Risk Factors of Pediatric Arterial Ischemic Stroke; A Regional Survey

Design and Harmonization Approach for the Multi-Institutional Neurocognitive Discovery Study (MINDS) of Adult Congenital Heart Disease (ACHD) Neuroimaging Ancillary Study: A Technical Note

Dramatic advances in the management of congenital heart disease (CHD) have improved survival to adulthood from less than 10% in the 1960s to over 90% in the current era, such that adult CHD (ACHD) patients now outnumber their pediatric counterparts. ACHD patients demonstrate domain-specific neurocognitive deficits associated with reduced quality of life that include deficits in educational attainment and social interaction. Our hypothesis is that ACHD patients exhibit vascular brain injury and structural/physiological brain alterations that are predictive of specific neurocognitive deficits modified by behavioral and environmental enrichment proxies of cognitive reserve (e.g., level of education and lifestyle/social habits). This technical note describes an ancillary study to the National Heart, Lung, and Blood Institute (NHLBI)-funded Pediatric Heart Network (PHN) "Multi-Institutional Neurocognitive Discovery Study (MINDS) in Adult Congenital Heart Disease (ACHD)". Leveraging clinical, neuropsychological, and biospecimen data from the parent study, our study will provide structural-physiological correlates of neurocognitive outcomes, representing the first multi-center neuroimaging initiative to be performed in ACHD patients. Limitations of the study include recruitment challenges inherent to an ancillary study, implantable cardiac devices, and harmonization of neuroimaging biomarkers. Results from this research will help shape the care of ACHD patients and further our understanding of the interplay between brain injury and cognitive reserve.

Diagnosis of Pediatric Stroke in Resource Limited Settings

Global awareness of stroke as a significant cause of neurologic sequelae and death in children has increased over the years as more data in this field becomes available. However, most published literature on pediatric stroke have limited geographic representation. Data on childhood stroke from developing countries remains limited. Thus, this paper reviewed geographic/ethnic differences in pediatric stroke risk factors highlighting those reported in low- and middle-income countries, and proposes a childhood arterial ischemic stroke diagnostic algorithm for resource limited settings. Stroke risk factors include cardiac disorders, infectious diseases, cerebral arteriopathies, hematologic disorders, inflammatory diseases, thrombophilia and genetic conditions. Infection of the central nervous system particularly tuberculous meningitis, is a leading cause of pediatric arterial ischemic stroke in developing countries. Stroke should be considered in children with acute focal neurologic deficit especially in the presence of aforementioned risk factors. Cranial magnetic resonance imaging with angiography is the neuroimaging modality of choice but if unavailable, cranial computed tomography with angiography may be performed as an alternative. If both are not available, transcranial doppler together with neurologic exam may be used to screen children for arterial ischemic stroke. Etiological diagnosis follows with the aid of appropriate laboratory tests that are available in each level of care. International collaborative research on stroke risk factors that are prevalent in low and middle income countries will provide information for drafting of stroke care guidelines that are universal yet inclusive taking into consideration regional differences in available resources with the goal of reducing global stroke burden.

Impaired Neurovascular Function Underlies Poor Neurocognitive Outcomes and Is Associated with Nitric Oxide Bioavailability in Congenital Heart Disease

We use a non-invasive MRI proxy of neurovascular function (pnvf) to assess the ability of the vasculature to supply baseline metabolic demand, to compare pediatric and young adult congenital heart disease (CHD) patients to normal referents and relate the proxy to neurocognitive outcomes and nitric oxide bioavailability. In a prospective single-center study, resting-state blood-oxygen-level-dependent (BOLD) and arterial spin labeling (ASL) MRI scans were successfully obtained from 24 CHD patients (age = 15.4 ± 4.06 years) and 63 normal referents (age = 14.1 ± 3.49) years. Pnvf was computed on a voxelwise basis as the negative of the ratio of functional connectivity strength (FCS) estimated from the resting-state BOLD acquisition to regional cerebral blood flow (rCBF) as estimated from the ASL acquisition. Pnvf was used to predict end-tidal CO2 (P_ETCO2) levels and compared to those estimated from the BOLD data. Nitric oxide availability was obtained via nasal measurements (nNO). Pnvf was compared on a voxelwise basis between CHD patients and normal referents and correlated with nitric oxide availability and neurocognitive outcomes as assessed via the NIH Toolbox. Pnvf was shown as highly predictive of P_ETCO2 using theoretical modeling. Pnvf was found to be significantly reduced in CHD patients in default mode network (DMN, comprising the ventromedial prefrontal cortex and posterior cingulate/precuneus), salience network (SN, comprising the insula and dorsal anterior cingulate), and central executive network (CEN, comprising posterior parietal and dorsolateral prefrontal cortex) regions with similar findings noted in single cardiac ventricle patients. Positive correlations of Pnvf in these brain regions, as well as the hippocampus, were found with neurocognitive outcomes. Similarly, positive correlations between Pnvf and nitric oxide availability were found in frontal DMN and CEN regions, with particularly strong correlations in subcortical regions (putamen). Reduced Pnvf in CHD patients was found to be mediated by nNO. Mediation analyses further supported that reduced Pnvf in these regions underlies worse neurocognitive outcome in CHD patients and is associated with nitric oxide bioavailability. Impaired neuro-vascular function, which may be non-invasively estimated via combined arterial-spin label and BOLD MR imaging, is a nitric oxide bioavailability dependent factor implicated in adverse neurocognitive outcomes in pediatric and young adult CHD.

Assessment of Post-Stroke Consequences in Pediatric Ischemic Stroke in the Context of Neuroimaging Results-Experience from a Single Medical Center

Arterial ischemic stroke (AIS) in children is a rare condition; its frequency is estimated at 0.58 to 7.9 new onsets in 100,000 children per year. The knowledge on risk factors, clinical outcomes and consequences of pediatric AIS is increasing. However, there are still many unknowns in the field. The aim of the study was to analyze the clinical presentation of pediatric AIS and its consequences according to the neuroimaging results and location of ischemia. The research was retrospective and observational. The analyzed group consisted of 75 AIS children (32 girls, 43 boys), whereby the age of the patients ranged from 9 months to 18 years at stroke onset. All the patients were diagnosed and treated in one tertiary center. The most frequent stroke subtype was total anterior circulation infarct (TACI) with most common ischemic focus location in temporal lobe and vascular pathology in middle cerebral artery (MCA). The location of ischemic focus in the brain correlated with post-stroke outcomes: intellectual delay and epilepsy, hemiparesis corresponded to the location of vascular pathology. A correlation found between ischemic lesion location and vascular pathology with post-stroke consequences in pediatric AIS may be important information and helpful in choosing proper early therapy. The expected results should lead to lesser severity of late post-stroke outcomes.