Sex Difference in Cigarette-Smoking Status and Its Association with Brain Volumes Using Large-Scale Community-Representative Data

BACKGROUND

Cigarette smoking is believed to accelerate age-related neurodegeneration. Despite significant sex differences in both smoking behaviors and brain structures, the active literature is equivocal in parsing out a sex difference in smoking-associated brain structural changes.

OBJECTIVE

The current study examined subcortical and lateral ventricle gray matter (GM) volume differences among smokers, active, past, and never-smokers, stratified by sex.

METHODS

The current study data included 1959 Dallas Heart Study (DHS) participants with valid brain imaging data. Stratified by gender, multiple-group comparisons of three cigarette-smoking groups were conducted to test whether there is any cigarette-smoking group differences in GM volumes of the selected regions of interest (ROIs).

RESULTS

The largest subcortical GM volumetric loss and enlargement of the lateral ventricle were observed among past smokers for both females and males. However, these observed group differences in GM volumetric changes were statistically significant only among males after adjusting for age and intracranial volumes.

CONCLUSIONS

The study findings suggest a sex difference in lifetime-smoking-associated GM volumetric changes, even after controlling for aging and intracranial volumes.

The Health & Aging Brain among Latino Elders (HABLE) study methods and participant characteristics

INTRODUCTION

Mexican Americans remain severely underrepresented in Alzheimer's disease (AD) research. The Health & Aging Brain among Latino Elders (HABLE) study was created to fill important gaps in the existing literature.

METHODS

Community-dwelling Mexican Americans and non-Hispanic White adults and elders (age 50 and above) were recruited. All participants underwent comprehensive assessments including an interview, functional exam, clinical labs, informant interview, neuropsychological testing, and 3T magnetic resonance imaging (MRI) of the brain. Amyloid and tau positron emission tomography (PET) scans were added at visit 2. Blood samples were stored in the Biorepository.

RESULTS

Data was examined from n = 1705 participants. Significant group differences were found in medical, demographic, and sociocultural factors. Cerebral amyloid and neurodegeneration imaging markers were significantly different between Mexican Americans and non-Hispanic Whites.

DISCUSSION

The current data provide strong support for continued investigations that examine the risk factors for and biomarkers of AD among diverse populations.

Objective measurement technologies for transforming the Australian & New Zealand livestock industries

This paper introduces the special edition of Meat Science focused upon the development, calibration and validation of technologies that measure traits influencing meat eating quality, or carcass fat and lean composition. These papers reflect the combined research efforts of groups in Australia, through the Advanced Livestock Measurement Technologies project, and New Zealand through AgResearch. We describe the various technologies being developed, how these devices are being trained upon common gold-standard measurements, and how their outputs are being simultaneously integrated into existing industry systems. We outline how this enhances the industry uptake and adoption of these technologies, and how this is further accelerated by education programs and strategic industry investment into their commercialisation.

Association of Concentric Left Ventricular Hypertrophy With Subsequent Change in Left Ventricular End-Diastolic Volume: The Dallas Heart Study

BACKGROUND

In the conventional paradigm of the progression of left ventricular hypertrophy, a thick-walled left ventricle (LV) ultimately transitions to a dilated cardiomyopathy. There are scant data in humans demonstrating whether this transition occurs commonly without an interval myocardial infarction.

METHODS AND RESULTS

Participants (n=1282) from the Dallas Heart Study underwent serial cardiac magnetic resonance ≈7 years apart. Those with interval cardiovascular events and a dilated LV (increased LV end-diastolic volume [EDV] indexed to body surface area) at baseline were excluded. Multivariable linear regression models tested the association of concentric hypertrophy (increased LV mass and LV mass/volume^0.67) with change in LVEDV. The study cohort had a median age of 44 years, 57% women, 43% black, and 11% (n=142) baseline concentric hypertrophy. The change in LVEDV in those with versus without concentric hypertrophy was 1 mL (-9 to 12) versus -2 mL (-11 to 7), respectively, P<0.01. In multivariable linear regression models, concentric hypertrophy was associated with larger follow-up LVEDV (P≤0.01). The progression to a dilated LV was uncommon (2%, n=25).

CONCLUSIONS

In the absence of interval myocardial infarction, concentric hypertrophy was associated with a small, but significantly greater, increase in LVEDV after 7-year follow-up. However, the degree of LV enlargement was minimal, and few participants developed a dilated LV. These data suggest that if concentric hypertrophy does progress to a dilated cardiomyopathy, such a transition would occur over a much longer timeframe (eg, decades) and perhaps less common than previously thought.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00344903.

Dynamic Relation of Changes in Weight and Indices of Fat Distribution With Cardiac Structure and Function: The Dallas Heart Study

BACKGROUND

Obesity may increase heart failure risk through cardiac remodeling. Cross-sectional associations between adiposity and cardiac structure and function have been elucidated, but the impact of longitudinal changes in adiposity on cardiac remodeling is less well understood.

METHODS AND RESULTS

Participants in the Dallas Heart Study without cardiovascular disease or left ventricular dysfunction underwent assessment of body weight, anthropometrics, and cardiac magnetic resonance imaging at baseline and 7 years later. Associations between changes in indices of generalized and central adiposity with changes in left ventricular mass, volume, mass/volume ratio (concentricity), wall thickness, and ejection fraction were assessed using multivariable linear regression. The study cohort (n=1262) mean age was 44 years with 57% women, 44% black, and 36% obese participants. At follow-up, 41% had ≥5% weight gain, and 15% had ≥5% weight loss. Greater weight gain was associated with younger age, lower risk factor burden, and lower body mass index at baseline. In multivariable models adjusting for age, sex, race, comorbid conditions at baseline and follow-up, baseline adiposity, and cardiac measurement, increasing weight was associated with increases in left ventricular mass (β=0.10, P<0.0001), wall thickness (β=0.10, P<0.0001), and concentricity (β=0.06, P=0.002), with modest effects on end-diastolic volume (β=0.04, P=0.044) and ejection fraction (β=0.05, P=0.046). Similar results were seen with other adiposity indices.

CONCLUSIONS

Concentric left ventricular remodeling is the predominant phenotype linked to increasing adiposity in middle age. Our findings support the importance of weight management to prevent secular changes in adiposity, concentric remodeling, and eventual heart failure over time.

Measurement of Peripheral Vision Reaction Time Identifies White Matter Disruption in Patients with Mild Traumatic Brain Injury

This study examined whether peripheral vision reaction time (PVRT) in patients with mild traumatic brain injury (mTBI) correlated with white matter abnormalities in centroaxial structures and impairments in neuropsychological testing. Within 24 h after mTBI, crossed reaction times (CRT), uncrossed reaction times (URT), and crossed-uncrossed difference (CUD) were measured in 23 patients using a laptop computer that displayed visual stimuli predominantly to either the left or the right visual field of the retina. The CUD is a surrogate marker of the interhemispheric transfer time (ITT). Within 7 days after the injury, patients received a diffusion tensor-MRI (DTI) scan and a battery of neuropsychological tests. Nine uninjured control subjects received similar testing. Patients 18-50 years of age were included if they had a post-resuscitation Glasgow Coma Scale >13 and an injury mechanism compatible with mTBI. Healthy controls were either age- and gender-matched family members of the TBI patients or healthy volunteers. CUD deficits >2 standard deviations (SD) were seen in 40.9% of patients. The CUD of injured patients correlated with mean diffusivity (MD) (p < 0.001, ρ = -0.811) in the posterior corpus callosum. Patients could be stratified on the basis of CUD on the Stroop 1, Controlled Oral Word Association Test (COWAT), and the obsessive-compulsive component of the Basic Symptom Inventory tests. These studies suggest that the PVRT indirectly measures white matter integrity in the posterior corpus callosum, a brain region frequently damaged by mTBI.

Ethnic Difference in Proximal Aortic Stiffness: An Observation From the Dallas Heart Study

OBJECTIVES

This study aims to compare ethnic difference in proximal aortic pulse wave velocity (PWV) and characteristic impedance (Zc).

BACKGROUND

Increased aortic stiffness is an independent predictor of target organ damage, incident hypertension, and all-cause mortality. However, previous studies have not directly assessed proximal aortic function in Blacks, the ethnic population with disproportionately high risk for incident hypertension and target organ complications.

METHODS

We evaluated the multiethnic, population-based DHS (Dallas Heart Study) participants (N = 2,544, 54.2% women, 49.7% Black) who underwent cardiac magnetic resonance at 1.5-T. Aortic stiffness and Zc were determined from aortic arch PWV and lumen area measurements. Linear regression was used to evaluate ethnic differences in proximal aortic wall stiffness using aortic arch PWV and Zc as dependent variables with and without adjustment for traditional cardiovascular risk factors. Because cardiac output was significantly higher in Blacks compared to Whites and Hispanics, additional comparisons of PWV and Zc were performed after adjustment for cardiac output and peripheral vascular resistance.

RESULTS

Compared with Whites, both Blacks and Hispanics had higher levels of aortic arch PWV (4.25, 95% confidence interval [CI]: 4.15 to 4.35 m/s, vs. 4.72, 95% CI: 4.64 to 4.81 m/s, vs. 4.48, 95% CI: 4.33 to 4.63 m/s, respectively, both p < 0.05 vs. White), and Zc (64.9, 95% CI: 63.3 to 66.6 dyne·s/cm⁵, vs. 75.6, 95% CI: 74.0 to 77.2 dyne·s/cm⁵, vs. 70.1, 95% CI: 67.6 to 72.8 dyne·s/cm⁵, respectively, both p < 0.01 vs. White) after adjustment for age, age squared, sex, body mass index, height, mean arterial blood pressure, antihypertensive treatment, heart rate, total cholesterol, diabetes mellitus, and smoking. Compared with Hispanics, Blacks also had higher level of both PWV and Zc (both p < 0.01). Ethnic differences in PWV and Zc persisted after adjustment for cardiac output and peripheral vascular resistance.

CONCLUSIONS

In a multiethnic population-based-sample, Blacks and Hispanics had higher proximal aortic stiffness compared with Whites independent of blood pressure and relevant risk factors.

Changes in Supraspinal Activation Patterns following Robotic Locomotor Therapy in Motor-Incomplete Spinal Cord Injury

Objectives. Body weight-supported treadmill training (BWSTT) is a task-specific rehabilitation strategy that enhances functional locomotion in patients following spinal cord injury (SCI). Supraspinal centers may play an important role in the recovery of over-ground locomotor function in patients with motor-incomplete SCI. The purpose of this study was to evaluate the potential for supraspinal reorganization associated with 12 weeks of robotic BWSTT using functional magnetic resonance imaging (fMRI). Methods. Four men with motor-incomplete SCI participated in this study. Time since onset ranged from 14 weeks to 48 months post-SCI injury. All subjects were trained with BWSTT 3 times weekly for 12 weeks. This training was preceded and followed by fMRI study of supraspinal activity during a movement task. Testing of locomotor disability included the Walking Index for Spinal Cord Injury (WISCI II) and over-ground gait speed. Results. All subjects demonstrated some degree of change in the blood-oxygen-level-dependent (BOLD) signal following BWSTT. fMRI results demonstrated greater activation in sensorimotor cortical regions (S1, S2) and cerebellar regions following BWSTT. Conclusions. Intensive task-specific rehabilitative training, such as robotic BWSTT, can promote supraspinal plasticity in the motor centers known to be involved in locomotion. Furthermore, improvement in over-ground locomotion is accompanied by an increased activation of the cerebellum.

Hippocampal volume in patients with asthma: Results from the Dallas Heart Study

INTRODUCTION

Asthma is associated with an increased risk of mild cognitive impairment and dementia. Depression and oral corticosteroid use are associated with atrophy of the hippocampus and are common in asthma. However, minimal neuroimaging data are available in asthma patients.

METHODS

We conducted a retrospective analysis of 1,287 adult participants from the Dallas Heart Study, an epidemiological sample of Dallas County residents. Study outcome variables were hippocampal volumes measured by FreeSurfer. ANOVA was used to examine a gender difference in hippocampal volumes. General Linear Models (GLM) were conducted to examine asthma diagnosis association with hippocampal volumes.

RESULTS

The prevalence rate of asthma among our study sample was 10.8% with 9.6% in males and 11.7% in females. After controlling for demographic characteristics, participants with asthma had significantly smaller total, right, and left hippocampal volumes than those without asthma. The association of asthma with smaller hippocampal volume was significant among males but not among females.

CONCLUSION

Hippocampal volume in a large and diverse sample of adults was significantly smaller in people with asthma as compared to those without asthma. These findings suggest that asthma may be associated with structural brain differences. Thus, medical illnesses without obvious direct neurodegenerative or even vascular involvement can be associated with brain changes. Because the hippocampus is a brain region involved in memory formation, these findings may have implications for treatment adherence that could have important implications for asthma treatment. Study limitations are the reliance on a self-reported asthma diagnosis and lack of additional asthma clinical information.

Cognitive impact of lacunar infarcts and white matter hyperintensity volume

Background

Subcortical lacunar infarcts and white matter hyperintensities (WMH) are common neuroradiological findings, but few studies associate between these insults and cognition in a community-dwelling population.

Methods

The Dallas Heart Study is a population-based initiative whose assessments included demographic and clinical findings including brain MRI and the Montreal Cognitive Assessment (MoCA). The presence and number of lacunes in subjects aged over 55 years were assessed by study physicians. The WMH volume was measured by an automated method. The association between the presence and number of lacunar infarcts and of WMH volume with the total MoCA score and subdomains was assessed using linear regression with adjustment for age, gender and self-reported ethnicity.

Results

In 609 subjects with valid data, both the presence and the increasing number of lacunes were associated with lower MoCA scores, even after adjusting for demographic variables. The presence of lacunes was also associated with lower scores in the memory, executive and attention subdomains. The WMH volume was not significantly associated with the MoCA score.

Conclusion

The presence and increasing number of lacunes in midlife is associated with a lower performance in multiple domains of a cognitive screening measure after adjusting for demographic factors.

Cytotoxic and vasogenic cerebral oedema in traumatic brain injury: assessment with FLAIR and DWI imaging

PRIMARY OBJECTIVE

Cerebral oedema is a common complication of traumatic brain injury (TBI). The use of Fluid-Attenuated Inversion Recovery (FLAIR) imaging in combination with Diffusion Weighted Imaging (DWI) has the potential to distinguish between cytotoxic and vasogenic oedema. This study hypothesized a significant relationship between cytotoxic lesion volume and outcome.

RESEARCH DESIGN

This observational study reports on a convenience sample where MRI was obtained for clinical purposes.

METHODS AND PROCEDURES

Clinical post-TBI FLAIR and DWI images were analysed. For this study, lesions were defined as primarily cytotoxic oedema if the ratio of FLAIR to DWI lesion volume was comparable, defined as a ratio <2. If the ratio of FLAIR to DWI lesion volume was ≥2, oedema was considered predominantly of vasogenic origin.

MAIN OUTCOMES AND RESULTS

The sample consisted primarily of males with TBIs whose injury severity ranged from complicated mild to severe. Analysis revealed that both oedema types are common after TBI and both are associated with functional deficits 6 months after injury.

CONCLUSIONS

Acute MRI may be useful to assess pathology at the tissue after traumatic brain injury. Clinical trials targeting cytotoxic and vasogenic mechanisms of oedema formation may benefit from using DWI and FLAIR MRI as a means to differentiate the predominant oedema type after TBI.

Association of depressive symptoms with hippocampal volume in 1936 adults

Hippocampal atrophy is reported in major depressive disorder (MDD). However, sample sizes were generally modest, and participant characteristics, including age, differed between studies. This study used a community sample to examine relationships between current depressive symptom severity and hippocampal volume across the adult lifespan. A total of 1936 adults with magnetic resonance images of the brain and Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR) scores were included. Brain volumes were quantified using the FSL program. Multiple linear regressions were performed using left, right, and total hippocampal volume as criterion variables, and predictor variables of QIDS-SR total, total brain volume, age, gender, education, psychotropic medications, alcohol use, and race/ethnicity. Post hoc analyses were conducted in participants with QIDS-SR scores 11 (moderate or greater depressive symptom severity) and <11, and older and younger adults. In the primary analysis (sample as a whole) QIDS-SR was inversely associated with total hippocampal volume (b=-0.044, p=0.032, (CI-0.019 to -0.001)) but not with left or right hippocampal volume evaluated individually. In participants with QIDS-SR scores of <11, hippocampal volumes were not associated with QIDS-SR scores. In those with QIDS-SR scores 11 total, right, and left hippocampal volumes were modestly, but significantly, associated with QIDS-SR scores. The association between QIDS-SR scores and the hippocampal volume was much stronger in older persons. Findings suggest smaller hippocampal volumes among those with greater reported depressive symptom severity-an association that is strongest in people with at least moderate depressive symptom levels.

Fully automated tool to identify the aorta and compute flow using phase-contrast MRI: validation and application in a large population based study

PURPOSE

To assess if fully automated localization of the aorta can be achieved using phase contrast (PC) MR images.

MATERIALS AND METHODS

PC cardiac-gated MR images were obtained as part of a large population-based study. A fully automated process using the Hough transform was developed to localize the ascending aorta (AAo) and descending aorta (DAo). The study was designed to validate this technique by determining: (i) its performance in localizing the AAo and DAo; (ii) its accuracy in generating AAo flow volume and DAo flow volume; and (iii) its robustness on studies with pathological abnormalities or imaging artifacts.

RESULTS

The algorithm was applied successfully on 1884 participants. In the randomly selected 50-study validation set, linear regression shows an excellent correlation between the automated (A) and manual (M) methods for AAo flow (r = 0.99) and DAo flow (r = 0.99). Bland-Altman difference analysis demonstrates strong agreement with minimal bias for: AAo flow (mean difference [A-M] = 0.47 ± 2.53 mL), and DAo flow (mean difference [A-M] = 1.74 ± 2.47 mL).

CONCLUSION

A robust fully automated tool to localize the aorta and provide flow volume measurements on phase contrast MRI was validated on a large population-based study.

MR imaging of hippocampal asymmetry at 3T in a multiethnic, population-based sample: results from the Dallas Heart Study

BACKGROUND AND PURPOSE

Asymmetry of the hippocampus is regarded as an important clinical finding, but limited data on hippocampal asymmetry are available for the general population. Here we present hippocampal asymmetry data from the Dallas Heart Study determined by automated methods and its relationship to age, sex, and ethnicity.

MATERIALS AND METHODS

3D magnetization-prepared rapid acquisition of gradient echo MR imaging was performed in 2082 DHS-2 participants. The MR images were analyzed by using 2 standard automated brain-segmentation programs, FSL-FIRST and FreeSurfer. Individuals with imaging errors, self-reported stroke, or major structural abnormalities were excluded. Statistical analyses were performed to determine the significance of the findings across age, sex, and ethnicity.

RESULTS

At the 90th percentile, FSL-FIRST demonstrated hippocampal asymmetry of 9.8% (95% CI, 9.3%-10.5%). The 90th percentile of hippocampal asymmetry, measured by the difference in right and left hippocampi volume and the larger hippocampus, was 17.9% (95% CI, 17.0%-19.1%). Hippocampal asymmetry increases with age (P=.0216), men have greater asymmetry than women as shown by FSL-FIRST (P=.0036), but ethnicity is not significantly correlated with asymmetry. To confirm these findings, we used FreeSurfer. FreeSurfer showed asymmetry of 4.4% (95% CI, 4.3%-4.7%) normalized to total volume and 8.5% (95% CI, 8.3%-9.0%) normalized by difference/larger hippocampus. FreeSurfer also showed that hippocampal asymmetry increases with age (P=.0024) and that men had greater asymmetry than women (P=.03).

CONCLUSIONS

There is a significant degree of hippocampal asymmetry in the population. The data provided will aid in the research, diagnosis, and treatment of temporal lobe epilepsy and other neurologic disease.

Donepezil effects on hippocampal and prefrontal functional connectivity in Alzheimer's disease: preliminary report

We used functional connectivity magnetic resonance imaging (fcMRI) to investigate changes in interhemispheric brain connectivity in 11 patients with mild Alzheimer's disease (AD) following eight weeks of treatment with the cholinesterase inhibitor donepezil. We examined functional connectivity between four homologous temporal, frontal, and occipital regions. These regions were selected to represent sites of AD neuropathology, sites of donepezil-related brain activation change in prior studies, and sites that are minimally affected by the pathologic changes of AD. Based on previous findings of selective, localized frontal responses to donepezil, we predicted that frontal connectivity would be most strongly impacted by treatment. Of the areas examined, we found that treatment had a significant effect only on functional connectivity between right and left dorsolateral prefrontal cortices. Implications for understanding the impact of donepezil treatment on brain functioning and behavior in patients with AD are discussed. This preliminary report suggests that fcMRI may provide a useful index of treatment outcome in diseases affecting brain connectivity. Future research should investigate these treatment-related changes in larger samples of patients and age-matched controls.

Abstract 171: CRP, IL-18, and BNP are Associated with Regional Brain Atrophy: Results from the Dallas Heart Study

Purpose: Multiple biomarkers have been associated with total brain atrophy. However, little is known about their relationship to segmental atrophy in a large, multi-ethnic, population-based sample.

Materials and Methods: 3D-MPRAGE brain images obtained at 3T from 2082 participants of the Dallas Heart Study (DHS) 2 were analyzed with Freesurfer and outlier analysis was performed. Divisive eigenvalue clustering of 89 brain segments yielded 24 groups with linked atrophy patterns. Plasma C-reactive protein (CRP), IL-18, homocsysteine and B-type natriuretic peptide (BNP) obtained 7 years prior during DHS 1 were available for 1343, 840, 1333 and 1331 participants, respectively. Multivariate linear regression analysis with adjustments for age, ethnicity, and gender were used to demonstrate associations between biomarkers and atrophy clusters.

Results: Nine atrophy clusters were associated with CRP, three atrophy clusters were associated with IL-18, and six atrophy clusters were associated with BNP (Table 1). Homocysteine did not have any significant correlations.

Conclusions: The markers studied had associations with distinct patterns of segmental atrophy indicating they may have unique interactions in different brain regions. This suggests that distinct inflammatory and other pathways may be at work in specific regions of the brain and that their localized effects may be obscured by approaches evaluating solely total brain volumes. Table 1:

Evaluation of a practical visual MRI rating scale of brain white matter hyperintensities for clinicians based on largest lesion size regardless of location

BACKGROUND AND PURPOSE

Age-related white matter hyperintensities have prognostic implications, but no accepted clinical standard exists for their assessment. We propose a simple objective visual rating system by using 3T brain MR imaging.

MATERIALS AND METHODS

MR imaging from 559 participants was processed by using an automated method to determine WMH volumes and evaluated with a new visual rating scale based on the single largest WMH lesion diameter regardless of location. The reproducibility of the visual system was assessed. The association of WMH visual scores and automated volumes was then compared with cognitive scores from the Montreal Cognitive Assessment, which was available for 510 participants.

RESULTS

Inter-reader reproducibility was good for subsamples with both high (n=52) and low (n=40) prevalence of large automated WMH volumes (agreement of 67% and 87.5%, κ=0.71 and 0.76, respectively). Correlation between increased WMH and cognitive deficit measurements was equal for our visual ratings and automated volumes (Spearman ρ=0.118 and 0.109; P values=0.008 and 0.014, respectively). The visual scale retained a significant association with MoCA score after adjusting for age, sex, and education (standardized β=-0.087, P=.042).

CONCLUSIONS

We propose a simple visual WMH scoring system suitable for use as a baseline evaluation in clinical practice.

Potential of electron beam computed tomography for coronary artery calcium screening to evaluate fatty liver: comparison with 1H magnetic resonance spectroscopy in the Dallas Heart Study

OBJECTIVES

Electron beam computed tomography (EBCT) for coronary artery calcification can potentially evaluate liver fat, another marker of cardiovascular risk. We compared quantitative estimates of hepatic steatosis measured by EBCT with those obtained by a well-validated, accurate-measure, magnetic resonance spectroscopy ((1)H MRS).

METHODS

EBCT and (1)H MRS were performed in 2159 subjects from the Dallas Heart Study. Forty subjects were randomly selected from each of 5 subgroups of liver fat percent by (1)H MRS (n = 200). EBCT average liver attenuation (HU) was determined in a 1- to 2-cm circular region of interest over the liver lobes. Pearson correlation coefficients were calculated. Using a previously defined (1)H MRS hepatic steatosis cut point (>5.5%), an optimized EBCT liver attenuation cut point was determined by receiver operating characteristic analysis.

RESULTS

(1)H MRS liver fat content and EBCT average right lobe liver attenuation were moderately negatively correlated (r = -0.64, P < 0.0001) in all subjects and in those with (1)H MRS hepatic steatosis (r = -0.71, P < 0.0001). This correlation did not improve with attenuation correction of the EBCT data using a standard calcium phantom or statistical transformation. Using an optimized receiver operating characteristic EBCT cut point (64.5 HU), sensitivity was 78% and specificity was 72% for detecting (1)H MRS hepatic steatosis, with a high false negative rate. Risk factors for hepatic steatosis (obesity, diabetes mellitus, insulin resistance, metabolic syndrome) were more strongly correlated with (1)H MRS than EBCT liver fat measures.

CONCLUSIONS

Liver attenuation on EBCT acquired for coronary artery calcification screening correlates modestly with (1)H MRS measures of liver fat content, with a high false negative rate.

Abstract 40: Updating White Matter Hyperintensity Visual Scoring: Incorporating Research Advances, Improving Reproducibility and Correlation with Automated Volumes

Introduction: White Matter Hyperintensities (WMH) have been implicated as a risk factor for motor and cognitive decline, dementia and stroke. A standard for use in clinical settings is needed to identify which cases are advanced or meet thresholds with implications for degree of impairment. The system of Fazekas is a promising candidate due to its simplicity and strong correlation with outcomes. The original Fazekas categorized deep and periventricular WMH separately. Advanced periventricular and deep WMH were later shown to have equivalent pathology and etiology. Subsequent work by De Carli showed the classification of deep and periventricular WMH on axial images to be arbitrary and suggested a common etiology for lesser degrees of WMH as well. We therefore adapted the Fazekas criteria to consider deep and periventricular WMH jointly. Questions persist about low reproducibility of grading systems. In a preliminary analysis we found frequent disagreement classifying lesions less than 3mm in diameter and decided to incorporate this threshold into our criteria to determine the effect on reproducibility and correlation of our final model with automated volumes.

Hypothesis: Modification of the Fazekas grading system to consider deep and periventricular WMH jointly is less arbitrary. Simple modifications of such a system will result in a high degree of reproducibility and high correlation with automated WMH volumes.

Methods: Axial 3T FLAIR MR images of the brain were obtained from community dwelling subjects. Grading measurements were applied to diameter of deep WMH and thickness of periventricular WMH. The initial system defined Grade 0 as no WMH, Grade 1 as < 10mm, Grade 2 as >=10mm but <20mm and Grade 3 as >=20mm. 52 studies were read separately by 2 reviewers. We then revised grade 0 to include intensities < 3mm and grade 1 as >=3mm but <10mm. 40 additional studies were then read and level of agreement was re-assessed. 563 studies were read for correlation with automated volumes.

Results: After modifications, inter-rater agreement for Fazekas white matter score increased from 72% to 89% with kappa increased from 0.45 to 0.78. There was good correlation of grade and automated volume (ANOVA R-Square: 0.52 P <.0001).

Conclusion: Advances in understanding of White Matter Hyperintensities suggest periventricular and deep lesions should be rated jointly. This modification was applied to the Fazekas system with excellent reproducibility after implementation of a 3mm size threshold as well as high agreement with automated volumes ammong community dwelling subjects.

Effects of lamotrigine on hippocampal activation in corticosteroid-treated patients

BACKGROUND

An extensive animal literature suggests that stress or excessive corticosteroid exposure is associated with changes in hippocampal function and memory. These findings are pertinent to psychiatric disorders with elevated cortisol, Cushing's disease and the millions of patients receiving prescription corticosteroids. In animals, agents that decrease glutamate release attenuate the effects of corticosteroids on the hippocampus. Minimal data are available on preventing or reversing the effects of corticosteroids on the human hippocampus. We previously reported improvement in memory in corticosteroid-treated patients given lamotrigine. In this report, we examined the impact of lamotrigine on task-related hippocampal activation in patients taking prescription corticosteroids.

METHODS

A total of 28 outpatients taking long-term oral prednisone for medical conditions, such as renal transplant rejection, were randomized to lamotrigine or placebo for 24 weeks. Hippocampal activation in response to a visual memory task was assessed with blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI).

RESULTS

Consistent with a reduction in glutamate release, the right posterior hippocampus showed a significant decrease in task-related activation in the lamotrigine group as compared to the placebo group.

LIMITATIONS

The modest sample size and an assessment period of only 24 weeks are study limitations.

CONCLUSIONS

Between-group differences in hippocampal activation were observed. The results suggest that an agent that modulates glutamate may modify the effects of long-term corticosteroid exposure on the human hippocampus.

Regionally selective atrophy after traumatic axonal injury

OBJECTIVES

To determine the spatial distribution of cortical and subcortical volume loss in patients with diffuse traumatic axonal injury and to assess the relationship between regional atrophy and functional outcome.

DESIGN

Prospective imaging study. Longitudinal changes in global and regional brain volumes were assessed using high-resolution magnetic resonance imaging-based morphometric analysis.

SETTING

Inpatient traumatic brain injury unit.

PATIENTS OR OTHER PARTICIPANTS

Twenty-five patients with diffuse traumatic axonal injury and 22 age- and sex-matched controls.

MAIN OUTCOME MEASURE

Changes in global and regional brain volumes between initial and follow-up magnetic resonance imaging were used to assess the spatial distribution of posttraumatic volume loss. The Glasgow Outcome Scale-Extended score was the primary measure of functional outcome.

RESULTS

Patients underwent substantial global atrophy with mean whole-brain parenchymal volume loss of 4.5% (95% confidence interval, 2.7%-6.3%). Decreases in volume (at a false discovery rate of 0.05) were seen in several brain regions including the amygdala, hippocampus, thalamus, corpus callosum, putamen, precuneus, postcentral gyrus, paracentral lobule, and parietal and frontal cortices, while other regions such as the caudate and inferior temporal cortex were relatively resistant to atrophy. Loss of whole-brain parenchymal volume was predictive of long-term disability, as was atrophy of particular brain regions including the inferior parietal cortex, pars orbitalis, pericalcarine cortex, and supramarginal gyrus.

CONCLUSION

Traumatic axonal injury leads to substantial posttraumatic atrophy that is regionally selective rather than diffuse, and volume loss in certain regions may have prognostic value for functional recovery.

Cerebral atrophy after traumatic white matter injury: correlation with acute neuroimaging and outcome

Traumatic brain injury (TBI) is a pathologically heterogeneous disease, including injury to both neuronal cell bodies and axonal processes. Global atrophy of both gray and white matter is common after TBI. This study was designed to determine the relationship between neuroimaging markers of acute diffuse axonal injury (DAI) and cerebral atrophy months later. We performed high-resolution magnetic resonance imaging (MRI) at 3 Tesla (T) in 20 patients who suffered non-penetrating TBI, during the acute (within 1 month after the injury) and chronic stage (at least 6 months after the injury). Volume of abnormal fluid-attenuated inversion-recovery (FLAIR) signal seen in white matter in both acute and follow-up scans was quantified. White and gray matter volumes were also quantified. Functional outcome was measured using the Functional Status Examination (FSE) at the time of the chronic scan. Change in brain volumes, including whole brain volume (WBV), white matter volume (WMV), and gray matter volume (GMV), correlates significantly with acute DAI volume (r = -0.69, -0.59, -0.58, respectively; p <0.01 for all). Volume of acute FLAIR hyperintensities correlates with volume of decreased FLAIR signal in the follow-up scans (r = -0.86, p < 0.001). FSE performance correlates with acute hyperintensity volume and chronic cerebral atrophy (r = 0.53, p = 0.02; r = -0.45, p = 0.03, respectively). Acute axonal lesions measured by FLAIR imaging are strongly predictive of post-traumatic cerebral atrophy. Our findings suggest that axonal pathology measured as white matter lesions following TBI can be identified using MRI, and may be a useful measure for DAI-directed therapies.

Brain connectivity in non-reading impaired children and children diagnosed with developmental dyslexia

Diffusion Tensor Imaging (DTI) was used to investigate the relationship between white matter and reading abilities in reading impaired and non-reading impaired children. Seventeen children (7 non-reading impaired, 10 reading impaired) participated in this study. DTI was performed with 2mm isotropic resolution to cover the entire brain along 30 noncollinear directions. Voxelwise analyses were conducted on data processed through Tract Based Spatial Statistics (TBSS). The data replicated previous results seen across multiple studies and extended findings to include measures of both real word and pseudoword decoding. Negative correlations were observed in the left posterior corpus callosum between fractional anisotropy (FA) values and both measures of decoding. Positive correlations between FA values and real word and pseudoword decoding were observed in the left superior corona radiata. This extension of findings regarding correlations between the corona radiata and reading skills suggests an important direction for future research into the neurological substrates of reading.

Exercise-induced decrease in insular cortex rCBF during postexercise hypotension

The insular cortex (IC), a region of the brain involved in blood pressure (BP) modulation, shows decreases in regional cerebral blood flow (rCBF) during postexercise hypotension (PEH).

PURPOSE

To determine whether changes in IC neural activity were caused by prior exercise or by changes in BP, this investigation compared patterns of rCBF during periods of hypotension, which was induced by prior exercise (i.e., PEH) and sodium nitroprusside (SNP) infusion and a cold pressor (CP), to restore BP.

METHODS

Ten subjects were studied on three different days with randomly assigned conditions: i) resting baseline; ii) PEH; and iii) SNP-induced hypotension (matched to the PEH BP decrease). Data were collected for heart rate (HR) and mean BP, and rCBF was assessed using single-photon emission computed tomography (SPECT) as an index of brain activation.

RESULTS

Using ANOVA across conditions, there were differences (P<0.05; mean +/- SD) from baseline during PEH for HR (+12 +/- 3 bpm) and mean BP (-8 +/- 2 mm Hg) and during SNP-induced hypotension (HR = +15 +/- 4 bpm; MBP = -9 +/- 2 mm Hg), with no differences between PEH and SNP. After exercise, there were decreases (P<0.05) in the leg sensorimotor area, anterior cingulate, and the right and left inferior thalamus, right inferior insula, and left anterior insular regions. During SNP-induced hypotension, there were significant increases in the right and left inferior thalamus and the right and left inferior anterior IC. CP during PEH increased BP and IC activity.

CONCLUSIONS

Data show that reductions in IC neural activity are not caused by acute BP decreases. Findings suggest that exercise can lead to a temporary decrease in IC neural activity, which may be a significant neural factor contributing to PEH.

Blood oxygen level dependent (BOLD) contrast MRI and breast cancer chemotherapy response

10514

Background: Tumor microcirculation and oxygenation play critical roles in tumor growth and response to cytotoxic treatment. Assessing these parameters in vivo may provide a useful tool for evaluating therapy in real time. Deoxyhemoglobin (dHbO2) can serve as an endogenous contrast agent causing signal loss in echo planar MR images. Tumor characteristics or interventions affecting tumor oxygenation, which convert dHbO2 to HbO2 produce a BOLD signal gain, may complement conventional MRI. Material and Methods: Ten patients with locally advanced breast cancer received doxorubicin and cyclophosphamide (AC) for four cycles every 2 or 3 weeks followed by paclitaxel for 4 cycles. Prior to chemotherapy and after 1 and 4 cycles of AC, MRI was performed on a 1.5 T scanner. For the BOLD study, patients breathed room air (RA) for 45 sec, then oxygen for 6 min and finally RA again. The BOLD imaging an Echo Planar technique with TR/TE (500/41.4 ms) 256 matrix and 20cm field of view. This was followed by dynamic contrast enhanced (DCE) MRI study. Pre and 1 to 4 day post-treatment tumor biopsies for hypoxia response proteins by immunohistochemistry and global RNA by gene array expression analysis (Illumina platform) were obtained. Results: MRI showed mild BOLD contrast enhancing regions in all evaluable patients with a typical signal enhancement of ∼2%. All 3 patients with an initial high BOLD-effect (>7%) achieved a pathological response after chemotherapy compared to 4 who did not (p < 0.03). The MRI-DCE tumor response signal decreased with chemotherapy, but no correlation with pathological response was seen. No clear difference in hypoxia-induced proteins (eg. HIF1-alpha, VEGF, CAIX) was seen according to pathological response or BOLD. Distinct gene expression patterns at baseline and after therapy emerged depending on BOLD response involving development, apoptosis and cell cycle pathways. Discussion: BOLD MRI can provide a non-invasive, easily repeatable in vivo approach to assess breast tumor physiology and its sensitivity to hypoxia (vascular oxygenation) may add value by measuring hypoxia and predicting response to therapy. BOLD MRI appears promising to select ideal candidates for hypoxia targeting with anti-angiogenic agents combined with chemotherapy and such studies are under way.

No significant financial relationships to disclose.

Magnetic resonance imaging of cerebellar-prefrontal and cerebellar-parietal functional connectivity

Recent studies of the cerebellum indicated its involvement in a diverse array of functions, and analyses of non-human primate neuroanatomy have revealed connections between cerebellum and cerebral cortex that might support cerebellar contributions to a wider range of functions than traditionally thought. These include cortico-ponto-cerebellar projections originating throughout cerebral cortex, in addition to projections from the dentate nucleus of the cerebellum to prefrontal and posterior parietal cortices via the thalamus. Such projections likely serve as important substrates for cerebellar involvement in human cognition, assuming their analogues are prominent in the human brain. These connections can be examined from a functional perspective through the use of functional connectivity MRI (FCMRI), a technique that allows the in vivo examination of coherence in MR signal among functionally related brain regions. Using this approach, low-frequency fluctuations in MR signal in the dentate nucleus correlated with signal fluctuations in cerebellar, thalamic, limbic, striatal, and cerebrocortical regions including parietal and frontal sites, with prominent coherence in dorsolateral prefrontal cortex. These findings indicate that FCMRI is a useful tool for examining functional relationships between the cerebellum and other brain regions, and they support the findings from non-human primate studies showing anatomic projections from cerebellum to regions of cerebral cortex with known involvement in higher cognitive functions. To our knowledge, this represents the first demonstration of functional coherence between the dentate nucleus and parietal and prefrontal cortices in the human brain, suggesting the presence of cerebellar-parietal and cerebellar-prefrontal functional connectivity.

Interaural cross correlation of event-related potentials and diffusion tensor imaging in the evaluation of auditory processing disorder: a case study

In a previous publication (Jerger et al, 2002), we presented event-related potential (ERP) data on a pair of 10-year-old twin girls (Twins C and E), one of whom (Twin E) showed strong evidence of auditory processing disorder. For the present paper, we analyzed cross-correlation functions of ERP waveforms generated in response to the presentation of target stimuli to either the right or left ears in a dichotic paradigm. There were four conditions; three involved the processing of real words for either phonemic, semantic, or spectral targets; one involved the processing of a nonword acoustic signal. Marked differences in the cross-correlation functions were observed. In the case of Twin C, cross-correlation functions were uniformly normal across both hemispheres. The functions for Twin E, however, suggest poorly correlated neural activity over the left parietal region during the three word processing conditions, and over the right parietal area in the nonword acoustic condition. Differences between the twins' brains were evaluated using diffusion tensor magnetic resonance imaging (DTI). For Twin E, results showed reduced anisotropy over the length of the midline corpus callosum and adjacent lateral structures, implying reduced myelin integrity. Taken together, these findings suggest that failure to achieve appropriate temporally correlated bihemispheric brain activity in response to auditory stimulation, perhaps as a result of faulty interhemispheric communication via corpus callosum, may be a factor in at least some children with auditory processing disorder.

Changes in regional cerebral blood flow distribution during postexercise hypotension in humans

This investigation compared patterns of regional cerebral blood flow (rCBF) during exercise recovery both with and without postexercise hypotension (PEH). Eight subjects were studied on 3 days with randomly assigned conditions: 1) after 30 min of rest; 2) after 30 min of moderate exercise (M-Ex) at 60-70% heart rate (HR) reserve during PEH; and 3) after 30 min of light exercise (L-Ex) at 20% HR reserve with no PEH. Data were collected for HR, mean blood pressure (MBP), and ratings of perceived exertion and relaxation, and rCBF was assessed by use of single-photon-emission computed tomography. With the use of ANOVA across conditions, there were differences ( P < 0.05; mean ± SD) from rest during exercise recovery from M-Ex (HR = +12 ± 3 beats/min; MBP = -9 ± 2 mmHg), but not from L-Ex (HR = +2 ± 2 beats/min; MBP = -2 ± 2 mmHg). After M-Ex, there were decreases ( P < 0.05) for the anterior cingulate (-6.7 ± 2%), right and left inferior thalamus (-10 ± 3%), right inferior insula (-13 ± 3%), and left inferior anterior insula (-8 ± 3%), not observed after L-Ex. There were rCBF decreases for leg sensorimotor regions after both M-Ex (-15 ± 4%) and L-Ex (-12 ± 3%) and for the left superior anterior insula (-7 ± 3% and -6 ± 3%), respectively. Data show that there are rCBF reductions within specific regions of the insular cortex and anterior cingulate cortex coupled with a postexercise hypotensive response after M-Ex. Findings suggest that these cerebral cortical regions, previously implicated in cardiovascular regulation during exercise, may also be involved in PEH.

Differential activation on fMRI of monozygotic twins discordant for AD

This is the first report of fMRI in monozygotic twins discordant for AD. FMRI brain activation patterns were examined during visuospatial and verbal working memory tasks. The affected twin had greater parietal involvement bilaterally during both working memory tasks and reduced left dorsolateral prefrontal cortex activity on the visuospatial memory task. Thus, fMRI may identify additional brain regions recruited in patients with AD to perform a given cognitive task.

Evidence for central command activation of the human insular cortex during exercise

The purpose of this investigation was to determine whether central command activated regions of the insular cortex, independent of muscle metaboreflex activation and blood pressure elevations. Subjects (n = 8) were studied during 1) rest with cuff occlusion, 2) static handgrip exercise (SHG) sufficient to increase mean blood pressure (MBP) by 15 mmHg, and 3) post-SHG exercise cuff occlusion (PECO) to sustain the 15-mmHg blood pressure increase. Data were collected for heart rate, MBP, ratings of perceived exertion and discomfort, and regional cerebral blood flow (rCBF) by using single-photon-emission computed tomography. When time periods were compared when MBP was matched during SHG and PECO, heart rate (7 +/- 3 beats/min; P < 0.05) and ratings of perceived exertion (15 +/- 2 units; P < 0.05) were higher for SHG. During SHG, there were significant increases in rCBF for hand sensorimotor (9 +/- 3%), right inferior posterior insula (7 +/- 3%), left inferior anterior insula (8 +/- 2%), and anterior cingluate regions (6 +/- 2%), not found during PECO. There was significant activation of the inferior (ventral) thalamus and right inferior anterior insular for both SHG and PECO. Although prior studies have shown that regions of the insular cortex can be activated independent of mechanoreflex input, it was not presently assessed. These findings provide evidence that there are rCBF changes within regions of the insular and anterior cingulate cortexes related to central command per se during handgrip exercise, independent of metaboreflex activation and blood pressure elevation.

Brain activation by central command during actual and imagined handgrip under hypnosis

The purpose was to compare patterns of brain activation during imagined handgrip exercise and identify cerebral cortical structures participating in "central" cardiovascular regulation. Subjects screened for hypnotizability, five with higher (HH) and four with lower hypnotizability (LH) scores, were tested under two conditions involving 3 min of 1) static handgrip exercise (HG) at 30% of maximal voluntary contraction (MVC) and 2) imagined HG (I-HG) at 30% MVC. Force (kg), forearm integrated electromyography, rating of perceived exertion, heart rate (HR), mean blood pressure (MBP), and differences in regional cerebral blood flow distributions were compared using an ANOVA. During HG, both groups showed similar increases in HR (+13 +/- 5 beats/min) and MBP (+17 +/- 3 mmHg) after 3 min. However, during I-HG, only the HH group showed increases in HR (+10 +/- 2 beats/min; P < 0.05) and MBP (+12 +/- 2 mmHg; P < 0.05). There were no significant increases or differences in force or integrated electromyographic activity between groups during I-HG. The rating of perceived exertion was significantly increased for the HH group during I-HG, but not for the LH group. In comparison of regional cerebral blood flow, the LH showed significantly lower activity in the anterior cingulate (-6 +/- 2%) and insular cortexes (-9 +/- 4%) during I-HG. These findings suggest that cardiovascular responses elicited during imagined exercise involve central activation of insular and anterior cingulate cortexes, independent of muscle afferent feedback; these structures appear to have key roles in the central modulation of cardiovascular responses.

Hypnotic manipulation of effort sense during dynamic exercise: cardiovascular responses and brain activation

The purpose of this investigation was to hypnotically manipulate effort sense during dynamic exercise and determine whether cerebral cortical structures previously implicated in the central modulation of cardiovascular responses were activated. Six healthy volunteers (4 women, 2 men) screened for high hypnotizability were studied on 3 separate days during constant-load exercise under three hypnotic conditions involving cycling on a 1) perceived level grade, 2) perceived downhill grade, and 3) perceived uphill grade. Ratings of perceived exertion (RPE), heart rate (HR), blood pressure (BP), and regional cerebral blood flow (rCBF) distributions for several sites were compared across conditions using an analysis of variance. The suggestion of downhill cycling decreased both the RPE [from 13 +/- 2 to 11 +/- 2 (SD) units; P < 0.05] and rCBF in the left insular cortex and anterior cingulate cortex, but it did not alter exercise HR or BP responses. Perceived uphill cycling elicited significant increases in RPE (from 13 +/- 2 to 14 +/- 1 units), HR (+16 beats/min), mean BP (+7 mmHg), right insular activation (+7.7 +/- 4%), and right thalamus activation (+9.2 +/- 5%). There were no differences in rCBF for leg sensorimotor regions across conditions. These findings show that an increase in effort sense during constant-load exercise can activate both insular and thalamic regions and elevate cardiovascular responses but that decreases in effort sense do not reduce cardiovascular responses below the level required to sustain metabolic needs.

Activation of the insular cortex is affected by the intensity of exercise

The purpose of this investigation was to determine whether there were differences in the magnitude of insular cortex activation across varying intensities of static and dynamic exercise. Eighteen healthy volunteers were studied: eight during two intensities of leg cycling and ten at different time periods during sustained static handgrip at 25% maximal voluntary contraction or postexercise cuff occlusion. Heart rate, blood pressure (BP), perceived exertion, and regional cerebral blood flow (rCBF) distribution data were collected. There were significantly greater increases in insular rCBF during lower (6.3 +/- 1.7%; P < 0.05) and higher (13.3 +/- 3.8%; P < 0.05) intensity cycling and across time during static handgrip (change from rest for right insula at 2-3 min, 3.8 +/- 1.1%, P < 0.05; and at 4-5 min, 8.6 +/- 2.8%, P < 0.05). Insular rCBF was decreased during postexercise cuff occlusion (-5.5 +/- 1.2%; P < 0.05) with BP sustained at exercise levels. Right insular rCBF data, but not left, were significantly related, with individual BP changes (r(2) = 0.80; P < 0.001) and with ratings of perceived exertion (r(2) = 0.79; P < 0.01) during exercise. These results suggest that the magnitude of insular activation varies with the intensity of exercise, which may be further related to the level of perceived effort or central command.

Activation of the insular cortex during dynamic exercise in humans

1. The insular cortex has been implicated as a region of cortical cardiovascular control, yet its role during exercise remains undefined. The purpose of the present investigation was to determine whether the insular cortex was activated during volitional dynamic exercise and to evaluate further its role as a site for regulation of autonomic activity. 2. Eight subjects were studied during voluntary active cycling and passively induced cycling. Additionally, four of the subjects underwent passive movement combined with electrical stimulation of the legs. 3. Increases in regional cerebral blood flow (rCBF) distribution were determined for each individual using single-photon emission-computed tomography (SPECT) co-registered with magnetic resonance (MR) images to define exact anatomical sites of cerebral activation during each condition. 4. The rCBF significantly increased in the left insula during active, but not passive cycling. There were no significant changes in rCBF for the right insula. Also, the magnitude of rCBF increase for leg primary motor areas was significantly greater for both active cycling and passive cycling combined with electrical stimulation compared with passive cycling alone. 5. These findings provide the first evidence of insular activation during dynamic exercise in humans, suggesting that the left insular cortex may serve as a site for cortical regulation of cardiac autonomic (parasympathetic) activity. Additionally, findings during passive cycling with electrical stimulation support the role of leg muscle afferent input towards the full activation of leg motor areas.