Sickle cell disease: the neurological complications

Pharmacology in childhood arterial ischemic stroke

In recent years, there has been increasing recognition of the impact of childhood stroke and interest in the role of drugs in the acute, chronic, and prophylactic management of this condition. Most treatment strategies are based on studies in adults with stroke, and the relative infrequency of stroke and the heterogeneity of etiologies in childhood compared with adults present significant challenges in study design for childhood stroke studies. The presence of thrombophilia has been associated with stroke in children, strengthening the concept that antithrombotic, antiplatelet, and even thrombolytic agents have a role in stroke treatment and prevention. There are several potential roles for drugs in the treatment of childhood stroke including hyperacute therapy, antithrombotic medication, antiplatelet medication, and disease-specific medications. Herein, we review the use and rationale of these medications in childhood arterial ischemic stroke.

Diagnosis and management of pediatric arterial ischemic stroke

Pediatric stroke is among the top 10 causes of death in children and an important cause of chronic morbidity, with an incidence of 3.3/100,000 children/year. Risk factors associated with stroke in children include cardiac diseases, hematologic and vascular disorders, and infection. Clinical presentation varies depending on age, underlying cause, and stroke location. Antithrombotics and anticoagulants are used in the treatment of pediatric stroke; however, there are no established guidelines for the use of these agents in children. In this article we review the cause, pathophysiology, clinical presentation, diagnosis, acute management, secondary prevention, and outcome of children with stroke. The approach to patients with sickle cell disease and Moyamoya disease is also discussed. Up to date studies to determine the optimal acute treatment of childhood stroke and secondary prevention and risk factor modification are critically needed.

Cerebral blood flow velocity and language functioning in pediatric sickle cell disease

We investigated the association of increased cerebral blood flow velocity with specific language abilities in children with sickle cell disease (SCD). Thirty-nine children ages 5 to 8 years old with high-risk genotypes of SCD underwent cognitive testing, which included tests of language skills, visual motor skills, and attention/working memory as part of a routine hematology health-maintenance visit. Transcranial Doppler (TCD) velocities were obtained from review of medical records, with the velocities that were in closest temporal proximity to the cognitive assessment used in the analysis. TCD velocities predicted scores on tests of syntactical skills, even when controlling for anemia severity. Semantic and phonological ability and other cognitive skills were not strongly related to TCD velocities. Elevated blood flow velocities in children with high-risk SCD may contribute to a specific language impairment or to a broader dysfunction of short-term and/or working memory. This study underscores the need for clinicians to monitor language skills of children with SCD who have elevated TCD velocities, as these cognitive abilities might be particularly sensitive to cerebrovascular disruption related to their disease.

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).

Pathological basis of symptoms and crises in sickle cell disorder: implications for counseling and psychotherapy

Sickle Cell Disorder (SCD) is a congenital hemoglobinopathy. There is little in literature regarding the psychological variables affecting individuals living with SCD and all of the significant people around them. There are also limited numbers of trained clinical psychologists and genetic counselors to cater for the psychotherapeutic needs of individuals living with SCD. Even among those who have been trained, only a few might have fully grasped the complexities of the disease pathology.Early understanding of its pathological nature, sources, types, complications, pathophysiological basis, and clinical severity of symptoms among clinical psychologists, genetic counselors and psychotherapists, as well as general medical practitioners, could guide them in providing holistic care for dealing with and reducing pain among individuals living with SCD. It could allow risk-based counseling for families and individuals. It could also justify the early use of disease-modifying or curative interventions, such as hydroxyurea (HU), chronic transfusions (CTs), or stem-cell transplantation (SCT) by general medical practitioners. Hence, the need for this paper on the pathophysiology of SCD.

The Clinical Application of Ozonetherapy

The reader may be eager to examine in which diseases ozonetherapy can be proficiently used and she/he will be amazed by the versatility of this complementary approach (Table 9 1). The fact that the medical applications are numerous exposes the ozonetherapist to medical derision because superficial observers or sarcastic sceptics consider ozonetherapy as the modern panacea. This seems so because ozone, like oxygen, is a molecule able to act simultaneously on several blood components with different functions but, as we shall discuss, ozonetherapy is not a panacea. The ozone messengers ROS and LOPs can act either locally or systemically in practically all cells of an organism. In contrast to the dogma that “ozone is always toxic”, three decades of clinical experience, although mostly acquired in private clinics in millions of patients, have shown that ozone can act as a disinfectant, an oxygen donor, an immunomodulator, a paradoxical inducer of antioxidant enzymes, a metabolic enhancer, an inducer of endothelial nitric oxide synthase and possibly an activator of stem cells with consequent neovascularization and tissue reconstruction.

Childhood stroke in Eastern Province, KSA: pattern, risk factors, diagnosis and outcome

BACKGROUND AND PURPOSE

Stroke has been increasingly recognized in children in recent years, but diagnosis and management can be difficult because of the diversity of underlying risk factors, atypical presentation and the absence of a uniform treatment approach. The aim of this study was to examine risk factors, clinical presentation, imaging findings and outcomes of paediatric stroke in Eastern Province, Kingdom of Saudi Arabia (KSA).

SUBJECTS AND METHODS

We evaluated 25 patients (11 boys and 14 girls) using computerized tomography scan of the brain, magnetic resonance (MR) imaging and MR angiography. Cardiac assessment, haematological tests, immunological tests, infection and metabolic screening were also performed in the patients. After discharge, the patients were monitored regularly in the neurology clinic to detect their outcomes.

RESULTS

A total of 76% of the patients presented with ischaemic stroke, while the remaining 24% had haemorrhagic stroke. Sickle cell disease (SCD) was the commonest risk factor for stroke (36%) followed by non determinate causes (20%). Seizure was the commonest clinical presentation (54%) followed by haemiplegia (31%) and decreased level of consciousness (30%). Recurrence occurred in SCD patients (80%) and patients with moyamoya disease (20%). Regarding the outcome, long-term deficit was the commonest (44%), while short-term deficit and death were equal (28% each).

CONCLUSION

Our study in Eastern Province, KSA, showed agreement with other studies regarding risk factors, clinical presentation, imaging features and outcomes of stroke in children, yet with some points of differences, which are as follows: (1) SCD is the commonest risk factor in our study population, while in Chinese study it was not, (2) The percentage of cardiac disorders as a risk factor in this study was less than that in the European and American studies, and (3) there was relative discrepancy regarding predictors of outcome.

Hemodynamic etiology of elevated flow velocity and stroke in sickle-cell disease

Elevation of blood flow velocity in the large cerebral vessels is known to be of substantial pathophysiologic and prognostic significance in sickle-cell disease (SCD). Its precise cause is not established, but the two obvious proximal mechanisms are obstructive vascular stenosis and hemodynamic dilatation. Here we revisit this distinction by analyzing cerebrovascular reserve capacity. Forty-two patients with SCD underwent measurements of global cerebral blood flow in grey matter by the 133Xe inhalation method during normocapnia and hypercapnia to quantify cerebrovascular reactivity. Cerebral blood flow was significantly higher in SCD patients (120+/-31 ml/100 g/min) than in controls (76+/-20 ml/100 g/min). Reactivity was significantly lower in SCD patients (1.06+/-1.92 versus 2.16+/-1.15%/mm Hg). Stepwise multiple regressions within the SCD sample determined that normocapnic cerebral blood flow was largely predicted by hematocrit (r=-0.59; P<0.0001), whereas hypercapnic reactivity was only predicted by normocapnic flow across all subjects (r=-0.52; P<0.0001). None of the controls, but 24% of the SCD patients showed 'steal' (negative reactivity, chi2=6.05; P<0.02). This impairment of vasodilatory capacity, occurring at perfusion levels above 150 ml/100 g/min, may reflect intrinsic limitations of the human cerebrovascular system and can explain both the elevated blood flow velocities and the high risk of stroke observed in such patients.

A critical assessment of transcranial doppler screening rates in a large pediatric sickle cell center: opportunities to improve healthcare quality

BACKGROUND

Transcranial Doppler ultrasound (TCD) has been demonstrated to be a powerful predictor of stroke risk due to sickle cell disease (SCD) in pediatric populations. Little is known about how this healthcare innovation has disseminated into preventive care for SCD. The objective of this study was to determine TCD screening rates and modifiable patient barriers in children with SCD.

PROCEDURE

We retrospectively assessed the screening of 207 children with SCD at the Texas Children's Sickle Cell Center over a 3-year period (2004-2006). Demographics, adherence to comprehensive care visits, severity of disease, and distance from the sickle cell center were obtained from computerized medical record databases. Screenings cancelled or missed by patients were extracted from a computerized order entry system.

RESULTS

The average yearly screening rate for eligible patients was 45%. The average yearly cancellation rate by patients was 20%. Patient with private insurance were three times more likely to be compliant with ordered screenings than patients with Medicaid (P = 0.0077). Patients adherent to hematology comprehensive care visits more likely underwent ordered screenings than those who were not (P = 0.0386). When given at least one opportunity per year, providers, on average, ordered TCD screening 74% of the time when it was indicated.

CONCLUSIONS

Despite evidence that routine screening to assess stroke risk is vital to the preventive care of SCD, implementation of this healthcare technology may be slow to disseminate due to patient and provider related factors.

Severity of obstructive sleep apnea in children with sickle cell disease

OBJECTIVE

To characterize polysomnographic (PSG) findings of children with sickle cell disease (SCD) suspected of having sleep disordered breathing (SDB).

METHODS

Families of 100 consecutively referred children with SCD completed the Children's Sleep Habit Questionnaire during a routine visit to identify concerns regarding sleep habits and sleep behavior. Of these, 48 children were identified as displaying behaviors suspicious of SDB. Nineteen agreed to an overnight PSG. The results from the PSGs of the SCD with obstructive sleep apnea syndrome (OSAS) group (SCD-OSAS; group 1) were compared with the results of 10 age, sex, and ethnicity-matched patients identified as OSAS with no medical comorbidities (uncomplicated OSAS; group 2).

RESULTS

SDB was identified in 79% of the SCD group. As compared with the uncomplicated OSAS group, the SCD with OSAS group displayed nocturnal desaturation with lower nadir values, of longer duration, with a 4-fold increased risk for oxygen desaturation below 85%, higher percentage of total sleep time with end-tidal carbon dioxide (ET CO2) values >50 mm Hg, with a 3.7-fold increased risk for spending more than 25% of total sleep time with ET CO2 more than 50 mm Hg and higher peak ET CO2 with a 7-fold increase for peak ET CO2 above 53 mm Hg.

CONCLUSIONS

Children with SCD suspicious of SDB may have not only a higher incidence of OSAS, but also more severe nocturnal desaturation and hypercapnia as compared with children with uncomplicated OSAS.

Genetic endothelial systems biology of sickle stroke risk

Genetic differences in endothelial biology could underlie development of phenotypic heterogeneity among persons afflicted with vascular diseases. We obtained blood outgrowth endothelial cells from 20 subjects with sickle cell anemia (age, 4-19 years) shown to be either at-risk (n=11) or not-at-risk (n=9) for ischemic stroke because of, respectively, having or not having occlusive disease at the circle of Willis. Gene expression profiling identified no significant single gene differences between the 2 groups, as expected. However, analysis of Biological Systems Scores, using gene sets that were predetermined to survey each of 9 biologic systems, showed that only changes in inflammation signaling are characteristic of the at-risk subjects, as supported by multiple statistical approaches. Correspondingly, subsequent biologic testing showed significantly exaggerated RelA activation on the part of blood outgrowth endothelial cells from the at-risk subjects in response to stimulation with interleukin-1beta/tumor necrosis factoralpha. We conclude that the pathobiology of circle of Willis disease in the child with sickle cell anemia predominantly involves inflammation biology, which could reflect differences in genetically determined endothelial biology that account for differing host responses to inflammation.

Beta-thalassaemia and sickle cell anaemia as paradigms of hypercoagulability

Thalassaemia and sickle cell disease (SCD) represent the most common forms of hereditary haemolytic anaemia and result from a partial or complete lack of synthesis of one of the major alpha- or beta-globin chains of haemoglobin A or from a single amino acid mutation (beta(6Glu-->Val)) of the beta-globin chain respectively. Although they have different pathophysiologies, patients with these conditions manifest both biochemical and clinical evidence of hypercoagulability. While the frequency of various thrombotic complications may vary in beta-thalassaemia and homozygous SCD [sickle cell anaemia (SCA)], patients with both diseases manifest decreased levels of natural anticoagulant proteins, as well as increased markers of thrombin generation and platelet activation. The abnormal phospholipid membrane assymetry present in the red blood cells of beta-thalassaemia and SCA patients, with resultant phosphatidylserine exposure appears to play a significant role in the aetiology of the observed hypercoagulable state. This review presents the available data on the aetiology and clinical manifestations of the coagulation and platelet activation that exist in both beta-thalassaemia and SCA, as well as the potential therapeutic implications resulting from this hypercoagulability.

Arterial ischemic stroke in children

Stroke in children is relatively rare. Advances in the clinical recognition and radiographic diagnosis of ischemic stroke have increased the frequency of the diagnosis in infants and children and have raised the need for immediate therapy. A vast amount of data has recently become available through basic research and neuroimaging techniques shedding new light on the chain of events that occur in ischemic stroke in animal models and in the adult population. Whether this new information can also be applied to the pediatric population remains to be seen, but it is likely that the active management of children with acute ischemic stroke in the near future will include brain protection, brain reperfusion, and prevention measures.

Overt and Incomplete (Silent) Cerebral Infarction in Sickle Cell Anemia: Diagnosis and Management

Cerebral vasculopathy in sickle cell anemia (HbSS) is manifest clinically as cerebral infarction and intracranial hemorrhage. The type of stroke, ischemic or hemorrhagic, is age specific with distinct differences in outcomes. Cerebral infarction with or without clinical stroke begins during early childhood and rarely causes death immediately.

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.

Coagulation in the Pathophysiology of Hemolytic Anemias

Coagulation abnormalities are frequently reported in hemolytic anemias (HA). Several pathophysiologic mechanisms are common to different HA. In this review three different hemolytic disorders will be discussed.

In sickle cell disease and in β-thalassemia, a thrombophilic status has been well documented as multifactorial involving hemostatic changes and activation of the coagulation cascade. Moreover, in such disorders, elevated levels of endothelial adhesion protein (ICAM-1, ELAM-1, VCAM-1, von Willebrand factor, and thrombomodulin) are often increased, suggesting that endothelial activation may be involved in vascular occlusion. As an additional mechanism of hypercoagulability in thalassemia, a procoagulant status of thalassemic red cells was recognized.

The main clinical manifestation of paroxysmal nocturnal hemoglobinuria (PNH) is HA, and the most common complications are thrombosis, pancytopenia, and myelodysplastic syndrome or acute leukemia. The intravascular hemolysis is explained by a deficiency of glycosil phosphatidylinositol (GPI)-anchored complement regulatory proteins such as CD59 and CD55 on the membrane of red blood cells (RBCs), but the mechanism responsible for the increased incidence of thrombotic events in PNH remains unclear.

Recent advances have been made in understanding the coagulation involvement in a heterogeneous group of diseases, thrombotic microangiopathies (TMA) characterized by microangiopathic hemolytic anemia and thrombocytopenia due to platelet clumping in the microcirculation, leading to ischemic organ dysfunction with neurologic symptoms and renal impairment.

Hypercoagulability in Sickle Cell Disease: New Approaches to an Old Problem

Patients with sickle cell disease (SCD) exhibit high plasma levels of markers of thrombin generation, depletion of natural anticoagulant proteins, abnormal activation of the fibrinolytic system, and increased tissue factor expression, even in the non-crisis steady state. In addition, platelets and other cellular elements are chronically activated in the non-crisis state. Despite an abundance of evidence for coagulation and platelet activation, it remains uncertain whether these changes contribute to the pathophysiology of SCD or are, rather, simple epiphenomena. With the occurrence of macrovascular thrombotic complications in SCD, as well as the recognition that soluble CD40 ligand is biologically active in SCD, coagulation and platelet activation may indeed play a role in SCD pathophysiology. Defining a role for hypercoagulability in SCD requires further understanding of its pathogenesis. Furthermore, the conduct of well-controlled clinical trials using anticoagulants and antiplatelet agents and using a variety of clinical endpoints is warranted.

Treatment and prevention of stroke in children with sickle cell disease

Stroke is one of the major complications in children with sickle cell disease (SCD). Ischemic stroke is associated with small asymptomatic subcortical infarcts to large territorial lesions causing major disability. Intracranial hemorrhages may be caused by aneurysm rupture or by leakage from moyamoya vessels or venous sources. There have been no acute stroke treatment studies in SCD, but hydration and exchange transfusion are often recommended. However, there is an evidence base for primary and to some extent secondary stroke prevention. Primary prevention of stroke was demonstrated in the Stroke Prevention Trial in Sickle Cell Anemia (STOP), in which children with transcranial Doppler (TCD) mean blood flow velocities of 200 cm/second (previously shown to indicate high stroke risk) or higher were randomized to either regular blood transfusions or no transfusion. The study showed a very significant 90% reduction in first stroke with transfusion. In STOP2, discontinuing transfusions after 30 months or more (even with normal TCD) resulted in a high rate of reversion to abnormal TCD values and stroke. TCD screening of all children with SCD, and initiation and maintenance of chronic transfusion to maintain hemoglobin S below 30% in the high-risk group, is the only proven prevention strategy for stroke in SCD. Hydroxyurea is being studied as secondary stroke prevention at this time. No recommendation specific to SCD regarding the use of antiplatelet agents or anticoagulants in ischemic stroke can be made. Bone marrow transplantation can be curative for SCD, and limited data support its use to prevent stroke in SCD.

Understanding mechanisms of gamma-globin gene regulation to develop strategies for pharmacological fetal hemoglobin induction

The developmental regulation of gamma-globin gene expression has shaped research efforts to establish therapeutic modalities for individuals affected with sickle cell disease (SCD). Fetal hemoglobin (Hb F) synthesis is high at birth, followed by a decline to adult levels by 10 months of age. The expression of gamma-globin is controlled by a developmentally regulated transcriptional program that is recapitulated during normal erythropoiesis in the adult bone marrow. It is known that naturally occurring mutations in the gamma-gene promoters cause persistent Hb F synthesis after birth, which ameliorates symptoms in SCD by inhibiting hemoglobin S polymerization and vaso-occlusion. Several pharmacological agents have been identified over the past 2 decades that reactivate gamma-gene transcription through different cellular systems. We will review the progress made in our understanding of molecular mechanisms that control gamma-globin expression and insights gained from Hb F-inducing agents that act through signal transduction pathways.

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.

Cerebrovascular disease associated with sickle cell pulmonary hypertension

In patients with sickle cell disease, anemia is a recognized risk factor for stroke, death, and the development of pulmonary hypertension. We have proposed that hemolytic anemia results in endothelial dysfunction and vascular instability and can ultimately lead to a proliferative vasculopathy leading to pulmonary hypertension. Consistent with this mechanism of disease, we now report a case series of six patients with obliterative central nervous system vasculopathy who also have pulmonary hypertension and high hemolytic rate. These patients, identified in the course of a prospective screening study for pulmonary hypertension, presented with neurological symptoms prompting neuroimaging studies. Compared to 164 other patients of similar age in the screened population, those with newly diagnosed or clinically active cerebrovascular disease have significantly lower hemoglobin levels and higher levels of lactate dehydrogenase. A review of the literature suggests that many clinical, epidemiological, and physiological features of the arteriopathy of pulmonary hypertension closely overlap with those of stroke in sickle cell disease, both known to involve proliferative vascular intimal and smooth muscle hypertrophy and thrombosis. These cases suggest that cerebrovascular disease and pulmonary hypertension in sickle cell disease share common mechanisms, in particular, reduced nitric oxide bioactivity associated with particularly high-grade hemolysis. Clinicians should suspect occult cerebrovascular disease in sickle cell patients with pulmonary hypertension.

Stroke in Black Americans

Black Americans bear a disproportionate stroke burden in the United States compared with other racial and ethnic groups. Poor stroke awareness, higher vascular risk factor burden, limited access to care, mistrust of the medical system, and inequities in diagnostic testing and treatment usage may account for some of the disparity. In addition, blacks have historically been under-represented in observational studies and clinical trials of stroke prevention and treatment. Therefore, our knowledge regarding stroke in black Americans is somewhat limited. This article provides an update on developments in our understanding regarding stroke in this at-risk population.

Regular Transfusion Lowers Plasma Free Hemoglobin in Children With Sickle-Cell Disease at Risk for Stroke

Background and Purpose— Intravascular hemolysis releases large amounts of free hemoglobin (PFH) in plasma of sickle- cell disease (SCD) patients. PFH has been associated with harmful endothelial actions including scavenging nitric oxide (NO). Whether PFH plays a role in stroke in SCD has not been examined.

Methods— Serum levels of PFH, lactate dehydrogenase, and total bilirubin were measured in stored sera from children at risk for stroke treated in a randomized controlled trial of regular red cell transfusion (STOP study). Baseline and post-treatment (≈1 year of transfusion) were compared to determine whether treatment (which reduces stroke risk by 90%) was associated with reduction in markers of hemolysis.

Results— Baseline serum PFH values did not differ between treatment groups. PFH declined with repeated transfusion from 78.7±8.2 mg/dL to 34.4±3.4 mg/dL ( P <0.001). With only episodic or no transfusion the drop was smaller: 80.9±7.5 to 62.8±5.0 ( P =0.019). The decrease was larger in those with regular transfusion (56% versus 22%; P <0.001). Reduction of lactate dehydrogenase and total bilirubin was observed only in those on regular transfusion.

Conclusions— Regular transfusion which lowers stroke risk is associated with a significant reduction in PFH. A role for PFH in promoting stroke in SCD should be investigated.

Single gene disorders causing ischaemic stroke

Stroke is the third most common cause of death and the leading cause of long-term neurological disability in the world. Conventional vascular risk factors for stroke contribute approximately to only forty to fifty percent of stroke risk. Genetic factors may therefore contribute to a significant proportion of stroke and may be polygenic, monogenic or multi-factorial. Monogenic (single gene) disorders may potentially account for approximately one percent of all ischaemic stroke. Monogenic stroke disorders include conditions such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) and hereditary endotheliopathy, retinopathy, nephropathy and stroke (HERNS). In addition, other monogenic conditions such as sickle cell and Fabry disease also lead to stroke. These monogenic disorders cause either small vessel or large vessel stroke (or a combination of both) and serve as useful models for understanding and studying conventional stroke and cerebrovascular disease and its accompaniments such as vascular dementia.

Discontinuing prophylactic transfusions used to prevent stroke in sickle cell disease

BACKGROUND

Prophylactic transfusion prevents strokes in children with sickle cell anemia who have abnormalities on transcranial Doppler ultrasonographic examination. However, it is not known how long transfusion should be continued in these children.

METHODS

We studied children with sickle cell disease who had a high risk of stroke on the basis of a transcranial Doppler screening examination and who had received transfusions for 30 months or longer, during which time the Doppler readings became normal. The children were randomly assigned to continued transfusion or no continued transfusion. Children with severe stenotic lesions on cerebral magnetic resonance angiography were excluded. The composite primary end point was stroke or reversion to a result on Doppler examination indicative of a high risk of stroke.

RESULTS

The study was stopped after 79 children of a planned enrollment of 100 underwent randomization. Among the 41 children in the transfusion-halted group, high-risk Doppler results developed in 14 and stroke in 2 others within a mean (+/-SD) of 4.5+/-2.6 months (range, 2.1 to 10.1) of the last transfusion. Neither of these events of the composite end point occurred in the 38 children who continued to receive transfusions. The average of the last two transcranial Doppler results before transfusion was started was the only predictor of the composite end point (P=0.05).

CONCLUSIONS

Discontinuation of transfusion for the prevention of stroke in children with sickle cell disease results in a high rate of reversion to abnormal blood-flow velocities on Doppler studies and stroke. (ClinicalTrials.gov number, NCT00006182.)

Sickle cell disease: ischemia and seizures

Although the prevalence of seizures in children with sickle cell disease (SCD) is 10 times that of the general population, there are few prospectively collected data on mechanism. With transcranial Doppler and magnetic resonance imaging (MRI) and angiography, we evaluated 76 patients with sickle cell disease, 29 asymptomatic and 47 with neurological complications (seizures, stroke, transient ischemic attack, learning difficulty, headaches, or abnormal transcranial Doppler), who also underwent bolus-tracking perfusion MRI. The six patients with recent seizures also had electroencephalography. Group comparisons (seizure, nonseizure, and asymptomatic) indicated that abnormal transcranial Doppler was more common in the seizure (4/6; 67%) and nonseizure (26/41; 63%) groups than in the asymptomatic (10/29; 34%) group (chi2; p = 0.045), but abnormal structural MRI (chi2; p = 0.7) or magnetic resonance angiography (chi2; p = 0.2) were not. Relative decreased cerebral perfusion was found in all seizure patients and in 16 of 32 of the remaining patients with successful perfusion MRI (p = 0.03). In the seizure patients, the perfusion abnormalities in five were ipsilateral to electroencephalographic abnormalities; one had normal electroencephalogram results. These findings suggest that vasculopathy and focal hypoperfusion may be factors in the development of sickle cell disease-associated seizures.

Overt and Incomplete (Silent) Cerebral Infarction in Sickle Cell Anemia: Diagnosis and Management

Regional complete infarctions in children with sickle cell anemia (HbSS) are often associated with stenosis of the large intracranial arteries and result in lifetime disability. Incomplete infarction occurs more frequently than previously recognized and has far-reaching effects on neurocognitive development and the risk for overt secondary strokes into adulthood. Clinical and neuroimaging modalities have been highlighted in an algorithmic approach, with the studies giving the highest yield in results and most likely to be available listed in sequential order. The recognition of an emerging "second peak" incidence in the third decade of life is worrisome and warrants more intense scrutiny and diagnosis of subtle findings of stroke in this young adult population.

Stroke in Latin America

Stroke is one of the leading causes of mortality in Latin America, with variable incidence and prevalence throughout the continent reflecting regional socioeconomic differences. In Latin America, uncontrolled hypertension is one of the major causes of stroke, but other modifiable risk factors also play a role, such as heavy alcohol consumption and smoking. Intracerebral hemorrhage and lacunar stroke are more frequent in Latin America than in North America and Europe. There are multiple causes of stroke that are endemic to Latin America, including neurocysticercosis, Chagas' disease, sickle cell anemia, malaria, hemorrhagic fever, and snake bites.

Development of a de novo cerebral arteriovenous malformation in a child with sickle cell disease and moyamoya arteriopathy

The authors report the unique case of a 6-year-old African-American girl with sickle cell disease (SCD) and an associated moyamoya arteriopathy who developed a de novo arteriovenous malformation (AVM) of the cerebral circulation. Based on preoperative cerebral angiography, computerized tomography angiography, and magnetic resonance imaging, the incidentally discovered lesion was originally thought to be a direct arteriovenous fistula with an associated varix. At surgery, however, a 1.5-cm AVM was identified adjacent to the deep surface of the varix, and it was successfully resected. The diagnosis of cerebral AVM was then confirmed histopathologically. Based on a review of the literature, no published correlation between cerebral AVMs and SCD exists. In addition to reporting this case, the authors provide a description of AVM pathogenesis, with particular emphasis on acquired AVMs of the cerebral circulation.

Genetics of cerebrovascular disorders

Physicians must be able to recognize stroke caused by a mendelian or mitochondrial disorder. Some genetic disorders such as sickle cell anemia and Fabry disease have proven disease-specific treatments, whereas others have no effective treatment, including cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Proper diagnosis of a genetic disorder has prognostic value and prevents patient exposure to unnecessary and potentially harmful therapeutic agents and diagnostic tests. This article reviews the clinical and genetic features of some mendellan and mitochondrial disorders associated with ischemic stroke, hemorrhagic stroke, and cerebrovascular malformations.

Toward the definition of cerebral arteriopathies of childhood

PURPOSE OF REVIEW

To facilitate and standardize the diagnosis of cerebrovascular conditions in childhood, particularly in the field of arterial ischemic diseases.

RECENT FINDINGS

Progress in diagnostic techniques in the past decade have led to newly established etiologies for childhood stroke, most of which represent some form of vascular pathology. These advances must be integrated into a modern nomenclature system with revised definitions of stroke and arterial wall diseases-arteriopathies-in childhood.

SUMMARY

This nomenclature system is intended to facilitate and enhance clinical research in childhood stroke, particularly multicenter collaborative studies.

Polymorphism of the human platelet antigen-5 system is a risk factor for occlusive vascular complications in patients with sickle cell anemia

BACKGROUND

Polymorphisms of platelet membrane glycoproteins such as human platelet antigen (HPA)-1b, HPA-2b, the -5T/C Kozak sequence and C807T have been described as risk factors for vascular disease. Vaso-occlusion episodes are a common feature of sickle cell anaemia (SCA), leading to complications such as stroke, acute chest syndrome, avascular head femur necrosis and priapism. Complex interactions are involved in vaso-occlusion, and activated platelets may play an important role. These data raised the question of whether platelet polymorphisms could be implicated in occlusive vascular complications (OVC) of SCA.

MATERIALS AND METHODS

In this study, 97 patients with SCA were analysed in two groups: 34 patients presenting with OVC (SCA-VC) and 63 without these complications (SCA-N). The distribution of the HPA-1, -2 and -5 systems, as well as C807T dimorphism and -5T/C Kozak sequence alleles, was evaluated using DNA-based methods.

RESULTS

Patients of the SCA-VC group showed a higher frequency of the HPA-5b allele (0.324) compared with those of the SCA-N group (0.111) (chi2 = 13.19, P = 0.0002). None of the other polymorphisms, isolated or associated as haplotypes, demonstrated any correlation with the development of OVC in these patients.

CONCLUSIONS

The findings of this study suggest that the HPA-5b allele is a genetic risk factor for the development of OVC in patients with SCA. This allele could be explored as a target for the development of new therapeutic approaches.

Is Chlamydia pneumoniae infection associated with stroke in children with sickle cell disease?

BACKGROUND

Stroke is often a devastating complication of sickle cell disease (SCD). Most children with SCD-related stroke have stenotic and occlusive disease of cerebral blood vessels due to intimal hyperplasia. This hyperplasia is hypothesized to result from an inflammatory response similar to that in atherosclerosis and has been attributed to infection by Chlamydia pneumoniae.

OBJECTIVE

To determine whether C pneumoniae infection is associated with stroke and cerebrovascular disease, including transient ischemic attacks and abnormal transcranial Doppler examinations, in children with SCD.

METHODS

Children with SCD on chronic transfusion due to a history of stroke, transient ischemic attack, or abnormal transcranial Doppler; children with SCD without stroke; healthy controls; and children being transfused for other reasons were enrolled. Peripheral blood and nasopharyngeal (NP) swab specimens were collected from all patients. In patients on transfusion, pretransfusion specimens and samples from the unit of packed red blood cells being transfused were obtained. Peripheral blood monocytic cells (PBMCs) and NP swab specimens were cultured for C pneumoniae in HEp-2 cells. C pneumoniae polymerase chain reaction was performed on PBMCs with a nested touch-down method with primers from the omp-1gene (in duplicate) and a second real-time polymerase chain reaction by using 16S ribosomal RNA primers.

RESULTS

C pneumoniae DNA was detected in the PBMCs of 1 of 14 (7.1%) children with SCD on chronic transfusion, 1 of 10 (10%) sickle cell controls, 1 of 10 (10%) healthy controls, and none of the 5 children receiving chronic transfusion for other reasons. It was not detected in specimens from transfusion units. One child with SCD and stroke, 1 sickle cell control, and 1 transfusion control had positive NP cultures for C pneumoniae. C pneumoniae DNA was not detected in their PBMCs, and all 3 children were asymptomatic. C pneumoniae was not detected by culture of PBMCs from any of the patients after 7 passages.

CONCLUSION

Stroke in children with SCD does not seem to be associated with C pneumoniae infection in our population.

Pseudotumor cerebri in children with sickle cell disease: a case series

Headache is a frequent symptom in sickle cell disease (SCD) that usually is attributable to anemia or cerebrovascular disease. We report 3 pediatric patients with SCD (1 patient with SCD-SC and 2 patients with SCD-SS) who presented with headache and were diagnosed with pseudotumor cerebri (PC). All 3 patients had elevated opening pressures during a lumbar puncture with normal cerebrospinal fluid studies. Magnetic resonance imaging revealed no evidence of hydrocephalus or arteriopathy in all 3 cases. Magnetic resonance venograms performed in 2 of the patients at diagnosis revealed no evidence of cerebral sinus thrombosis. Each patient received a thorough ophthalmologic examination. A diagnostic funduscopic examination revealed bilateral papilledema without signs of retinopathy in all 3 patients. There were no clinically significant changes in visual acuity or abnormalities of color vision in any patient. Goldmann or Humphrey visual-field assessment was abnormal only in patient 1, who demonstrated bilaterally enlarged blind spots at diagnosis and later developed reduced sensitivity in the inferomedial quadrant of the left eye in an arcuate pattern (which later resolved). The diagnosis of PC was made in all 3 patients, and acetazolamide treatment was started. Two of the patients' symptoms resolved completely with medical treatment, whereas the third patient's symptoms improved. None of these patients had permanent visual-field deficits as a result of their syndrome. PC has been reported in several other types of anemia including SCD-SC, but these cases are the first reported in conjunction with pediatric SCD. Early recognition of the signs and symptoms of PC in patients with SCD who present with headache can expedite proper diagnosis and treatment and prevent long-term ophthalmologic sequelae.

Understanding the causes of problematic pain management in sickle cell disease: evidence that pseudoaddiction plays a more important role than genuine analgesic dependence

Treatment of painful episodes in sickle cell disease (SCD) is sometimes complicated by disputes between patients and staff and patient behaviors that raise concerns about analgesic misuse. Those concern-raising behaviors could indicate either drug seeking caused by analgesic dependence or pseudoaddiction caused by undertreatment of pain. To make a systematic assessment of concern-raising behaviors and examine their associations with other factors, including DSM-IV symptoms of substance dependence, individual, in-depth interviews with SCD patients were conducted to apply pre-established criteria for concern-raising behaviors. These included disputes with staff tampering with analgesic delivery systems, passing prescribed analgesics from one person to another, being suspected or accused of analgesic misuse, self-discharging from hospital, obtaining analgesic prescriptions from multiple sources, using illicit drugs, and injecting analgesics. Assessments were also made of pain-related symptoms of substance dependence (where behaviors resemble substance dependence but reflect attempts to manage pain, increasing the risk of pseudoaddiction), non-pain-related symptoms of substance dependence (where substance dependence reflects analgesic use beyond pain management), and pain coping strategies (using the Pain Coping Strategies Questionnaire). Inter-rater reliability for the assessment of concern-raising behaviors was high, with Kappa coefficients of 0.63 to 1.0. The most frequent concern-raising behaviors were disputes with staff about pain or analgesics. The least frequent were tampering with analgesic delivery systems and passing analgesics between patients in hospital. The odds of concern-raising behaviors in hospital were raised eightfold by less use of ignoring pain as a coping strategy, and more than doubled by each additional pain-related symptom of substance dependence. Non-pain-related symptoms of substance dependence had no independent effect on concern-raising behaviors. Concern-raising behaviors were more closely associated with pain behaviors that make patients vulnerable to misperceptions of substance dependence than they were with genuine substance dependence. The results show how pseudoaddiction can adversely influence hospital pain management, and suggest that more emphasis should be placed on patients' pain and analgesic needs when responding to concern-raising behaviors in hospital.

The paediatric overview

Stroke in children, both ischaemic and haemorrhagic, is increasingly recognised as an important paediatric illness. This review looks at the wide number of causes, highlighting the fact that often no single factor is causative on its own. There has been an increased recognition worldwide of the importance of sickle cell disease and of the importance of venous sinus thrombosis. Radiology is mandatory in diagnosis and management. Unfortunately, it is not always possible to extrapolate experience from adult stroke in terms of management of these children, and further detailed trials are necessary to understand the natural history, outcome and best forms of management.

Brain injury in children with sickle cell disease: Prevalence and etiology

Our objective was to evaluate the relationship between brain injury by magnetic resonance imaging (MRI) and vasculopathy by magnetic resonance angiography (MRA) in children with hemoglobin SS, the most serious form of sickle cell disease. We reviewed imaging for all 146 SS patients imaged at St. Jude Children's Research Hospital since 1993. Standard MRI criteria were used to identify cystic infarction, leukoencephalopathy, encephalomalacia, or atrophy. Standard MRA criteria were used to identify arterial tortuousity (limited vasculopathy), and stenosis or occlusion (extensive vasculopathy). At an average age of 10 years, the estimated prevalence of infarction, ischemic damage, or atrophy in SS patients was 46%, and of vasculopathy was 64%. Only 28% of patients were normal by both modalities, and patients abnormal by MRA often were abnormal by MRI (p < 0.00001). Patients with cystic infarction had limited vasculopathy, whereas patients with encephalomalacia had stenosis or occlusion (p < 0.0001). Large arteries were affected in 31% of brain injury patients, whereas small arteries are inferred to be abnormal in up to 69% of patients with brain injury. The degree of vasculopathy is closely related to the degree of brain injury, implying that vasculopathy is prodromal to most forms of brain injury in hemoglobin SS.

Sickle blood contains tissue factor-positive microparticles derived from endothelial cells and monocytes

Blood microparticles (MPs) in sickle cell disease (SCD) are reportedly derived only from erythrocytes and platelets. Yet in SCD, endothelial cells and monocytes are activated and abnormally express tissue factor (TF). Thus, sickle blood might contain TF-positive MPs derived from these cells. With the use of flow cytometry to enumerate and characterize MPs, we found total MPs to be elevated in crisis (P =.0001) and steady state (P =.02) in subjects with sickle cell disease versus control subjects. These MPs were derived from erythrocytes, platelets, monocytes, and endothelial cells. Erythrocyte-derived MPs were elevated in sickle crisis (P =.0001) and steady state (P =.02) versus control subjects, as were monocyte-derived MPs (P =.0004 and P =.009, respectively). Endothelial and platelet-derived MPs were elevated in sickle crisis versus control subjects. Total TF-positive MPs were elevated in sickle crisis versus steady state (P =.004) and control subjects (P <.0001) and were derived from both monocytes and endothelial cells. Sickle MPs shortened plasma-clotting time compared with control MPs, and a TF antibody partially inhibited this procoagulant activity. Markers of coagulation were elevated in patients with sickle cell disease versus control subjects and correlated with total MPs and TF-positive MPs (P <.01 for both). These data support the concept that SCD is an inflammatory state with monocyte and endothelial activation and abnormal TF activity.