Toward Automated Detection of Silent Cerebral Infarcts in Children and Young Adults With Sickle Cell Anemia

BACKGROUND

Silent cerebral infarcts (SCI) in sickle cell anemia (SCA) are associated with future strokes and cognitive impairment, warranting early diagnosis and treatment. Detection of SCI, however, is limited by their small size, especially when neuroradiologists are unavailable. We hypothesized that deep learning may permit automated SCI detection in children and young adults with SCA as a tool to identify the presence and extent of SCI in clinical and research settings.

METHODS

We utilized UNet-a deep learning model-for fully automated SCI segmentation. We trained and optimized UNet using brain magnetic resonance imaging from the SIT trial (Silent Infarct Transfusion). Neuroradiologists provided the ground truth for SCI diagnosis, while a vascular neurologist manually delineated SCI on fluid-attenuated inversion recovery and provided the ground truth for SCI segmentation. UNet was optimized for the highest spatial overlap between automatic and manual delineation (dice similarity coefficient). The optimized UNet was externally validated using an independent single-center prospective cohort of SCA participants. Model performance was evaluated through sensitivity and accuracy (%correct cases) for SCI diagnosis, dice similarity coefficient, intraclass correlation coefficient (metric of volumetric agreement), and Spearman correlation.

RESULTS

The SIT trial (n=926; 31% with SCI; median age, 8.9 years) and external validation (n=80; 50% with SCI; age, 11.5 years) cohorts had small median lesion volumes of 0.40 and 0.25 mL, respectively. Compared with the neuroradiology diagnosis, UNet predicted SCI presence with 100% sensitivity and 74% accuracy. In magnetic resonance imaging with SCI, UNet reached a moderate spatial agreement (dice similarity coefficient, 0.48) and high volumetric agreement (intraclass correlation coefficient, 0.76; ρ=0.72; P<0.001) between automatic and manual segmentations.

CONCLUSIONS

UNet, trained using a large pediatric SCA magnetic resonance imaging data set, sensitively detected small SCI in children and young adults with SCA. While additional training is needed, UNet may be integrated into the clinical workflow as a screening tool, aiding in SCI diagnosis.

"Reversible cytotoxic lesion of the corpus callosum following SARS-CoV-2 mRNA vaccine administration: a finding to be aware of"

Cytotoxic lesions of the corpus callosum (CLOCCs) are a clinical-radiological spectrum of disorders secondary to several etiopathogeneses. Cytotoxic lesions of the corpus callosum are typically associated with mild clinical symptoms including fever, headache, confusion, and altered mental status. We present a case of a 51-year-old Caucasian woman who developed a reversible lesion of the splenium of the corpus callosum associated with small round-shaped white matter hyperintensities after the first dose of SARS-CoV-2 mRNA vaccine. Magnetic resonance imaging is fundamental for diagnosis and no treatment is generally required.

The White Matter Rounds experience: The importance of a multidisciplinary network to accelerate the diagnostic process for adult patients with rare white matter disorders

Introduction

Adult genetic leukoencephalopathies are rare neurological disorders that present unique diagnostic challenges due to their clinical and radiological overlap with more common white matter diseases, notably multiple sclerosis (MS). In this context, a strong collaborative multidisciplinary network is beneficial for shortening the diagnostic odyssey of these patients and preventing misdiagnosis. The White Matter Rounds (WM Rounds) are multidisciplinary international online meetings attended by more than 30 physicians and scientists from 15 participating sites that gather every month to discuss patients with atypical white matter disorders. We aim to present the experience of the WM Rounds Network and demonstrate the value of collaborative multidisciplinary international case discussion meetings in differentiating and preventing misdiagnoses between genetic white matter diseases and atypical MS.

Methods

We retrospectively reviewed the demographic, clinical and radiological data of all the subjects presented at the WM Rounds since their creation in 2013.

Results

Seventy-four patients (mean age 44.3) have been referred and discussed at the WM Rounds since 2013. Twenty-five (33.8%) of these patients were referred by an MS specialist for having an atypical presentation of MS, while in most of the remaining cases, the referring physician was a geneticist (23; 31.1%). Based on the WM Rounds recommendations, a definite diagnosis was made in 36/69 (52.2%) patients for which information was available for retrospective review. Of these diagnosed patients, 20 (55.6%) had a genetic disease, 8 (22.2%) had MS, 3 (8.3%) had both MS and a genetic disorder and 5 (13.9%) had other non-genetic conditions. Interestingly, among the patients initially referred by an MS specialist, 7/25 were definitively diagnosed with MS, 5/25 had a genetic condition (e.g., X-linked adrenoleukodystrophy and hereditary small vessel diseases like Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) and COL4A1-related disorder), and one had both MS and a genetic demyelinating neuropathy. Thanks to the WM Rounds collaborative efforts, the subjects who currently remain without a definite diagnosis, despite extensive investigations performed in the clinical setting, have been recruited in research studies aimed at identifying novel forms of genetic MS mimickers.

Conclusions

The experience of the WM Rounds Network demonstrates the benefit of collective discussions on complex cases to increase the diagnostic rate and decrease misdiagnosis in patients with rare or atypical white matter diseases. Networks of this nature allow physicians and scientists to compare and share information on challenging cases from across the world, provide a basis for future multicenter research studies, and serve as model for other rare diseases.

Cumulative Blood Pressure Exposure During Young Adulthood and Mobility and Cognitive Function in Midlife

BACKGROUND

High blood pressure (BP) is a known risk factor for mobility and cognitive impairment in older adults. This study tested the association of cumulative BP exposure from young adulthood to midlife with gait and cognitive function in midlife. Furthermore, we tested whether these associations were modified by cerebral white matter hyperintensity (WMH) burden.

METHODS

We included 191 participants from the CARDIA study (Coronary Artery Risk Development in Young Adults), a community-based cohort of young individuals followed over 30 years. Cumulative BP was calculated as the area under the curve (mm Hg×years) from baseline up to year 30 examination. Gait and cognition were assessed at the year 30 examination. Cerebral WMH was available at year 30 in a subset of participants (n=144) who underwent magnetic resonance imaging. Multiple linear regression models were used to assess the association of cumulative BP exposure with gait and cognition. To test effect modification by WMH burden, participants were stratified at the median of WMH and tested for interaction.

RESULTS

Higher cumulative systolic and diastolic BPs were associated with slower walking speed (both P=0.010), smaller step length (P=0.011 and 0.005, respectively), and higher gait variability (P=0.018 and 0.001, respectively). Higher cumulative systolic BP was associated with lower cognitive performance in the executive (P=0.021), memory (P=0.015), and global domains (P=0.010), and higher cumulative diastolic BP was associated with lower cognitive performance in the memory domain (P=0.012). All associations were independent of socio-demographics and vascular risk factors (body mass index, smoking, diabetes mellitus and total cholesterol). The association between cumulative BP and gait was moderated by WMH burden (interaction P<0.05). However, the relation between cumulative BP and cognitive function was not different based on the WMH burden (interaction P>0.05).

CONCLUSIONS

Exposure to higher BP levels from young to midlife is associated with worse gait and cognitive performance in midlife. Furthermore, WMH moderates the association of cumulative BP exposure with gait, but not with cognitive function in midlife. The mechanisms underpinning the impact of BP exposure on brain structure and function must be investigated in longitudinal studies using a life course approach.

Magnetization transfer in liposome and proteoliposome samples that mimic the protein and lipid composition of myelin

Although magnetization transfer (MT) has been widely used in brain MRI, for example in brain inflammation and multiple sclerosis, the detailed molecular origin of MT effects and the role that proteins play in MT remain unclear. In this work, a proteoliposome model system was used to mimic the myelin environment and to examine the roles of protein, cholesterol, brain cerebrosides, and sphingomyelin embedded in the liposome matrix. Exchange parameters were determined using a double-quantum filter experiment. The goal was to determine the relative contributions to exchange and MT of cerebrosides, sphingomyelin, cholesterol, and proteins in 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayers. The main finding was that cerebrosides produced the strongest exchange effects, and that these were even more pronounced than those found for proteins. Sphingomyelin (which also has exchangeable groups at the head of the fatty acid chains, albeit closer to the lipid acyl chains) and cholesterol showed only minimal transfer. Overall, the extracted exchange rates appeared much smaller than commonly assumed for -OH and -NH groups.

Early regional cuprizone-induced demyelination in a rat model revealed with MRI

The cuprizone model of demyelination is well established in the mouse as a tool for the study of the mechanisms of both demyelination and remyelination. It is often desirable, however, to have a larger model, such as the rat, especially for imaging-based studies, yet initial work has failed to show demyelination in cuprizone-fed rats. Several recent studies have demonstrated demyelination in the rat, but only in the corpus callosum. In this study, we acquired high-resolution, three-dimensional images of the whole brain every 2 weeks, using a T₁ -weighted magnetization-prepared rapid acquisition gradient echo imaging sequence, optimized for myelin contrast, in order to assess myelination across the entire rat brain over a period of 8 weeks on a 1% cuprizone diet. We observed a consistent pattern of demyelination, beginning in the cerebellum by 4 weeks and involving more rostral regions of the brain by 8 weeks on the cuprizone diet, with validation using Luxol fast blue histology. This imaging technique permits the effects of cuprizone-induced demyelination to be followed longitudinally in a single animal, over the entire brain. In turn, this may facilitate the establishment of the cuprizone model of demyelination in the rat.

Neuroimaging in pediatric phakomatoses. An educational review

Phakomatoses are a group of more than 30 entities with an inheritance pattern that primarily affects the central nervous system, skin, viscera and connective tissue. The aim of this paper is to make an educational review of the most common radiological findings on phakomatoses through the iconography of the cases collected in our magnetic resonance imaging (MRI) and computer tomography (CT) units over the last ten years. Also, we describe and illustrate by these techniques the main features of the most common entities within the wide spectrum of diseases. As highly variable and age dependent, imaging techniques have an important role in the diagnosis and follow-up of these patients. Increased awareness for the need to implement and conduct screening programs could be considered as a solution to prevent late diagnosis and to treat the patients in early stages of disease.

In vivo diffusion tensor imaging of amyloid-β-induced white matter damage in mice

BACKGROUND

Diffusion tensor imaging (DTI) suggests the presence of white matter abnormality at the prodromal stage in human Alzheimer's disease (AD).

OBJECTIVE

To use a mouse model of AD to determine whether the white matter abnormality detected by in vivo DTI is associated with functional deficits and axon damage.

METHODS

Amyloid-β1-42 (Aβ1-42) was injected into the left lateral ventricle in mice. Two months after the injection, in vivo DTI and visual evoked potential (VEP) recordings were performed, followed by immunohistochemistry of phosphorylated neurofilament and myelin basic protein.

RESULTS

DTI of Aβ1-42-treated mice showed a significant increase of radial diffusivity in white matter including the optic nerves and tracts. The abnormality was associated with decreased amplitude and increased latency of VEP. Immunohistochemistry confirmed a significant loss of axons and myelin integrity.

CONCLUSION

White matter damage induced by Aβ1-42 in mice can be detected non-invasively by DTI.

Hematopoietic stem cell transplantation in the leukodystrophies: a systematic review of the literature

OBJECTIVE

The objective of this study is to systematically review the literature on worldwide numbers of leukodystrophy patients undergoing hematopoietic stem cell transplantation (HSCT) as well as the safety and efficacy of the procedure in this patient population.

MATERIALS AND METHODS

A PubMed and EMBASE search up to June 2012 was conducted with a manual search of references from relevant articles. Selected studies were evaluated using internationally accepted criteria. The effect estimates of HSCT upon survival in early-stage disease versus late-stage disease were compared.

RESULTS

One hundred and fifty-two studies qualified for inclusion and reported on a total of 689 patients. Study quality ranged from poor to good; no study was rated excellent. Small sample sizes limited most studies. Meta-analysis in a subset of larger studies indicates that transplantation in earlier stages of disease fairs better than in the late stages. Beyond survival, little longitudinal data on functional outcome is reported and neurological outcome is sparse.

CONCLUSION

Further studies are needed to determine the neurological outcome following HSCT in the leukodystrophies. HSCT in the early stages of cerebral disease is still recommended for select leukodystrophies.

Recognition memory impairments after subcortical white matter stroke in mice

BACKGROUND AND PURPOSE

Small subcortical white matter infarcts are a common stroke subtype often associated with cognitive deficits. The lack of relevant models confined to white matter has limited the investigation of its pathophysiology. Here, we examine tissue and functional outcome after an ischemic lesion within corpus callosum in wild-type (WT) mice and in mice null for a gene, NOTCH3, linked to white matter ischemic injury in patients.

METHODS

WT and NOTCH3 knockout mice were subjected to stereotactic microinjections of the potent vasoconstrictor endothelin-1 at the level of periventricular white matter to induce a focal ischemic lesion. Infarct location was confirmed by MRI, and brains were examined for lesion size and histology; behavioral deficits were assessed ≤1 month in WT mice.

RESULTS

Ischemic damage featured an early cerebral blood flow deficit, blood-brain barrier opening, and a lesion largely confined to white matter. At later stages, myelin and axonal degeneration and microglial/macrophage infiltration were found. WT mice displayed prolonged cognitive deficit when tested using a novel object recognition task. NOTCH3 mutants showed larger infarcts and greater cognitive deficit at 7 days post stroke.

CONCLUSIONS

Taken together, these data show the usefulness of microinjections of endothelin-1 into periventricular white matter to study focal infarcts and cognitive deficit in WT mice. In short-term studies, stroke outcome was worse in NOTCH3 null mice, consistent with the notion that the lack of the NOTCH3 receptor affects white matter stroke susceptibility.

White matter involvement beyond the optic nerves in CRION as assessed by diffusion tensor imaging

BACKGROUND

Chronic relapsing inflammatory optic neuropathy (CRION) is an inflammatory optic neuropathy, characterized by relapses and remissions in patients with normal brain and spinal magnetic resonance imaging (MRI). Discrepancy from other demyelinating diseases is important, and it is still uncertain whether CRION is restricted to the optic pathways or it affects other brain white matter (WM) structures.

OBJECTIVE

To assess WM structure in patients with CRION by using diffusion tensor imaging (DTI).

METHODS

DTI was performed in six CRION patients and six age- and sex-matched healthy controls on a 3 T scanner. Tract-based spatial statistics (TBSS) was used for voxelwise statistical analysis of DTI data. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) measures were obtained.

RESULTS

TBSS analysis revealed two different patterns of WM alterations in patients with CRION. The optic chiasm and connected structures had significantly higher FA and lower RD, AD and MD in the patients than in the healthy controls. On the other hand, anterior frontal bundles of inferior fronto-occipital tracts, left uncinate fascicule and internal capsule showed decreased FA and increased RD. No correlation was found between the clinical variables and diffusion measures.

CONCLUSION

WM appearing normal on brain MRI shows widespread abnormalities in a cohort of CRION patients as assessed by DTI.

Oxidative stress interferes with white matter renewal after prolonged cerebral hypoperfusion in mice

BACKGROUND AND PURPOSE

White matter injury caused by cerebral hypoperfusion may contribute to the pathophysiology of vascular dementia and stroke, but the underlying mechanisms remain to be fully defined. Here, we test the hypothesis that oxidative stress interferes with endogenous white matter repair by disrupting renewal processes mediated by oligodendrocyte precursor cells (OPCs).

METHODS

In vitro, primary rat OPCs were exposed to sublethal CoCl2 for 7 days to induce prolonged chemical hypoxic stress. Then, OPC proliferation/differentiation was assessed. In vivo, prolonged cerebral hypoperfusion was induced by bilateral common carotid artery stenosis in mice. Then, reactive oxygen species production, myelin density, oligodendrocyte versus OPC counts, and cognitive function were evaluated. To block oxidative stress, OPCs and mice were treated with the radical scavenger edaravone.

RESULTS

Prolonged chemical hypoxic stress suppressed OPC differentiation in vitro. Radical scavenging with edaravone ameliorated these effects. After 28 days of cerebral hypoperfusion in vivo, reactive oxygen species levels were increased in damaged white matter, along with the suppression of OPC-to-oligodendrocyte differentiation and loss of myelin staining. Concomitantly, mice showed functional deficits in working memory. Radical scavenging with edaravone rescued OPC differentiation, ameliorated myelin loss, and restored working memory function.

CONCLUSIONS

Our proof-of-concept study demonstrates that after prolonged cerebral hypoperfusion, oxidative stress interferes with white matter repair by disrupting OPC renewal mechanisms. Radical scavengers may provide a potential therapeutic approach for white matter injury in vascular dementia and stroke.

Subclinical left ventricular dysfunction and silent cerebrovascular disease: the Cardiovascular Abnormalities and Brain Lesions (CABL) study

BACKGROUND

Silent brain infarcts (SBIs) and white matter hyperintensities are subclinical cerebrovascular lesions associated with incident stroke and cognitive decline. Left ventricular ejection fraction (LVEF) is a predictor of stroke in patients with heart failure, but its association with subclinical brain disease in the general population is unknown. Left ventricular global longitudinal strain (GLS) can detect subclinical cardiac dysfunction even when LVEF is normal. We investigated the relationship of LVEF and GLS with subclinical brain disease in a community-based cohort.

METHODS AND RESULTS

LVEF and GLS were assessed by 2-dimensional and speckle-tracking echocardiography in 439 participants free of stroke and cardiac disease from the Cardiovascular Abnormalities and Brain Lesions (CABL) study. SBIs and white matter hyperintensities were assessed by brain MRI. Mean age of the study population was 69±10 years, 61% were women, LVEF was 63.8±6.4%, GLS was -17.1±3.0%. SBIs were detected in 53 participants (12%), white matter hyperintensity volume was 0.63±0.86%. GLS was significantly lower in participants with SBI versus those without (-15.7±3.5% versus -17.3±2.9%, P<0.01), whereas no difference in LVEF was observed (63.3±8.6% versus 63.8±6.0%, P=0.60). In multivariate analysis, lower GLS was associated with SBI (odds ratio/unit decrease=1.18; 95% confidence interval, 1.05-1.33; P<0.01), whereas LVEF was not (odds ratio/unit increase=1.00; 95% confidence interval, 0.96-1.05; P=0.98). Lower GLS was associated with greater white matter hyperintensity volume (adjusted β=0.11, P<0.05), unlike LVEF (adjusted β=-0.04, P=0.42).

CONCLUSIONS

Lower GLS was independently associated with subclinical brain disease in a community-based cohort without overt cardiac disease. GLS can provide additional information on cerebrovascular risk burden beyond LVEF assessment.

Age-related decline in oligodendrogenesis retards white matter repair in mice

BACKGROUND AND PURPOSE

Aging is one of the major risk factors for white matter injury in cerebrovascular disease. However, the effects of age on the mechanisms of injury/repair in white matter remain to be fully elucidated. Here, we ask whether, compared with young brains, white matter regions in older brains may be more vulnerable in part because of decreased rates of compensatory oligodendrogenesis after injury.

METHODS

A mouse model of prolonged cerebral hypoperfusion was prepared by bilateral common carotid artery stenosis in 2-month and 8-month-old mice. Matching in vitro studies were performed by subjecting oligodendrocyte precursor cells to sublethal 7-day CoCl2 treatment to induce chemical hypoxic stress.

RESULTS

Baseline myelin density in the corpus callosum was similar in 2-month and 8-month-old mice. But after induction of prolonged cerebral hypoperfusion, older mice showed more severe white matter injury together with worse deficits in working memory. The numbers of newborn oligodendrocytes and their precursors were increased by cerebral hypoperfusion in young mice, whereas these endogenous responses were significantly dampened in older mice. Defects in cyclic AMP response element-binding protein signaling may be involved because activating cyclic AMP response element-binding protein with the type-III phosphodiesterase inhibitor cilostazol in older mice restored the differentiation of oligodendrocyte precursor cells, alleviated myelin loss, and improved cognitive dysfunction during cerebral hypoperfusion. Cell culture systems confirmed that cilostazol promoted the differentiation of oligodendrocyte precursor cells.

CONCLUSIONS

An age-related decline in cyclic AMP response element-binding protein-mediated oligodendrogenesis may compromise endogenous white matter repair mechanisms, and therefore, drugs that activate cyclic AMP response element-binding protein signaling provide a potential therapeutic approach for treating white matter injury in aging brains.

Differential diagnosis of white matter diseases in the tropics: An overview

In hospitals in the tropics, the availability of magnetic resonance imaging (MRI) facilities in urban areas and especially in teaching institutions have resulted in white matter diseases being frequently reported in a variety of clinical settings. Unlike the west where multiple sclerosis (MS) is the commonest white matter disease encountered, in the tropics, there are myriad causes for the same. Infectious and post infectious disorders probably account for the vast majority of these diseases. Human immunodeficiency virus (HIV) infection tops the list of infective conditions. Central nervous system (CNS) tuberculosis occasionally presents with patchy parenchymal lesions unaccompanied by meningeal involvement. Human T cell leukemia virus (HTLV) infection and cystic inflammatory lesions such as neurocysticercosis are important causes to be considered in the differential diagnosis. Diagnosing post infectious demyelinating disorders is equally challenging since more than a third of cases seen in the tropics do not present with history of past infection or vaccinations. Metabolic and deficiency disorders such as Wernicke's encephalopathy, osmotic demyelinating syndrome associated with extra pontine lesions and Vitamin B12 deficiency states can occassionaly cause confusion in diagnosis. This review considers a few important disorders which manifest with white matter changes on MRI and create diagnostic difficulties in a population in the tropics.