Cerebral cortical atrophy in pediatric patients with end-stage renal disease

Impact of Chronic Kidney Disease on Brain Structure and Function

Chronic kidney disease (CKD) affects more than 37 million American adults. Adult-onset CKD is typically attributed to acquired comorbidities such as aging, type II diabetes, and cardiovascular disease. Conversely, congenital abnormalities of the kidney and urinary tract are the most common cause of CKD in children. Both adult and pediatric patients with CKD are at risk for neurocognitive dysfunction, particularly in the domain of executive function. The exact mechanism for neurocognitive dysfunction in CKD is not known; however, it is conceivable that the multisystemic effects of CKD—including hypertension, acidosis, anemia, proteinuria, and uremic milieu—exert a detrimental effect on the brain. Quantitative neuroimaging modalities, such as magnetic resonance imaging (MRI), provide a non-invasive way to understand the neurobiological underpinnings of cognitive dysfunction in CKD. Adult patients with CKD show differences in brain structure; however, much less is known about the impact of CKD on neurodevelopment in pediatric patients. Herein, this review will summarize current evidence of the impact of CKD on brain structure and function and will identify the critical areas for future research that are needed to better understand the modifiable risk factors for abnormal brain structure and function across both pediatric and adult CKD populations.

The brain in pediatric chronic kidney disease-the intersection of cognition, neuroimaging, and clinical biomarkers

Brain growth and development occur at peak rates in early childhood through adolescence, and for some children, this must happen in conjunction with chronic kidney disease (CKD), associated medical conditions, and their treatment(s). This review provides an overview of key findings to date on the topic of the brain in pediatric CKD. Here, we specifically address the topics of neuroimaging and cognition in pediatric CKD with consideration to biomarkers of disease progression that may impact cognition. Current cognitive data suggest that most children with mild to moderate CKD do not exhibit significant cognitive impairments, but, rather, the presence of somewhat lower intellectual abilities and subtle deficits in selected executive functions. Although promising, modern neuroimaging data remain inconclusive in linking cognitive findings to neuroimaging correlates in the pediatric CKD population. Certainly, it is important to note that even subtle cognitive concerns can present barriers to learning, social functioning, and overall quality of life if not appropriately recognized or addressed. Further longitudinal research utilizing concurrent and targeted cognitive and neuroimaging evaluations is warranted to better understand the impact of CKD progression on brain development and associated neurocognitive outcomes.

Brain abnormalities in children and adolescents with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a risk factor for vascular disease and stroke. The spectrum of brain injury and microstructural white matter abnormalities in children with CKD is largely unknown.

METHODS

Cross sectional study at two North American pediatric hospitals. A cohort of 49 children, 29 with CKD, including renal transplant (mean age 14.4 ± 2.9 years; range 9-18), and 20 healthy controls (mean age 13.7 ± 3.1 years; range 9-18) had their conventional brain magnetic resonance images (MRIs) reviewed by one neuroradiologist to determine the prevalence of brain injury. Fractional anisotropy (FA) maps calculated from diffusion tensor imaging (DTI) were generated to compare white matter microstructure in CKD compared to controls, using tract-based spatial statistics (TBSS).

RESULTS

Focal and multifocal white matter injury was seen on brain MRI in 6 children with CKD (21%). Relative to controls, CKD subjects showed reduced white matter fractional anisotropy and increased mean diffusivity and radial diffusivity in the anterior limb of the internal capsule, suggestive of abnormal myelination.

CONCLUSION

Cerebral white matter abnormalities, including white matter injury, are under-recognized in pediatric CKD patients. Brain imaging studies through progression of CKD are needed to determine the timing of white matter injury and any potentially modifiable risk factors.

Brain Magnetic Resonance Imaging Findings in Children and Young Adults With CKD

BACKGROUND

The neuroanatomic basis for cognitive impairment in chronic kidney disease (CKD) is incompletely characterized. We performed advanced quantitative structural magnetic resonance imaging (MRI) to determine whether CKD affects brain structure and whether poorer neurocognitive performance in CKD is associated with structural brain differences.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

85 individuals with CKD stages 2 to 5 and 63 healthy controls, aged 8 to 25 years PREDICTORS: CKD versus control, estimated glomerular filtration rate (eGFR), and kidney transplant status were analyzed as predictors of MRI findings. MRI volumes in 19 prespecified regions of gray matter (GM), white matter (WM), and cerebrospinal fluid were analyzed as predictors of neurocognitive performance (median z scores) in 7 prespecified domains.

OUTCOMES

19 prespecified brain regions of interest (ROIs) in 7 prespecified domains. Neurocognitive performance in 7 prespecified domains.

MEASUREMENTS

ROI volumes were compared in CKD versus controls using unadjusted t tests and analysis of covariance (ANCOVA). Associations of ROI volumes with eGFR and kidney transplant status in participants with CKD were analyzed using ANCOVA and linear regression. Associations of neurocognitive performance and ROI volumes were analyzed by linear regression.

RESULTS

Participants with CKD had lower whole-brain, cortical, and left parietal GM volumes than controls in unadjusted analyses, but no differences were found in adjusted analysis. In participants with CKD, lower eGFR was associated with higher WM volume in whole-brain (P=0.05) and frontal (P=0.04) ROIs, but differences were not significant after multiple comparisons correction. Kidney transplant recipients had lower GM volumes in whole-brain (P=0.01; Q=0.06), frontal (P=0.02; Q=0.08), and left and right parietal (P=0.01; Q=0.06; and P=0.03; Q=0.1) ROIs and higher whole-brain WM volume (P=0.04; Q=0.1). Neurocognitive performance in the CKD group was not associated with ROI volumes.

LIMITATIONS

Unable to assess changes in brain structure and kidney function over time; analysis limited to prespecified ROIs and neurocognitive domains.

CONCLUSIONS

CKD in children and young adults may be associated with lower GM and higher WM volumes in some ROIs. Differences were relatively subtle in the CKD group as a whole, but were more prominent in recipients of a kidney transplant. However, neurocognitive performance was not explained by differences in brain ROI volumes, suggesting a functional rather than structural basis for neurocognitive impairment in CKD.

Episodic ventriculomegaly due to hypernatremia mimicking shunt malfunction: case report

Patients with shunted hydrocephalus presenting with altered mental status and ventriculomegaly are generally considered to be in shunt failure requiring surgical treatment. The authors describe a case of shunted hydrocephalus secondary to a disseminated neuroectodermal tumor in a pediatric patient in whom rapid fluctuations in sodium levels due to diabetes insipidus repeatedly led to significant changes in ventricle size, with invasively confirmed normal shunt function and low intracranial pressure. This clinical picture exactly mimics shunt malfunction, requires urgent nonsurgical therapy, and underscores the importance of considering serum osmolar abnormalities in the differential diagnosis for ventriculomegaly.

Design and methods of the NiCK study: neurocognitive assessment and magnetic resonance imaging analysis of children and young adults with chronic kidney disease

Background

Chronic kidney disease is strongly linked to neurocognitive deficits in adults and children, but the pathophysiologic processes leading to these deficits remain poorly understood. The NiCK study (Neurocognitive Assessment and Magnetic Resonance Imaging Analysis of Children and Young Adults with Chronic Kidney Disease) seeks to address critical gaps in our understanding of the biological basis for neurologic abnormalities in chronic kidney disease. In this report, we describe the objectives, design, and methods of the NiCK study.

Design/methods

The NiCK Study is a cross-sectional cohort study in which neurocognitive and neuroimaging phenotyping is performed in children and young adults, aged 8 to 25 years, with chronic kidney disease compared to healthy controls. Assessments include (1) comprehensive neurocognitive testing (using traditional and computerized methods); (2) detailed clinical phenotyping; and (3) multimodal magnetic resonance imaging (MRI) to assess brain structure (using T1-weighted MRI, T2-weighted MRI, and diffusion tensor imaging), functional connectivity (using functional MRI), and blood flow (using arterial spin labeled MRI). Primary analyses will examine group differences in neurocognitive testing and neuroimaging between subjects with chronic kidney disease and healthy controls. Mechanisms responsible for neurocognitive dysfunction resulting from kidney disease will be explored by examining associations between neurocognitive testing and regional changes in brain structure, functional connectivity, or blood flow. In addition, the neurologic impact of kidney disease comorbidities such as anemia and hypertension will be explored. We highlight aspects of our analytical approach that illustrate the challenges and opportunities posed by data of this scope.

Discussion

The NiCK study provides a unique opportunity to address key questions about the biological basis of neurocognitive deficits in chronic kidney disease. Understanding these mechanisms could have great public health impact by guiding screening strategies, delivery of health information, and targeted treatment strategies for chronic kidney disease and its related comorbidities.

Duration of chronic kidney disease reduces attention and executive function in pediatric patients

Chronic kidney disease (CKD) in childhood is associated with neurocognitive deficits. Affected children show worse performance on tests of intelligence than their unaffected siblings and skew toward the lower end of the normal range. Here we further assessed this association in 340 pediatric patients (ages 6 to 21) with mild-moderate CKD in The Chronic Kidney Disease in Childhood cohort from 48 pediatric centers in North America. Participants underwent a battery of age-appropriate tests including Conner’s Continuous Performance Test-II (CPT-II), Delis- Kaplan Executive Function System Tower task, and the Digit Span Backwards task from the age-appropriate Wechsler Intelligence Scale. Test performance was compared across the range of estimated GFR and duration of CKD with relevant covariates including maternal education, household income, IQ, blood pressure and preterm birth. Among the 340 patients, 35% had poor performance (below the mean by1.5 or more standard deviations) on at least one test of executive function. By univariate nonparametric comparison and multiple logistic regression, longer duration of CKD was associated with increased odds ratio for poor performance on the CPT-II Errors of Commission, a test of attention regulation and inhibitory control. Thus, in a population with mild to moderate CKD, the duration of disease rather than estimated GFR was associated with impaired attention regulation and inhibitory control.

Systematic review of structural and functional neuroimaging findings in children and adults with CKD

CKD has been linked with cognitive deficits and affective disorders in multiple studies. Analysis of structural and functional neuroimaging in adults and children with kidney disease may provide additional important insights into the pathobiology of this relationship. This paper comprehensively reviews neuroimaging studies in both children and adults. Major databases (PsychLit, MEDLINE, WorldCat, ArticleFirst, PubMed, Ovid MEDLINE) were searched using consistent search terms, and studies published between 1975 and 2012 were included if their samples focused on CKD as the primary disease process. Exclusion criteria included case reports, chapters, and review articles. This systematic process yielded 43 studies for inclusion (30 in adults, 13 in children). Findings from this review identified several clear trends: (1) presence of cerebral atrophy and cerebral density changes in patients with CKD; (2) cerebral vascular disease, including deep white matter hyperintensities, white matter lesions, cerebral microbleeds, silent cerebral infarction, and cortical infarction, in patients with CKD; and (3) similarities in regional cerebral blood flow between patients with CKD and those with affective disorders. These findings document the importance of neuroimaging procedures in understanding the effect of CKD on brain structure, function, and associated behaviors. Results provide a developmental linkage between childhood and adulthood, with respect to the effect of CKD on brain functioning across the lifespan, with strong implications for a cerebrovascular mechanism contributing to this developmental linkage. Use of neuroimaging methods to corroborate manifest neuropsychological deficits or perhaps to indicate preventive actions may prove useful to individuals with CKD.

The central nervous system in childhood chronic kidney disease

Neurodevelopmental deficits in pediatric and adult survivors of childhood onset chronic kidney disease (CKD) have been documented for many years. This paper reviews the available literature on central nervous system involvement incurred in childhood CKD. The studies reviewed include recent work in neuroimaging, electrophysiology, and neuropsychology, along with commentary on school functioning and long-term outcomes. The paper concludes with suggestions for monitoring the neurodevelopmental status and pursuing appropriate early interventions for children with CKD.

Neurocognitive outcomes in children with chronic kidney disease: Current findings and contemporary endeavors

Given the rise in chronic kidney disease (CKD) in both children and adults, CKD has recently been targeted as a public health priority. Childhood onset kidney disease is generally a noncurable and progressive condition that leads to kidney failure by early adulthood. Fortunately, improved identification of kidney problems allows for early intervention, which is thought to slow progression toward end-stage renal disease. In addition, medical interventions for pediatric end-stage renal disease have also improved, allowing children to take advantage of lifesaving renal replacement treatments such as dialysis and kidney transplantation. In spite of improvements in identification and treatment, CKD causes both direct and indirect insults to a variety of organ systems. This paper reviews recently published studies pertaining to the neurocognitive and psychosocial impact of CKD on children of various ages and at various stages of kidney failure. Specific attention is focused on summarizing peer reviewed research that describes associations between kidney functioning and cognitive functioning, language acquisition, visual spatial abilities, memory, and executive functioning. In addition, peer reviewed research describing psychosocial outcomes associated with CKD related to academic achievement, social-behavioral functioning, and quality of life are summarized. The authors also identified disease-specific factors that likely mediate neurocognitive outcomes (e.g., anemia, hypertension, cardiovascular) and endorse the importance of continued interdisciplinary research collaborations that will provide a better understanding of the mechanisms responsible for improved neurocognitive functioning after transplantation. The authors conclude this review by describing a multicenter, prospective, longitudinal, National Institutes of Health funded study that is currently examining the developmental outcomes of children with mild to moderate CKD. The authors speculate that the Chronic Kidney Disease in Children Prospective Cohort Study (CKiD) findings will provide additional evidence-based guidance for clinicians and researchers working with children and adolescents with deteriorating kidney function to improve medical and developmental outcomes.

Priority for children in cadaveric kidney sharing: the strategy adopted in Sao Paulo, Brazil

Early kidney transplantation is crucial in order to accomplish both optimal mental development and the best adult height in children with end-stage renal disease. The aim was to evaluate the efficacy of the child priority policy for cadaveric kidney sharing adopted in the State of Sao Paulo (Brazil). We performed a retrospective study of data collected by the Government Transplant Department in São Paulo, involving all patients included in the waiting list from August 13, 1998 to December 31, 2001. During the study period, the child priority policy had been changed giving: period A--from the outset up to March 14, 2001, where the rule was to direct cadaveric kidneys obtained from children <12 yr, to recipients <12 yr; period B--from March 14, 2001 onwards, where the policy had been broadened to include cadaveric donors <18 yr, destined for recipients <18 yr. We performed the analysis of the data comprising 8940 patients, 8622 being adults (mean age = 48.6 +/- 14.1 yr, 3594 females) and 318 children (mean age = 11.9 +/- 5.1 yr, 156 females). Over the 3.5-yr follow-up there were 1964 deaths [1933 adults and 31 children, odds ratio (OR) 0.37; 95% CI 0.25-0.55], 1032 living donor kidney transplants (963 adults and 69 children, OR 2.20; 95% CI 1.66-2.93), and 556 cadaveric kidney transplants (444 adults and 112 children, OR 10.11; 95% CI 7.75-12.94). Three and a half years after being enrolled on the list, 24% of the children and 75% of the adults, respectively, were still awaiting a cadaveric kidney transplant (log rank test = 539, p < 0.00001). The analysis of period A vs. period B, suggests that the raising of the inclusion age upper limit to 18 yr, resulted in a twofold increase in the percentage of children being grafted within 6 months of enrollment. Overall, our data shows a slow rate of cadaveric kidney transplantation activity in Sao Paulo. Children's chances of receiving a living donor kidney almost doubled. Moreover, 19.5% of pediatric recipients had received their kidney within the first year of being enrolled on the waiting list. The scheme adopted in Sao Paulo is encouraging, but the results remain less favorable than those observed in other countries. The adoption of the priority policy did not result in an unacceptable increase of adult waiting time, given that the number of adults on our waiting list outweighs by far the number of children.

Inhibition of pyruvate kinase activity by cystine in brain cortex of rats

Cystinosis is a metabolic disturb associated with excessive lysosomal cystine accumulation secondary to defective cystine efflux. Patients affected by this disease develop a variable degree of symptoms depending of the involved tissues. Accumulation of cystine in the brain may lead to severe neurological symptoms. However, the mechanisms by which cystine is neurotoxic are not fully understood. Considering that pyruvate kinase (PK) is a thiolic enzyme crucial for the glycolytic pathway, and disulfides like cystine may alter thiolic enzymes by thiol/disulfide exchange, the main objective of the present study was to investigate the effect of cystine on PK activity in the brain cortex of developing Wistar rats. We also performed kinetic studies and investigated the effects of GSH, a biologically occurring thiol groups protector, and cysteamine (CysN), the drug used for cystinosis treatment, on the enzyme activity. We observed that cystine inhibited the enzyme activity by two different mechanisms, one through the competition with ADP and phosphoenolpyruvate (PEP), and the other non-competitively, probably through oxidation of the thiol groups of PK. We also observed that GSH and cysteamine fully prevented and reversed the inhibition caused by cystine. Considering that cysteamine is used in patients with cystinosis because it causes parenkimal organ cystine depletion, the present data provides a possible new beneficial effect for the use of this drug.

Neuroradiologic findings in children with renal transplantation under 5 years of age

Chronic renal failure (CRF) is known to have adverse effects on the neurodevelopmental outcome of affected children. Some of these effects can be ameliorated by transplantation (TX). The cause and nature of the underlying brain injury is not known. We performed a brain magnetic resonance imaging (MRI) study on a group of children after TX to look for brain abnormalities and, if possible, to draw conclusions about their origin. Thirty-three children who received a renal allograft before 5 yr of age were studied. The most common diagnosis was the congenital nephrotic syndrome of Finnish type (29 patients). The male/female ratio was 22/11, the age range 6-11 yr. Pre-TX CT studies of 26 patients were available for comparison. The patient files were studied for relevant clinical history, including pre- and perinatal events, infections, hypertension, hypertensive crises, hypovolemic states and medical emergencies. These risk factors were correlated with the MRI findings. Eighteen patients (54%) had ischemic lesions in the vascular border zones. Mild lesions were seen in 10 patients, moderate in six and severe in two patients. Other findings were rare, including infarcts in the main vascular territories and basal ganglia, and central and cortical atrophy. The pre-TX CT's revealed border zone infarcts in six patients. Hemodynamic crises were reported in 14 patients and correlated well with border zone infarcts. The age at TX was greater and the duration of dialysis longer in those with border zone infarcts than in those without. Low gestational age, perinatal complications, and septic infections were not statistically significant risk factors. Because of the lack on serial imaging studies we do not know the exact timing of these brain infarcts. The good correlation to pre-TX hemodynamic crises seems, however, to indicate that most of these lesions could be prevented by careful clinical monitoring and early TX.

Neurodevelopmental outcome in high-risk patients after renal transplantation in early childhood

Patient and graft survival rates of pediatric renal transplant recipients are currently excellent, but there are few reports regarding the long-term neurodevelopmental outcome after renal transplantation (Tx) in early childhood. Children with renal failure from infancy would be expected to have a less favorable developmental prognosis. We report the neurodevelopmental outcome in 33 school-age children transplanted between 1987 and 1995 when < 5 yr of age. We prospectively performed a neurological examination, magnetic resonance imaging (MRI) of the brain, electroencephalograms (EEGs), audiometry, and neuropsychological tests (NEPSY), and measured cognitive performance (WISC-R); we related these results to school performance and to retrospective risk factors prior to Tx. Twenty-six (79%) children attended normal school and 76% had normal motor performance. Six of the seven children attending a special school had brain infarcts on MRI. The EEG was abnormal in 11 (35%), and five (15%) received anti-convulsive treatment after Tx. Sensorineural hearing loss was documented in six patients. The mean intelligence quotient (IQ) was 87, and 6-24% showed impairment in neuropsychological tests. The children attending a special school had been more premature, but had not had a greater number of pre- or neonatal complications. They had experienced a greater number of hypertensive crises (p = 0.002) and seizures (p = 0.03), mainly during dialysis, but the number of septic infections and the mean serum aluminum levels were not significantly greater than in the children with normal school performance. In these previously lethal diseases, the overall neurodevelopmental outcome is reassuring. However, it is of crucial importance to further minimize the risk factors prior to Tx.

Convulsions in children undergoing renal transplantation

We reviewed the records of 154 children who received 207 renal transplants for end-stage renal disease from 1965 to 1987, and discovered that 48 (31%) had had convulsive seizures, some before transplant surgery, others only after transplant, and some during both before and after transplantation. The majority of children had minimal long-term problems, and 60% of the children had only a single convulsion. In six of the patients, convulsions were a manifestation of more serious underlying conditions that produced significant morbidity. Seizures of differing clinical type occurred, with hypertension being the most significant etiologic factor. In children with renal failure, there are minimal symptoms heralding the hypertensive encephalopathy. Rapid resolution without recurrence of seizures after control of hypertension is a major sign that hypertension was the cause and that the long-term prognosis is good.

Unexpected seizures during hemodialysis. Effect of dialysate prescription

To assess the effects of the dialysate prescription on the intradialytic neurological stability of children requiring chronic hemodialysis (HD), continuous EEG monitoring (CEM) was performed on five children before, during and after HD against: (1) low sodium acetate (LAc: Na 132 mEq/l, acetate 38 mEq/l); (2) high sodium acetate (HAc: Na 144 mEq/l, acetate 41 mEq/l), and (3) low sodium bicarbonate (LBi: Na 133 mEq/l, bicarbonate 35 mEq/l) dialysate. Three children, two with clinically well-controlled seizure disorders and one with no seizure history, exhibited subclinical seizures on LAc and HAc but improved neurological stability on LBi. Two children had essentially unchanged CEM studies on any HD regimen. Symptoms of disequilibrium were noted in four of the five children on LAc, two of the five on HAc and only one of the five on LBi. The data suggest that bicarbonate HD may enhance intradialytic neurological stability, particularly in children with known seizure disorders. Furthermore, CEM was found to be a useful tool for evaluating the neurological stability of children during HD.

Complications of nephropathic cystinosis after renal failure

Fifteen patients with nephropathic cystinosis, ranging in age from 13 to 27 years, were studied. Two were in renal failure; 13 had functioning renal allografts; 5 had severe, uncorrectable loss of visual acuity as well as posterior synechiae and crystal deposits on the lens surface. All 15 patients had photophobia and corneal erosions to variable degrees. All patients were growth retarded with delayed bone ages. Puberty occurred late, but was generally complete by 17 years of age. Hepatic function appeared normal. Only 1 patient had neurological deterioration, but 11 patients had some degree of cerebral atrophy radiologically. The continued accumulation of cystine within cystinotic tissues results in serious extrarenal complications many years after renal transplantation in cystinosis.