications of chronic kidney disease

Chronic kidney disease (CKD) is a critical and rapidly growing global health problem. Neurological complications occur in almost all patients with severe CKD, potentially affecting all levels of the nervous system, from the CNS through to the PNS. Cognitive impairment, manifesting typically as a vascular dementia, develops in a considerable proportion of patients on dialysis, and improves with renal transplantation. Patients on dialysis are generally weaker, less active and have reduced exercise capacity compared with healthy individuals. Peripheral neuropathy manifests in almost all such patients, leading to weakness and disability. Better dialysis strategies and dietary modification could improve outcomes of transplantation if implemented before surgery. For patients with autonomic neuropathy, specific treatments, including sildenafil for impotence and midodrine for intradialytic hypotension, are effective and well tolerated. Exercise training programs and carnitine supplementation might be beneficial for neuromuscular complications, and restless legs syndrome in CKD responds to dopaminergic agonists and levodopa treatment. The present Review dissects the pathophysiology of neurological complications related to CKD and highlights the spectrum of therapies currently available.

High Prevalence of Leukoaraiosis in Cerebral Magnetic Resonance Images of Patients on Peritoneal Dialysis

BACKGROUND

Leukoaraiosis is a term used to define the abnormal appearance of subcortical white matter of the brain by means of neuroimaging and is regarded as an intermediate surrogate of stroke. The goal of this study is to identify the prevalence of leukoaraiosis and analyze predictors of risk of leukoaraiosis.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

57 peritoneal dialysis (PD) patients without diabetes treated in 3 academic medical-associated dialysis units who did not have a history of cerebrovascular disease or neurological symptoms compared with a convenience sample of 57 age- and sex-matched hypertensive control subjects with normal renal function.

PREDICTOR

End-stage renal disease treated by PD compared with hypertension, adjusted for clinical and laboratory characteristics.

OUTCOME & MEASUREMENT

Hyperintense areas on magnetic resonance imaging T2 high-signal intensity scoring system.

RESULTS

The prevalence of leukoaraiosis was significantly greater in patients on PD therapy than controls (68.4% versus 17.5%; P < 0.001). High T2 signal intensity score in patients on PD therapy compared with controls was significantly higher in the anterior circulation of the brain, relatively sparing the posterior fossa. End-stage renal disease, age, and poor control of blood pressure were significant independent predictors of leukoaraiosis.

LIMITATIONS

There is the possibility that biases regarding the selection of enrolled patients had an influence on a study result.

CONCLUSIONS

Cerebral magnetic resonance imaging of PD patients without evidence of cerebrovascular disease showed a high prevalence of leukoaraiosis in the anterior circulation of the brain. Old age, poorly controlled hypertension, and the PD procedure itself and/or end-stage renal disease seem to be associated with the presence of leukoaraiosis.

Silent Cerebral White Matter Lesions and Their Relationship With Vascular Risk Factors in Middle-Aged Predialysis Patients With CKD

BACKGROUND

Silent cerebral white matter lesions are observed on magnetic resonance imaging (MRI) scans in elderly people, and they are related to vascular risk factors, particularly hypertension. No data on the prevalence and risk factors of white matter lesions in patients with chronic kidney disease (CKD) are available. The aim is to analyze the prevalence of white matter lesions and their determinants in this population.

METHODS

We studied 52 patients without diabetes with CKD (stage 3 or 4) aged 30 to 60 years (average, 49 years) and a group of 32 normotensive control subjects. MRI studies were performed and subcortical and periventricular white matter lesions were evaluated by using semiquantitative measures. Patients were classified into 2 groups depending on the presence or absence of white matter lesions. Echocardiographic studies and measures of markers of systemic inflammation (C-reactive protein and interleukin 6) also were performed.

RESULTS

White matter lesions were more prevalent in patients with CKD than controls (33% versus 6%; P = 0.008). Patients with CKD who had white matter lesions were older; had a greater history of cardiovascular disease and vascular nephropathy as a primary cause of renal disease and greater levels of systolic blood pressure, pulse pressure, left ventricular mass index, and C-reactive protein; and were administered more antihypertensive drugs than patients with CKD without white matter lesions. Stage and duration of CKD were not related to the presence of white matter lesions. After adjusting for several factors, only vascular nephropathy (odds ratio, 15.6; 95% confidence interval, 1.27 to 191.54; P = 0.03) independently predicted an increased risk for white matter lesions.

CONCLUSION

One third of middle-aged patients with CKD have silent cerebral white matter lesions. Vascular nephropathy seems to be the most important factor related to the presence of these lesions, suggesting that white matter lesions reflect ischemic brain damage caused by generalized vascular damage.

Cognitive function in dialysis patients

There are few detailed studies of cognitive function in dialysis patients. However, appreciating the prevalence and risk factors for cognitive impairment is important because cognitive impairment may decrease an individual's quality of life, increase resource utilization, and result in suboptimal medical care because of difficulty following caregiver recommendations. Cognitive impairment also is likely to become more of a problem as the dialysis population ages. In this review, we argue that cerebrovascular disease is an important cause of cognitive impairment in dialysis patients and discuss risk factors specific for vascular disease, as well as other factors that may influence cognitive function. We describe the structural brain abnormalities frequently seen in dialysis patients and the specific neurocognitive changes noted in prior studies. We explore potential measures to reduce cognitive impairment in this population. We conclude that additional research is needed in this area.

Clinical demographics and long-term prognosis after stroke in patients on chronic haemodialysis. The Okinawa Dialysis Study (OKIDS) Group

BACKGROUND

Stroke is one of the leading causes of death in chronic dialysis patients. However, few epidemiological studies have reported on the demographics and long-term prognosis after stroke.

METHODS

We have observed the occurrence of stroke in the chronic dialysis population for the past 10 years in Okinawa, Japan. Definite cases of stroke were registered and categorized as cerebral haemorrhage (CB), cerebral infarction (CI), and subarachnoid hemorrhage (SAH).

RESULTS

Among 3741 chronic dialysis patients (2073 men, 1668 women), 271 patients (164 men, 107 women) had strokes (CB 162, CI 97, SAH 12) at least once during the study period from 1 April 1988 to 31 March 1998. The total duration of observation was 15 pound 748.8 patient-years (males 8990.5, females 6758.3). The incidence of stroke per 1000 patient-years was 17.2 overall, 10.3 for CB, 6.2 for CI, and 0.8 for SAH. Twenty-four per cent of stroke cases occurred within 1 year of starting dialysis therapy, and 57.7% occurred within 5 years after the beginning of therapy. The mean (SD) age at onset of stroke was 59.8 (13.0) years overall, 57.2 (12.6) for CB, 65.0 (12.1) for CI, and 53.6 (13.0) years for SAH. The survival rates after stroke were 53.4% at 1 month, 43.5% at 6 months, 35.7% at 12 months, and 23.2% at 60 months. Patients with diabetes mellitus (DM) had higher incidence of CI and a poorer prognosis than those without DM.

CONCLUSION

Incidence of stroke was high (17.2 per 1000 patient-years) in the dialysis population of our area and the long-term prognosis after stroke was poor.