Hemodynamic Impairment Measured by Positron-Emission Tomography Is Regionally Associated with Decreased Cortical Thickness in Moyamoya Phenomenon

BACKGROUND AND PURPOSE

Impaired cerebrovascular reactivity has been associated with decreased cortical thickness in patients with arterial occlusive diseases. This study tests the hypothesis that severe hemodynamic impairment, indicated by increased oxygen extraction fraction ratios on positron-emission tomography with ¹⁵O tracers, is associated with decreased cortical thickness in patients with Moyamoya phenomenon.

MATERIALS AND METHODS

Patients with unilateral or bilateral idiopathic Moyamoya phenomenon were recruited. Oxygen extraction fraction ratio maps were generated from cerebral images of O[¹⁵O] counts divided by H₂[¹⁵O] counts with normalization by corresponding cerebellar counts. The normal range of the oxygen extraction fraction ratio was estimated from historically available healthy control subjects. Cortical thickness was estimated from T1-weighted MR imaging and FreeSurfer. Regional samples of oxygen extraction fraction ratios and cortical thicknesses were drawn using FreeSurfer parcellations, retaining only parcellations from the vascular territory of the middle cerebral artery.

RESULTS

Complete MR imaging and PET datasets were available in 35 subjects, including 23 women; the mean age at scanning was 44 years. Patients with Moyamoya phenomenon had a significantly increased regional oxygen extraction fraction ratio compared with 15 healthy control subjects (P < .001). Regional oxygen extraction fraction ratio and age were significant predictors of cortical thickness (P < .001 for each) in a generalized linear mixed-effects model. Using hemisphere averages and patient averages, we found that only age was a significant predictor of cortical thickness (P < .001).

CONCLUSIONS

Chronic hemodynamic impairment, as indicated by a higher regional oxygen extraction fraction ratio, was significantly predictive of reduced cortical thickness in mixed-effects analysis of FreeSurfer regions. This phenomenon may be related to reversible metabolic down-regulation.

Spatial and Temporal Organization of the Individual Human Cerebellum

The cerebellum contains the majority of neurons in the human brain and is unique for its uniform cytoarchitecture, absence of aerobic glycolysis, and role in adaptive plasticity. Despite anatomical and physiological differences between the cerebellum and cerebral cortex, group-average functional connectivity studies have identified networks related to specific functions in both structures. Recently, precision functional mapping of individuals revealed that functional networks in the cerebral cortex exhibit measurable individual specificity. Using the highly sampled Midnight Scan Club (MSC) dataset, we found the cerebellum contains reliable, individual-specific network organization that is significantly more variable than the cerebral cortex. The frontoparietal network, thought to support adaptive control, was the only network overrepresented in the cerebellum compared to the cerebral cortex (2.3-fold). Temporally, all cerebellar resting state signals lagged behind the cerebral cortex (125-380 ms), supporting the hypothesis that the cerebellum engages in a domain-general function in the adaptive control of all cortical processes.

Prenatal to postnatal trajectory of brain growth in complex congenital heart disease

Altered brain development is a common feature of the neurological sequelae of complex congenital heart disease (CHD). These alterations include abnormalities in brain size and growth that begin prenatally and persist postnatally. However, the longitudinal trajectory of changes in brain volume from the prenatal to postnatal environment have not been investigated. We aimed to evaluate the trajectory of brain growth in a cohort of patients with complex CHD (n = 16) and healthy controls (n = 15) to test the hypothesis that patients with complex CHD would have smaller total brain volume (TBV) prenatally, which would become increasingly prominent by three months of age. Participants underwent fetal magnetic resonance imaging (MRI) at a mean of 32 weeks gestation, a preoperative/neonatal MRI shortly after birth, a postoperative MRI (CHD only), and a 3-month MRI to evaluate the trajectory of brain growth. Three-dimensional volumetric analysis was applied to the MRI data to measure TBV, as well as tissue-specific volumes of the cortical gray matter (CGM), white matter (WM), subcortical (deep nuclear) gray matter (SCGM), cerebellum, and cerebrospinal fluid (CSF). A random coefficients model was used to investigate longitudinal changes in TBV and demonstrated an altered trajectory of brain growth in the CHD population. The estimated slope for TBV from fetal to 3-month MRI was 11.5 cm³ per week for CHD infants compared to 16.7 cm³ per week for controls (p = 0.0002). Brain growth followed a similar trajectory for the CGM (p < 0.0001), SCGM (p = 0.002), and cerebellum (p = 0.005). There was no difference in growth of the WM (p = 0.30) or CSF (p = 0.085). Brain injury was associated with reduced TBV at 3-month MRI (p = 0.02). After removing infants with brain injury from the model, an altered trajectory of brain growth persisted in CHD infants (p = 0.006). These findings extend the existing literature by demonstrating longitudinal impairments in brain development in the CHD population and emphasize the global nature of disrupted brain growth from the prenatal environment through early infancy.

Validation of diffusion tensor imaging measures of nigrostriatal neurons in macaques

Objective

Interpretation of diffusion MRI in the living brain requires validation against gold standard histological measures. We compared diffusion values of the nigrostriatal tract to PET and histological results in non-human primates (NHPs) with varying degrees of unilateral nigrostriatal injury induced by MPTP, a toxin selective for dopaminergic neurons.

Methods

Sixteen NHPs had MRI and PET scans of three different presynaptic radioligands and blinded video-based motor ratings before and after unilateral carotid artery infusion of variable doses of MPTP. Diffusion measures of connections between midbrain and striatum were calculated. Then animals were euthanized to quantify striatal dopamine concentration, stereologic measures of striatal tyrosine hydroxylase (TH) immunostained fiber density and unbiased stereologic counts of TH stained nigral cells.

Results

Diffusion measures correlated with MPTP dose, nigral TH-positive cell bodies and striatal TH-positive fiber density but did not correlate with in vitro nigrostriatal terminal field measures or in vivo PET measures of striatal uptake of presynaptic markers. Once nigral TH cell count loss exceeded 50% the stereologic terminal field measures reached a near zero floor effect but the diffusion measures continued to correlate with nigral cell counts.

Conclusion

Diffusion measures in the nigrostriatal tract correlate with nigral dopamine neurons and striatal fiber density, but have the same relationship to terminal field measures as a previous report of striatal PET measures of presynaptic neurons. These diffusion measures have the potential to act as non-invasive index of the severity of nigrostriatal injury. Diffusion imaging of the nigrostriatal tract could potentially have diagnostic value in humans with Parkinson disease or related disorders.

Stronger prediction of motor recovery and outcome post-stroke by cortico-spinal tract integrity than functional connectivity

OBJECTIVES

To examine longitudinal changes in structural and functional connectivity post-stroke in patients with motor impairment, and define their importance for recovery and outcome at 12 months.

METHODS

First-time stroke patients (N = 31) were studied at 1-2 weeks, 3 months, and 12 months post-injury with a validated motor battery and resting-state fMRI to measure inter-hemispheric functional connectivity (FC). Fractional anisotropy (FA) of the cortico-spinal tract (CST) was derived from diffusion tensor imaging as a measure of white matter organization. ANOVAs were used to test for changes in FC, FA, and motor performance scores over time, and regression analysis related motor outcome to clinical and neuroimaging variables.

RESULTS

FA of the ipsilesional CST improved significantly from 3 to 12 months and was strongly correlated with motor performance. FA improved even in the absence of direct damage to the CST. Inter-hemispheric FC also improved over time, but did not correlate with motor performance at 12 months. Clinical variables (early motor score, education level, and age) predicted 80.4% of the variation of motor outcome, and FA increased the predictability to 84.6%. FC did not contribute to the prediction of motor outcome.

CONCLUSIONS

Stroke causes changes to the CST microstructure that can account for behavioral variability even in the absence of demonstrable lesion. Ipsilesional CST undergoes remodeling post-stroke, even past the three-month window when most of the motor recovery happens. FA of the CST, but not inter-hemispheric FC, can improve to the prediction of motor outcome based on early motor scores.

Resting state signal latency predicts laterality in pediatric medically refractory temporal lobe epilepsy

PURPOSE

Temporal lobe epilepsy (TLE) affects resting state brain networks in adults. This study aims to correlate resting state functional MRI (rsMRI) signal latency in pediatric TLE patients with their laterality.

METHODS

From 2006 to 2016, 26 surgical TLE patients (12 left, 14 right) with a mean age of 10.7 years (range 0.9-18) were prospectively studied. Preoperative rsMRI was obtained in patients with concordant lateralizing structural MRI, EEG, and PET studies. Standard preprocessing techniques and seed-based rsMRI analyses were performed. Additionally, the latency in rsMRI signal between each 6 mm voxel sampled was examined, compared to the global mean signal, and projected onto standard atlas space for individuals and the cohort.

RESULTS

All but one of the 26 patients improved seizure frequency postoperatively with a mean follow-up of 2.9 years (range 0-7.7), with 21 patients seizure-free. When grouped for epileptogenic laterality, the latency map qualitatively demonstrated that the right TLE patients had a relatively early signal pattern, whereas the left TLE patients had a relatively late signal pattern compared to the global mean signal in the right temporal lobe. Quantitatively, the two groups had significantly different signal latency clusters in the bilateral temporal lobes (p < 0.001).

CONCLUSION

There are functional MR signal latency changes in medical refractory pediatric TLE patients. Qualitatively, signal latency in the right temporal lobe precedes the mean signal in right TLE patients and is delayed in left TLE patients. With larger confirmatory studies, preoperative rsMRI latency analysis may offer an inexpensive, noninvasive adjunct modality to lateralize pediatric TLE.

Regional oxygen extraction predicts border zone vulnerability to stroke in sickle cell disease

OBJECTIVE

To determine mechanisms underlying regional vulnerability to infarction in sickle cell disease (SCD) by measuring voxel-wise cerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen utilization (CMRO2) in children with SCD.

METHODS

Participants underwent brain MRIs to measure voxel-based CBF, OEF, and CMRO2. An infarct heat map was created from an independent pediatric SCD cohort with silent infarcts and compared to prospectively obtained OEF maps.

RESULTS

Fifty-six participants, 36 children with SCD and 20 controls, completed the study evaluation. Whole-brain CBF (99.2 vs 66.3 mL/100 g/min, p < 0.001), OEF (42.7% vs 28.8%, p < 0.001), and CMRO2 (3.7 vs 2.5 mL/100 g/min, p < 0.001) were higher in the SCD cohort compared to controls. A region of peak OEF was identified in the deep white matter in the SCD cohort, delineated by a ratio map of average SCD to control OEF voxels. CMRO2 in this region, which encompassed the CBF nadir, was low relative to all white matter (p < 0.001). Furthermore, this peak OEF region colocalized with regions of greatest infarct density derived from an independent SCD cohort.

CONCLUSIONS

Elevated OEF in the deep white matter identifies a signature of metabolically stressed brain tissue at increased stroke risk in pediatric patients with SCD. We propose that border zone physiology, exacerbated by chronic anemic hypoxia, explains the high risk in this region.

Red cell exchange transfusions lower cerebral blood flow and oxygen extraction fraction in pediatric sickle cell anemia

Blood transfusions are the mainstay of stroke prevention in pediatric sickle cell anemia (SCA), but the physiology conferring this benefit is unclear. Cerebral blood flow (CBF) and oxygen extraction fraction (OEF) are elevated in SCA, likely compensating for reduced arterial oxygen content (CaO2). We hypothesized that exchange transfusions would decrease CBF and OEF by increasing CaO2, thereby relieving cerebral oxygen metabolic stress. Twenty-one children with SCA receiving chronic transfusion therapy (CTT) underwent magnetic resonance imaging before and after exchange transfusions. Arterial spin labeling and asymmetric spin echo sequences measured CBF and OEF, respectively, which were compared pre- and posttransfusion. Volumes of tissue with OEF above successive thresholds (36%, 38%, and 40%), as a metric of regional metabolic stress, were compared pre- and posttransfusion. Transfusions increased hemoglobin (Hb; from 9.1 to 10.3 g/dL; P < .001) and decreased Hb S (from 39.7% to 24.3%; P < .001). Transfusions reduced CBF (from 88 to 82.4 mL/100 g per minute; P = .004) and OEF (from 34.4% to 31.2%; P < .001). At all thresholds, transfusions reduced the volume of peak OEF found in the deep white matter, a location at high infarct risk in SCA (P < .001). Reduction of elevated CBF and OEF, both globally and regionally, suggests that CTT mitigates infarct risk in pediatric SCA by relieving cerebral metabolic stress at patient- and tissue-specific levels.

Cortical Functional Connectivity Evident After Birth and Behavioral Inhibition at Age 2

OBJECTIVE

The infant temperament behavioral inhibition is a potent risk factor for development of an anxiety disorder. It is difficult to predict risk for behavioral inhibition at birth, however, and the neural underpinnings are poorly understood. The authors hypothesized that neonatal functional connectivity of the ventral attention network is related to behavioral inhibition at age 2 years beyond sociodemographic and familial factors. This hypothesis is supported by the ventral attention network's role in attention to novelty, a key feature of behavioral inhibition.

METHOD

Using a longitudinal design (N=45), the authors measured functional connectivity using MRI in neonates and behavioral inhibition at age 2 using the Infant-Toddler Social and Emotional Assessment. Whole-brain connectivity maps were computed for regions from the ventral attention, default mode, and salience networks. Regression analyses related these maps to behavioral inhibition at age 2, covarying for sex, social risk, and motion during scanning.

RESULTS

Decreased neonatal functional connectivity of three connections was associated with increased behavioral inhibition at age 2. One connection (between the right ventrolateral prefrontal cortex and the right temporal-parietal junction) included the ventral attention network seed, and two connections (between the medial prefrontal cortex and both the right superior parietal lobule and the left lateral occipital cortex) included the default mode network seed.

CONCLUSIONS

Neonatal functional connectivity of the ventral attention and default mode networks is associated with behavioral inhibition at age 2. These results inform the developmental neurobiology of behavioral inhibition and anxiety disorders and may aid in early risk assessment and intervention.

Behavioral interventions for reducing head motion during MRI scans in children

A major limitation to structural and functional MRI (fMRI) scans is their susceptibility to head motion artifacts. Even submillimeter movements can systematically distort functional connectivity, morphometric, and diffusion imaging results. In patient care, sedation is often used to minimize head motion, but it incurs increased costs and risks. In research settings, sedation is typically not an ethical option. Therefore, safe methods that reduce head motion are critical for improving MRI quality, especially in high movement individuals such as children and neuropsychiatric patients. We investigated the effects of (1) viewing movies and (2) receiving real-time visual feedback about head movement in 24 children (5-15 years old). Children completed fMRI scans during which they viewed a fixation cross (i.e., rest) or a cartoon movie clip, and during some of the scans they also received real-time visual feedback about head motion. Head motion was significantly reduced during movie watching compared to rest and when receiving feedback compared to receiving no feedback. However, these results depended on age, such that the effects were largely driven by the younger children. Children older than 10 years showed no significant benefit. We also found that viewing movies significantly altered the functional connectivity of fMRI data, suggesting that fMRI scans during movies cannot be equated to standard resting-state fMRI scans. The implications of these results are twofold: (1) given the reduction in head motion with behavioral interventions, these methods should be tried first for all clinical and structural MRIs in lieu of sedation; and (2) for fMRI research scans, these methods can reduce head motion in certain groups, but investigators must keep in mind the effects on functional MRI data.

Spinal Cord Injury Disrupts Resting-State Networks in the Human Brain

Despite 253,000 spinal cord injury (SCI) patients in the United States, little is known about how SCI affects brain networks. Spinal MRI provides only structural information with no insight into functional connectivity. Resting-state functional MRI (RS-fMRI) quantifies network connectivity through the identification of resting-state networks (RSNs) and allows detection of functionally relevant changes during disease. Given the robust network of spinal cord afferents to the brain, we hypothesized that SCI produces meaningful changes in brain RSNs. RS-fMRIs and functional assessments were performed on 10 SCI subjects. Blood oxygen-dependent RS-fMRI sequences were acquired. Seed-based correlation mapping was performed using five RSNs: default-mode (DMN), dorsal-attention (DAN), salience (SAL), control (CON), and somatomotor (SMN). RSNs were compared with normal control subjects using false-discovery rate-corrected two way t tests. SCI reduced brain network connectivity within the SAL, SMN, and DMN and disrupted anti-correlated connectivity between CON and SMN. When divided into separate cohorts, complete but not incomplete SCI disrupted connectivity within SAL, DAN, SMN and DMN and between CON and SMN. Finally, connectivity changed over time after SCI: the primary motor cortex decreased connectivity with the primary somatosensory cortex, the visual cortex decreased connectivity with the primary motor cortex, and the visual cortex decreased connectivity with the sensory parietal cortex. These unique findings demonstrate the functional network plasticity that occurs in the brain as a result of injury to the spinal cord. Connectivity changes after SCI may serve as biomarkers to predict functional recovery following an SCI and guide future therapy.

Dissociation Between Hormonal Counterregulatory Responses and Cerebral Glucose Metabolism During Hypoglycemia

Hypoglycemia is the most common complication of diabetes, causing morbidity and death. Recurrent hypoglycemia alters the cascade of physiological and behavioral responses that maintain euglycemia. The extent to which these responses are normally triggered by decreased whole-brain cerebral glucose metabolism (CMR_glc) has not been resolved by previous studies. We measured plasma counterregulatory hormonal responses and whole-brain CMR_glc (along with blood-to-brain glucose transport rates and brain glucose concentrations) with 1-[¹¹C]-d-glucose positron emission tomography during hyperinsulinemic glucose clamps at nominal plasma glucose concentrations of 90, 75, 60, and 45 mg/dL (5.0, 4.2, 3.3, and 2.5 mmol/L) in 18 healthy young adults. Clear evidence of hypoglycemic physiological counterregulation was first demonstrated between 75 mg/dL (4.2 mmol/L) and 60 mg/dL (3.3 mmol/L) with increases in both plasma epinephrine (P = 0.01) and glucagon (P = 0.01). In contrast, there was no statistically significant change in CMR_glc (P = 1.0) between 75 mg/dL (4.2 mmol/L) and 60 mg/dL (3.3 mmol/L), whereas CMR_glc significantly decreased (P = 0.02) between 60 mg/dL (3.3 mmol/L) and 45 mg/dL (2.5 mmol/L). Therefore, the increased epinephrine and glucagon secretion with declining plasma glucose concentrations is not in response to a decrease in whole-brain CMR_glc.

Resting-state functional magnetic resonance imaging for surgical planning in pediatric patients: a preliminary experience

OBJECTIVE Cerebral mapping for surgical planning and operative guidance is a challenging task in neurosurgery. Pediatric patients are often poor candidates for many modern mapping techniques because of inability to cooperate due to their immature age, cognitive deficits, or other factors. Resting-state functional MRI (rs-fMRI) is uniquely suited to benefit pediatric patients because it is inherently noninvasive and does not require task performance or significant cooperation. Recent advances in the field have made mapping cerebral networks possible on an individual basis for use in clinical decision making. The authors present their initial experience translating rs-fMRI into clinical practice for surgical planning in pediatric patients. METHODS The authors retrospectively reviewed cases in which the rs-fMRI analysis technique was used prior to craniotomy in pediatric patients undergoing surgery in their institution. Resting-state analysis was performed using a previously trained machine-learning algorithm for identification of resting-state networks on an individual basis. Network maps were uploaded to the clinical imaging and surgical navigation systems. Patient demographic and clinical characteristics, including need for sedation during imaging and use of task-based fMRI, were also recorded. RESULTS Twenty patients underwent rs-fMRI prior to craniotomy between December 2013 and June 2016. Their ages ranged from 1.9 to 18.4 years, and 12 were male. Five of the 20 patients also underwent task-based fMRI and one underwent awake craniotomy. Six patients required sedation to tolerate MRI acquisition, including resting-state sequences. Exemplar cases are presented including anatomical and resting-state functional imaging. CONCLUSIONS Resting-state fMRI is a rapidly advancing field of study allowing for whole brain analysis by a noninvasive modality. It is applicable to a wide range of patients and effective even under general anesthesia. The nature of resting-state analysis precludes any need for task cooperation. These features make rs-fMRI an ideal technology for cerebral mapping in pediatric neurosurgical patients. This review of the use of rs-fMRI mapping in an initial pediatric case series demonstrates the feasibility of utilizing this technique in pediatric neurosurgical patients. The preliminary experience presented here is a first step in translating this technique to a broader clinical practice.

Resting-state Functional Magnetic Resonance Imaging in Presurgical Functional Mapping: Sensorimotor Localization

This article compares resting-state functional magnetic resonance (fMR) imaging with task fMR imaging for presurgical functional mapping of the sensorimotor (SM) region. Before tumor resection, 38 patients were scanned using both methods. The SM area was anatomically defined using 2 different software tools. Overlap of anatomic regions of interest with task activation maps and resting-state networks was measured in the SM region. A paired t-test showed higher overlap between resting-state maps and anatomic references compared with task activation when using a maximal overlap criterion. Resting state-derived maps are more comprehensive than those derived from task fMR imaging.

A validated clinical MRI injury scoring system in neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Deep nuclear gray matter injury in neonatal hypoxic-ischemic encephalopathy (HIE) is associated with worse neurodevelopmental outcomes. We previously published a qualitative MRI injury scoring system utilizing serial T1-weighted, T2-weighted and diffusion-weighted imaging (DWI), weighted for deep nuclear gray matter injury.

OBJECTIVES

To establish the validity of the MRI scoring system with neurodevelopmental outcome at 18-24 months.

MATERIALS AND METHODS

MRI scans from neonates with moderate to severe HIE treated with therapeutic hypothermia were evaluated. Signal abnormality was scored on T1-weighted, T2-weighted and DWI sequences and assessed using an established system in five regions: (a) subcortical: caudate nucleus, globus pallidus and putamen, thalamus and the posterior limb of the internal capsule; (b) white matter; (c) cortex, (d) cerebellum and (e) brainstem. MRI injury was graded as none, mild, moderate or severe. Inter-rater reliability was tested on a subset of scans by two independent and blinded neuroradiologists. Surviving infants underwent the Bayley Scales of Infant and Toddler Development-III (Bayley-III) at 18-24 months. Data were analyzed using univariate and multivariate linear and logistic regression.

RESULTS

Fifty-seven eligible neonates underwent at least one MRI scan in the first 2 weeks of life. Mean postnatal age at scan 1 was 4±2 days in 50/57 (88%) neonates and 48/54 (89%) surviving infants underwent scan 2 at 10±2 days. In 54/57 (95%) survivors, higher MRI injury grades were significantly associated with worse outcomes in the cognitive, motor and language domains of the Bayley-III.

CONCLUSION

A qualitative MRI injury scoring system weighted for deep nuclear gray matter injury is a significant predictor of neurodevelopmental outcome at 18-24 months in neonates with HIE.

Diffusion Tensor Tractography of the Cerebellar Peduncles in Prematurely Born 7-Year-Old Children

The objective of this study was to correlate neurodevelopmental outcome of preterm-born children and their perinatal clinical and imaging characteristics with diffusion magnetic resonance imaging (MRI) measures of the three cerebellar peduncles at age 7. Included in this prospective longitudinal study were 140 preterm-born children (<30 weeks gestation) who underwent neurodevelopmental assessment (IQ, motor, language, working memory) and diffusion-weighted imaging (DWI) at age 7 years. White matter tracts in the superior, middle, and inferior cerebellar peduncles were delineated using regions of interest drawn on T2-weighted images and fractional anisotropy (FA) maps. Diffusion measures (mean diffusivity (MD) and FA) and tract volumes were calculated. Linear regression was used to assess relationships with outcome. The severity of white matter injury in the neonatal period was associated with lower FA in the right superior cerebellar peduncle (SCP) and lower tract volumes of both SCPs and middle cerebellar peduncles (MCPs). In the MCP, higher IQ was associated with lower MD in the whole group and higher FA in right-handed children. In the SCP, lower motor scores were associated with higher MD and higher language scores were associated with higher FA. These associations remained significant in multivariable models. This study adds to the body of literature detailing the importance of cerebellar involvement in cognitive function related to reciprocal connections with supratentorial structures.

Adaptive anatomical preservation optimal denoising for radiation therapy daily MRI

Low-field magnetic resonance imaging (MRI) has recently been integrated with radiation therapy systems to provide image guidance for daily cancer radiation treatments. The main benefit of the low-field strength is minimal electron return effects. The main disadvantage of low-field strength is increased image noise compared to diagnostic MRIs conducted at 1.5 T or higher. The increased image noise affects both the discernibility of soft tissues and the accuracy of further image processing tasks for both clinical and research applications, such as tumor tracking, feature analysis, image segmentation, and image registration. An innovative method, adaptive anatomical preservation optimal denoising (AAPOD), was developed for optimal image denoising, i.e., to maximally reduce noise while preserving the tissue boundaries. AAPOD employs a series of adaptive nonlocal mean (ANLM) denoising trials with increasing denoising filter strength (i.e., the block similarity filtering parameter in the ANLM algorithm), and then detects the tissue boundary losses on the differences of sequentially denoised images using a zero-crossing edge detection method. The optimal denoising filter strength per voxel is determined by identifying the denoising filter strength value at which boundary losses start to appear around the voxel. The final denoising result is generated by applying the ANLM denoising method with the optimal per-voxel denoising filter strengths. The experimental results demonstrated that AAPOD was capable of reducing noise adaptively and optimally while avoiding tissue boundary losses. AAPOD is useful for improving the quality of MRIs with low-contrast-to-noise ratios and could be applied to other medical imaging modalities, e.g., computed tomography.

Precision Functional Mapping of Individual Human Brains

Human functional MRI (fMRI) research primarily focuses on analyzing data averaged across groups, which limits the detail, specificity, and clinical utility of fMRI resting-state functional connectivity (RSFC) and task-activation maps. To push our understanding of functional brain organization to the level of individual humans, we assembled a novel MRI dataset containing 5 hr of RSFC data, 6 hr of task fMRI, multiple structural MRIs, and neuropsychological tests from each of ten adults. Using these data, we generated ten high-fidelity, individual-specific functional connectomes. This individual-connectome approach revealed several new types of spatial and organizational variability in brain networks, including unique network features and topologies that corresponded with structural and task-derived brain features. We are releasing this highly sampled, individual-focused dataset as a resource for neuroscientists, and we propose precision individual connectomics as a model for future work examining the organization of healthy and diseased individual human brains.

Treatment of Leukoencephalopathy With Calcifications and Cysts With Bevacizumab

BACKGROUND

Leukoencephalopathy with calcifications and cysts is a rare, autosomal recessive cerebral microangiopathy that causes progressive white matter disease, calcifications, and cysts within the brain. It is typically associated with slowly progressive psychomotor regression, seizures, and movement disorders. Although leukoencephalopathy with calcifications and cysts affects only the central nervous system, it demonstrates remarkable neuropathologic and radiologic overlap with Coats plus, a disorder of small vessels of the brain, eyes, gastrointestinal tract, and bone. Coats disease without extraocular involvement, a genetically distinct disorder from Coats plus, is characterized by retinal telangiectasias and exudative retinopathy, accompanied by neovascularization. Inhibition of vascular endothelial growth factor (VEGF) signaling with the monoclonal anti-VEGF antibody bevacizumab can improve retinal edema and exudates in Coats disease. Given these observations, we reasoned that VEGF inhibition might also be effective in treating leukoencephalopathy with calcifications and cysts and Coats plus, neither of which has any known therapy.

METHODS

We treated an 18-year-old man with leukoencephalopathy with calcifications and cysts using biweekly infusions of the VEGF inhibitor bevacizumab for more than one year and performed clinical examinations and brain imaging at three month intervals.

RESULTS

After treatment for more than one year, the patient showed improved bradykinesia and range of motion, and brain magnetic resonance imaging demonstrated a marked reduction in cyst volume and white matter lesions.

CONCLUSIONS

Further studies in a cohort of patients are warranted to investigate the efficacy of VEGF inhibition as a treatment for leukoencephalopathy with calcifications and cysts.

The use of hippocampal volumetric measurements to improve diagnostic accuracy in pediatric patients with mesial temporal sclerosis

OBJECTIVE Many patients with medically intractable epilepsy have mesial temporal sclerosis (MTS), which significantly affects their quality of life. The surgical excision of MTS lesions can result in marked improvement or even complete resolution of the epileptic episodes. Reliable radiological diagnosis of MTS is a clinical challenge. The purpose of this study was to evaluate the utility of volumetric mapping of the hippocampi for the identification of MTS in a case-controlled series of pediatric patients who underwent resection for medically refractory epilepsy, using pathology as a gold standard. METHODS A cohort of 57 pediatric patients who underwent resection for medically intractable epilepsy between 2005 and 2015 was evaluated. On pathological investigation, this group included 24 patients with MTS and 33 patients with non-MTS findings. Retrospective quantitative volumetric measurements of the hippocampi were acquired for 37 of these 57 patients. Two neuroradiologists with more than 10 years of experience who were blinded to the patients' MTS status performed the retrospective review of MR images. To produce the volumetric data, MR scans were parcellated and segmented using the FreeSurfer software suite. Hippocampal regions of interest were compared against an age-weighted local regression curve generated with data from the pediatric normal cohort. Standard deviations and percentiles of specific subjects were calculated. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined for the original clinical read and the expert readers. Receiver operating characteristic curves were generated for the methods of classification to compare results from the readers with the authors' results, and an optimal threshold was determined. From that threshold the sensitivity, specificity, PPV, and NPV were calculated for the volumetric analysis. RESULTS With the use of quantitative volumetry, a sensitivity of 72%, a specificity of 95%, a PPV of 93%, an NPV of 78%, and an area under the curve of 0.84 were obtained using a percentage difference of normalized hippocampal volume. The resulting specificity (95%) and PPV (93%) are superior to the original clinical read and to Reader A and Reader B's findings (range for specificity 74%-86% and for PPV 64%-71%). The sensitivity (72%) and NPV (78%) are comparable to Reader A's findings (73% and 81%, respectively) and are better than those of the original clinical read and of Reader B (sensitivity 45% and 63% and NPV 71% and 70%, respectively). CONCLUSIONS Volumetric measurement of the hippocampi outperforms expert readers in specificity and PPV, and it demonstrates comparable to superior sensitivity and NPV. Volumetric measurements can complement anatomical imaging for the identification of MTS, much like a computer-aided detection tool would. The implementation of this approach in the daily clinical workflow could significantly improve diagnostic accuracy.

Cognitive Training for Adults With Bothersome Tinnitus: A Randomized Clinical Trial

Importance

Individuals with tinnitus have poorer working memory, slower processing speeds and reaction times, and deficiencies in selective attention, all of which interfere with readiness and performance. Brain Fitness Program-Tinnitus (BFP-T) is a cognitive training program specially designed to exploit neuroplasticity for preservation and expansion of cognitive health in adults with tinnitus.

Objective

To evaluate the effect of the BFP-T on tinnitus.

Design, Setting, and Participants

This open-label, intention-to-treat randomized clinical trial prescreened 191 patients with tinnitus and 64 healthy controls (HCs) from June 1, 2012, through October 31, 2013. Participants were 40 adults with bothersome tinnitus for more than 6 months and 20 age-matched HCs. Patients with tinnitus were randomized to a BFP-T or non-BFP-T control group. The BFP-T was completed online, and assessments were completed at Washington University School of Medicine.

Interventions

Participants in the intervention group were required to complete the BFP-T online 1 hour per day 5 days per week for 8 weeks. Tinnitus assessment, neuroimaging, and cognitive testing were completed at baseline and 8 weeks later. The HCs underwent neuroimaging and cognitive assessments.

Main Outcomes and Measures

The primary outcome measure was the change in Tinnitus Handicap Inventory (THI) score. Behavioral measures, neuroimaging, and cognitive tests were performed before and after the intervention.

Results

A total of 40 patients with tinnitus and 20 HCs participated in the study (median [range] age, 56 [35-64] years in the BFP-T group, 52 [24-64] years in the non-BFP-T group, and 50 [30-64] years in the HC group; 13 [65%] in the BFP-T group, 14 [70%] in the non-BFP-T group, and 13 [65%] in the HC group were males; and 16 [80%] in the BFP-T group, 16 [80%] in the non-BFP-T group, and 15 [75%] in the HC group were white). There was a reduction in the THI score in the BFP-T group (median, 7; range, -16 to 64) and non-BFP-T group (median, 11; range, -6 to 26), but this reduction was not significantly different between the 2 groups (median difference, 0; 95% CI, -10 to 8). There was no difference in cognitive test scores and other behavioral measures. There was a significant difference between baseline and follow-up in functional connectivity in cognitive control regions in the BFP-T group but not in HCs or individuals with untreated tinnitus. Of the 20 patients in the BFP-T group, 10 (50%) self-reported improvement attributable to the intervention, and 6 (30%) reported to be much improved in the domains of tinnitus, memory, attention, and concentration.

Conclusions and Relevance

These findings suggest that the computer-based cognitive training program is associated with self-reported changes in attention, memory, and perception of tinnitus. A possible mechanistic explanation for these changes could be neuroplastic changes in key brain systems involved in cognitive control. Cognitive training programs might have a role in the future treatment of patients with tinnitus.

Trial Registration

clinicaltrials.gov Identifier: NCT01458821.

Large-Vessel Vasculopathy in Children With Sickle Cell Disease: A Magnetic Resonance Imaging Study of Infarct Topography and Focal Atrophy

BACKGROUND

Large-vessel vasculopathy (LVV) increases stroke risk in pediatric sickle cell disease beyond the baseline elevated stroke risk in this vulnerable population. The mechanisms underlying this added risk and its unique impact on the developing brain are not established.

METHODS

We analyzed magnetic resonance imaging and angiography scans of 66 children with sickle cell disease and infarcts by infarct density heatmaps and Jacobian determinants, a metric utilized to delineate focal volume change, to investigate if infarct location, volume, frequency, and cerebral atrophy differed among hemispheres with and without LVV.

RESULTS

Infarct density heatmaps demonstrated infarct "hot spots" within the deep white matter internal border zone region in both LVV and non-LVV hemispheres, but with greater infarct density and larger infarct volumes in LVV hemispheres (2.2 mL versus 0.25 mL, P < 0.001). Additional scattered cortical infarcts in the internal carotid artery territory occurred in LVV hemispheres, but were rare in non-LVV hemispheres. Jacobian determinants revealed greater atrophy in gray and white matter of the parietal lobes of LVV compared with non-LVV hemispheres.

CONCLUSION

Large-vessel vasculopathy in sickle cell disease appears to increase ischemic vulnerability in the borderzone region, as demonstrated by the increased frequency and extent of infarction within deep white matter, and increased risk of focal atrophy. Scattered infarctions across the LVV-affected hemispheres suggest additional stroke etiologies of vasculopathy (i.e., thromboembolism) in addition to chronic hypoxia-ischemia.

The impact of high grade glial neoplasms on human cortical electrophysiology

Objective

The brain’s functional architecture of interconnected network-related oscillatory patterns in discrete cortical regions has been well established with functional magnetic resonance imaging (fMRI) studies or direct cortical electrophysiology from electrodes placed on the surface of the brain, or electrocorticography (ECoG). These resting state networks exhibit a robust functional architecture that persists through all stages of sleep and under anesthesia. While the stability of these networks provides a fundamental understanding of the organization of the brain, understanding how these regions can be perturbed is also critical in defining the brain’s ability to adapt while learning and recovering from injury.

Methods

Patients undergoing an awake craniotomy for resection of a tumor were studied as a unique model of an evolving injury to help define how the cortical physiology and the associated networks were altered by the presence of an invasive brain tumor.

Results

This study demonstrates that there is a distinct pattern of alteration of cortical physiology in the setting of a malignant glioma. These changes lead to a physiologic sequestration and progressive synaptic homogeneity suggesting that a de-learning phenomenon occurs within the tumoral tissue compared to its surroundings.

Significance

These findings provide insight into how the brain accommodates a region of “defunctionalized” cortex. Additionally, these findings may have important implications for emerging techniques in brain mapping using endogenous cortical physiology.