Neuropsychological impairment in children with sickle cell anemia and cerebrovascular accidents

Blood Transfusion Vs. Hydroxyurea for Stroke Prevention in Children With Sickle Cell Anemia: A Systematic Review and Meta-Analysis

Sickle cell anemia (SCA) is a hereditary condition that can lead to severe complications in children such as acute coronary syndrome, splenic sequestration, renal failure, and stroke. Blood transfusion and hydroxyurea (HU) therapy are used to prevent stroke in children with sickle cell disease (SCD). Preliminary data show considerable variation and inconsistency in the use of these two therapeutic interventions. Therefore, this systematic review was carried out to compare the effects of blood transfusion to HU therapy in preventing stroke for children with sickle cell disease. There was an extensive literature search in reliable and authentic databases like PubMed, Medline, Scopus, Cochrane, and Science Direct to obtain relevant articles. This study used the standards and guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). During the systematic review, data were obtained focusing on the following parameters: the size of the sample in the study, the age of the subjects involved in the study, the type of Intervention, and the outcome. After an initial search of 163 papers, 25 studies were included. The results of the research give the first evidence that HU is effective in the treatment of cerebrovascular problems in children with SCD. However, it is unclear under what circumstances HU may prevent a second stroke. It can be concluded that children with SCA can effectively avoid primary strokes through chronic blood transfusions and HU.

A Traditional Review of Sickle Cell Disease and the Associated Onset of Dementia: Hematological and Neurocognitive Crossroads

Sickle cell trait and disease are potential risk factors for dementia and cognitive dysfunction in African Americans, as are genetic variants. This illness affects around 300 million people globally. Due to its ability to defend against severe malaria, it represents an evolutionary survival advantage. It has been shown that sickle cell disease and trait are independent risk factors for the prevalence and incidence of albuminuria and chronic renal disease. Sickle cell anemia impairs cognitive performance in people with minimal or mild manifestations of the genetic blood disorder, owing mostly to its cerebrovascular implications. Similarly, various cerebral minor vascular disorders, such as silent cerebral infarcts, have been linked to the sickle cell trait, which is associated with impaired cognitive ability. It has been found that patients with sickle cell disease have a significantly decreased subcortical and cortical brain volume. Adults and children with sickle cell disease have been documented to have attention-related issues, particularly reduced sustained attention.

SC411 treatment can enhance survival in a mouse model of sickle cell disease

Sickle cell disease (SCD) is one of the most common inherited blood disorder among African Americans affecting 70,000-100,000 individuals in the United States. It is characterized by abnormal hemoglobin (HbS) which develops into severe hemolytic anemia and vaso-occlusive crisis. Therefore, patients with SCD suffer from a chronic state of inflammation, which is responsible for multiple organ damage, ischemic attacks, and premature death. Another major hallmark of SCD patients is the abnormally low levels of omega-3 fatty acids, especially docosahexaenoic acid (DHA) in their red blood cell membranes. Treatment with DHA can reduce red blood cell adhesion and enhance cerebral blood flow, thus, our main goal is to investigate the effect of SC411, which is a novel, highly purified DHA ethyl ester formulation with a proprietary delivery platform in SCD. Utilizing a transgenic mouse model of SCD (HbSS-Townes) and recurrent hypoxic challenges (10%O₂, 0.5% CO₂ and balance N₂ for 3 h) to mimic ischemic-like conditions, our data suggest that SC411 can elevate blood DHA and eicosapentaenoic acid (EPA) levels after 8 weeks of treatment. SC411 can also decrease arachidonic acid (AA) and sickling of red blood cells. In addition, SC411-treated SCD mice showed presented with cerebral blood flow, alleviated neuroinflammation, and revived working memory which ultimately enhanced overall survival. In summary, this study suggests that treatment with SC411 improves cellular and functional outcomes in SCD mice. This finding may provide novel therapeutic opportunities in the treatment against ischemic injury elicited by SCD.

Targeting pain at its source in sickle cell disease

Sickle cell disease (SCD) is a genetic disorder associated with hemolytic anemia, end-organ damage, reduced survival, and pain. One of the unique features of SCD is recurrent and unpredictable episodes of acute pain due to vasoocclusive crisis requiring hospitalization. Additionally, patients with SCD often develop chronic persistent pain. Currently, sickle cell pain is treated with opioids, an approach limited by adverse effects. Because pain can start at infancy and continue throughout life, preventing the genesis of pain may be relatively better than treating the pain once it has been evoked. Therefore, we provide insights into the cellular and molecular mechanisms of sickle cell pain that contribute to the activation of the somatosensory system in the peripheral and central nervous systems. These mechanisms include mast cell activation and neurogenic inflammation, peripheral nociceptor sensitization, maladaptation of spinal signals, central sensitization, and modulation of neural circuits in the brain. In this review, we describe potential preventive/therapeutic targets and their targeting with novel pharmacologic and/or integrative approaches to ameliorate sickle cell pain.

Differences in Activation and Deactivation in Children with Sickle Cell Disease Compared with Demographically Matched Controls

BACKGROUND AND PURPOSE

Declines in both functional activation and functional connectivity have been reported in patients with sickle cell disease. In this study, we derived the functional and default mode responses to a word stem paradigm in age-, ethnicity-, and background-matched subjects with sickle cell disease and control groups, with the aim of testing whether both networks were similarly attenuated and whether the changes were related to physiologic parameters that characterize sickle cell disease.

MATERIALS AND METHODS

Both the functional and default mode responses were obtained from age- and background-matched controls and the sickle cell population by using a visually presented word stem paradigm on a 3T scanner.

RESULTS

We observed an attenuated response to both activation and deactivation in the sickle cell disease group. There were no significant differences in the activation response between the 2 groups for the contrast control > sickle cell disease; however, significant differences were observed in the medial parietal cortex, the auditory cortex, and the angular gyrus for the default mode. For the sickle cell group, a significant correlation between the activation z scores and the physiologic parameters was observed; for the deactivation, the results were not significant but the trend was similar.

CONCLUSIONS

The results indicate that the physiologic parameters modulate the activation in the expected fashion, but that the effect was weaker for deactivation. Given that significant differences between the 2 groups were only seen for deactivation, additional factors must modulate the deactivation in sickle cell disease.

Hypoxia and inflammation in children with sickle cell disease: implications for hippocampal functioning and episodic memory

Children with sickle cell disease (SCD) suffer from systemic processes (e.g., chronic anemia, recurrent hypoxic-ischemic events, chronic inflammation) that have been associated with neurocognitive impairment in a range of clinical populations, but which have been largely understudied in relation to specific domains of cognitive functioning in children with SCD. This review focuses on episodic memory, as the hippocampus may be especially vulnerable to the systemic processes associated with SCD. The first part of the paper outlines the pathophysiology of SCD and briefly reviews the extant literature on academic and cognitive functioning in children with SCD, emphasizing the dearth of research on episodic memory. Next, the complex systemic processes of hypoxia and inflammation associated with SCD are reviewed, along with research that has associated these processes with hippocampal damage and memory impairment. The paper concludes with suggestions for future research that are informed, in part, by the literature on developmental amnesia.

The use of stimulant medication to treat neurocognitive deficits in patients with pediatric cancer, traumatic brain injury, and sickle cell disease: a review

Several chronic health conditions of childhood, including pediatric cancers, traumatic brain injury (TBI), and sickle cell disease (SCD) are associated with significant neurocognitive impairments that can compromise educational attainment and future vocational opportunities. The prominence of attentional deficits as part of the neurocognitive sequelae associated with each of these conditions has led some researchers to draw parallels with another chronic condition that manifests in childhood, specifically the inattentive subtype of attention-deficit/hyperactivity disorder (ADHD). Because ADHD shares similar neurocognitive and symptomatological features with pediatric cancer, TBI, and SCD, stimulant medications may be indicated to treat associated deficits in each condition. However, relatively few studies have investigated the safety and effectiveness of stimulant medications in treating neurocognitive sequelae in children with cancer, TBI, or SCD. Thus, clinicians have received little guidance regarding a potentially useful treatment modality for ameliorating the neurocognitive deficits that can profoundly impact the educational, psychosocial, and vocational development of youth with these chronic health conditions. We provide a review of the literature and synthesize current developments in research regarding treatment with stimulant medication for children with cancer, TBI, and SCD, as well as discuss special considerations for each condition.

White matter damage in asymptomatic patients with sickle cell anemia: screening with diffusion tensor imaging

BACKGROUND AND PURPOSE

Ischemic injury to the brain is a common complication of SCA. To better understand the neurologic impact of SCA, TBSS were applied to DTI data to investigate white matter injuries in pediatric patients with SCA.

MATERIALS AND METHODS

TBSS comparisons of a range of anisotropy and diffusion measures were carried out between age- and background-matched population groups: patients with SCA with no visible lesions, patients with SCA with mild gliosis, and normal controls.

RESULTS

TBSS analysis revealed that both SCA populations exhibited reduced anisotropy and increased diffusivity compared with normal controls in multiple brain regions, including the corpus callosum and centrum semiovale. Furthermore, the results suggest that the severity of SCA is positively correlated with the white matter changes in the corpus callosum.

CONCLUSIONS

The study demonstrates that TBSS is a viable technique in detecting subtle white matter damage in patients with SCA whose conventional anatomic MR imaging scans show no, or minimal, abnormalities and has the potential to evaluate the neurologic impact of the treatment of SCA.

Association of Pulsatility Index in the Middle Cerebral Artery with Intelligence Quotient in Children with Sickle Cell Disease

The aim of this study was to explore whether intellectual performance in children with Sickle Cell Disease and with low risk of stroke as determined with conventional transcranial Doppler ultrasonography (TCD) criteria was associated with hemodynamic parameters in imaging TCD, when controlling for hematological and socio-economical variables and presence of silent infarcts. We performed neuropsychological testing with Kaufman Brief Intelligence Test (K-BIT-IQ) and imaging TCD examinations to measure blood flow velocities and pulsatility indexes (PI) in the middle cerebral arteries (MCA) In 46 children with homozygous HbSS (mean age 108±34 months, range limits: 47–166 months; 24 females), without a history of stroke or transient ischemic attack, with no stenosis on magnetic resonance angiography and with velocities below 170 cm/s in screening conventional TCD. Mean K-BIT IQ Composite and Vocabulary scores (91±13 and 86±14 respectively) were significantly below the average scores of 100 for the age-matched population (one sample t-test=5.21, p<0.001). Using univariate and multivariate regression models, we found that lower PI in the right MCA was associated with lower K-BIT-IQ Composite and Vocabulary scores. Furthermore, we found that interhemispheric differences in PIs were even more strongly associated with neuropsychological performance, whereas flow velocities were not associated with the K-BIT-IQ score. Using a model of chronic anemia, we found that cognitive functioning was associated with cerebral hemodynamics.

Ameliorating attention problems in children with sickle cell disease: a pilot study of methylphenidate

OBJECTIVE

This pilot study examined whether methylphenidate (MPH) was effective in enhancing cognitive performance and attention for children with sickle cell disease (SCD) with cerebrovascular complications who evidence attention problems.

METHODS

In this multisite, pilot study, we evaluated 2 separate double-blind controlled clinical trials, including a laboratory trial of the short-term efficacy of MPH, with the second study a 3-week home/school crossover trial evaluating the efficacy of MPH. The laboratory trial included 14 participants between the age of 7 and 16 years. Assessments included measures of sustained attention, reaction time, executive functions, and verbal memory. The home/school trial included 20 participants. The outcome measures were parent and teacher ratings of attention. The first study compared MPH with placebo, while the second trial compared placebo, low-dose (LD) MPH, and moderate-dose MPH.

RESULTS

In the laboratory trial, significant effects were revealed for measures of memory and inhibitory control. Parent and teacher reports from the home/school trial indicate that moderate-dose MPH produced superior improvement in attention relative to the placebo and LD MPH.

CONCLUSIONS

Stimulant medication positively impacted select measures of memory and inhibitory control in some children with SCD. Attention, as rated by parent and teachers, was improved for a greater number of children and adolescents on higher doses of MPH relative to LD MPH and placebo. Stimulant medication may provide an effective intervention for some children with SCD and cerebrovascular complications who demonstrate attention problems.

Event-based prospective memory in children with sickle cell disease: effect of cue distinctiveness

Event-based prospective memory (EB-PM) is the formation of an intention and remembering to perform it in response to a specific event. Currently, EB-PM performance in children with sickle cell disease (SCD) is unknown. In this study, we designed a computer-based task of EB-PM; No-Stroke, Silent-Infarct, and Overt-Stroke groups performed significantly below the demographically similar control group without SCD. Cue distinctiveness was varied to determine if EB-PM could be improved. All groups, with the exception of the Overt-Stroke group, performed significantly better with a perceptually distinctive cue. Overall, these results suggest that EB-PM can be improved significantly in many children with SCD.

Brain morphometry and intelligence quotient measurements in children with sickle cell disease

OBJECTIVE

To verify the hypothesis that volume of regional gray matter accounts substantially for variability in intelligence quotient (IQ) score among children with sickle cell disease, who have no magnetic resonance visible infarcts.

METHODS

We studied 31 children with sickle cell disease, homozygous for hemoglobin S, with no history of stroke, no magnetic resonance signal-intensity abnormality, and transcranial Doppler velocities <170 cm/sec, with a T1-weighted magnetic resonance sequence and the Kaufman Brief Intelligence Test. On the basis of Kaufman Brief Intelligence Test, we classified these children into 2 groups: high and low IQ based on a median split. We then used an automated and novel Bayesian voxel-based morphometry technique, called Graphical-Model-Based Multivariate Analysis (GAMMA), to assess the probabilistic association between IQ score and regional gray matter volume.

RESULTS

GAMMA found 1 region linking low IQ with smaller cortical gray matter volume. In comparison with the children in the high-IQ group, children in the low-IQ group had smaller regional gray matter volume in both frontal lobes, both temporal lobes, and both parietal lobes.

CONCLUSIONS

In children with sickle cell disease, we found a linear association between IQ and regional gray matter volume. This finding suggests that some variance in intellectual ability in children with sickle cell disease is accounted for by regional variability of gray matter volume, which is independent of neuroradiological evidence of infarct.

Detection and assessment of stroke in patients with sickle cell disease: neuropsychological functioning and magnetic resonance imaging

Sickle cell disease (SCD) is associated with increased risk of stroke and cognitive impairment. This study describes a retrospective review of 65 patients who underwent routine neuropsychological testing and MRI during treatment at a comprehensive sickle cell center. It was hypothesized that (1) children with no evidence of CVA would perform lower than expected on cognitive tasks compared to population-based normative data, (2) children with strokes and children with silent infarcts would perform lower on cognitive tasks and motor skills as compared to patients with no evidence of CVA, and (3) children with evidence of silent infarcts would perform better than children with known overt strokes. This final hypothesis has not been studied previously, as children with known overt stroke and silent infarct were grouped together. Sixty-five children with SCD who were sent for routine neuropsychological testing and brain MRI were identified via retrospective chart review. Patients had been administered neuropsychological tests to assess cognitive, executive and motor function. Brain MRI was obtained from each patient and was analyzed for evidence of cerebrovascular accident (CVA). Based on MRI analysis, 27% of patients with SCD had experienced a stroke and 13% a silent infarct. The majority (59%) of patients diagnosed with stroke or infarct sustained cortical damage to the frontal lobe. Patients with SCD and no evidence of CVA functioned normally on tests of cognitive ability and achievement, but patients with CVA displayed impairments in cognitive function and comparatively lower scores on verbal and performance scales. Neuropsychological testing can identify impairments in patients with SCD with no known cerebrovascular accident. Investigations of neurocognitive functioning will help characterize patterns of deficits and can inform the ability to implement comprehensive care strategies for patients with SCD and cognitive impairment.

Neurocognitive sequelae of pediatric sickle cell disease: a review of the literature

This literature review summarizes all studies relating neuropsychological performance to neuroimaging findings in pediatric sickle cell disease (N=28; published 1991-2005). Although inconsistencies exist within and across domains, deficits in intelligence (IQ), attention and executive functions, memory, language, visuomotor abilities, and academic achievement have been identified. Overall neurocognitive compromise was revealed to be related to the level of neurological injury and the location of silent infarct. Attentional and executive dysfunction is prevalent and related to frontal lobe abnormalities.

Physiological correlates of intellectual function in children with sickle cell disease: hypoxaemia, hyperaemia and brain infarction

Lowered intelligence relative to controls is evident by mid-childhood in children with sickle cell disease. There is consensus that brain infarct contributes to this deficit, but the subtle lowering of IQ in children with normal MRI scans might be accounted for by chronic systemic complications leading to insufficient oxygen delivery to the brain. We investigated the relationship between daytime oxyhaemoglobin saturation (SpO2), cerebral blood flow velocity (CBFV) and intellectual function (IQ) using path-analysis in 30 adolescents with sickle cell disease (mean age 17.4 years, SD 4.2). Initial analyses revealed that the association between SpO2 and Full Scale IQ (FSIQ) was fully mediated by increased CBFV, whereby SpO2 was negatively correlated with CBFV and CBFV was negatively correlated with FSIQ, i.e. decreases in oxygen saturation are associated with increases in velocity, and increased velocity is associated with lowered IQ scores. The mediated relationship suggests that lowered IQ may be a function of abnormal oxygen delivery to the brain. Further analyses showed that the association between CBFV and IQ was significant for verbal but not for performance IQ. The pathophysiology characteristic of SCD can interfere with brain function and constrain intellectual development, even in the absence of an infarct. This supports the hypothesis that lowered intellectual function is partly explained by chronic hypoxia, and has wider implications for our understanding of SCD pathophysiology.

Detecting white matter injury in sickle cell disease using voxel-based morphometry

OBJECTIVE

Sickle cell disease (SCD) is associated with cerebrovascular disease, cerebral infarction, and cognitive dysfunction. This study aimed to detect the presence and extent of white matter abnormalities in individuals with SCD using voxel-based morphometry (VBM).

METHODS

Thirty-six children and adolescents with SCD (age range, 9-24 years) and 31 controls (8-25 years) underwent magnetic resonance investigations using T1- and T2-weighted protocols. White and gray matter density maps were obtained from three-dimensional magnetic resonance imaging (MRI) data sets. Using VBM, we compared the maps between controls and SCD individuals with silent white matter infarct lesions (SCD+L; n = 16), and those without visible abnormality (SCD-L; n = 20).

RESULTS

In comparison with controls, intelligence quotients (IQs) were lower in both SCD groups irrespective of presence of visible lesions. VBM showed widespread bilateral white matter abnormalities in the SCD+L group, extending beyond the regions of focal infarction in the deep anterior and posterior white matter borderzones. Bilateral white matter abnormalities were also observed in the SCD-L group, in locations similar to those in the SCD+L group.

INTERPRETATION

VBM is sensitive to detection of widespread white matter injury in SCD patients in borderzones between arterial territories even in the absence of evidence of infarction. Those changes may contribute to cognitive deficits in this population.

Prevention and management of stroke in sickle cell anemia

As the overall health of patients with sickle cell anemia (SS) improves and diagnostic techniques become more sensitive, physicians are seeing patients with an increasingly wide range of subtle and not-so-subtle brain injury. The major breakthrough in the field of sickle-related brain injury has been the unprecedented success of transcranial Doppler ultrasonography (TCD) to identify asymptomatic patients at high risk of stroke, coupled with chronic transfusion therapy to prevent it. The evidence for TCD screening and preventive treatment is strong and compelling, but there are still important unanswered questions regarding the implications of "silent infarcts" found in the magnetic resonance images (MRIs) of asymptomatic individuals, and the growing awareness of the burden of neuropsychiatric dysfunction in otherwise apparently healthy individuals.

Radiographic predictors of neurocognitive functioning in pediatric Sickle Cell disease

We compared magnetic resonance imaging (MRI), magnetic resonance angiography, and transcranial Doppler ultrasonography as predictors of specific neurocognitive functions in children with sickle cell disease. Participants were 27 children with sickle cell anemia (hemoglobin SS) who were participants in the Stroke Prevention Trial in Sickle Cell Anemia (STOP) and had no documented history of stroke. Children's MRIs were classified as normal or silent infarct, and their magnetic resonance angiograms were classified as normal or abnormal. The highest time-averaged mean flow velocity on transcranial Doppler ultrasonographic examination of the major cerebral arteries was analyzed. Age and hematocrit also were analyzed as predictor variables. The battery of neurocognitive tests included measures of intellectual functioning, academic achievement, attention, memory, visual-motor integration, and executive functions. MRI, magnetic resonance angiography, transcranial Doppler ultrasonography, age, and hematocrit were analyzed as predictors of participants' performance on the various measures of neurocognitive functioning. Age and hematocrit were robust predictors of a number of global and specific neurocognitive functions. When age and hematocrit were controlled, transcranial Doppler ultrasonography was a significantly unique predictor of verbal memory. We found an association between low hemoglobin and neurocognitive impairment. We also found that abnormalities on transcranial Doppler ultrasonography can herald subtle neurocognitive deficits. (J Child Neurol 2006;21:37-44).

Decreased corpus callosum size in sickle cell disease: relationship with cerebral infarcts and cognitive functioning

We assessed midsagittal corpus callosum size in sickle cell disease (SCD) and its relationship to lesion volume, lesion location, and cognitive functioning. Twenty-eight children with SCD and 16 demographic controls completed magnetic resonance imaging (MRI) and neuropsychological testing. Corpus callosum (CC) size was smaller for children with silent infarcts (n = 8) or overt stroke (n = 8) than for those without visible infarcts (n = 12) or control participants. Lesion volume was a robust predictor of IQ and other cognitive scores; total CC size did not typically add explanatory power for these measures. The size of the rostral body of the CC, however, independently predicted measures of distractibility, speeded production, and working memory. Posterior CC size was also decreased among many of the children with SCD, even in the absence of visible infarcts in this region. Brain morphology appears to provide additional information about SCD-related effects on the brain above and beyond visible infarcts.

Neurocognitive sequelae of sickle cell disease: current issues and future directions

Sickle cell disease is a genetic disorder with an autosomal recessive pattern of inheritance. This disease is most prevalent among those of African American and Mediterranean descent. Cerebral vascular accident (CVA) or stroke is one of the major complications of hemoglobin SS (Hgb SS) disease. CVA has implications for physical as well as neurocognitive function for children. Recent literature suggests that some children with sickle cell disease without overt signs of CVA may still have evidence of neurological deficit, both on magnetic resonance imaging and neurological examination. There is a growing body of knowledge that further aids in delineation of risk factors for CVA, silent infarct, and neurocognitive deficits in children with Hgb SS disease. More research is needed to continue to explore avenues for identification and intervention. The purpose of this article is to delineate areas of ongoing research in this important area.

Psychological complications in sickle cell disease

This review examines the evidence for some of the common psychological complications found across the life span of patients with sickle cell disease (SCD), which are likely to be encountered by haematologists responsible for their medical management. Electronic searches of medical and psychological databases were conducted with a focus on three main areas: psychological coping, quality of life and neuropsychology. Psychological complications were identified in both children and adults with SCD, and included inappropriate pain coping strategies; reduced quality of life owing to restrictions in daily functioning, anxiety and depression; and neurocognitive impairment. There were wide variations in design and consistency of the studies, therefore, some caution needs to be observed in the findings. Moreover, interventional studies were lacking in some areas such as neuropsychology. Utilization of psychological interventions including patient education, cognitive behavioural therapy, and special educational support to help improve the quality of life of patients are recommended.

Cognitive deficits in children with sickle cell disease

We tested a hypothesis that children with sickle cell disease who are completely normal by magnetic resonance imaging can still be cognitively impaired, as predicted by a model of diffuse brain injury. Fifty-four patients with hemoglobin SS (average age 10.9 years +/- 2.9 years SD) were examined with the Wechsler Intelligence Scale for Children-III (WISC-III) and were randomly matched by age, race, and gender with healthy children from the Wechsler normative database. Patients were also imaged at 1.5 Tesla with standard imaging sequences. Among 30 patients who were normal by magnetic resonance imaging, there were substantial deficits in Wechsler Full-Scale IQ, Verbal IQ, and Performance IQ (all P < .01) compared with African-American controls. The patient Wechsler Full-Scale IQ was 12.9 points lower than that of controls and decreased as a function of age (probability = .014). The findings suggest that there is diffuse brain injury in patients and that patient deficits increase with age.

Stroke and elevated blood flow velocity in the anterior cerebral artery in sickle cell disease

Transcranial Doppler ultrasonography provides a noninvasive method of predicting stroke risk in children with sickle cell disease. Elevated cerebral blood flow velocity in the terminal internal carotid or middle cerebral artery is associated with an increased stroke risk, but the clinical significance of elevated velocities in the other large intracranial vessels is unknown. The authors report stroke in two children with sickle cell disease and high blood flow velocity limited to the anterior cerebral artery. This suggests that elevated velocity in this vessel may be associated with an increased risk of stroke.

Patterns of verbal long-term and working memory performance reveal deficits in strategic processing in children with frontal infarcts related to sickle cell disease

Frontal brain regions are thought to mediate strategic processes that facilitate memory. We hypothesized that children with frontal cerebral infarcts related to sickle cell disease (SCD) would exhibit impairments in long-term and working memory as a result of disruptions in strategic processing. Word-list learning and digit span tasks were used to assess verbal memory and strategic processing in 21 children with SCD without infarcts (controls) and in 10 children with SCD with frontal infarcts. On the word-list learning task, children with frontal infarcts performed more poorly in terms of learning and free recall, although recognition and cued recall were adequate; this pattern suggested intact encoding and storage with impaired retrieval. Children with frontal infarcts performed more poorly on backward digit span, although forward digit span was adequate; this pattern suggested intact maintenance with impaired manipulation of information in working memory. Overall, these findings support the notion that disruptions in strategic processing contribute to memory impairments in children with frontal infarcts.

Transcranial Doppler ultrasonography and neurocognitive functioning in children with sickle cell disease

OBJECTIVE

We examined the relationship between cerebral blood flow velocity, measured by transcranial Doppler (TCD) ultrasonography, and neurocognitive functioning.

METHODS

Participants were 60 children who had sickle cell disease (HbSS) and had no documented history of stroke. Children were classified according to Stroke Prevention Trial in Sickle Cell Anemia criteria (normal, conditional, and abnormal), and their performance was compared on measures of intellectual abilities, academic achievement, sustained attention/concentration, executive function, and parent and teacher ratings of executive function.

RESULTS

Children with abnormal TCD values performed more poorly than children with conditional TCD values on measures of verbal intelligence and executive function. Children with conditional TCD values performed more poorly than children with normal TCD values on measures of sustained attention/concentration and executive function. TCD values also were a significant predictor of auditory working memory in exploratory analyses.

CONCLUSIONS

Our findings support the hypothesis that neurocognitive functions subserved by the frontal systems (eg, sustained attention/concentration and executive function) seem to be the most useful indices of progressive cerebrovasculopathy in children with HbSS disease.

Psychological aspects of hematologic diseases

This article focused on two hematologic diseases that have received significant attention in the pediatric literature: sickle cell anemia and hemophilia. As the data indicate, these illnesses present lifelong challenges to individuals afflicted. With advances in medical interventions, many children with these hematologic diseases are living longer and with fewer serious complications. Intervention efforts only recently have begun to consider issues related to quality of life and increased psychological adjustment, including active coping strategies by children and their parents and necessary social support for all family members. Theoretical models [54] have highlighted the multiple factors that play a role in illness adjustment and the complex interactions of these factors. Individual, family, and community characteristics are impacted by and, in turn, impact on illness-related characteristics. The notion that illness severity is predictive of psychological adjustment has been discarded in favor of a model that recognizes multiple influences and multiple outcomes. Child coping, parent coping, social support, adaptive functioning, treatment compliance, and illness severity are being considered to better understand and influence overall psychological functioning. The field of pediatric psychology has made tremendous advances in improving knowledge of illness and its impact on development. Even with these advances, however, there remains much to be discovered. To date, pediatric psychology research has focused primarily on individual illness categories, making comparisons across illness types difficult. By considering different illnesses within the same study, characteristics that are crucial to improved adjustment and common across illnesses can be identified. As we continue to work for cures for these debilitating illnesses, our goal remains to improve quality of life for children.

Sickle cell disease and stroke in a pediatric population

Cerebrovascular complications are common in SCD and constitute a major source of concern to the pediatric hematologist. These complications can be either clinically overt or covert. The authors' review of the diagnostic tests does not offer absolute indications for neuroimaging because most of the evidence is based on studies that are not randomized controlled trials. Imaging guidelines for children have emerged based on the available level 2 and 3 literature, however, CT and MR imaging remain the initial tests of choice for stroke assessment, and TCD is the imaging tool of choice for stroke prevention. Based on guidelines handed down from the NIH, TCD has become a part of routine continuing care of children with SCD.

Attention deficits in children with sickle cell disease

Previous research has suggested that children with sickle cell disease may exhibit cognitive deficits even in the absence of direct cerebrovascular involvement (stroke). This study was designed to assess specific attentional deficits in children with sickle cell disease. 12 children with sickle cell disease (Hb SS) with a prior history of stroke, 14 children with sickle cell disease (Hb SS) without evidence of stroke, and 13 similar aged siblings (Hb AA or Hb AS) were compared on measures of attention, intellectual functioning, achievement, and adaptive functioning. Significant differences were found between children with sickle cell disease (with or without stroke) and healthy controls on a timed test of visual scanning, the Coding subtest of the Wechsler Intelligence Scale for Children-Revised, and subtests of Reading, Arithmetic, and Spelling from the Wide Range Achievement Test-Revised. The differences between children with sickle cell disease and their healthy siblings appear to be the result of strokes rather than sickle cell disease itself as children with sickle cell disease without strokes did not significantly differ from controls. Implications for the effects of sickle cell disease and stroke on academic performance are discussed.

Neuropsychological aspects of pediatric sickle cell disease

Sickle cell disease (SCD), a class of genetic disorders characterized by abnormal, sickled red blood cells, is a chronic illness that results in progressive cerebrovascular disease. Neurocognitive sequelae of clinically apparent cerebrovascular accidents in children with SCD are characterized by pervasive impairments, including decrements in general intellectual functioning, language and verbal abilities, visual-motor and visual-spatial processing, memory, academic achievement, and processing of subtle prosodic information. In contrast, subtle neurocognitive deficits in the areas of attention and concentration, executive function, and visual-motor speed and coordination appear to be associated with silent infarcts that are not necessarily detected on physical examination. Investigation of the disease course and associated neurocognitive sequelae suggest a disease-specific model of neuropsychological impairment. Recommendations are made for clinical and research efforts in the field of pediatric neuropsychology.

Neurocognitive functioning and magnetic resonance imaging in children with sickle cell disease

OBJECTIVE

To examine neurocognitive functioning in children classified with overt cerebral vascular accidents (CVAs), silent infarcts, or without central nervous system (CNS) pathology on magnetic resonance imaging.

METHODS

Participants were 63 children and adolescents with sickle cell disease (SCD).

RESULTS

Children with overt CVAs and silent infarcts differed from their peers without CNS pathology on measures of attention and executive functioning.

CONCLUSIONS

We consider these deficits the result of the high frequency of frontal lobe deficits incurred by children with SCD. Recommendations include the use of tests designed to measure attention and executive functioning as a way of screening children with SCD for possible CNS pathology. We also suggest that future research examine the mechanism underlying frontal lobe involvement for individuals with SCD.

Multicenter prospective study of children with sickle cell disease: radiographic and psychometric correlation

After obtaining familial informed consent, between January 1996 and July 1997, 173 children (5 to 15 years old) with sickle cell disease were enrolled in a prospective multicenter study using blood screening, transcranial Doppler ultrasonography (n = 143), cerebral magnetic resonance imaging (n = 144), and neuropsychologic performance evaluation (n = 156) (Wechsler Intelligence tests WISC-III, WIPPSI-R), which were also performed in 76 sibling controls (5 to 15 years old). Among the 173 patients with sickle cell disease (155 homozygous for hemoglobin SS, 8 sickle cell beta0 thalassemia, 3 sickle cell beta+ thalassemia, 7 sickle cell hemoglobin C disease SC), 12 (6.9%) had a history of overt stroke, and the incidence of abnormal transcranial Doppler ultrasonography (defined as mean middle cerebral artery velocity > 200 cm/sec or absent) was 8.4% in the overall study population and 9.6% in patients with homozygous sickle cell anemia The silent stroke rate was 15%. Significantly impaired cognitive functioning was observed in sickle cell disease patients with a history of stroke (Performance IQ and Full Scale IQ), but also in patients with silent strokes (Similarities, Vocabulary, and Verbal Comprehension). However, infarcts on magnetic resonance imaging were not the only factors of cognitive deficit: Verbal IQ, Performance IQ, and Full Scale IQ were strongly impaired in patients with severe chronic anemia (hematocrit < or = 20%) and in those with thrombocytosis (platelets > 500 x 10(9)/L). Multivariate logistic regression analysis showed that abnormal magnetic resonance imaging (odds ratio [OR] = 2.76) (P = .047), hematocrit < or =20% (OR = 5.85) (P = .005), and platelets > 500 x 10(9)/L (OR = 3.99) (P = .004) were independent factors of cognitive deficiency (Full Scale IQ < 75) in sickle cell disease patients. The unfavorable effect of low hematocrit has already been suggested, but this is the first report concerning an effect of thrombocytosis and showing that silent stroke alone is not a factor of cognitive deficit when not associated with low hematocrit or thrombocytosis. The effect of hydroxyurea, which is known to increase hematocrit and decrease platelet count, on cognitive functioning of sickle cell patients should be evaluated prospectively.

Hydroxyurea as an Alternative to Blood Transfusions for the Prevention of Recurrent Stroke in Children With Sickle Cell Disease

Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Hydroxyurea as an Alternative to Blood Transfusions for the Prevention of Recurrent Stroke in Children With Sickle Cell Disease

Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Cognitive and behavioral function in children with sickle cell disease: a review and discussion of methodological issues

PURPOSE

A review of the literature regarding cognitive and behavioral function in children with sickle cell disease (SCD) is presented, including a discussion of methodological issues to be considered when evaluating these patients and research in this area.

DESIGN

Sixteen studies were examined that addressed cognition and behavior in children with SCD.

RESULTS

Most studies of children with SCD who were classified as neurologically normal probably included a substantial number of children who had experienced silent strokes; this misclassification error likely resulted in erroneous findings of deficits in children thought to be free of brain injury. In most studies of children with SCD-related infarct, investigators failed to consider that patterns of impairment will vary depending upon lesion location. Many studies relied upon data from inappropriate control groups when examining the function of children with SCD.

CONCLUSIONS

Future studies should address a number of methodological factors. Brain imaging must be conducted to verify the presence or absence of cerebral infarcts. In children with imaging-verified infarcts, greater attention must be given to the relationship between lesion location and distinct patterns of cognitive or behavioral deficits. Sibling controls are the best choice in studies of children with SCD.

Cognitive deficits associated with frontal-lobe infarction in children with sickle cell disease

This study examined the cognitive manifestations of frontal-lobe infarction in a population of children with sickle cell disease (SCD). Forty-one patients with SCD underwent MRI. Five patients with stroke symptoms had large infarcts encroaching on the tissue of the frontal lobes. Four patients without symptoms had smaller frontal-lobe infarcts. The patients with stroke were significantly impaired on measures of intelligence, memory, and frontal-lobe function (Wisconsin Card Sorting Test, WCST) compared with both the patients with normal MRI scans (N=30) and a group of sibling controls (N=15), who did not differ from each other. Patients with covert infarction obtained scores on the intelligence tests and the WCST that fell in between those of the stroke patients and the other two groups. This trend toward impairment suggests that patients with covert infarction are at similar risk for cognitive deficits to those with stroke.

Ischemic strokes in children

Ischemic stroke is an uncommon, but significant cause of disability in childhood. Children with strokes present with predictable deficits as adults do; however, fever and seizures at stroke onset are more common in children than in adults. Strokes in children have diverse etiologies and require extensive evaluation. Etiology remains obscure in up to half of the patients. Prognosis in childhood stroke is not benign and up to 50% of pediatric stroke patients have chronic sequelae. Emerging therapies may alter prognosis in certain populations of children at risk for stroke, but more research is necessary.