An exploratory study of physiological correlates of neurodevelopmental delay in infants with sickle cell anaemia

Brain Volumes and Cognition in Patients with Sickle Cell Anaemia: A Systematic Review and Meta-Analysis

Cognitive decline is a major problem in paediatric and adult patients with sickle cell anaemia (SCA) and affects the quality of life. Multiple studies investigating the association between quantitative and qualitative neuroimaging findings and cognition have had mixed results. Hence, the aetiology of cognitive decline in this population is not clearly understood. Several studies have established cerebral atrophy in SCA children as well as adults, but the relationship between cognition and brain volumes remains unclear. The purpose of this systematic review was therefore to evaluate the literature on regional brain volumes and their association with cognitive outcomes. We also meta-analysed studies which compared regional brain volumes between patients and controls. Studies report that patients with SCA tend to have lower grey matter volumes, including total subcortical volumes in childhood as compared to controls, which stabilise in young adulthood and may be subjected to decline with age in older adulthood. White matter volumes remain stable in children but are subjected to reduced volumes in young adulthood. Age and haemoglobin are better predictors of cognitive outcomes as compared to regional brain volumes.

Neuroimaging and Cognitive Function in Sickle Cell Disease: A Systematic Review

Sickle cell disease (SCD) is the most common inherited single-gene disease. Complications include chronic anaemia, reduced oxygen-carrying capability, and cerebral vasculopathy, resulting in silent cerebral infarction, stroke, and cognitive dysfunction with impairments in measures of executive function, attention, reasoning, language, memory, and IQ. This systematic review aims to investigate the association between neuroimaging findings and cognition in children with SCD. Searches of PubMed and Embase were conducted in March 2022. Studies were included if participants were <18 years, if original data were published in English between 1960 and 2022, if any genotype of SCD was included, and if the relationship between cognition and neuroimaging was examined. Exclusion criteria included case studies, editorials, and reviews. Quality was assessed using the Critical Appraisal Skills Programme Case Control Checklist. A total of 303 articles were retrieved; 33 met the eligibility criteria. The presence of overt or silent strokes, elevated blood flow velocities, abnormal functional connectivity, and decreased fMRI activation were associated with neuropsychological deficits in children with SCD when compared to controls. There is a critical need to address the disease manifestations of SCD early, as damage appears to begin at a young age. Most studies were cross-sectional, restricting the interpretation of the directionality of relationships. Future research employing longitudinal neuroimaging and neuropsychological assessments could improve our understanding of the cumulative consequences of SCD on the developing brain.

Individual-level behavioral interventions to support optimal development of children with sickle cell disease: A systematic review

This review aimed to identify and describe individual-level behavioral interventions for children 0-18 years of age with sickle cell disease (SCD). PRISMA guidelines were followed at each stage of this review. Twenty-seven studies were included, representing six intervention types: disease knowledge (n = 7), self-management (n = 7), pain management (n = 4), school functioning (n = 4), cognitive health (n = 4), and mental health (n = 2). Most interventions targeted older children (5+ years), while only two examined interventions for children 0-3 years. This review suggests that offering education about disease knowledge, self-management, and pain management interventions can be beneficial for this population. Future research is needed to understand interventions to support young children and the impact of SCD on development.

Effects of regional brain volumes on cognition in sickle cell anemia: A developmental perspective

Background and objectives

Cognitive difficulties in people with sickle cell anemia (SCA) are related to lower processing speed index (PSI) and working memory index (WMI). However, risk factors are poorly understood so preventative strategies have not been explored. Brain volumes, specifically white matter volumes (WMV) which increases through early adulthood, have been associated with better cognition in healthy typically developing individuals. In patients with SCA, the reduced WMV and total subcortical volumes noted could explain cognitive deficits. We therefore examined developmental trajectories for regional brain volumes and cognitive endpoints in patients with SCA.

Methods

Data from two cohorts, the Sleep and Asthma Cohort and Prevention of Morbidity in SCA, were available. MRI data included T1-weighted axial images, pre-processed before regional volumes were extracted using Free-surfer. PSI and WMI from the Weschler scales of intelligence were used to test neurocognitive performance. Hemoglobin, oxygen saturation, hydroxyurea treatment and socioeconomic status from education deciles were available.

Results

One hundred and twenty nine patients (66 male) and 50 controls (21 male) aged 8-64 years were included. Brain volumes did not significantly differ between patients and controls. Compared with controls, PSI and WMI were significantly lower in patients with SCA, predicted by increasing age and male sex, with lower hemoglobin in the model for PSI but no effect of hydroxyurea treatment. In male patients with SCA only, WMV, age and socioeconomic status predicted PSI, while total subcortical volumes predicted WMI. Age positively and significantly predicted WMV in the whole group (patients + controls). There was a trend for age to negatively predict PSI in the whole group. For total subcortical volume and WMI, age predicted decrease only in the patient group. Developmental trajectory analysis revealed that PSI only was significantly delayed in patients at 8 years of age; the rate of development for the cognitive and brain volume data did not differ significantly from controls.

Discussion

Increasing age and male sex negatively impact cognition in SCA, with processing speed, also predicted by hemoglobin, delayed by mid childhood. Associations with brain volumes were seen in males with SCA. Brain endpoints, calibrated against large control datasets, should be considered for randomized treatment trials.

The Development of Neuroimaging Biomarkers for Cognitive Decline in Sickle Cell Disease

Sickle cell disease (SCD) is complicated by neurologic complications including vasculopathy, hemorrhagic or ischemic overt stroke, silent cerebral infarcts and cognitive dysfunction. Patients with SCD, even in the absence of vasculopathy or stroke, have experience cognitive dysfunction that progresses with age. Transcranial Doppler ultrasound and structural brain MRI are currently used for primary and secondary stroke prevention, but laboratory or imaging biomarkers do not currently exist that are specific to the risk of cognitive dysfunction in patients with SCD. Recent investigations have used advanced MR sequences assessing cerebral hemodynamics, white matter microstructure and functional connectivity to better understand the pathophysiology of cognitive decline in SCD, with the long-term goal of developing neuroimaging biomarkers to be used in risk prediction algorithms and to assess the efficacy of treatment options for patients with SCD.

Neurodevelopmental Outcomes in Preterm Children with Sickle Cell Disease

OBJECTIVES

To explore the combined effect of pediatric sickle cell disease (SCD) and preterm birth on cognitive functioning.

METHODS

Cognitive functioning was examined in children ages 6-8 with high risk SCD genotypes born preterm (n = 20) and full-term (n = 59) and lower risk SCD genotypes/no SCD born preterm (n = 11) and full-term (n = 99) using tests previously shown to be sensitive to SCD-related neurocognitive deficits. Factorial ANOVAs and log linear analyses were conducted to examine the relationship between SCD risk, preterm birth status, and cognitive outcomes. Continuous scores were examined for specific tests. Children were categorized as having an abnormal screening outcome if at least one cognitive score was ≥1.5 standard deviations below the population mean.

RESULTS

Children with elevated risk due to high risk SCD and preterm birth performed worse than other groups on a test of expressive language but not on tests that emphasize processing speed and working memory. There was a three-way interaction between preterm status, SCD risk, and abnormal screening outcome, which was largely driven by the increased likelihood of abnormal cognitive scores for children with high risk SCD born preterm.

CONCLUSIONS

The combination of SCD and preterm birth may confer increased risk for language deficits and elevated rates of abnormal cognitive screenings. This suggests that neurodevelopmental risk imparted by comorbid SCD and preterm birth may manifest as heterogenous, rather than specific, patterns of cognitive deficits. Future studies are needed to clarify the domains of cognitive functioning most susceptible to disease-related effects of comorbid SCD and preterm birth.

Neurocognitive Changes in Sickle Cell Disease: A Comprehensive Review

Background:

Sickle cell disease (SCD) is a type of hemoglobinopathy characterized by abnormal hemoglobin molecules, which includes numerous acute and chronic complications. Ischemic stroke, silent cerebral infarction, headache, and neurocognitive impairment are the most common neurological complications associated with SCD.

Summary:

Acute anemia because of SCD can cause cognitive impairments because of cerebral hypoxia. Cognitive abnormalities in SCD manifest in various aspects such as working memory, verbal learning, executive functions, and attention. These neurocognitive impairments have been associated with poor functional results, such as transitioning from juvenile to adult care, adherence to medications, and unemployment.

Key message:

In this review, we focus on neurocognitive aspects of SCD patients based on different imaging techniques, psychological batteries, associated neuromarkers, and interventions for managing of cognitive deficiencies..

Developmental delay in infants and toddlers with sickle cell disease: a systematic review

AIM

To summarize developmental delay among infants and toddlers with sickle cell disease (SCD).

METHOD

This systematic review included studies that reported developmental outcomes of children with SCD between 0 months and 48 months of age and followed standards set forth by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Ten studies were included, describing 596 unique developmental assessments. The rate of developmental delay ranged from 17.5% to 50% and increased with age. Cognition was the only domain included in all studies and the most frequently identified delay. One study reported that more severe SCD genotypes predicted worse development, while five studies reported no difference in rates of developmental delay across genotypes.

INTERPRETATION

These findings emphasize the need for standardized screening to identify children with SCD at risk of delay at a young age to facilitate appropriate referrals for therapeutic intervention. Frequent and comprehensive developmental screening is necessary among all SCD genotypes.

Neuronal injuries in cerebral infarction and ischemic stroke: From mechanisms to treatment (Review)

Stroke is the leading cause of disabilities and cognitive deficits, accounting for 5.2% of all mortalities worldwide. Transient or permanent occlusion of cerebral vessels leads to ischemic strokes, which constitutes the majority of strokes. Ischemic strokes induce brain infarcts, along with cerebral tissue death and focal neuronal damage. The infarct size and neurological severity after ischemic stroke episodes depends on the time period since occurrence, the severity of ischemia, systemic blood pressure, vein systems and location of infarcts, amongst others. Ischemic stroke is a complex disease, and neuronal injuries after ischemic strokes have been the focus of current studies. The present review will provide a basic pathological background of ischemic stroke and cerebral infarcts. Moreover, the major mechanisms underlying ischemic stroke and neuronal injuries are summarized. This review will also briefly summarize some representative clinical trials and up-to-date treatments that have been applied to stroke and brain infarcts.

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.

Epidemiology of Stroke in Sickle Cell Disease

Sickle cell disease is the most common cause of stroke in childhood, both ischaemic and haemorrhagic, and it also affects adults with the condition. Without any screening or preventative treatment, the incidence appears to fall within the range 0.5 to 0.9 per 100 patient years of observation. Newborn screening with Penicillin prophylaxis and vaccination leading to reduced bacterial infection may have reduced the incidence, alongside increasing hydroxyurea prescription. Transcranial Doppler screening and prophylactic chronic transfusion for at least an initial year has reduced the incidence of stroke by up to 10-fold in children with time averaged mean of the maximum velocity >200 cm/s. Hydroxyurea also appears to reduce the incidence of first stroke to a similar extent in the same group but the optimal dose remains controversial. The prevention of haemorrhagic stroke at all ages and ischaemic stroke in adults has not yet received the same degree of attention. Although there are fewer studies, silent cerebral infarction on magnetic resonance imaging (MRI), and other neurological conditions, including headache, epilepsy and cognitive dysfunction, are also more prevalent in sickle cell disease compared with age matched controls. Clinical, neuropsychological and quantitative MRI screening may prove useful for understanding epidemiology and aetiology.

Developmental screening of three-year-old children with sickle cell disease compared to controls

We previously found that neurodevelopmental deficits commonly occurred in three-year-olds with sickle cell disease (SCD), but clinical significance was uncertain because a comparison group was lacking. Our objective in the current study was to prospectively compare neurodevelopment in three-year-old children with SCD to an age-appropriate control group. The Brigance Preschool Screen II is a neurodevelopmental screening examination which can be administered in 15-20 min. SCD patients (Group 1) were compared with community controls of similar age and ethnicity enrolled in daycare/preschool (Group 2). SCD patients who were receiving hydroxycarbamide treatment were also compared (Group 3). Two hundred forty-five three-year-olds were evaluated: Group 1, 111; Group 2, 114; and Group 3, 20. The below cut-off rate on the Brigance test was higher in Group 1 (73%) than in Group 2 (61%; P = 0·04). In multivariate analysis of Group 1 patients, only lower household income and more persons living in the home were independent predictors of this. Patients with SCD and matched controls had high rates of 'failing' the Brigance test. The below cut-off rate in untreated children with SCD was associated with low household income and increased number of persons living in the home.

Pediatric Neurodevelopmental Delays in Children 0 to 5 Years of Age With Sickle Cell Disease: A Systematic Literature Review

INTRODUCTION

Sickle cell disease (SCD) is the most common abnormal genetic blood disease that affects ∼100,000 Americans. Approximately 20% to 37% of children with sickle cell anemia have silent cerebral infarcts by the age of 14 years old. Neurocognitive deficits are identified in infants and preschool children with SCD. The purpose of this systematic literature review is to provide a comprehensive understanding of the prevalence, severity, and the associated risk factors for neurodevelopmental delays (NDDs) in children with SCD 5 years of age and younger.

METHODS

Systematic search of 6 databases identified 2467 potentially relevant publications and 8 were identified through a manual search. Only 24 articles met the inclusion criteria.

RESULTS

We identified an increased prevalence of NDDs (cognitive, motor, or both). Children experienced deficits with language, attention and behavior, executive functioning, school readiness and/or academic performance, and motor skills (fine and gross motor functioning). Risk factors include silent cerebral infarcts and strokes, SCD genotype (HbSS>HbSC), other biologic, and social factors.

CONCLUSION

NDDs are common in children ages 0 to 5 years old with SCD. There is an opportunity to improve adherence to national guideline recommendations and early detection practices by pediatricians, hematologists, and other health care providers.

Associations of transcranial doppler velocity, age, and gender with cognitive function in children with sickle cell anemia in Nigeria

Children with sickle cell anemia (SCA) have elevated cerebral blood velocity relative to healthy peers. The primary aim of this study was to evaluate the association between cerebral blood velocity, measured by transcranial Doppler (TCD) ultrasound, age, and gender with cognitive function in children with SCA in Nigeria. Eighty-three children (Mage = 9.10, SD = 1.90 years; 55% female) with SCA in Nigeria completed cognitive assessments and a TCD ultrasound. The association between TCD velocity and measures of perceptual reasoning (Raven's Progressive Matrices), working memory (WISC-IV Digit Span), and executive planning (Tower of London, TOL) were assessed. Results showed that elevated TCD velocity significantly predicted lower scores on TOL Time Violations and Total Problem-Solving Time when controlling for BMI, hemoglobin level, and parent education, suggesting that TCD velocity is related to the efficiency of executive function. Further, age was negatively related to children's performance on the Ravens Matrices and TOL Total Correct, and boys showed greater deficits on the TOL Total Correct relative to girls. Moderation analyses for gender showed that there was a conditional negative association between TCD velocity and Digit Span for boys, but not for girls. Findings suggest that children with SCA in Nigeria with elevated TCD velocity are at risk for deficits in efficiency of executive planning, and boys with elevated TCD velocity are particularly at increased risk for deficits in auditory working memory. Implications of this study are important for interventions to reduce cerebral blood velocity and the use of TCD in this population.

Predictive validity of developmental screening in young children with sickle cell disease: a longitudinal follow-up study

AIM

To assess the predictive validity of developmental screenings in children with sickle cell disease (SCD) for academic outcomes and stroke risk.

METHOD

Parent questionnaires and medical record data were collected for a cohort receiving developmental screenings between September 2004 and May 2008 as toddlers or early school age. Screening outcomes were dichotomized (positive, negative) by a priori criteria. Questionnaires assessed school and social functioning, services received, and quality of life. Medical record data assessed general SCD morbidity and stroke risk.

RESULTS

Forty-one toddlers (mean age 2y 5mo; 25 males, 16 females) and 49 early school-age children (mean age 6y 5mo; 26 males, 23 females) completed follow-up. The mean follow-up period was 8 years 6 months (range 6.1-10.8y). For toddlers, positive screenings for language delays predicted lower academic performance (p=0.023). For older children, positive screenings for cognitive delays predicted more frequent academic/attentional problems at school (p<0.001), grade retention (p=0.007), and lower academic performance (p=0.001). Positive screenings were associated with an earlier onset of school problems and lower quality of life. Positive screenings for language/cognitive delays predicted increased stroke risk (both p<0.05).

INTERPRETATION

Screening for language or cognitive development in young children with SCD predicts academic outcomes and stroke risk.

WHAT THIS PAPER ADDS

Developmental screening predicts academic outcomes in sickle cell disease. Children with concerning language/cognitive screenings have early-onset school difficulties. Developmental screenings may help predict cerebrovascular complications.

Silent cerebral infarct definitions and full-scale IQ loss in children with sickle cell anemia

OBJECTIVE

To evaluate whether application of the adult definition of silent cerebral infarct (SCI) (T2-weighted hyperintensity ≥5 mm with corresponding T1-weighted hypointensity on MRI) is associated with full-scale IQ (FSIQ) loss in children with sickle cell anemia (SCA), and if so, whether this loss is greater than that of the reference pediatric definition of SCI (T2-weighted hyperintensity ≥3 mm in children on MRI; change in FSIQ -5.2 points; p = 0.017; 95% confidence interval [CI] -9.48 to -0.93).

METHODS

Among children with SCA screened for SCI in the Silent Cerebral Infarct Transfusion trial, ages 5-14 years, a total of 150 participants (107 with SCIs and 43 without SCIs) were administered the Wechsler Abbreviated Scale of Intelligence. A multivariable linear regression was used to model FSIQ in this population, with varying definitions of SCI independently substituted for the SCI covariate.

RESULTS

The adult definition of SCI applied to 27% of the pediatric participants with SCIs and was not associated with a statistically significant change in FSIQ (unstandardized coefficient -3.9 points; p = 0.114; 95% CI -8.75 to 0.95), with predicted mean FSIQ of 92.1 and 96.0, respectively, for those with and without the adult definition of SCI.

CONCLUSIONS

The adult definition of SCI may be too restrictive and was not associated with significant FSIQ decline in children with SCA. Based on these findings, we find no utility in applying the adult definition of SCI to children with SCA and recommend maintaining the current pediatric definition of SCI in this population.

[Cerebral vasculopathy in children with sickle cell disease: Key issues and the latest data]

Cerebral vasculopathy is a common and severe complication of sickle cell disease in children. The pathophysiology consists of progressive damage to the basal intracranial arteries and cerebral microcirculation, while chronic anemia worsens exposure to cerebral hypoxia. It results in stroke and subclinical or poorly symptomatic ischemic lesions. Many clinical, biological, and radiological risk factors have been identified. The prevention strategy through systematic transcranial Doppler screening of large-vessel vasculopathy has revolutionized the management of this disease and has greatly decreased the risk of developing stroke. MRI-MRA is a complementary diagnostic tool for anatomical analysis of parenchymal and vascular lesions, which is used for chronic disease monitoring or in the context of an acute neurological event. New exploration opportunities are offered by submandibular Doppler sonography and indirect evaluation methods of cerebral oxygenation and perfusion. If chronic blood transfusion therapy is used to prevent the occurrence and recurrence of cerebral complications of sickle cell disease, only allogeneic hematopoietic stem cell transplantation can safely and definitively stop the transfusion program. It should therefore be proposed early, before irreversible cerebral or vascular lesions occur. Hydroxycarbamide treatment has recently emerged as a potential substitute for chronic transfusions for the maintenance of transcranial Doppler velocities, but only after an initial treatment by transfusions and provided there is close follow-up. In the long run, cerebral vascular damage can cause progressive cognitive impairment and disability, even in children without radiologically identified lesions, indicating the importance of systematic and repeated neuropsychological testing.

Anemia in children: prevalence, causes, diagnostic work-up, and long-term consequences

INTRODUCTION

Anemia in children is a major public health problem throughout the world. It is often multifactorial, iron deficiency being the most frequent etiology. Consequences are diverse and largely under evaluated. Areas covered: This paper briefly reviews the main causes and focus on the potential consequences of acute and chronic anemia in children. Expert commentary: Anemia in children should never be trivialized. Even if iron deficiency is frequently involved, other potentially life-threatening causes are possible and should be looked for. The exact contribution of anemia to child mortality and morbidity is difficult to assess because of overlapping comorbidities. Chronic anemia may impair growth, cardiac function and cognitive development in infants but other consequences are rather poorly described and should be explored more thoroughly.

Developmental Screening in Pediatric Sickle Cell Disease: Disease-Related Risk and Screening Outcomes in 4 Year Olds

OBJECTIVE

Studies of early child development in sickle cell disease (SCD) have found modest associations between disease-related risks and developmental status in infants and toddlers, but such associations are evident by early elementary school. We screened 4-year-old children with SCD using 2 screening strategies to assess if biomedical risk factors for neurologic disease are related to developmental screening outcomes at this intermediate age.

METHODS

Seventy-seven 4-year-old children with SCD (M = 4.5 yrs, SD = 0.3 yrs) completed developmental screenings at routine hematology visits using child testing (Fluharty Preschool Speech and Language Screenings Test, 2nd edition) and parent-report (Ages and Stages Questionnaire, 2nd edition) procedures. Genotype and other biomedical variables were coded from medical records.

RESULTS

Children with higher-risk SCD genotypes (n = 52) showed lower performance than children with lower-risk genotypes (n = 25) on a measure related to neurologic disease risk in older children (syntactic processing); genotype risk was also related to rates of positive screenings on parent-reported developmental milestones (52% positive screenings in high-risk genotypes vs 12% in low-risk genotypes). Screening outcomes were also related to transcranial Doppler ultrasound findings assessing cerebral blood flow.

CONCLUSION

Developmental screening at age 4 may be a useful target age for identifying preschoolers with sickle cell-related neurodevelopmental concerns. Parent report of developmental milestones and behavioral testing each may have a role in screening for children in need of follow-up services to address potential neurodevelopmental effects from SCD.

A pilot study of parent education intervention improves early childhood development among toddlers with sickle cell disease

BACKGROUND

Young children with sickle cell disease (SCD) are at risk for cognitive delay. In addition to biologic risk factors associated with SCD, environmental factors contribute to cognitive dysfunction within this cohort.

METHODS

We completed a single-arm, prospective cohort study. Children with SCD between the ages of 3 and 36 months and their caregivers were followed between October 2010 and December 2013. The aim was to describe the role of a home visitation model, the home environment, and socioeconomic status in the development of young children with SCD. Primary outcome measures were the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) and the Home Observation for Measurement of the Environment (HOME). We hypothesized that the home visitation model, Parents as Teachers^® (PAT), would encourage positive parent-child interactions and improve cognitive outcomes.

RESULTS

Thirty-five participants had at least two PAT visits and BSID-III assessments. Mean scores within all five subtests of the BSID-III improved between enrollment and exit, with significant changes within cognitive (P = 0.016) and expressive language (EL) domains (P = 0.002). Multivariate modeling found the HOME score associated with the exit results of the cognitive domain.

CONCLUSION

We report longitudinal results of the first home visitation program within the early childhood SCD population and show significant improvement in cognitive and EL development. Additionally, home environment was a significant predictor of cognitive development. Randomized controlled trials to test the impact of interventions targeting the home environment are warranted for this vulnerable population.

Prevalence of Developmental Delay and Contributing Factors Among Children With Sickle Cell Disease

BACKGROUND

Children with sickle cell disease (SCD) are at higher risk for deficits in cognition compared to the general population, even at young ages. Disease severity has been co-assessed in earlier studies, but the home environment has not. The purpose of the current study was to investigate the development of young children with SCD and secondarily, the impact of environmental and family factors.

METHODS

The current study is a baseline cross-sectional evaluation of a prospective, single-center cohort. Children with SCD between the ages of 1 and 42 months and their primary caregiver were included. Participants lived within 30 miles of the site and spoke English. Children underwent developmental evaluation using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Home visits were completed and screened using the Home Observation for Measurement of the Environment (HOME).

RESULTS

Over 3 years, 43 caregiver-child dyads consented and participated. Over 50% of children scored significantly below average on cognition and expressive language subscales. SCD severity was not associated with BSID-III scores. Socioeconomic status (SES) determined by the Diez-Roux method positively correlated (r = 0.401, P < 0.01) with the home environment. The HOME correlated (r = 0.360, P < 0.05) with the cognitive subscale on the BSID-III.

CONCLUSIONS

Given the high prevalence of developmental delay in this population, identifying modifiable factors to maximize developmental progress is essential. The home environment would be a targeted method for intervention. Future research is needed to identify the benefits of home-based intervention for this population.

Health-related Quality of Life in Infants With Sickle Cell Disease

Using historical cohorts of healthy, acutely ill, and chronically ill infants for comparison, we sought to determine whether infants with sickle cell disease (SCD) have impaired health-related quality of life (HRQL). We conducted a cross-sectional study at 2 sites: the Medical College of Wisconsin/Children's of Wisconsin and the University of Alabama School of Medicine/Children's of Alabama. Parents of 90 infants with SCD completed the PedsQL Infant Module corresponding to their infant's age (1 to 12 mo or 13 to 24 mo) during a regular clinic visit. At 1 to 12 months, infants with SCD displayed lower Physical HRQL than healthy infants, but better HRQL than chronically ill infants. By 13 to 24 months, infants with SCD had worse HRQL in all areas than healthy infants and worse Physical and Total HRQL than acutely ill infants. Compared with chronically ill infants in this age group, infants with SCD had similar Physical HRQL and better Psychosocial and Total HRQL. By 13 to 24 months, a greater proportion of infants with SCD had impaired Physical and Total HRQL compared with infants aged 1 to 12 months. All differences were significant at the (P<0.05) level. Impaired HRQL can be detected in infants with SCD.

Cerebrovascular function and cognition in childhood: a systematic review of transcranial Doppler studies

Background

The contribution of cerebrovascular function to cognitive performance is gaining increased attention. Transcranial doppler (TCD) is portable, reliable, inexpensive and extremely well tolerated by young and clinical samples. It enables measurement of blood flow velocity in major cerebral arteries at rest and during cognitive tasks.

Methods

We systematically reviewed evidence for associations between cognitive performance and cerebrovascular function in children (0-18 years), as measured using TCD. A total of 2778 articles were retrieved from PsychInfo, Pubmed, and EMBASE searches and 25 relevant articles were identified.

Results

Most studies investigated clinical groups, where decreased blood flow velocities in infants were associated with poor neurological functioning, and increased blood flow velocities in children with Sickle cell disease were typically associated with cognitive impairment and lower intelligence. Studies were also identified assessing autistic behaviour, mental retardation and sleep disordered breathing. In healthy children, the majority of studies reported cognitive processing produced lateralised changes in blood flow velocities however these physiological responses did not appear to correlate with behavioural cognitive performance.

Conclusion

Poor cognitive performance appears to be associated with decreased blood flow velocities in premature infants, and increased velocities in Sickle cell disease children using TCD methods. However knowledge in healthy samples is relatively limited. The technique is well tolerated by children, is portable and inexpensive. It therefore stands to make a valuable contribution to knowledge regarding the underlying functional biology of cognitive performance in childhood.

Development and feasibility of a home-based education model for families of children with sickle cell disease

BACKGROUND

Children with sickle cell disease (SCD) commonly have cognitive deficits, even among toddlers. Much medical literature emphasizes disease-based factors to account for these deficits. However, the social environment plays a large role in child development. To address the specific needs of early childhood, a monthly hospital-based education program was initiated to educate parents about child development. Education sessions were poorly attended (20-25%) and deemed unsuccessful. This study describes the development and implementation of a home-based education service to teach parents about SCD, developmental milestones and positive parenting techniques.

METHODS

This was a prospective, single-arm intervention to study the feasibility of a home-based caregiver education program for families with infants and toddlers with SCD. Parents of children aged 0-3 years with SCD from one Midwestern hospital were approached to participate in a home-based program. The program followed the Born to Learn™ curriculum provided through the Parents as Teachers™ National Center. Reminder calls or texts were provided the day before each visit. Results of the first twenty-six months of the program are presented.

RESULTS

A total of 62% (56 of 91) of families approached agreed to participate; all were African American. The majority of caregivers were single mothers with a high school education or less and whose children had Medicaid for health coverage. The phenotypes of SCD represented in this sample were similar to those in the general SCD population. Over 26 months, 39 families received at least one home visit. Parents of infants (younger than 8 months) were more likely to participate in the home-based education program than parents of older children, (Fisher's exact test, p < .001).

CONCLUSIONS

For participating families, home-based visits were a feasible method for reinforcing clinic education. About 43% of eligible families participated in the education, a two-fold increase in the poor attendance (20%) for a previous hospital-based program. A home visitation program for parents of infants with SCD could offer an effective approach to helping these children overcome adverse environmental conditions that are compounded by the complexities of a chronic health condition.

Parent education and biologic factors influence on cognition in sickle cell anemia

Children with sickle cell anemia have a high prevalence of silent cerebral infarcts (SCIs) that are associated with decreased full-scale intelligence quotient (FSIQ). While the educational attainment of parents is a known strong predictor of the cognitive development of children in general, the role of parental education in sickle cell anemia along with other factors that adversely affect cognitive function (anemia, cerebral infarcts) is not known. We tested the hypothesis that both the presence of SCI and parental education would impact FSIQ in children with sickle cell anemia. A multicenter, cross-sectional study was conducted in 19 US sites of the Silent Infarct Transfusion Trial among children with sickle cell anemia, age 5-15 years. All were screened for SCIs. Participants with and without SCI were administered the Wechsler Abbreviated Scale of Intelligence. A total of 150 participants (107 with and 43 without SCIs) were included in the analysis. In a multivariable linear regression model for FSIQ, the absence of college education for the head of household was associated with a decrease of 6.2 points (P = 0.005); presence of SCI with a 5.2 point decrease (P = 0.017); each $1000 of family income per capita with a 0.33 point increase (P = 0.023); each increase of 1 year in age with a 0.96 point decrease (P = 0.023); and each 1% (absolute) decrease in hemoglobin oxygen saturation with 0.75 point decrease (P = 0.030). In conclusion, FSIQ in children with sickle cell anemia is best accounted for by a multivariate model that includes both biologic and socioenvironmental factors.

Precursors of executive function in infants with sickle cell anemia

Executive dysfunction occurs in sickle cell anemia, but there are few early data. Infants with sickle cell anemia (n = 14) and controls (n = 14) performed the "A-not-B" and Object Retrieval search tasks, measuring precursors of executive function at 9 and 12 months. Significant group differences were not found. However, for the A-not-B task, 7 of 11 sickle cell anemia infants scored in the lower 2 performance categories at 9 months, but only 1 at 12 months (P = .024); controls obtained scores at 12 months that were statistically comparable to the scores they had already obtained at 9 months. On the Object Retrieval task, 9- and 12-month controls showed comparable scores, whereas infants with sickle cell anemia continued to improve (P = .027); at 9 months, those with lower hemoglobin oxygen saturation passed fewer trials (R s = 0.670, P = .024) and took longer to obtain the toy (R s = -0.664, P = .013). Subtle delays in acquiring developmental skills may underlie abnormal executive function in childhood.

Neurodevelopmental deficits among infants and toddlers with sickle cell disease

OBJECTIVE

Neurodevelopmental deficits are among the serious complications of sickle cell disease (SCD). However, few studies have prospectively evaluated neurodevelopmental deficits in very young children with SCD. We analyzed baseline neurodevelopmental data from a cohort of 80 infants and toddlers with SCD to identify primary disease-related events and sociodemographic risk factors associated with early developmental delay.

METHODS

This is an analysis of baseline date of a 4-year mixed, cross-sectional/longitudinal study. Full-term children at age 3.5 years or younger with SCD (any genotype) were eligible. Neurodevelopmental evaluations (Bayley II) were conducted at ages 9, 15, 21, 30, and 40 months. Demographics, hematologic variables, and medical events were obtained.

RESULTS

Significant neurodevelopmental deficits were evident: 17.5% scoring >2SD below the mean on Bayley Mental Index or Motor Index. Odds ratio of significant developmental delay was >9 times more likely among those who had experienced vaso-occlusive pain episodes, after controlling for socioeconomic status (SES), gender, pneumonia/acute chest syndrome, and hemoglobin concentration. Male gender was also a risk factor for developmental delay.

CONCLUSIONS

Early cognitive and motor delays were present in young children with SCD, with higher prevalence among those who had experienced pain crises. Increased vulnerability of male gender is consistent with other at-risk populations but has not been previously addressed in SCD research. Furthermore, these delays are not sufficiently explained by lower SES. Significant developmental delay in children with SCD may go unrecognized by primary care practices, medical specialty clinics, or parents. The importance of routine neurodevelopmental assessment for children with chronic medical conditions is clear.

Intellectual function evaluation of first generation immigrant children with sickle cell disease: the role of language and sociodemographic factors

Background

Sickle Cell Disease (SCD) is the most common genetic disease worldwide. Neurological events are among the most worrisome clinical complications of SCD and are frequently accompanied by cognitive impairment. Intellectual function in SCD may vary according to genetic and environmental factors. Immigrant children with SCD are increasing at a global level and display specific health care needs. The aim of our multicenter study was to describe the intellectual function of first generation African immigrants with SCD and the influence of sociodemographic factors on its characteristics.

Methods

The Wechsler Intelligence Scales were administered to evaluate broad intellectual functions in children with SCD and in age-matched healthy siblings. Patients’ clinical, socio-demographic, Magnetic Resonance Imaging (MRI) and Angiography (MRA) data were correlated to intellectual function scores.

Results

68 children, mean age 8.95 years were evaluated. 72% spoke three languages, 21% two. FSIQ was <75 in 25% of the children. Mean VIQ was lower than PIQ in 75%. Mean verbal subtest scores were lower than performance scores. Female gender, number of languages spoken at home and mother’s employment were associated with single subtest performances (p < 0.05). MRA was abnormal in 73.4% and MRI in 35.9%. No significant correlation was established between silent lesions and intellectual function, even if patients with lesions performed worse. Fifteen siblings performed better than patients on cognitive domains, including language (p < 0.05).

Conclusions

Immigrant bilingual children with SCD seem to display a rate of cognitive impairment similar to their monolingual counterparts but a more pronounced and precocious onset of language difficulties. Adjunctive tests need to be considered in this group of patients to better define their specific deficits.

Silent cerebral infarcts: a review on a prevalent and progressive cause of neurologic injury in sickle cell anemia

Silent cerebral infarct (SCI) is the most common form of neurologic disease in children with sickle cell anemia (SCA). SCI is defined as abnormal magnetic resonance imaging (MRI) of the brain in the setting of a normal neurologic examination without a history or physical findings associated with an overt stroke. SCI occurs in 27% of this population before their sixth, and 37% by their 14th birthdays. In adults with SCA, the clinical history of SCI is poorly defined, although recent evidence suggests that they too may have ongoing risk of progressive injury. Risk factors for SCI include male sex, lower baseline hemoglobin concentration, higher baseline systolic blood pressure, and previous seizures. Specific morbidity associated with SCI includes a decrement in general intellectual abilities, poor academic achievement, progression to overt stroke, and progressive SCI. In addition, children with previous stroke continue to have both overt strokes and new SCI despite receiving regular blood transfusion therapy for secondary stroke prevention. Studies that only include overt stroke as a measure of CNS injury significantly underestimate the total cerebral injury burden in this population. In this review, we describe the epidemiology, natural history, morbidity, medical management, and potential therapeutic options for SCI in SCA.

Neurocognitive screening with the Brigance preschool screen-II in 3-year-old children with sickle cell disease

BACKGROUND

Neurocognitive deficits have been described in school age children with sickle cell disease (SCD), even in the absence of stroke or silent infarcts. However, the age of onset and factors contributing to this problem have not been well studied. We hypothesized that in children with SCD the failure rate with Brigance screening would be higher than in the normal population.

METHODS

We reviewed retrospectively the Brigance Preschool Screen-II test results in 3-year-old children with SCD. Findings were correlated with hemoglobinopathy genotype, hemoglobin level, transcranial Doppler ultrasound (TCD) velocities, and treatment with hydroxyurea, as well as with psychosocial factors.

RESULTS

Eighty-eight children with SCD followed by the St. Jude Sickle Cell Center (mean age 3.5 years) had neurocognitive screening during their regular clinic visits. Forty-four (50%) children had scores below the normal cut-off value for their age (twice the national failure rate of 25%). Failures were associated with less parental education (P = 0.005 for maternal and P = 0.03 for paternal education levels) and with speech deficits (P = 0.01), but were not associated with sickle cell genotype or hemoglobin concentration.

CONCLUSION

These preliminary data suggest that psychosocial factors may have more profound effects on early childhood development than disease-related factors in this group of young sickle cell patients. A larger prospective study with appropriate controls is warranted to validate these findings, which have implications for the etiology and prevention of neurocognitive decline in children with SCD.

Transcranial doppler ultrasonography (TCD) in infants with sickle cell anemia: baseline data from the BABY HUG trial

BACKGROUND

Transcranial Doppler ultrasonography (TCD) is used to predict stroke risk in children with sickle cell anemia (SCA), but has not been adequately studied in children under age 2 years.

PROCEDURE

TCD was performed on infants with SCA enrolled in the BABY HUG trial. Subjects were 7-17 months of age (mean 12.6 months). TCD examinations were successfully performed in 94% of subjects (n = 192).

RESULTS

No patient had an abnormal TCD as defined in the older child (time averaged maximum mean TAMM velocity > or =200 cm/sec) and only four subjects (2%) had velocities in the conditional range (170-199 cm/sec). TCD velocities were inversely related to hemoglobin (Hb) concentration and directly related to increasing age.

CONCLUSION

Determination of whether the TCD values in this very young cohort of infants with SCA can be used to predict stroke risk later in childhood will require analysis of exit TCD's and long-term follow-up, which is ongoing (ClinicalTrials.gov number, NCT00006400).

Neuroimaging in assessment of risk of stroke in children with sickle cell disease

PURPOSE

Stroke and subclinical "silent infarcts" are major causes of morbidity in children with Sickle Cell Disease (SCD). Ischemic strokes are more common in younger children while hemorrhagic strokes are more frequent in adults. The goal of neuroimaging in acute stroke is to document whether the stroke is ischemic or hemorrhagic, to assess the extent of parenchymal abnormalities and to determine the presence of other cerebrovascular lesions. Computed Tomography (CT) is the primary modality for the assessment of acute stroke patients because of its 24/7 availability and ability to exclude hemorrhagic causes. Magnetic resonance imaging (MRI) and MR angiography (MRA) are recommended to determine precisely extent of infarction and detect cerebrovascular abnormalities. The goal of neuroimaging in patients with hemorrhagic stroke is to identify an arteriovenous malformation or aneurysm(s) amenable to surgery or catheter intervention.The risk of first stroke is very high in asymptomatic children with intracranial arterial mean velocities over 200 cm/s on transcranial Doppler (TCD) examination. The risk can be substantially reduced if chronic blood transfusions are timely implemented. Large cerebral vessel disease detected by TCD can be confirmed or excluded by MRI/MRA. Those with evidence of parenchymal and/or cerebrovascular lesions should be followed by preventive therapy. In patients with neurologic symptoms and negative MRI/MRA findings Positron Emission Tomography or single photon emission CT is recommended. There are no specific neuroimaging findings that suggest that blood transfusions can be safely halted in children with SCD.

MRI abnormalities of the brain in one-year-old children with sickle cell anemia

BACKGROUND

Sickle cell anemia (SCA) frequently results in damage to the central nervous system (CNS), but the age of onset of these effects is uncertain. We performed MRI examinations of the brain in infants with SCA, who were evaluated as part of the multicenter randomized double-blinded Pediatric Hydroxyurea Phase III Clinical Trial (BABY HUG).

METHODS

Determination of eligibility for enrollment in the trial originally required baseline MRI and magnetic resonance angiography (MRA) of the brain. A standardized imaging protocol was utilized across eight clinical centers. MRI/MRA exams were reviewed by a panel of three neurology/neuroradiology readers and interpretations reported to the coordinating center. Results were correlated with patient age, gender, history, WBC count, platelet count, hemoglobin (Hb), HbF level, score on the Bayley Scales of Infant Development, and velocity on transcranial Doppler ultrasonography (TCD).

RESULTS

Twenty-three subjects with HbSS were examined at average age 13.7 months (range 10-18 months); 13 were male. Three (13%, CI: 3-34%) had silent infarcts on MRI, two in the right frontal area and one bilaterally. None had MRA abnormalities. The lesions were correlated with increased right-sided TCD velocity and low HbF level, but not with age, history, Hb level, developmental score, or left-sided velocity.

CONCLUSIONS

Silent brain infarcts occur in a small but significant number of infants with SCA as early as a year of age. This finding indicates a need for thorough evaluation of the CNS very early in life in children with SCA in order to develop timely intervention strategies.

A simple index using age, hemoglobin, and aspartate transaminase predicts increased intracerebral blood velocity as measured by transcranial Doppler scanning in children with sickle cell anemia

OBJECTIVE

Increased intracerebral blood velocity measured by transcranial Doppler scanning identifies children with sickle cell anemia who are at increased risk of stroke. We have tried to develop an index based on routine clinical measurements that also predicts increased intracerebral blood flow.

METHOD

Routinely collected clinical and laboratory data were correlated with transcranial Doppler measurements on children with sickle cell anemia seen in a single institution in 2006. The index produced was validated on a second independent data set from children with sickle cell anemia.

RESULTS

The time-averaged mean of the maximum velocity in centimeters per second in the middle cerebral artery circulation correlated significantly with age, hemoglobin, lactate dehydrogenase, and aspartate transaminase levels, white blood cell count, and creatinine level. On multiple regression, hemoglobin and aspartate transaminase levels maintained their significance, whereas age had borderline significance, and an index was developed linked to a time-averaged mean of the maximum velocity of 220 - (8 x hemoglobin) - (1.4 x age) + (0.4 x aspartate transaminase). This detected a time-averaged mean of the maximum velocity of >170 cm/second with 100% sensitivity and 58% specificity. The index was validated on the second data set and again showed 100% sensitivity with 73% specificity.

CONCLUSION

This simple index has the potential to identify children who are at higher risk of cerebrovascular disease to allow them to be prioritized for transcranial Doppler scanning and other intracerebral imaging.

Neurodevelopmental screening in toddlers and early preschoolers with sickle cell disease

Sickle cell disease is associated with an elevated risk for neurologic complications beginning in early childhood. Detecting higher-risk cases with developmental screening instruments may be a cost-effective method for identifying young children in need of more frequent or intensive assessment. We evaluated the validity of the Denver II test as a tool to detect lower levels of developmental attainment and their association with neurologic risk in 50 young children with sickle cell disease. Children with suspect Denver II outcomes showed lower scores for functional communication skills, had lower hematocrit percentage, higher mean velocities on transcranial Doppler ultrasound imaging, and were more likely to have had preterm birth. Validity of age equivalencies from specific Denver II areas was demonstrated for Language and Fine Motor scores, suggesting the instrument could be used to index children's developmental levels in these domains. The Denver II may be a useful behavioral screening tool for neurodevelopmental risk in sickle cell disease.

Neuropsychological assessment, neuroimaging, and neuropsychiatric evaluation in pediatric and adult patients with sickle cell disease (SCD)

Traditionally, neuropsychological deficits due to Sickle Cell Disease (SCD) have been understudied in adults. We have begun to suspect, however, that symptomatic and asymptomatic Cerebrovascular Events (CVE) may account for an alarming number of deficits in this population. In the current brief review, we critically evaluated the pediatric and adult literatures on the neurocognitive effects of SCD. We highlighted the studies that have been published on this topic and posit that early detection of CVE via neurocognitive testing, neuropsychiatric evaluations, and neuroimaging may significantly reduce adult cognitive and functional morbidities.

Neurobehavioral impact of sickle cell disease in early childhood

The physical effects of sickle cell disease (SCD) begin in infancy or early childhood, yet most behavioral studies have focused on school-age children. We evaluated the impact of higher versus lower neurologic risk on language, motor abilities, executive functions, and temperament in toddlers and early preschoolers with SCD. Thirty-nine children with higher risk SCD were compared to 22 children with lower risk SCD. Language and motor abilities were lower in older compared with younger children but were unrelated to sickle cell subgroups. Executive functions, particularly working memory, were poorer in children with higher risk SCD regardless of age. Parent-reported activity level was also lower in children with higher risk. Specific behavioral influences of SCD are evident early in childhood and include working memory decrements. Executive function deficits in SCD can emerge early in life and may be an important context for other areas of cognitive and behavioral development.

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.

Therapy Insight: stroke risk and its management in patients with sickle cell disease

Children with sickle cell disease, a chronic hemolytic anemia, present with a wide variety of neurological syndromes, including ischemic and hemorrhagic stroke, transient ischemic attacks, 'soft neurological signs', seizures, headache, coma, visual loss, altered mental status, cognitive difficulties, and covert or 'silent' infarction. Those with ischemic stroke usually have stenosis or occlusion of the distal internal carotid and proximal middle cerebral arteries. Indefinite transfusion prevents recurrence in most patients who have had a stroke, and can prevent first stroke in those with high transcranial Doppler velocities. High white cell count, low hemoglobin and oxyhemoglobin desaturation predict neurological complications. Other risk factors for overt ischemic stroke include hypertension, previous transient ischemic attack, covert infarction and chest crisis. For hemorrhagic stroke, aneurysms are common in adults but not children, who often present with hypertension after transfusion or corticosteroids. Seizures are particularly common in patients with cerebrovascular disease and covert infarction; the latter is also associated with hyposplenism and infrequent pain. Factors associated with cognitive difficulties include thrombocytosis, infarction, large-vessel disease, and perfusion abnormality on neuroimaging. As well as investigating the role of genes and the possibility that hydroxyurea or blood pressure control reduce neurological complications, we should explore the modifiable effects of poor nutrition, chronic infection, hemolysis and oxyhemoglobin desaturation on stroke risk.

Sickle cell disease as a neurodevelopmental disorder

Sickle cell disease (SCD) is a blood disorder; however, the central nervous system (CNS) is one of the organs frequently affected by the disease. Brain disease can begin early in life and often leads to neurocognitive dysfunction. Approximately one-fourth to one-third of children with SCD have some form of CNS effects from the disease, which typically manifest as deficits in specific cognitive domains and academic difficulties. We discuss SCD as a neurodevelopmental disorder by reviewing the mechanisms of neurological morbidity in SCD, the timing of these mechanisms, the types of cognitive and behavioral morbidity that is typical, and the interaction of social-environmental context with disease processes. The impact of the disease on families shares many features similar to other neurodevelopmental disorders; however, social-environmental factors related to low socioeconomic status, worry and concerns about social stigma, and recurrent, unpredictable medical complications can be sources of relatively higher stress in SCD. Greater public awareness of the neurocognitive effects of SCD and their impact on child outcomes is a critical step toward improved treatment, adaptation to illness, and quality of life.

Increased cerebral blood flow velocity in children with mild sleep-disordered breathing: a possible association with abnormal neuropsychological function

OBJECTIVE

Sleep-disordered breathing describes a spectrum of upper airway obstruction in sleep from simple primary snoring, estimated to affect 10% of preschool children, to the syndrome of obstructive sleep apnea. Emerging evidence has challenged previous assumptions that primary snoring is benign. A recent report identified reduced attention and higher levels of social problems and anxiety/depressive symptoms in snoring children compared with controls. Uncertainty persists regarding clinical thresholds for medical or surgical intervention in sleep-disordered breathing, underlining the need to better understand the pathophysiology of this condition. Adults with sleep-disordered breathing have an increased risk of cerebrovascular disease independent of atherosclerotic risk factors. There has been little focus on cerebrovascular function in children with sleep-disordered breathing, although this would seem an important line of investigation, because studies have identified abnormalities of the systemic vasculature. Raised cerebral blood flow velocities on transcranial Doppler, compatible with raised blood flow and/or vascular narrowing, are associated with neuropsychological deficits in children with sickle cell disease, a condition in which sleep-disordered breathing is common. We hypothesized that there would be cerebral blood flow velocity differences in sleep-disordered breathing children without sickle cell disease that might contribute to the association with neuropsychological deficits.

DESIGN

Thirty-one snoring children aged 3 to 7 years were recruited from adenotonsillectomy waiting lists, and 17 control children were identified through a local Sunday school or as siblings of cases. Children with craniofacial abnormalities, neuromuscular disorders, moderate or severe learning disabilities, chronic respiratory/cardiac conditions, or allergic rhinitis were excluded. Severity of sleep-disordered breathing in snoring children was categorized by attended polysomnography. Weight, height, and head circumference were measured in all of the children. BMI and occipitofrontal circumference z scores were computed. Resting systolic and diastolic blood pressure were obtained. Both sleep-disordered breathing children and the age- and BMI-similar controls were assessed using the Behavior Rating Inventory of Executive Function (BRIEF), Neuropsychological Test Battery for Children (NEPSY) visual attention and visuomotor integration, and IQ assessment (Wechsler Preschool and Primary Scale of Intelligence Version III). Transcranial Doppler was performed using a TL2-64b 2-MHz pulsed Doppler device between 2 pm and 7 pm in all of the patients and the majority of controls while awake. Time-averaged mean of the maximal cerebral blood flow velocities was measured in the left and right middle cerebral artery and the higher used for analysis.

RESULTS

Twenty-one snoring children had an apnea/hypopnea index <5, consistent with mild sleep-disordered breathing below the conventional threshold for surgical intervention. Compared with 17 nonsnoring controls, these children had significantly raised middle cerebral artery blood flow velocities. There was no correlation between cerebral blood flow velocities and BMI or systolic or diastolic blood pressure indices. Exploratory analyses did not reveal any significant associations with apnea/hypopnea index, apnea index, hypopnea index, mean pulse oxygen saturation, lowest pulse oxygen saturation, accumulated time at pulse oxygen saturation <90%, or respiratory arousals when examined in separate bivariate correlations or in aggregate when entered simultaneously. Similarly, there was no significant association between cerebral blood flow velocities and parental estimation of child's exposure to sleep-disordered breathing. However, it is important to note that whereas the sleep-disordered breathing group did not exhibit significant hypoxia at the time of study, it was unclear to what extent this may have been a feature of their sleep-disordered breathing in the past. IQ measures were in the average range and comparable between groups. Measures of processing speed and visual attention were significantly lower in sleep-disordered breathing children compared with controls, although within the average range. There were similar group differences in parental-reported executive function behavior. Although there were no direct correlations, adjusting for cerebral blood flow velocities eliminated significant group differences between processing speed and visual attention and decreased the significance of differences in Behavior Rating Inventory of Executive Function scores, suggesting that cerebral hemodynamic factors contribute to the relationship between mild sleep-disordered breathing and these outcome measures.

CONCLUSIONS

Cerebral blood flow velocities measured by noninvasive transcranial Doppler provide evidence for increased cerebral blood flow and/or vascular narrowing in childhood sleep-disordered breathing; the relationship with neuropsychological deficits requires further exploration. A number of physiologic changes might alter cerebral blood flow and/or vessel diameter and, therefore, affect cerebral blood flow velocities. We were able to explore potential confounding influences of obesity and hypertension, neither of which explained our findings. Second, although cerebral blood flow velocities increase with increasing partial pressure of carbon dioxide and hypoxia, it is unlikely that the observed differences could be accounted for by arterial blood gas tensions, because all of the children in the study were healthy, with no cardiorespiratory disease, other than sleep-disordered breathing in the snoring group. Although arterial partial pressure of oxygen and partial pressure of carbon dioxide were not monitored during cerebral blood flow velocity measurement, assessment was undertaken during the afternoon/early evening when the child was awake, and all of the sleep-disordered breathing children had normal resting oxyhemoglobin saturation at the outset of their subsequent sleep studies that day. Finally, there is an inverse linear relationship between cerebral blood flow and hematocrit in adults, and it is known that iron-deficient erythropoiesis is associated with chronic infection, such as recurrent tonsillitis, a clinical feature of many of the snoring children in the study. Preoperative full blood counts were not performed routinely in these children, and, therefore, it was not possible to exclude anemia as a cause of increased cerebral blood flow velocity in the sleep-disordered breathing group. However, hemoglobin levels were obtained in 4 children, 2 of whom had borderline low levels (10.9 and 10.2 g/dL). Although there was no apparent relationship with cerebral blood flow velocity in these children (cerebral blood flow velocity values of 131 and 130 cm/second compared with 130 and 137 cm/second in the 2 children with normal hemoglobin levels), this requires verification. It is of particular interest that our data suggest a relationship among snoring, increased cerebral blood flow velocities and indices of cognition (processing speed and visual attention) and perhaps behavioral (Behavior Rating Inventory of Executive Function) function. This finding is preliminary: a causal relationship is not established, and the physiologic mechanisms underlying such a relationship are not clear. Prospective studies that quantify cumulative exposure to the physiologic consequences of sleep-disordered breathing, such as hypoxia, would be informative.

Hypoxic adaptation during development: relation to pattern of neurological presentation and cognitive disability

Children with acute hypoxic-ischaemic events (e.g. stroke) and chronic neurological conditions associated with hypoxia frequently present to paediatric neurologists. Failure to adapt to hypoxia may be a common pathophysiological pathway linking a number of other conditions of childhood with cognitive deficit. There is evidence that congenital cardiac disease, asthma and sleep disordered breathing, for example, are associated with cognitive deficit, but little is known about the mechanism and whether there is any structural change. This review describes what is known about how the brain reacts and adapts to hypoxia, focusing on epilepsy and sickle cell disease (SCD). We prospectively recorded overnight oxyhaemoglobin saturation (SpO2) in 18 children with intractable epilepsy, six of whom were currently or recently in minor status (MS). Children with MS were more likely to have an abnormal sleep study defined as either mean baseline SpO2 <94% or >4 dips of >4% in SpO2/hour (p = .04). In our series of prospectively followed patients with SCD who subsequently developed acute neurological symptoms and signs, mean overnight SpO2 was lower in those with cerebrovascular disease on magnetic resonance angiography (Mann-Whitney, p = .01). Acute, intermittent and chronic hypoxia may have detrimental effects on the brain, the clinical manifestations perhaps depending on rapidity of presentation and prior exposure.