Cognitive evoked potentials and neural networks are abnormal in children with sickle cell disease and not related to the degree of anaemia, pain and silent infarcts

Neurodevelopmental Outcomes in Preterm Children with Sickle Cell Disease

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Neurocognitive Changes in Sickle Cell Disease: A Comprehensive Review

Background:

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

Summary:

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

Key message:

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

Disease burden and quality of life of in children with sickle cell disease in Italy: time to be considered a priority

The objective of the present article is to highlight the need for attention to Quality of Life of patients with Sickle Cell Disease living in Italy. The transformation of sickle cell disease from a severe life-threatening disease of childhood into a chronic, lifelong condition due to the significant improvements in care and treatment options, imposes increasing new challenges to health care providers and patients. Patients now face physical, psychosocial and emotional challenges throughout their lives. They generally have to receive chronic treatments and regular multidisciplinary monitoring which increase social and emotional burden rendering adherence to treatment sometimes complicated. A chronic disease impacts all aspects of patients’ lives, not only the physical one, but also the social and emotional aspects as well as the educational and working life. The entire “Quality of Life” is affected and recent evidence demonstrates the importance quality of life has for patients with chronic illness. The results of this review focus on emerging data regarding quality of life across the lifespan of patients with Sickle Cell Disease, and highlight the need for more action in this field in Italy, where recent immigration and improved care determine an increasing population of children with sickle cell disease being taken into long term care.

Visual cortex changes in children with sickle cell disease and normal visual acuity: a multimodal magnetic resonance imaging study

The visual system is primarily affected in sickle cell disease (SCD), and eye examination is recommended starting in late childhood. So far, to our knowledge, all studies have focused on the retina, neglecting the changes that might be present in the cortical portion of the visual system. We performed a multimodal magnetic resonance imaging (MRI) evaluation of the visual cortex in 25 children with SCD (mean age: 12·3 ± 1·9 years) and 31 controls (mean age: 12·7 ± 1·6 years). At ophthalmologic examination, 3/25 SCD children had mild visual acuity deficits and 2/25 had mild tortuosity of the retinal vessels. None showed optic pathway infarcts at MRI or Transcranial Doppler abnormal blood velocities, and 6/25 disclosed posterior cerebral artery stenosis (five mild and one severe) at MR-angiography. Compared to controls, SCD children had increased posterior pericalcarine cortical thickness, with a different trajectory of cortical maturation and decreased connectivity within medial and ventral visual neural networks. Our findings suggest that SCD affects the development and the tuning of the visual cortex, leading to anatomical and functional changes in childhood even in the absence of retinopathy, and set the basis for future studies to determine if these changes can represent useful predictors of visual impairment in adulthood, biomarkers of disease progression or treatment response.

Selective Difficulties in Lexical Retrieval and Nonverbal Executive Functioning in Children With HbSS Sickle Cell Disease

Language deficits in multilingual children with sickle cell disease (SCD) are poorly understood. We tested the hypothesis that selective language deficits in this population could relate to an impaired frontal lobe functioning often associated with high-risk homozygous HbS disease (HbSS). In all, 32 children from immigrant communities with HbSS SCD aged 6 to 12 years (mean age = 9.03, n = 9 with silent infarcts) and 35 demographically matched healthy controls (mean age = 9.14) were tested on their naming skills, phonological and semantic fluency, attention, and selected executive functions (response inhibition and planning skills). Analyses of variance showed significant differences between patients and controls in inhibition and planning (p = .001 and .001), and phonological fluency (p = .004). The poorer performance in phonological fluency of the children with SCD was not associated with any visible brain damage to language areas. Hierarchical regression analyses showed that, whereas the control children's vocabulary knowledge explained their performance in the phonological fluency tasks, only inhibition skills accounted for variance in the performance of the children with SCD. These results suggest a selective impairment of verbal and nonverbal executive functioning (i.e., planning, inhibition, and phonological fluency) in children with SCD, with deficits possibly owing to frontal area hypoxia.

Graph theory analysis reveals how sickle cell disease impacts neural networks of patients with more severe disease

Sickle cell disease (SCD) is a hereditary blood disorder associated with many life-threatening comorbidities including cerebral stroke and chronic pain. The long-term effects of this disease may therefore affect the global brain network which is not clearly understood. We performed graph theory analysis of functional networks using non-invasive fMRI and high resolution EEG on thirty-one SCD patients and sixteen healthy controls. Resting state data were analyzed to determine differences between controls and patients with less severe and more severe sickle cell related pain. fMRI results showed that patients with higher pain severity had lower clustering coefficients and local efficiency. The neural network of the more severe patient group behaved like a random network when performing a targeted attack network analysis. EEG results showed the beta1 band had similar results to fMRI resting state data. Our data show that SCD affects the brain on a global level and that graph theory analysis can differentiate between patients with different levels of pain severity.

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Graph theory used to study global impact of long term sickle cell disease on brain.

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EEG and fMRI results compared to study spatial and temporal impact of disease.

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More severe patients have less clustering and efficiency.

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Small world values correlated with past hospitalizations, linking results to pain.

Increased theta band EEG power in sickle cell disease patients

Objective

Pain is a major issue in the care of patients with sickle cell disease (SCD). The mechanisms behind pain and the best way to treat it are not well understood. We studied how electroencephalography (EEG) is altered in SCD patients.

Methods

We recruited 20 SCD patients and compared their resting state EEG to that of 14 healthy controls. EEG power was found across frequency bands using Welch's method. Electrophysiological source imaging was assessed for each frequency band using the eLORETA algorithm.

Results

SCD patients had increased theta power and decreased beta2 power compared to controls. Source localization revealed that areas of greater theta band activity were in areas related to pain processing. Imaging parameters were significantly correlated to emergency department visits, which indicate disease severity and chronic pain intensity.

Conclusion

The present results support the pain mechanism referred to as thalamocortical dysrhythmia. This mechanism causes increased theta power in patients.

Significance

Our findings show that EEG can be used to quantitatively evaluate differences between controls and SCD patients. Our results show the potential of EEG to differentiate between different levels of pain in an unbiased setting, where specific frequency bands could be used as biomarkers for chronic pain.

Targeting novel mechanisms of pain in sickle cell disease

Patients with sickle cell disease (SCD) suffer from intense pain that can start during infancy and increase in severity throughout life, leading to hospitalization and poor quality of life. A unique feature of SCD is vaso-occlusive crises (VOCs) characterized by episodic, recurrent, and unpredictable episodes of acute pain. Microvascular obstruction during a VOC leads to impaired oxygen supply to the periphery and ischemia reperfusion injury, inflammation, oxidative stress, and endothelial dysfunction, all of which may perpetuate a noxious microenvironment leading to pain. In addition to episodic acute pain, patients with SCD also report chronic pain. Current treatment of moderate to severe pain in SCD is mostly reliant upon opioids; however, long-term use of opioids is associated with multiple side effects. This review presents up-to-date developments in our understanding of the pathobiology of pain in SCD. To help focus future research efforts, major gaps in knowledge are identified regarding how sickle pathobiology evokes pain, pathways specific to chronic and acute sickle pain, perception-based targets of "top-down" mechanisms originating from the brain and neuromodulation, and how pain affects the sickle microenvironment and pathophysiology. This review also describes mechanism-based targets that may help develop novel therapeutic and/or preventive strategies to ameliorate pain in SCD.

Targeting novel mechanisms of pain in sickle cell disease

Patients with sickle cell disease (SCD) suffer from intense pain that can start during infancy and increase in severity throughout life, leading to hospitalization and poor quality of life. A unique feature of SCD is vaso-occlusive crises (VOCs) characterized by episodic, recurrent, and unpredictable episodes of acute pain. Microvascular obstruction during a VOC leads to impaired oxygen supply to the periphery and ischemia reperfusion injury, inflammation, oxidative stress, and endothelial dysfunction, all of which may perpetuate a noxious microenvironment leading to pain. In addition to episodic acute pain, patients with SCD also report chronic pain. Current treatment of moderate to severe pain in SCD is mostly reliant upon opioids; however, long-term use of opioids is associated with multiple side effects. This review presents up-to-date developments in our understanding of the pathobiology of pain in SCD. To help focus future research efforts, major gaps in knowledge are identified regarding how sickle pathobiology evokes pain, pathways specific to chronic and acute sickle pain, perception-based targets of "top-down" mechanisms originating from the brain and neuromodulation, and how pain affects the sickle microenvironment and pathophysiology. This review also describes mechanism-based targets that may help develop novel therapeutic and/or preventive strategies to ameliorate pain in SCD.

Characterization of functional brain activity and connectivity using EEG and fMRI in patients with sickle cell disease

Sickle cell disease (SCD) is a red blood cell disorder that causes many complications including life-long pain. Treatment of pain remains challenging due to a poor understanding of the mechanisms and limitations to characterize and quantify pain. In the present study, we examined simultaneously recording functional MRI (fMRI) and electroencephalogram (EEG) to better understand neural connectivity as a consequence of chronic pain in SCD patients. We performed independent component analysis and seed-based connectivity on fMRI data. Spontaneous power and microstate analysis was performed on EEG-fMRI data. ICA analysis showed that patients lacked activity in the default mode network (DMN) and executive control network compared to controls. EEG-fMRI data revealed that the insula cortex's role in salience increases with age in patients. EEG microstate analysis showed patients had increased activity in pain processing regions. The cerebellum in patients showed a stronger connection to the periaqueductal gray matter (involved in pain inhibition), and negative connections to pain processing areas. These results suggest that patients have reduced activity of DMN and increased activity in pain processing regions during rest. The present findings suggest resting state connectivity differences between patients and controls can be used as novel biomarkers of SCD pain.

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Simultaneous EEG-fMRI recordings revealed altered connectivity in sickle cell patients.

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Reduced activity observed in default mode network and executive control network.

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Patients' salience network strength increases with age; opposite seen in controls.

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EEG-fMRI parameters reflect disease severity in sickle cell patients.

New insights into sickle cell disease: mechanisms and investigational therapies

PURPOSE OF REVIEW

Sickle cell disease (SCD) afflicts millions worldwide. The simplicity of its single nucleotide mutation belies the biological and psychosocial complexity of the disease. Despite only a single approved drug specifically for the treatment of SCD, new findings reviewed from 2015 provide the direction forward.

RECENT FINDINGS

The last year has provided a wealth of support for mechanisms affecting the red cell, hemolysis and vasculopathy, the innate immune system activation, blood cell and endothelial adhesiveness, central sensitization to pain, and chronic brain injury. The evidence supporting expanded use of hydroxyurea continues to mount. Many promising therapies are reaching clinical trial, including curative therapies, with more on the horizon.

SUMMARY

Evidence is compelling that the use of hydroxyurea must be expanded by clinicians to gain the full pleiotropic benefits of this approved drug. Clinicians must become aware that severe acute and chronic pain has a biological and neurologic basis, and the understanding of this basis is growing. Researchers are testing investigational therapies at an unprecedented pace in SCD, and partnership between patients, researchers, and the private sector provides the most rapid and productive way forward.

Cognition and the Default Mode Network in Children with Sickle Cell Disease: A Resting State Functional MRI Study

Cerebrovascular complications are frequent events in children with sickle cell disease, yet routinely used techniques such as Transcranial Doppler (TCD), Magnetic Resonance (MRI) and Angiography (MRA), insufficiently explain the cause of poor cognitive performances. Forty children with SS-Sβ° (mean age 8 years) underwent neurocognitive evaluation and comprehensive brain imaging assessment with TCD, MRI, MRA, Resting State (RS) Functional MRI with evaluation of the Default Mode Network (DMN). Sixteen healthy age-matched controls underwent MRI, MRA and RS functional MRI.Children with SCD display increased brain connectivity in the DMN even in the absence of alterations in standard imaging techniques. Patients with low neurocognitive scores presented higher brain connectivity compared to children without cognitive impairment or controls, suggesting an initial compensatory mechanism to maintain performances. In our cohort steady state haemoglobin level was not related to increased brain connectivity, but SatO2<97% was. Our findings provide novel evidence that SCD is characterized by a selective disruption of connectivity among relevant regions of the brain, potentially leading to reduced cognition and altered functional brain dynamics. RS functional MRI could be used as a useful tool to evaluate cognition and cerebral damage in SCD in longitudinal trials.