Joshua S Shimony

Washington University in St. Louis, San Luis, Missouri, United States

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Publications (119)505.28 Total impact

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    ABSTRACT: The purpose of this manuscript is to provide an introduction to resting-state functional magnetic resonance imaging (RS-fMRI) and to review the current application of this new and powerful technique in the preoperative setting using our institute's extensive experience. RS-fMRI has provided important insights into brain physiology and is an increasingly important tool in the clinical setting. As opposed to task-based functional MRI wherein the subject performs a task while being scanned, RS-fMRI evaluates low-frequency fluctuations in the blood oxygen level dependent (BOLD) signal while the subject is at rest. Multiple resting state networks (RSNs) have been identified, including the somatosensory, language, and visual networks, which are of primary importance for presurgical planning. Over the past 4 years, we have performed over 300 RS-fMRI examinations in the clinical setting and these have been used to localize eloquent somatosensory and language cortices before brain tumor resection. RS-fMRI is particularly useful in this setting for patients who are unable to cooperate with the task-based paradigm, such as young children or those who are sedated, paretic, or aphasic.Although RS-fMRI is still investigational, our experience indicates that this method is ready for clinical application in the presurgical setting.
    No preview · Article · Feb 2016 · Topics in magnetic resonance imaging: TMRI
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    ABSTRACT: Currently, functional magnetic resonance imaging (fMRI) facilitates a preoperative awareness of an association of an eloquent region with a tumor. This information gives the neurosurgeon helpful information that can aid in creating a surgical strategy. Typically, task-based fMRI has been employed to preoperatively localize speech and motor function. Task-based fMRI depends on the patient's ability to comply with the task paradigm, which often is impaired in the setting of a brain tumor. This problem is overcome by using resting-state fMRI (rs-fMRI) to localize function. rs-fMRI measures spontaneous fluctuations in the blood oxygen level-dependent (BOLD) signal, representing the brain's functional organization. In a neurosurgical context, it allows noninvasive simultaneous assessment of multiple large-scale distributed networks. Compared with task-related fMRI, rs-fMRI provides more comprehensive information on the functional architecture of the brain and is applicable in settings where task-related fMRI may provide inadequate information or could not be performed. Taken together, rs-fMRI substantially expands the preoperative mapping capability in efficiency, effectiveness, and scope. In this article, a brief introduction into rs-fMRI processing methods is followed by a detailed discussion on the role rs-fMRI plays in presurgical planning.
    No preview · Article · Jan 2016 · Stereotactic and Functional Neurosurgery
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    ABSTRACT: We evaluated 22 measures of cortical folding, 20 derived from local curvature (curvature-based measures) and two based on other features (sulcal depth and gyrification index), for their capacity to distinguish between normal and aberrant cortical development. Cortical surfaces were reconstructed from 12 term-born control and 63 prematurely-born infants. Preterm infants underwent 2-4 MR imaging sessions between 27 and 42weeks postmenstrual age (PMA). Term infants underwent a single MR imaging session during the first postnatal week. Preterm infants were divided into two groups. One group (38 infants) had no/minimal abnormalities on qualitative assessment of conventional MR images. The second group (25 infants) consisted of infants with injury on conventional MRI at term equivalent PMA. For both preterm infant groups, all folding measures increased or decreased monotonically with increasing PMA, but only sulcal depth and gyrification index differentiated preterm infants with brain injury from those without. We also compared scans obtained at term equivalent PMA (36-42weeks) for all three groups. No curvature-based measured distinguished between the groups, whereas sulcal depth distinguished term control from injured preterm infants and gyrification index distinguished all three groups. When incorporating total cerebral volume into the statistical model, sulcal depth no longer distinguished between the groups, though gyrification index distinguished between all three groups and positive shape index distinguished between the term control and uninjured preterm groups. We also analyzed folding measures averaged over brain lobes separately. These results demonstrated similar patterns to those obtained from the whole brain analyses. Overall, though the curvature-based measures changed during this period of rapid cerebral development, they were not sensitive for detecting the differences in folding associated with brain injury and/or preterm birth. In contrast, gyrification index was effective in differentiating these groups.
    No preview · Article · Nov 2015 · NeuroImage
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    Preview · Article · Nov 2015 · Neuro-Oncology
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    ABSTRACT: Purpose: To assess retinal nerve fiber layer (RNFL) thickness at term-equivalent age in very preterm (<32 weeks gestational age) versus term-born infant cohorts, and compare very preterm infant RNFL thickness with brain anatomy and neurodevelopment. Design: Cohort study. Methods: RNFL was semi-automatically segmented (one eye per infant) in 57 very preterm and 50 term infants with adequate images from bedside portable, handheld spectral domain optical coherence tomography (Bioptigen, Inc., Research Triangle Park, NC) imaging at 37-42 weeks postmenstrual age. Mean RNFL thickness was calculated for the papillomacular bundle (-15° to +15°) and temporal quadrant (-45° to +45°) relative to the fovea-optic nerve axis. Brain magnetic resonance imaging (MRI) scans clinically obtained in 26 very preterm infants were scored for global structural abnormalities by an expert masked to data except for age. Cognitive, language, and motor skills were assessed with Bayley Scales of Infant and Toddler Development-III (Pearson, San Antonio, TX) in 33 of the very preterm infants at 18-24 months corrected age. Results: RNFL was thinner for very preterm versus term infants at the papillomacular bundle ([mean ± standard deviation] 61 ± 17 versus 72 ± 13 μm, p<0.001) and temporal quadrant (72 ± 21 versus 82 ± 16 μm, p=0.005). In very preterm infants, thinner papillomacular bundle RNFL correlated with higher global brain MRI lesion burden index (R(2)=0.35, p=0.001) and lower cognitive (R(2)=0.18, p=0.01) and motor (R(2)=0.17, p=0.02) scores. Relationships were similar for temporal quadrant. Conclusions: Thinner RNFL in very preterm infants relative to term-born infants may relate to brain structure and neurodevelopment.
    No preview · Article · Sep 2015 · American Journal of Ophthalmology
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    ABSTRACT: Background: Preterm infants are at risk for white matter injury and adverse neurodevelopmental outcomes. Methods: Serial diffusion tensor MRI data were obtained from very preterm infants (N=78) born <30 weeks gestation imaged up to four times from 26-42 weeks postmenstrual age. Slopes were calculated for fractional anisotropy (FA) and mean diffusivity (MD) within regions of interest for infants with ≥2 scans (N=50). Sixty-five children underwent neurodevelopmental testing at age two years. Results: FA slope for the posterior limb of the internal capsule was greater than other regions. The anterior limb of the internal capsule (ALIC), corpus callosum and optic radiations demonstrated greater FA slope with increasing gestational age. Infants with PDA had lower FA slope in the ALIC. MD slope was lower with prolonged ventilation or lack of antenatal steroids. At age 2 years, lower motor scores were associated with lower FA in the left but higher FA in the right inferior temporal lobe at term-equivalent. Better social-emotional competence was related to lower FA in the left cingulum bundle. Conclusion: This study demonstrates regional variability in the susceptibility/sensitivity of white matter maturation to perinatal factors and relationships between altered diffusion measures and developmental outcomes in preterm neonates.Pediatric Research (2015); doi:10.1038/pr.2015.172.
    No preview · Article · Sep 2015 · Pediatric Research

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  • No preview · Article · Jul 2015
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    ABSTRACT: Axonal injury is a major contributor to adverse outcomes following brain trauma. However, the extent of axonal injury cannot currently be assessed reliably in living humans. Here, we used two experimental methods with distinct noise sources and limitations in the same cohort of 15 patients with severe traumatic brain injury to assess axonal injury. One hundred kilodalton cut-off microdialysis catheters were implanted at a median time of 17 h (13-29 h) after injury in normal appearing (on computed tomography scan) frontal white matter in all patients, and samples were collected for at least 72 h. Multiple analytes, such as the metabolic markers glucose, lactate, pyruvate, glutamate and tau and amyloid-β proteins, were measured every 1-2 h in the microdialysis samples. Diffusion tensor magnetic resonance imaging scans at 3 T were performed 2-9 weeks after injury in 11 patients. Stability of diffusion tensor imaging findings was verified by repeat scans 1-3 years later in seven patients. An additional four patients were scanned only at 1-3 years after injury. Imaging abnormalities were assessed based on comparisons with five healthy control subjects for each patient, matched by age and sex (32 controls in total). No safety concerns arose during either microdialysis or scanning. We found that acute microdialysis measurements of the axonal cytoskeletal protein tau in the brain extracellular space correlated well with diffusion tensor magnetic resonance imaging-based measurements of reduced brain white matter integrity in the 1-cm radius white matter-masked region near the microdialysis catheter insertion sites. Specifically, we found a significant inverse correlation between microdialysis measured levels of tau 13-36 h after injury and anisotropy reductions in comparison with healthy controls (Spearman's r = -0.64, P = 0.006). Anisotropy reductions near microdialysis catheter insertion sites were highly correlated with reductions in multiple additional white matter regions. We interpret this result to mean that both microdialysis and diffusion tensor magnetic resonance imaging accurately reflect the same pathophysiological process: traumatic axonal injury. This cross-validation increases confidence in both methods for the clinical assessment of axonal injury. However, neither microdialysis nor diffusion tensor magnetic resonance imaging have been validated versus post-mortem histology in humans. Furthermore, future work will be required to determine the prognostic significance of these assessments of traumatic axonal injury when combined with other clinical and radiological measures. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email:
    No preview · Article · Jun 2015 · Brain

  • No preview · Conference Paper · Jun 2015
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    ABSTRACT: The particular importance of Ca2+ signaling to neurons demands its precise regulation within their cytoplasm. Isoform 3 of the plasma membrane Ca2+ ATPase (the PMCA3 pump), which is highly expressed in brain and cerebellum, plays an important role in the regulation of neuronal Ca2+. A genetic defect of the function of the PMCA3 pump has been described in one family with X-linked congenital cerebellar ataxia. Here we describe a novel mutation of the PMCA3 pump (ATP2B3) in a patient with global developmental delay, generalized hypotonia and cerebellar ataxia. The mutation (a R482H replacement) impairs the Ca2+ ejection function of the pump. It reduces the ability of the pump expressed in model cells to control Ca2+ transients generated by cell stimulation and impairs its Ca2+ extrusion function under conditions of low resting cytosolic Ca2+ as well. In silico analysis of the structural effect of the mutation suggests a reduced stabilization of the portion of the pump surrounding the mutated residue in the Ca2+-bound state. The patient also carries two missense mutations in LAMA1, encoding for laminin subunit 1α. On the basis of the family pedigree of the patient, the presence of both PMCA3 and LAMA1 mutations appears to be necessary for the development of the disease. Considering the observed defect in cellular Ca2+ homeostasis and the previous finding that PMCAs act as digenic modulators in Ca2+-linked pathologies, the PMCA3 dysfunction along with LAMA1 mutations could act synergistically to cause the neurological phenotype. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
    Full-text · Article · May 2015 · Journal of Biological Chemistry
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    ABSTRACT: Increased intracranial pressure and ventriculomegaly in children with hydrocephalus are known to have adverse effects on white matter structure. This study seeks to investigate the impact of hydrocephalus on topological features of brain networks in children. The goal was to investigate structural network connectivity, at both global and regional levels, in the brains in children with hydrocephalus using graph theory analysis and diffusion tensor tractography. Three groups of children were included in the study (29 normally developing controls, 9 preoperative hydrocephalus patients, and 17 postoperative hydrocephalus patients). Graph theory analysis was applied to calculate the global network measures including small-worldness, normalized clustering coefficients, normalized characteristic path length, global efficiency, and modularity. Abnormalities in regional network parameters, including nodal degree, local efficiency, clustering coefficient, and betweenness centrality, were also compared between the two patients groups (separately) and the controls using two tailed t-test at significance level of p < 0.05 (corrected for multiple comparison). Children with hydrocephalus in both the preoperative and postoperative groups were found to have significantly lower small-worldness and lower normalized clustering coefficient than controls. Children with hydrocephalus in the postoperative group were also found to have significantly lower normalized characteristic path length and lower modularity. At regional level, significant group differences (or differences at trend level) in regional network measures were found between hydrocephalus patients and the controls in a series of brain regions including the medial occipital gyrus, medial frontal gyrus, thalamus, cingulate gyrus, lingual gyrus, rectal gyrus, caudate, cuneus, and insular. Our data showed that structural connectivity analysis using graph theory and diffusion tensor tractography is sensitive to detect abnormalities of brain network connectivity associated with hydrocephalus at both global and regional levels, thus providing a new avenue for potential diagnosis and prognosis tool for children with hydrocephalus.
    Full-text · Article · Apr 2015 · Clinical neuroimaging
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    ABSTRACT: Manganese (Mn) exposure is associated with increased T1-weighted Magnetic Resonance Imaging (MRI) signal in the basal ganglia. T1 signal intensity has been correlated with occupational Mn exposure but not with clinical symptomatology or neuropathology. This study investigated predictors of ex-vivo T1 MRI basal ganglia signal intensity in neuropathologic tissue obtained from deceased South African mine workers. A 3.0T MRI was performed on ex-vivo brain tissue obtained from 19 Mn mine workers and 10 race- and sex-matched mine workers of other commodities. Basal ganglia regions of interest were identified for each subject with T1-weighted intensity indices generated for each region. In a pathology subset, regional T1 indices were compared to neuronal and glial cell density and tissue metal concentrations. Intensity indices were higher in Mn mine workers than non-Mn mine workers for the globus pallidus, caudate, anterior putamen, and posterior putamen with the highest values in subjects with the longest cumulative Mn exposure. Intensity indices were inversely correlated with the neuronal cell density in the caudate (p=0.040) and putamen (p=0.050). Tissue Mn concentrations were similar in Mn and non-Mn mine workers. Tissue iron (Fe) concentration trended lower across all regions in Mn mine workers. Mn mine workers demonstrated elevated basal ganglia T1 indices when compared to non-Mn mine workers. Predictors of ex-vivo T1 MRI signal intensity in Mn mine workers include duration of Mn exposure and neuronal density. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Apr 2015 · NeuroToxicology
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    ABSTRACT: Magnetic resonance images of children with hydrocephalus often include a rim of hyperintensity in the periventricular white matter (halo). The purpose of this study was to decide between the hypothesis that the halo is caused by cerebrospinal fluid (CSF) flow during the cardiac cycle, and the alternate hypothesis that the halo is caused by anatomical changes (stretching and compression of white matter). Participants were selected from a multicenter imaging study of pediatric hydrocephalus. We compared 19 children with hydrocephalus to a group of 52 controls. We quantified ventricle enlargement using the frontal-occipital horn ratio. We conducted qualitative and quantitative analysis of diffusion tensor imaging in the corpus callosum and posterior limb of the internal capsule. Parameters included the fractional anisotropy (FA), mean diffusivity, axial diffusivity and radial diffusivity. The halo was seen in 16 of the 19 children with hydrocephalus but not in the controls. The corpus callosum of the hydrocephalus group demonstrated FA values that were significantly decreased from those in the control group (P = 4 · 10(-6)), and highly significant increases were seen in the mean diffusivity and radial diffusivity in the hydrocephalus group. In the posterior limb of the internal capsule the FA values of the hydrocephalus group were higher than those for the control group (P = 0.002), and higher values in the hydrocephalus group were also noted in the axial diffusivity. We noted correlations between the diffusion parameters and the frontal-occipital horn ratio. Our results strongly support the hypothesis that the halo finding in hydrocephalus is caused by structural changes rather than pulsatile CSF flow.
    No preview · Article · Mar 2015 · Pediatric Radiology
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    ABSTRACT: Concussion, or mild traumatic brain injury (mTBI), can cause persistent behavioral symptoms and cognitive impairment, but it is unclear if this condition is associated with detectable structural or functional brain changes. At two sites, chronic mTBI human subjects with persistent post-concussive symptoms (3 months to 5 years after injury) and age- and education-matched healthy human control subjects underwent extensive neuropsychological and visual smooth pursuit eye movement tracking tests. At one site, patients and controls also performed the visual tracking tasks while blood-oxygen-level-dependent (BOLD) signals were measured with functional magnetic resonance imaging (fMRI). Although neither neuropsychological nor visual tracking measures distinguished patients from controls at the level of individual subjects, abnormal BOLD signals were reliably detected in patients. The most consistent changes were localized in white matter regions: anterior internal capsule and superior longitudinal fasciculus. In contrast, BOLD signals were normal in cortical regions, such as the frontal eye field and intraparietal sulcus, that mediate oculomotor and attention functions necessary for visual tracking. The abnormal BOLD signals accurately differentiated chronic mTBI patients from healthy controls at the single-subject level, although they did not correlate with symptoms or neuropsychological performance. We conclude that subjects with persistent post-concussive symptoms can be identified years after their TBI using fMRI and an eye-tracking task despite showing normal structural MRI and DTI.
    No preview · Article · Mar 2015 · Journal of Neurotrauma
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    ABSTRACT: Assessment of ventricular size is essential in clinical management of hydrocephalus and other neurological disorders. At present, ventricular size is assessed using indices derived from the dimensions of the ventricles rather than the actual volumes. In a population of 22 children with congenital hydrocephalus and 22 controls, the authors evaluated the relationship between ventricular volume and linear indices in common use, such as the frontooccipital horn ratio, Evans' index, and the bicaudate index. Ventricular volume was measured on high-resolution anatomical MR images. The frontooccipital horn ratio was found to have a stronger correlation with both absolute and relative ventricular volume than other indices. Further analysis of the brain volumes found that congenital hydrocephalus produced a negligible decrease in the volume of the brain parenchyma.
    No preview · Article · Mar 2015 · Journal of Neurosurgery Pediatrics
  • David L Brody · Christine L Mac Donald · Joshua S Shimony
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    ABSTRACT: Brain imaging plays a key role in the assessment of traumatic brain injury. In this review, we present our perspectives on the use of computed tomography (CT), conventional magnetic resonance imaging (MRI), and newer advanced modalities such as diffusion tensor imaging. Specifically, we address assessment for immediately life-threatening intracranial lesions (noncontrast head CT), assessment of progression of intracranial lesions (noncontrast head CT), documenting intracranial abnormalities for medicolegal reasons (conventional MRI with blood-sensitive sequences), presurgical planning for post-traumatic epilepsy (high spatial resolution conventional MRI), early prognostic decision making (conventional MRI with diffusion-weighted imaging), prognostic assessment for rehabilitative planning (conventional MRI and possibly diffusion tensor imaging in the future), stratification of subjects and pharmacodynamic tracking of targeted therapies in clinical trials (specific MRI sequences or positron emission tomography (PET) ligands, e.g., diffusion tensor imaging for traumatic axonal injury). We would like to emphasize that all of these methods, especially the newer research approaches, require careful radiologic-pathologic validation for optimal interpretation. We have taken this approach in a mouse model of pericontusional traumatic axonal injury. We found that the extent of reduction in the diffusion tensor imaging parameter relative anisotropy directly correlated with the number of amyloid precursor protein (APP)-stained axonal varicosities (r(2)=0.81, p<0.0001, n=20 injured mice). Interestingly, however, the least severe contusional injuries did not result in APP-stained axonal varicosities, but did cause reduction in relative anisotropy. Clearly, both the imaging assessments and the pathologic assessments will require iterative refinement. © 2015 Elsevier B.V. All rights reserved.
    No preview · Article · Feb 2015 · Handbook of Clinical Neurology
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    ABSTRACT: Objectives: A common complaint of cancer patients is the experience of cognitive difficulty during and after chemotherapy. We hypothesized that cognitive impairment may result from dysfunction in large-scale brain networks, particularly those involved in attentional control. Methods: Using a case-control design, this study includes women with a history of invasive ductal or lobular triple-negative breast cancer who completed standard adjuvant chemotherapy within 2 years of study entry. Women who reported cognitive impairment by the Global Rating of Cognition question were considered to be cases (n = 15). Women who reported no cognitive impairment were considered to be controls (n = 13). All enrolled participants were eligible for MRI investigation and underwent resting-state functional connectivity MRI. Results: Women who self-reported cognitive impairment were found to have disrupted resting-state functional connectivity, as measured by MRI, when compared to women who did not self-report cognitive impairment. These findings suggest that some women may be more sensitive to the standard treatments for breast cancer and that this increased sensitivity may result in functional connectivity alterations in the brain networks supporting attention and executive function. Conclusions: Neuroimaging analyses confirmed self-reported cognitive deficits in women with breast cancer treated with chemotherapy.
    No preview · Article · Feb 2015 · Oncology

  • No preview · Conference Paper · Feb 2015

  • No preview · Article · Jan 2015 · American Journal of Obstetrics and Gynecology

Publication Stats

5k Citations
505.28 Total Impact Points

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  • 1999-2015
    • Washington University in St. Louis
      • • Department of Neurology
      • • Department of Radiology
      • • Department of Medicine
      San Luis, Missouri, United States
  • 1997
    • University of Illinois, Urbana-Champaign
      • Department of Molecular and Integrative Physiology
      Urbana, Illinois, United States