Silent brain infarcts in adult Kuwaiti sickle cell disease patients

Silent Cerebral Infarcts in Iraqi Patients with Sickle Cell Disease

Silent ischemic infarcts have been reported to be the most frequent neurological abnormalities in sickle cell disease (SCD) in several studies worldwide. However, no previous studies investigated this neurological disorder in Iraqi SCD patients. To address this issue, a total of 52 patients with a median age of 20 years (range 10-46) and including 46.2% males were enrolled. Patients were clinically evaluated and their records were reviewed. They had full blood and reticulocyte counts, hemoglobin F estimation, serum lactic dehydrogenase and bilirubin assayed, as well as brain magnetic resonance imaging (MRI) to screen for silent cerebral infarcts. Six out of the 52 patients (11.5%) had silent cerebral infarcts, all of which were in the deep white matter, ranging from 6 to 10 mm in their largest diameters. There were no significant differences in age, sex, or sickle cell genotype between those with silent cerebral infarcts and those without it. Those with silent cerebral infarcts had lower median hemoglobin, higher reticulocytes and lower pain frequencies than those without it, yet again this was not significant. Follow up MRI in four out of the six silent infarct patients showed no additional lesions and no increase in size of the original ones after six to eight months. In conclusion, it appears that the frequency of silent cerebral infarcts in Iraqi SCD patients is lower than the bulk of the literature from other populations. Further studies to screen for genetic polymorphisms that may explain this lower rate may be informative.

Repeat transcranial Doppler ultrasound imaging in Kuwaiti children with sickle cell disease after a 10‐year interval: A prospective, cohort study

Objectives

Transcranial Doppler imaging (TCDI) of the cerebral arteries is the method of choice to predict patients with sickle cell disease (SCD) at risk for stroke. This study reports TCDI follow‐up of cerebral blood flow in a cohort of Kuwaiti children with SCD after a 10‐year interval.

Methods

Twenty‐one pediatric patients with SCD, aged 16.0 ± 1.6 years were initially studied when they were aged 6.5 ± 1.2 years. TCDI scanning was carried out using a phased‐array transducer of 1–3 MHz through the trans‐temporal window. Peak systolic velocity (PSV), end‐diastolic velocity (EDV), time‐averaged mean of the maximum velocity (TAMMV), resistive index (RI), and pulsatility index (PI) were obtained in the anterior and posterior Circle of Willis vessels.

Results

The follow‐up indices were mostly lower than in the initial study although they remained within the normal range in all the arteries. TAMMV was less than 170 cm/s, and PSV did not exceed 200 cm/s in all vessels. The initial and follow‐up TAMMV (mean ± SD) were: 77.3 ± 20.9 and 71.6 ± 9.9 in the terminal internal carotid artery, 94.3 ± 25.8 and 82 ± 18.2 in the middle cerebral artery, 76.6 ± 25.6 and 70.6 ± 10.7 in the anterior cerebral artery, and 59.1 ± 15.8 and 63.9 ± 8.5 in the posterior cerebral artery, respectively. The mean differences between the old and follow‐up data for RI, and PI were statistically significant (p < 0.05).

Conclusions

Kuwaiti patients with SCD appear to be largely protected from cerebral artery vasculopathy in childhood.

Stroke is a common complication in sickle cell disease (SCD) in many parts of the world and it tends to be recurrent.

Transcranial Doppler Imaging (TCDI) is used to identify patients at risk for stroke.

Patients with timed average mean of the maximum velocity (TAMMV) > 200 cm/s in the arteries of the Circle of Willis, are at increased risk of stroke and need chronic transfusion for the primary prevention of stroke.

However, stroke is uncommon among Kuwaiti SCD patients with high HbF.

A previous study carried out, about 10 years ago, in a cohort of Kuwaiti pediatric SCD found none with abnormal TAMMV values.

A repeat TCDI study has now been carried out on 21 patients from the cohort that was studied 10 years ago.

We found that TCD remains in the normal range in all the patients and, in fact, the TAMMV and other values were significantly lower in the latest study compared to the initial data.

Cerebral vasculopathy is uncommon among Kuwaiti SCD patients.

A case-control and seven-year longitudinal neurocognitive study of adults with sickle cell disease in Ghana

Ageing in sickle cell disease (SCD) is associated with a myriad of end-organ complications, including cerebrovascular damage and cognitive impairment (CI). Although CI is very common in SCD, little is known about cognitive functioning and how it changes with age. This study examines cognitive patterns of 63 adults with SCD and 60 non-SCD, age- and education-matched controls in Ghana. Of those adults with SCD, 34 completed the neuropsychological battery at baseline and again seven years later. In cross-sectional data, adults with SCD performed worse than controls in all cognitive test domains (p < 0.01 for all). The seven-year follow-up data showed that the group exhibited a significant decline in visuospatial abilities (ranging from Cohen's d = 1.40 to 2.38), and to a lesser extent, in processing speed and executive functioning. Exploratory analyses showed a significant time-by-education interaction, indicating that education may be protective from decline in cognitive performance. These findings have implications for clinical practice. Early neuropsychological surveillance coupled with early assessment and remedial programmes will provide avenues for enhancing the quality of life of adults living with SCD in Ghana.

The Genetic and Clinical Significance of Fetal Hemoglobin Expression in Sickle Cell Disease

Sickle cell disease (SCD) is phenotypically heterogeneous. One major genetic modifying factor is the patient's fetal hemoglobin (HbF) level. The latter is determined by the patient's β-globin gene cluster haplotype and cis- and trans-acting single nucleotide polymorphisms (SNPs) at other distant quantitative trait loci (QTL). The Arab/India haplotype is associated with persistently high HbF levels and also a relatively mild phenotype. This haplotype carries the Xmn1 (C/T) SNP, rs7482144, in the HBG2 locus. The major identified trans-acting QTL contain SNPs residing in the BCL11A on chromosome 2 and the HMIP locus on chromosome 6. These collectively account for 15-30% of HbF expression in different world populations and in patients with SCD or β-thalassemia. Patients with SCD in Kuwait and Eastern Saudi Arabia uniformly carry the Arab/India haplotype, but despite this, the HbF and clinical phenotypes show considerable heterogeneity. Pain episodes and avascular necrosis of the femoral head are particularly common, but severe bacterial infections, stroke, priapism, and leg ulcers are uncommon. Moreover, the HbF modifiers appear to be different; the reported BCL11A and HMIP SNPs appear to play insignificant roles. There are probably novel modifiers to be discovered in this population. This review examines the common clinical phenotypes in Kuwaiti patients with elevated HbF and the available information on HbF modifiers. The response of the patients to hydroxyurea is discussed. The presentation of patients with other sickle compound heterozygotes (Sβthal and HbSD), vis-à-vis their HbF levels, is also addressed critically.

Silent cerebral infarcts in patients with sickle cell disease: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

Silent cerebral infarcts (SCIs) are the most common neurological complication in children and adults with sickle cell disease (SCD). In this systematic review, we provide an overview of studies that have detected SCIs in patients with SCD by cerebral magnetic resonance imaging (MRI). We focus on the frequency of SCIs, the risk factors involved in their development and their clinical consequences.

METHODS

The databases of Embase, MEDLINE ALL via Ovid, Web of Science Core Collection, Cochrane Central Register of Trials via Wiley and Google Scholar were searched from inception to June 1, 2019.

RESULTS

The search yielded 651 results of which 69 studies met the eligibility criteria. The prevalence of SCIs in patients with SCD ranges from 5.6 to 80.6% with most studies reported in the 20 to 50% range. The pooled prevalence of SCIs in HbSS and HbSβ⁰ SCD patients is 29.5%. SCIs occur more often in patients with the HbSS and HbSβ⁰ genotype in comparison with other SCD genotypes, as SCIs are found in 9.2% of HbSC and HbSβ⁺ patients. Control subjects showed a mean pooled prevalence of SCIs of 9.8%. Data from included studies showed a statistically significant association between increasing mean age of the study population and mean SCI prevalence. Thirty-three studies examined the risk factors for SCIs. The majority of the risk factors show no clear association with prevalence, since more or less equal numbers of studies give evidence for and against the causal association.

CONCLUSIONS

This systematic review and meta-analysis shows SCIs are common in patients with SCD. No clear risk factors for their development were identified. Larger, prospective and controlled clinical, neuropsychological and neuroimaging studies are needed to understand how SCD and SCIs affect cognition.

Interventions for preventing silent cerebral infarcts in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Silent cerebral infarcts are the commonest neurological complication in children and probably adults with SCD. Silent cerebral infarcts also affect academic performance, increase cognitive deficits and may lower intelligence quotient.

OBJECTIVES

To assess the effectiveness of interventions to reduce or prevent silent cerebral infarcts in people with SCD.

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 14 November 2019. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register: 07 October 2019.

SELECTION CRITERIA

Randomised controlled trials comparing interventions to prevent silent cerebral infarcts in people with SCD. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

We included five trials (660 children or adolescents) published between 1998 and 2016. Four of the five trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of SCD. One trial focused on preventing silent cerebral infarcts or stroke; three trials were for primary stroke prevention and one trial dealt with secondary stroke prevention. Three trials compared the use of regular long-term red blood cell transfusions to standard care. Two of these trials included children with no previous long-term transfusions: one in children with normal transcranial doppler (TCD) velocities; and one in children with abnormal TCD velocities. The third trial included children and adolescents on long-term transfusion. Two trials compared the drug hydroxyurea and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children), and one in secondary prevention (children and adolescents). The quality of the evidence was moderate to very low across different outcomes according to GRADE methodology. This was due to trials being at high risk of bias because they were unblinded; indirectness (available evidence was only for children with HbSS); and imprecise outcome estimates. Long-term red blood cell transfusions versus standard care Children with no previous long-term transfusions and higher risk of stroke (abnormal TCD velocities or previous history of silent cerebral infarcts) Long-term red blood cell transfusions may reduce the incidence of silent cerebral infarcts in children with abnormal TCD velocities, risk ratio (RR) 0.11 (95% confidence interval (CI) 0.02 to 0.86) (one trial, 124 participants, low-quality evidence); but make little or no difference to the incidence of silent cerebral infarcts in children with previous silent cerebral infarcts on magnetic resonance imaging and normal or conditional TCDs, RR 0.70 (95% CI 0.23 to 2.13) (one trial, 196 participants, low-quality evidence). No deaths were reported in either trial. Long-term red blood cell transfusions may reduce the incidence of: acute chest syndrome, RR 0.24 (95% CI 0.12 to 0.49) (two trials, 326 participants, low-quality evidence); and painful crisis, RR 0.63 (95% CI 0.42 to 0.95) (two trials, 326 participants, low-quality evidence); and probably reduces the incidence of clinical stroke, RR 0.12 (95% CI 0.03 to 0.49) (two trials, 326 participants, moderate-quality evidence). Long-term red blood cell transfusions may improve quality of life in children with previous silent cerebral infarcts (difference estimate -0.54; 95% confidence interval -0.92 to -0.17; one trial; 166 participants), but may have no effect on cognitive function (least squares means: 1.7, 95% CI -1.1 to 4.4) (one trial, 166 participants, low-quality evidence). Transfusions continued versus transfusions halted: children and adolescents with normalised TCD velocities (79 participants; one trial) Continuing red blood cell transfusions may reduce the incidence of silent cerebral infarcts, RR 0.29 (95% CI 0.09 to 0.97 (low-quality evidence). We are very uncertain whether continuing red blood cell transfusions has any effect on all-cause mortality, Peto odds ratio (OR) 8.00 (95% CI 0.16 to 404.12); or clinical stroke, RR 0.22 (95% CI 0.01 to 4.35) (very low-quality evidence). The trial did not report: comparative numbers for SCD-related adverse events; quality of life; or cognitive function. Hydroxyurea and phlebotomy versus transfusions and chelation Primary prevention, children (121 participants; one trial) We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: silent cerebral infarcts (no infarcts); all-cause mortality (no deaths); risk of stroke (no strokes); or SCD-related complications, RR 1.52 (95% CI 0.58 to 4.02) (very low-quality evidence). Secondary prevention, children and adolescents with a history of stroke (133 participants; one trial) We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: silent cerebral infarcts, Peto OR 7.28 (95% CI 0.14 to 366.91); all-cause mortality, Peto OR 1.02 (95%CI 0.06 to 16.41); or clinical stroke, RR 14.78 (95% CI 0.86 to 253.66) (very low-quality evidence). Switching to hydroxyurea and phlebotomy may increase the risk of SCD-related complications, RR 3.10 (95% CI 1.42 to 6.75) (low-quality evidence). Neither trial reported on quality of life or cognitive function.

AUTHORS' CONCLUSIONS

We identified no trials for preventing silent cerebral infarcts in adults, or in children who do not have HbSS SCD. Long-term red blood cell transfusions may reduce the incidence of silent cerebral infarcts in children with abnormal TCD velocities, but may have little or no effect on children with normal TCD velocities. In children who are at higher risk of stroke and have not had previous long-term transfusions, long-term red blood cell transfusions probably reduce the risk of stroke, and other SCD-related complications (acute chest syndrome and painful crises). In children and adolescents at high risk of stroke whose TCD velocities have normalised, continuing red blood cell transfusions may reduce the risk of silent cerebral infarcts. No treatment duration threshold has been established for stopping transfusions. Switching to hydroxyurea with phlebotomy may increase the risk of silent cerebral infarcts and SCD-related serious adverse events in secondary stroke prevention. All other evidence in this review is of very low-quality.

Sickle Cell Disease and Stroke

Cerebral infarction is a common complication of sickle cell disease and may manifest as overt stroke or cognitive impairment associated with "silent" cerebral infarction on magnetic resonance imaging. Vasculopathy may be diagnosed on transcranial Doppler or magnetic resonance angiography. The risk factors in sickle cell disease for cognitive impairment, overt ischemic stroke, silent cerebral infarction, overt hemorrhagic stroke, and vasculopathy defined by transcranial Doppler or magnetic resonance angiography overlap, with severe acute and chronic anemia, acute chest crisis, reticulocytosis, and low oxygen saturation reported with the majority. However, there are differences reported in different cohorts, which may reflect age, geographic location, or neuroimaging techniques, for example, magnetic resonance imaging field strength. Regular blood transfusion reduces, but does not abolish, the risk of neurological complications in children with sickle cell disease and either previous overt stroke or silent cerebral infarction or abnormal transcranial Doppler. There are relatively few data on the use of hydroxyurea or other management strategies. Early assessment of the risk of neurocognitive complications is likely to become increasingly important in the management of sickle cell disease.

Utility of the Montreal Cognitive Assessment as a Screening Test for Neurocognitive Dysfunction in Adults with Sickle Cell Disease

OBJECTIVES

Neurocognitive dysfunction is an important complication of sickle cell disease (SCD), but little is published on the utility of screening tests for cognitive impairment in people with the disease. The purpose of this study was to evaluate the Montreal Cognitive Assessment (MoCA) as a screening tool and identify predictors of MoCA performance in adults with sickle cell disease.

METHODS

We conducted a retrospective, cross-sectional study of the first 100 adult patients with SCD who completed the MoCA as part of routine clinical care at the Johns Hopkins Sickle Cell Center for Adults. We abstracted demographic, laboratory, and clinical data from each participant's electronic medical record up to the date that the MoCA was administered. The factorial validity of each MoCA domain was analyzed using standard psychometric statistics. We evaluated the abstracted data for associations with the composite MoCA score and looked for independent predictors of performance using multivariable regressions.

RESULTS

Components of the MoCA performed well in psychometric analyses and identified deficits in executive function that were described in other studies. Forty-six percent of participants fell below the cutoff for mild cognitive impairment. Increased education was an independent predictor of increased MoCA score (3.1, 95% confidence interval [CI] 1.5-4.7), whereas cerebrovascular accidents and chronic kidney disease were independent predictors of decreased score (-3.3, 95% CI -5.7 to -0.97 and -3.2, 95% CI -6.2 to -0.11, respectively). When analysis was restricted to patients with SCA, increased education (3.7, 95% CI 2.2-5.2) and a history of hydroxyurea therapy (2.0, 95% CI -0.022 to 4.0) were independent predictors of a higher score, whereas chronic kidney disease (-3.3, 95% CI -6.4 to -0.24) and increased aspartate transaminase (-0.045, 95% CI -0.089 to -0.0010) were independent predictors of a decreased score.

CONCLUSIONS

The MoCA showed promise by identifying important cognitive deficits and associations with chronic complications and therapy.

Interventions for preventing silent cerebral infarcts in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Silent cerebral infarcts are the commonest neurological complication in children and probably adults with SCD. Silent cerebral infarcts also affect academic performance, increase cognitive deficits and may lower intelligence quotient.

OBJECTIVES

To assess the effectiveness of interventions to reduce or prevent silent cerebral infarcts in people with SCD.

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 19 September 2016. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register: 06 October 2016.

SELECTION CRITERIA

Randomised controlled trials comparing interventions to prevent silent cerebral infarcts in people with SCD. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

We included five trials (660 children or adolescents) published between 1998 and 2016. Four of the five trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of SCD. One trial focused on preventing silent cerebral infarcts or stroke; three trials were for primary stroke prevention and one trial dealt with secondary stroke prevention.Three trials compared the use of regular long-term red blood cell transfusions to standard care. Two of these trials included children with no previous long-term transfusions: one in children with normal transcranial doppler (TCD) velocities; and one in children with abnormal TCD velocities. The third trial included children and adolescents on long-term transfusion.Two trials compared the drug hydroxyurea and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children), and one in secondary prevention (children and adolescents).The quality of the evidence was moderate to very low across different outcomes according to GRADE methodology. This was due to trials being at high risk of bias because they were unblinded; indirectness (available evidence was only for children with HbSS); and imprecise outcome estimates. Long-term red blood cell transfusions versus standard care Children with no previous long-term transfusions and higher risk of stroke (abnormal TCD velocities or previous history of silent cerebral infarcts) Long-term red blood cell transfusions may reduce the incidence of silent cerebral infarcts in children with abnormal TCD velocities, risk ratio (RR) 0.11 (95% confidence interval (CI) 0.02 to 0.86) (one trial, 124 participants, low-quality evidence); but make little or no difference to the incidence of silent cerebral infarcts in children with previous silent cerebral infarcts on magnetic resonance imaging and normal or conditional TCDs, RR 0.70 (95% CI 0.23 to 2.13) (one trial, 196 participants, low-quality evidence).No deaths were reported in either trial.Long-term red blood cell transfusions may reduce the incidence of: acute chest syndrome, RR 0.24 (95% CI 0.12 to 0.49) (two trials, 326 participants, low-quality evidence); and painful crisis, RR 0.63 (95% CI 0.42 to 0.95) (two trials, 326 participants, low-quality evidence); and probably reduces the incidence of clinical stroke, RR 0.12 (95% CI 0.03 to 0.49) (two trials, 326 participants, moderate-quality evidence).Long-term red blood cell transfusions may improve quality of life in children with previous silent cerebral infarcts (difference estimate -0.54; 95% confidence interval -0.92 to -0.17; one trial; 166 participants), but may have no effect on cognitive function (least squares means: 1.7, 95% CI -1.1 to 4.4) (one trial, 166 participants, low-quality evidence). Transfusions continued versus transfusions halted: children and adolescents with normalised TCD velocities (79 participants; one trial)Continuing red blood cell transfusions may reduce the incidence of silent cerebral infarcts, RR 0.29 (95% CI 0.09 to 0.97 (low-quality evidence).We are very uncertain whether continuing red blood cell transfusions has any effect on all-cause mortality, Peto odds ratio (OR) 8.00 (95% CI 0.16 to 404.12); or clinical stroke, RR 0.22 (95% CI 0.01 to 4.35) (very low-quality evidence).The trial did not report: comparative numbers for SCD-related adverse events; quality of life; or cognitive function. Hydroxyurea and phlebotomy versus transfusions and chelation Primary prevention, children (121 participants; one trial)We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: silent cerebral infarcts (no infarcts); all-cause mortality (no deaths); risk of stroke (no strokes); or SCD-related complications, RR 1.52 (95% CI 0.58 to 4.02) (very low-quality evidence). Secondary prevention, children and adolescents with a history of stroke (133 participants; one trial)We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: silent cerebral infarcts, Peto OR 7.28 (95% CI 0.14 to 366.91); all-cause mortality, Peto OR 1.02 (95%CI 0.06 to 16.41); or clinical stroke, RR 14.78 (95% CI 0.86 to 253.66) (very low-quality evidence).Switching to hydroxyurea and phlebotomy may increase the risk of SCD-related complications, RR 3.10 (95% CI 1.42 to 6.75) (low-quality evidence).Neither trial reported on quality of life or cognitive function.

AUTHORS' CONCLUSIONS

We identified no trials for preventing silent cerebral infarcts in adults, or in children who do not have HbSS SCD.Long-term red blood cell transfusions may reduce the incidence of silent cerebral infarcts in children with abnormal TCD velocities, but may have little or no effect on children with normal TCD velocities. In children who are at higher risk of stroke and have not had previous long-term transfusions, long-term red blood cell transfusions probably reduce the risk of stroke, and other SCD-related complications (acute chest syndrome and painful crises).In children and adolescents at high risk of stroke whose TCD velocities have normalised, continuing red blood cell transfusions may reduce the risk of silent cerebral infarcts. No treatment duration threshold has been established for stopping transfusions.Switching to hydroxyurea with phlebotomy may increase the risk of silent cerebral infarcts and SCD-related serious adverse events in secondary stroke prevention.All other evidence in this review is of very low-quality.

Evaluation of von Willebrand factor and ADAMTS-13 antigen and activity levels in sickle cell disease patients in Kuwait

Sickle cell disease (SCD) is a severe form of hemolytic anemia characterized by chronic hemolysis and is associated with increased thrombotic risk. Elevated von Willebrand factor (vWF) levels in SCD have been attributed to increased secretion and impaired processing by its cleaving protease ADAMTS-13. In this study we measured vWF and ADAMTS-13 antigen and activity levels in our SCD patients. Hematological and biochemical parameters for 59 SCD patients (20 children and 39 adults) were analyzed and compared to 59 age- and sex-matched controls. Commercially available ELISA kits were used to measure vWF and ADAMTS-13 antigen and activity levels in patients and controls. Patients had significantly higher levels of vWF (p < 0.006) and ADAMTS-13 activity (p < 0.006) compared to controls. When patients were analyzed according to age and genotype, adult patients (23 SS and 16 Sβ⁰thal) maintained higher vWF antigen levels (p < 0.001), but with reduced ADAMTS-13 activity to vWF:Ag ratio (p < 0.003) compared to controls. Pediatric patients (8 SS and 12 Sβ⁰thal) had comparable vWF antigen levels to controls (p > 0.05), but had higher levels of ADAMTS-13 activity (p < 0.011) and ADAMTS-13 activity to vWF:Ag ratio (p < 0.038). Age is an important factor to consider when vWF and ADAMTS-13 proteins are analyzed among our patients. Increased vWF in adult patients may be attributed to increased production and resistance of vWF to proteolysis rather than ADAMTS-13 deficiency. This outcome was not seen in pediatric patients as higher ADAMTS-13 activity maintained vWF antigen at comparable levels to normal controls.

Interventions for preventing silent cerebral infarcts in people with sickle cell disease

This is the protocol for a review and there is no abstract. The objectives are as follows: To assess the effectiveness of red blood transfusions and hydroxyurea alone or in combination and HSCT to reduce or prevent SCI in people with SCD.

Transcranial Doppler and brain MRI in children with sickle cell disease and high hemoglobin F levels

BACKGROUND/OBJECTIVE

While overt stroke and silent brain infarcts (SBI) are uncommon among Kuwaiti patients with sickle cell disease (SCD), there have been no previous transcranial Doppler (TCD) studies in this population. The main objective of this study is to determine TCD velocities in a group of Kuwaiti children with SCD and correlate same with brain magnetic resonance imaging (MRI) and angiography (MRA) findings.

MATERIALS AND METHODS

Forty-three steady-state, pediatric patients with SCD aged 10.1 ± 3.9 years (21 SS, 19 Sβ(0)Thal, and 3 SD) were studied. Twenty-six age-matched, normal siblings of the patients served as controls. TCD was performed using a General Electric (GE), Vivid 3 equipment and MRI/MRA with a GE Signa Excite HD 1.5 Tesla magnet. Complete blood count was with an electronic counter and Hb quantitation with cation-exchange high performance liquid chromatography (HPLC).

RESULTS

The mean time-averaged mean of the maximum velocity (TAMV) was significantly higher in the SCD group than the controls, but was normal (<170 cm/second) in all. The mean values were comparable among the SS and Sβ(0)thal groups. Five (11.1%) patients had SBI and all were between 12 and 16 years of age. There was no significant difference of TAMV in this group compared to those without infarcts. No patient showed evidence of stenosis or any other abnormalities in the circle of Willis vessels.

CONCLUSION

The mild phenotype among Kuwaiti patients with SCD is reflected in normal TCD velocities and a low prevalence of SBI in children with the disease.

Transthoracic echocardiography and 6-minute walk test in Kuwaiti sickle cell disease patients

OBJECTIVE

The aim of this study was to investigate cardiac abnormalities in Kuwaiti sickle cell disease (SCD) patients using markers such as tricuspid regurgitant jet velocity (TRJV), pulmonary artery systolic pressure (PASP), and the 6-minute walk (6MW) test and correlate these findings with clinical, hematological, and biochemical parameters.

MATERIALS AND METHODS

Seventy-three patients with SCD and 70 matched controls were studied. The cardiac status was investigated using transthoracic echocardiography in 57 patients; the 6MW test was carried out in patients and controls. Complete blood counts and hemolytic parameters were assessed.

RESULTS

Reticulocytes, bilirubin, and lactate dehydrogenase were significantly higher (p < 0.0001) in patients, while hemoglobin (Hb) and haptoglobin were lower (p < 0.0001) than in controls. The mean fetal Hb among patients was 15.85 ± 8.7%. Of the 57 patients, 14 (24.5%) and 15 (26%) had mild tricuspid and mitral regurgitation, respectively. The mean ejection fraction, TRJV, and PASP were 63.9 ± 6.3%, 1.7 ± 0.5 m/s, and 23.0 ± 7.3 mm Hg, respectively. Three (5.2%) patients had mildly raised TRJV (2.6-2.97 m/s, normal range <2.5 m/s) while 8 (14%) had high PASP (mean 35.3 ± 5.1 mm Hg, normal range <30 mm Hg). Hb, hematocrit, and reticulocytes were different (p = 0.010, p = 0.006, and p = 0.011, respectively) between patients with normal and high PASP. All 3 patients who had a high TRJV had a high PASP, and 2 of these patients died during follow-up. The systolic and diastolic blood pressure, oxygen saturation before and after the 6MW test, and distance walked were lower (p = 0.006, p = 0.000, p = 0.002, p = 0.000, and p = 0.000, respectively) in patients compared to controls.

CONCLUSION

Raised PASP was common in Kuwaiti SCD patients while raised TRJV was not.

Sickle cell disease in Saudi Arabia: the phenotype in adults with the Arab-Indian haplotype is not benign

Sickle cell disease (SCD) in Saudi patients from the Eastern Province is associated with the Arab-Indian (AI) HBB (β-globin gene) haplotype. The phenotype of AI SCD in children was described as benign and was attributed to their high fetal haemoglobin (HbF). We conducted a hospital-based study to assess the pattern of SCD complications in adults. A total of 104 patients with average age of 27 years were enrolled. Ninety-six per cent of these patients reported history of painful crisis; 47% had at least one episode of acute chest syndrome, however, only 15% had two or more episodes; symptomatic osteonecrosis was reported in 18%; priapism in 17%; overt stroke in 6%; none had leg ulcers. The majority of patients had persistent splenomegaly and 66% had gallstones. Half of the patients co-inherited α-thalassaemia and about one-third had glucose-6-phosphate dehydrogenase deficiency. Higher HbF correlated with higher rate of splenic sequestration but not with other phenotypes. The phenotype of adult patients with AI SCD is not benign despite their relatively high HbF level. This is probably due to the continued decline in HbF level in adults and the heterocellular and variable distribution of HbF amongst F-cells.

Cerebrovascular events in sickle cell-beta thalassemia treated with hydroxyurea: a single center prospective survey in adult Italians

Stroke is a common cause of morbidity and mortality in sickle cell disease (SCD) and silent cerebral infarction is the most common form of neurologic injury. The frequency and risk factors for new silent cerebral infarction are incompletely understood. Moreover, no recommended treatment has been established. Although hydroxyurea (HU) is recommended for SCD, concerns remain regarding its role in the prevention of cerebrovascular events, including silent cerebral infarction. A single center population of 104 Italian patients with HbS-ß thalassemia treated with HU has been followed for a mean of 11 years. Clinical evaluation and brain imaging by Magnetic Resonance Imaging were done before and during HU treatment. During follow-up, the number of sickle cell crises (86%, 7.8 ± 6.9 vs. 1.2 ± 0.5 per year, P < 0.0001), hospitalizations (2.5 ± 2.9 vs. 0.3 ± 1.5 per year, P < 0.0001), and days in the hospital (22.4 ± 21.9 vs. 0.3±1.5 per year, P < 0.0001) decreased significantly and HbF increased from a mean of 8-20.8%. Cerebral infarcts occurred in 37.5% of patients. Among these, 6.7% had overt strokes, while 30% had new or progressive silent cerebral infarction. Stroke and silent cerebral infarction were not related to clinical hematologic or HbF response to HU. These findings suggest that in adults, HU treatment does not prevent new cerebrovascular events or the progression of existent silent cerebral infarcts in HbS-β thalassemia. A major benefit of HU is the increase in HbF; the association of high HbF and reduced cerebrovascular disease has been weak. New treatment strategies should be developed for the prevention of sickle cerebrovascular disease.

Sickle cell disease: new opportunities and challenges in Africa

Sickle cell disease (SCD) is one of the most common genetic causes of illness and death in the world. This is a review of SCD in Africa, which bears the highest burden of disease. The first section provides an introduction to the molecular basis of SCD and the pathophysiological mechanism of selected clinical events. The second section discusses the epidemiology of the disease (prevalence, morbidity, and mortality), at global level and within Africa. The third section discusses the laboratory diagnosis and management of SCD, emphasizing strategies that been have proven to be effective in areas with limited resources. Throughout the review, specific activities that require evidence to guide healthcare in Africa, as well as strategic areas for further research, will be highlighted.

Extent of silent cerebral infarcts in adult sickle-cell disease patients on magnetic resonance imaging: is there a correlation with the clinical severity of disease?

The aim of this paper is to correlate the extent of silent cerebral infarcts (SCIs) on magnetic resonance imaging (MRI) with the clinical severity of sickle cell disease (SCD) in adult patients. Twenty-four consecutive adult asymptomatic SCD patients (11 male and 13 female) with a mean age of 38.4 years (range 20-59) were submitted to brain MRI on a 1 Tesla Gyroscan Intera, Philips MR scanner with a dedicated head coil. The protocol consisted of TSE T2-weighted and FLAIR images on the axial and coronal planes. MRI readings were undertaken by two radiologists and consensus readings. Patients were compound heterozygotes (HbS/β-thal). The extent of SCIs was classified from 0-2 with 0 designating no lesions. Clinical severity was graded as 0-2 by the hematologist, according to the frequency and severity of vaso-occlusive crises. There was no statistically significant correlation between the severity of clinical disease and the extent of SCIs on MR imaging. The extent of SCI lesions did not differ statistically between younger and older patients. Patients receiving hydroxyurea had no statistically significant difference in the extent of SCI lesions. The extent of SCIs in heterozygous (HbS/β-thal) SCD patients is not age related and may be quite severe even in younger (<38.4 years) patients. However the extent of SCIs is not correlated with the severity of clinical disease.

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.

Limitations of Hb F as a phenotypic modifier in sickle cell disease: study of Kuwaiti Arab patients

Sickle cell disease is characterized by phenotypic heterogeneity and many genetic modifiers have been identified with elevated Hb F being the most recognized ameliorating factor. Kuwaiti sickle cell disease patients carry the India/Arab chromosomal haplotype, which is associated with elevated Hb F (on average ~22%) on account of the Xmn1 site in the (G)γ-globin gene promoter. Most patients had either Hb SS or Hb S-β(0)-thalassemia (β(0)-thal) and there are a few Hb SD compound heterozygotes. We have carried out longitudinal clinical studies of these patients to document the pattern of morbidity, spleen function, brain and hip magnetic resonance imaging (MRI) for prevalence of silent brain infarcts and avascular necrosis of the femoral head (AVNFH), respectively. In addition, pulmonary function, SPECT (single photon emission computerized tomography) brain cerebral blood flow and response of selected patients to hydroxyurea (HU) treatment were also studied. The Hb SS and Hb S-β-thal patients have a generally mild phenotype compared to sickle cell disease in other populations and most patients do not have their first pain crisis until about the age of 4 years. Spleen function is retained till late childhood; pneumococcemia and other severe bacterial infections are rare. Overt stroke and silent brain infarcts are uncommon in childhood (~3% prevalence) although SPECT reveals cerebral blood flow deficits in ~30%. Avascular necrosis of the femoral head is, however, common with a prevalence of ~26% in children and 50% in adults. There is brisk response to HU in patients with frequent pain crises, with marked increases in Hb F levels. Patients who are compound heterozygotes for Hbs S and D-Los Angeles, have the most severe phenotype despite Hb F levels of >20% and Hb S <30%. In conclusion, although the patients have a uniformly elevated Hb F level, there are still considerable phenotypic heterogeneity and other modulating genetic factors that require further studies.

Epidemiology of sickle cell disease in Saudi Arabia

Sickle cell disease (SCD) is an autosomal recessive disorder characterized by production of abnormal hemoglobin S and is associated with high morbidity and mortality. Information about the prevalence of SCD in Saudi Arabia is patchy and probably underestimated, but studies have reported that SCD is a relatively common genetic disorder in this part of the world. The prevalence of SCD in Saudi Arabia varies significantly in different parts of the country, with the highest prevalence is in the Eastern province, followed by the southwestern provinces. The reported prevalence for sickle-cell trait ranges from 2% to 27%, and up to 2.6% will have SCD in some areas. Clinical and hematological variability exists in SCD in Saudi Arabia with two major phenotypes: a mild phenotype and a severe phenotype. Further studies on the prevalence, molecular and clinical epidemiology of SCD may help predict disease severity and risk stratification of patients to determine whether to receive early intensive care or continued symptomatic care.

Neuropsychological dysfunction and neuroimaging abnormalities in neurologically intact adults with sickle cell anemia

CONTEXT

Sickle cell anemia (SCA) is a chronic illness causing progressive deterioration in quality of life. Brain dysfunction may be the most important and least studied problem affecting individuals with this disease.

OBJECTIVE

To measure neurocognitive dysfunction in neurologically asymptomatic adults with SCA vs healthy control individuals.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study comparing neuropsychological function and neuroimaging findings in neurologically asymptomatic adults with SCA and controls from 12 SCA centers, conducted between December 2004 and May 2008. Participants were patients with SCA (hemoglobin [Hb] SS and hemoglobin level < or = 10 mg/dL) aged 19 to 55 years and of African descent (n = 149) or community controls (Hb AA and normal hemoglobin level) (n = 47). Participants were stratified on age, sex, and education.

MAIN OUTCOME MEASURES

The primary outcome measure was nonverbal function assessed by the Wechsler Adult Intelligence Scale, third edition (WAIS-III) Performance IQ Index. Secondary exploratory outcomes included performance on neurocognitive tests of executive function, memory, attention, and language and magnetic resonance imaging measurement of total intracranial and hippocampal volume, cortical gray and white matter, and lacunae.

RESULTS

The mean WAIS-III Performance IQ score of patients with SCA was significantly lower than that of controls (adjusted mean, 86.69 for patients with SCA vs 95.19 for controls [mean difference, -5.50; 95% confidence interval {CI}, -9.55 to -1.44]; P = .008), with 33% performing more than 1 SD (<85) below the population mean. Among secondary measures, differences were observed in adjusted mean values for global cognitive function (full-scale IQ) (90.47 for patients with SCA vs 95.66 for controls [mean difference, -5.19; 95% CI, -9.24 to -1.13]; P = .01), working memory (90.75 vs 95.25 [mean difference, -4.50; 95% CI, -8.55 to -0.45]; P = .03), processing speed (86.50 vs 97.95 [mean difference, -11.46; 95% CI, -15.51 to -7.40]; P < .001), and measures of executive function. Anemia was associated with poorer neurocognitive function in older patients. No differences in total gray matter or hippocampal volume were observed. Lacunae were more frequent in patients with SCA but not independently related to neurocognitive function.

CONCLUSION

Compared with healthy controls, adults with SCA had poorer cognitive performance, which was associated with anemia and age.

Brain magnetic resonance imaging abnormalities in adult patients with sickle cell disease: correlation with transcranial Doppler findings

BACKGROUND AND PURPOSE

Brain imaging abnormalities were reported in up to 44% of children with sickle cell disease (SCD). The prevalence of neuroimaging abnormalities in adult patients with SCD and their relationship to transcranial Doppler is still unclear. Our objectives were to study the frequency of MRI and MR angiography abnormalities in adults with SCD and to define what transcranial Doppler velocities are associated with intracranial stenoses detected by MR angiography.

METHODS

We examined all adult patients (>16 years) with SCD followed in the hematology outpatient clinic at our university hospital with MRI, MR angiography, and transcranial Doppler.

RESULTS

We evaluated 50 patients. The overall prevalence of MRI abnormalities was 60%. Abnormal MRI findings were more frequent when vessel tortuosity or stenoses were present on MR angiography (P<0.01). Patients with intracranial stenoses had significantly higher time-averaged maximum mean velocities (P=0.01). A time-averaged maximum mean velocity of 123.5 cm/s allowed the diagnosis of middle cerebral artery or internal carotid artery intracranial stenosis with sensitivity of 100% and specificity of 73% with an area under the receiver operator characteristic curve of 0.91 (CI, 0.79 to 1.00).

CONCLUSIONS

The frequency of brain imaging abnormalities detected by MRI/MR angiography in adults with SCD was higher than that described for children. Transcranial Doppler velocities in adult patients with intracranial stenoses were lower than those described for the pediatric population with SCD.

Neurological complications of sickle cell anemia in Nigerian Africans--a case-control study

PURPOSE

To determine the neurological complications associated with sickle cell anaemia (SCA) in Nigerians and evaluate the relative frequencies.

METHODOLOGY

Six-hundred-thirteen patients with SCA attending outpatient clinics of Lagos University Teaching Hospital and 616 control subjects were evaluated using a uniform structured questionnaire to determine the occurrence of neurological complications. The relative frequencies of neurological abnormalities in patients and controls were compared.

RESULTS

Neurological abnormalities occurred in a significantly higher percentage of patients (76%) compared to controls (32.1%). Among children, these abnormalities included stroke, febrile seizures and headache. Among adolescents and adults, the abnormalities included paraplegia, epileptic seizures and localized sensory neuropathy. Headache occurred in a significantly higher percentage in children and adolescents compared to controls, but not in adults.

CONCLUSIONS

We conclude that SCA is associated with neurological complications: stroke and febrile seizures in children, epileptic seizures, paraplegia and localized sensory neuropathy in adolescents and adults, headache in children and adolescents. Detailed studies of each of these complications would be required to provide further insight into their significance.

Regional cerebral blood flow in patients with sickle cell disease: study with single photon emission computed tomography

OBJECTIVE

Neurological complications have been reported in patients with sickle-cell disease (SCD) using positron emission tomography (PET), magnetic resonance imaging (MRI), and computed tomography (CT), but not with single photon emission computed tomography (SPECT). The objective of this study was to investigate brain perfusion in the patients with SCD using SPECT after technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO), was administered and compare the findings with those of demography, physical examination, MRI and hematological profile.

METHODS

The study involved 21 patients (12 males, 9 females, age at study 8-45 years) who were known to be having SCD for a duration of at least 5 years. The patients were not in acute crisis and had normal neurological assessments with no known history of stroke or transient ischemic episode or previous abnormal CT or MRI brain scan, and were right-handed. The brain SPECT was performed after intravenous injection of 740 MBq (20 mCi) 99mTc-HMPAO in adults or an appropriate dose in pediatric patients. The scans were visually interpreted by two nuclear medicine physicians and a decision was reached by consensus. An MRI done 3 months later was interpreted by a radiologist. The demographic data and hematological profile were obtained from the medical records of the patients.

RESULTS

Of the 21 patients, 7 (age 11-22 years) had brain perfusion deficit mostly in the frontal lobe either alone or in combination with temporal and/or parietal lobe. The MRI was abnormal in 2 patients. The brain perfusion deficit was not associated with the demographic data of the patients or hematological profiles.

CONCLUSIONS

The findings show that SPECT was useful in detecting brain perfusion deficit in SCD patients, and such an early detection may be clinically useful in the subsequent follow-up of such patients, since it is known that cerebral perfusion deficit can lead to silent infarct and/or overt stroke, and affect cognitive skills.

Silent brain infarcts: a systematic review

As the availability and quality of imaging techniques improve, doctors are identifying more patients with no history of transient ischaemic attack or stroke in whom imaging shows brain infarcts. Until recently, little was known about the relevance of these lesions. In this systematic review, we give an overview of the frequency, causes, and consequences of MRI-defined silent brain infarcts, which are detected in 20% of healthy elderly people and up to 50% of patients in selected series. Most infarcts are lacunes, of which hypertensive small-vessel disease is thought to be the main cause. Although silent infarcts, by definition, lack clinically overt stroke-like symptoms, they are associated with subtle deficits in physical and cognitive function that commonly go unnoticed. Moreover, the presence of silent infarcts more than doubles the risk of subsequent stroke and dementia. Future studies will have to show whether screening and treating high-risk patients can effectively reduce the risk of further infarcts, stroke, and dementia.

Hemoglobin F concentration as a function of age in Kuwaiti sickle cell disease patients

OBJECTIVE

This study aimed to document the transition of hemoglobin (Hb) F levels from early childhood to adulthood in Kuwaiti sickle cell disease patients, investigating its relationship to sex, Hb genotype and coexistence of alpha-thalassemia trait.

SUBJECTS AND METHODS

The following parameters were extracted from the patients' records: age, sex, Hb, mean corpuscular volume, mean corpuscular Hb, red blood cell count, Hb F, Hb S, Hb A(2) and alpha-globin genotype. Hb quantitation was performed with cation exchange HPLC, while alpha-globin genotype was determined by PCR.

RESULTS

Records were available for 149 patients, made up of 94 SS and 55 Sbeta(0)thal; 83 males and 66 females, aged 3 months to 60 years (mean 10.5 +/- 1.8). The mean Hb F level in the whole population was 21.5 +/- 8.1% and was not significantly different between males and females, and SS or Sbeta(0)thal. When the age groups were analyzed, the Hb F level was highest (28.9 +/- 10.9%) in those below 5 years. Indeed, patients < or =2 years had a mean level of 31.9 +/- 13.0%. There was no significant difference in the Hb F levels in SS patients with or without coexistent alpha-thal trait.

CONCLUSIONS

Kuwaiti sickle cell disease patients below 5 years of age have close to 30% Hb F and this is probably a major reason why they usually do not present before this age, unlike patients elsewhere who present within the first year of life.

Defining stroke risk in children with sickle cell anaemia

Sickle cell anaemia (SCA) is the most common cause of childhood stroke, occurring with the highest frequency before the age of 6 years. Despite the relative frequency of stroke in SCA, few predictors of risk exist. Anaemia, leucocytosis, hypertension, silent infarction, and history of acute chest syndrome are well-documented risk factors for ischaemic stroke in SCA. Recent data suggest that other environmental and genetic factors, many unrelated to SCA, influence the development of cerebrovascular disease. Non-invasive assessment of individual stroke risk using transcranial Doppler ultrasonography has provided a means of selecting and prophylactically treating SCA children at highest risk. With the ultimate goal of preventing stroke, the information gained from the studies reviewed here may lead to improved prediction of stroke so that clinical trials to assess risk-based therapy may be carried out on selected children with SCA.

Stroke in children with sickle cell disease

Children with sickle disease are at high risk for ischemic stroke and transient ischemic attacks, usually secondary to intracranial arteriopathy involving the terminal internal carotid and proximal middle cerebral and anterior cerebral arteries, which may be diagnosed using transcranial Doppler ultrasound or magnetic resonance angiography (MRA). Other central nervous system (CNS) complications include seizures and coma, which may be secondary to ischemic stroke, sinovenous thrombosis, reversible posterior leukoencephalopathy, or acute demyelination. The immediate priority after an acute CNS event is to improve cerebral oxygenation with oxygen supplementation to maintain peripheral saturation measured using pulse oximetry between 96% and 99%, and a simple transfusion of packed cells within an hour of presentation if the patient's hemoglobin is less than 10 g/dL. The patient then should have erythrocytapheresis or manual exchange to reduce the hemoglobin S percentage to below 30%. Computed tomography to exclude hemorrhage is mandatory and MR T2-weighted imaging with MRA, fat-saturated imaging of the neck (dissection), MR venography (sinovenous thrombosis), and diffusion-weighted imaging usually distinguishes between arterial ischemic stroke and the differential diagnoses. Comatose patients with widespread focal or global cerebral edema may have good functional outcome after surgical decompression. Anticoagulation may be indicated for dissection or sinovenous thrombosis and steroids for demyelination. Blood pressure should be reduced slowly if raised in patients with reversible posterior leukoencephalopathy. Seizures should be treated aggressively and electroencephalogram monitoring should be done to exclude subclinical seizures if the patient is unconscious. Hemorrhagic stroke may require craniectomy and drainage and/or management of vasospasm. Interventional neuroradiology with coils is an alternative to surgical clipping for aneurysms. For secondary prevention, regular blood transfusion to hemoglobin S of less than 30% reduces the risk of recurrent stroke from approximately 67% to approximately 10%. Hydroxyurea and phlebotomy may be used in patients who are alloimmunized. Moyamoya syndrome is a risk factor for recurrence despite prophylactic blood transfusion. Revascularization may prevent additional stroke. Bone marrow transplantation may be offered to patients with human leukocyte antigen-compatible siblings. Blood transfusion prevents stroke in patients with velocities greater than 200 cm per second on TCD; a phase III trial studying the prevention of the progression of silent infarction is being done. Emerging primary prophylaxis regimens being tested include citrulline and arginine, aspirin, and overnight oxygen supplementation. Physicians caring for children with sickle cell disease also should ensure adequate nutrition, including five servings of fruit and vegetables a day. The role of vitamin supplementation is controversial, particularly when patients must take daily penicillin prophylaxis.

Is there a genetic basis for pediatric stroke?

PURPOSE OF REVIEW Childhood: stroke is more common than brain tumor, but because there is a wide spectrum in terms of etiology and most centers see only a few cases every year, there have been few large studies of genetic and environmental risk factors until recently. This review focuses on the clinical and radiologic methodology required to distinguish phenotypes in patients, and it focuses on the available data on genetic predisposition.

RECENT FINDINGS

A number of conditions with Mendelian inheritance (eg, sickle cell disease) predispose to childhood stroke, but the search for epistatic polymorphisms that explain why some but not all of these patients are affected has been hampered by our poor understanding of the pathophysiology. Emergency vascular imaging, including arteriography and venography, will almost certainly assist with the description of stroke subtypes with different genetic predisposition in these patients and in the important group of children who were completely healthy before their stroke. Environmental exposure (eg, to infection, hypoxemia, and vitamins) may play a crucial role in modifying genetic expression and must be described carefully in prospective studies.

SUMMARY

Now that much of the work on classifying stroke subtypes in children has been undertaken, international collaboration is likely to lead to identification of the genetic and environmental risk factors, and thus to primary and secondary prevention.