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ABSTRACT: PURPOSETo compare regional brain volumes in adult long-term survivors of childhood acute lymphoblastic leukemia (ALL) and healthy controls. PATIENTS AND METHODS
We investigated 130 survivors of childhood ALL diagnosed between 1970 and 2002 with magnetic resonance imaging (MRI) and neuropsychological testing at a median of 22.5 years after diagnosis. Morphometric analyses including whole-brain segmentation were performed using a validated automated procedure; 130 healthy adults served as controls.ResultsCompared with healthy controls, ALL survivors showed significantly smaller volumes of cortical gray matter, cerebral white matter, amygdala, caudate, hippocampus, thalamus, and estimated intracranial volume. Effect sizes ranged from small to medium. The strongest effect was found for the caudate, which on average was 5.2% smaller in ALL survivors. Caudate volumes were also smaller when controlling for intracranial volume, suggesting a specific effect. Neither age at diagnosis nor treatment variables such as radiation therapy or drug dose had a major impact on neuroanatomic volumes. Neuropsychological assessment revealed reduced processing speed, executive function, and verbal learning/memory in survivors compared with controls but no difference in estimated general intellectual ability. In ALL survivors, but not in controls, neuropsychological test results correlated with volumes of cortical gray matter, caudate, and thalamus as well as intracranial volume. CONCLUSION
Structural MRI of long-term survivors of childhood ALL demonstrated smaller volumes of multiple brain structures compared with healthy controls. Because of possible selection biases, these results must be interpreted with caution. Future studies are required to clarify the significance of these findings and the neurobiologic mechanisms involved.
Journal of Clinical Oncology 04/2013; · 18.37 Impact Factor
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Christian K Tamnes,
Kristine B Walhovd,
Anders M Dale,
Ylva Ostby,
Håkon Grydeland,
George Richardson,
Lars T Westlye,
J Cooper Roddey,
Donald J Hagler, Paulina Due-Tønnessen,
Dominic Holland,
Anders M Fjell
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ABSTRACT: Early-life development is characterized by dramatic changes, impacting lifespan function more than changes in any other period. Developmental origins of neurocognitive late-life functions are acknowledged, but detailed longitudinal magnetic resonance imaging studies of brain maturation and direct comparisons with aging are lacking. To these aims, a novel method was used to measure longitudinal volume changes in development (n=85, 8-22years) and aging (n=142, 60-91years). Developmental reductions exceeded 1% annually in much of cortex, more than double that seen in aging, with a posterior-to-anterior gradient. Cortical reductions were greater than subcortical during development, while the opposite held in aging. The pattern of lateral cortical changes was similar across development and aging, but the pronounced medial temporal reduction in aging was not precast in development. Converging patterns of change in adolescents and elderly, particularly in medial prefrontal areas, suggest that late developed cortices are especially vulnerable to atrophy in aging. A key question in future research will be to disentangle the neurobiological underpinnings for the differences and the similarities between brain changes in development and aging.
NeuroImage 12/2012; · 5.89 Impact Factor
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Per Selnes,
Dag Aarsland,
Atle Bjørnerud,
Leif Gjerstad,
Anders Wallin,
Erik Hessen,
Ivar Reinvang,
Ramune Grambaite,
Eirik Auning,
Veslemøy Krohn Kjærvik, Paulina Due-Tønnessen,
Vidar Stenset,
Tormod Fladby
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ABSTRACT: Neuropathological correlates of Alzheimer's disease (AD) emerge years before dementia. Biomarkers preceding cognitive decline and reflecting the causative processes can potentially aid early intervention and diagnosis. Diffusion tensor imaging (DTI) indirectly reflects tissue microstructure. To answer whether DTI is an early biomarker for AD and to explore the relationship between DTI and the established biomarkers of medial temporal lobe atrophy and cerebrospinal fluid (CSF) Aβ42, T-tau, and P-tau, we longitudinally studied normal controls and patients with subjective (SCI) or mild (MCI) cognitive impairment. 21 controls and 64 SCI or MCI cases recruited from a university-hospital based memory clinic were re-examined after two to three years. FreeSurfer was used for longitudinal processing of morphometric data, and DTI derived fractional anisotropy, radial diffusivity, and mean diffusivity were analyzed in Tract-Based Spatial Statistics. Using regression models, we explored and compared the predictive powers of DTI and CSF biomarkers in regard to cognitive change and atrophy of the medial temporal lobe. Both DTI and CSF biomarkers significantly predicted cognitive decline and atrophy in the medial temporal lobe. In this population, however, DTI was a better predictor of dementia and AD-specific medial temporal lobe atrophy than the CSF biomarkers. The case for DTI as an early biomarker for AD is strengthened, but further studies are needed to confirm these results.
Journal of Alzheimer's disease: JAD 11/2012; · 3.74 Impact Factor
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Inge K Amlien,
Anders M Fjell,
Kristine B Walhovd,
Per Selnes,
Vidar Stenset,
Ramune Grambaite,
Atle Bjørnerud, Paulina Due-Tønnessen,
Anders Skinningsrud,
Leif Gjerstad,
Ivar Reinvang,
Tormod Fladby
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ABSTRACT: Purpose:To evaluate the relationship between (a) pathologic levels of cerebrospinal fluid (CSF) total tau as an index of the intensity of ongoing neuronal degeneration and (b) longitudinal changes in white matter (WM) integrity in patients with mild cognitive impairment (MCI).Materials and Methods:Participants gave written informed consent, and the Norwegian committee for medical research ethics approved the study. Thirty patients with MCI and nonpathologic CSF total tau levels, nine patients with MCI and pathologic CSF total tau levels, and 16 age-matched healthy control subjects underwent diffusion-tensor imaging at baseline and after a mean follow-up of 2.6 years ± 0.54 (standard deviation), with range of 1.58-3.98 years. The effect of diagnosis (MCI vs no MCI) at baseline and CSF tau levels at fractional anisotropy (FA), mean diffusivity, radial diffusivity (D(R)), and axial diffusivity were tested with tract-based spatial statistics. Differences in WM integrity at baseline and follow-up and change over time were compared among patients with pathologic CSF total tau levels (MCI high tau), patients with normal CSF total tau levels (MCI low tau), and healthy control subjects. Linear mixed-model between-group within-subject analyses were conducted to examine differences in rate of change over time in FA and D(R).Results:Longitudinal analysis of regional WM change revealed significant decrease in FA (P = .038) and increase in D(R) (P = .018) in the MCI high-tau group relative to control subjects. For D(R), the changes were regionally specific to the right cingulum and the right superior and inferior longitudinal fasciculi.Conclusion:Reduction in WM integrity was greater in patients with MCI who had the most intense neuronal degeneration as indexed by using CSF total tau, suggesting that these patients might represent a subgroup of MCI with more intense WM degeneration who are possibly at greater risk of developing Alzheimer disease.© RSNA, 2012.
Radiology 11/2012; · 5.73 Impact Factor
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ABSTRACT: To determine whether white matter (WM) memory network changes accompany early cognitive impairment and whether these changes represent early, pathologically independent axonal affection, we combined WM diffusion tensor imaging and cortical morphometric measurements of normal control subjects, patients with only subjective cognitive impairment (SCI), or mild cognitive impairment (MCI).
We included 66 patients with SCI or MCI and 21 control subjects from a university-hospital-based memory clinic in a cross-sectional study. Morphometric analysis was performed in FreeSurfer, and Tract-Based Spatial Statistics was used for analysis of diffusion tensor imaging-derived WM fractional anisotropy, radial diffusivity (DR), and mean diffusivity (MD). Relationships between WM measures and stage were assessed with whole-brain voxelwise statistics and on a region-of-interest basis, with subsequent correction for cortical atrophy.
In SCI patients, as compared with control subjects, there were widespread changes in DR and MD. No significant differences in thickness could be demonstrated. In MCI patients, as compared with control subjects, there were widespread changes in DR, MD, and fractional anisotropy; the precuneal and inferior parietal cortices were thinner; and the hippocampus was smaller. Multiple logistic regression analysis eliminated morphometry as an explanatory variable in favor of DR/MD for all regions of interest, except in the precuneus, where both thickness and DR/MD were significant explanatory variables.
WM tract degeneration is prominent in SCI and MCI patients, and is at least in part independent of overlying gray matter atrophy.
Alzheimer's & dementia: the journal of the Alzheimer's Association 10/2012; 8(5 Suppl):S112-21. · 5.90 Impact Factor
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ABSTRACT: Neuroanatomical correlates of developmental psychopathology such as attention deficit hyperactivity and conduct disorder have been identified. The majority of studies point to lesser gray matter in psychopathology, often involving prefrontal cortices. The goal of this study was to test whether similar neural correlates exist for behavioral variance in healthy children and adolescents. A large sample (n = 106) aged 8-19 years underwent MR scanning and their parents completed the Strength and Difficulties Questionnaire. The relationships between cortical thickness and conduct problems and hyperactivity/inattention scale scores were investigated throughout the cerebrum. No associations were found between normal variance in hyperactivity/inattention and cortical thickness. Normal variance in conduct problems was associated with thinner left hemisphere prefrontal and supramarginal cortices. Relationships between conduct problems and cortical thickness interacted with age, with the greatest differences in cortical thickness seen in the younger children. These interactions were observed in the anterior cingulate, orbitofrontal, middle and superior frontal, as well as lateral and medial temporal cortices. In conclusion, the results indicate neurobiological continuity between symptoms of conduct problems within the normal range, and conduct disorder. Relationships of thinner cortices and conduct problems were primarily seen in younger children, and appeared to decrease with age, indicative of different maturational trajectories in the groups. The long-term consequences are unknown, and the results point to a need for longitudinal studies of developmental trajectories of neuroanatomical foundations of behavioral adjustment.
European Child & Adolescent Psychiatry 02/2012; · 2.82 Impact Factor
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ABSTRACT: A systematic comparison of magnetic resonance imaging (MRI) options for glioma diagnosis is lacking.
To investigate multiple MR-derived image features with respect to diagnostic accuracy in tumor grading and survival prediction in glioma patients.
T1 pre- and post-contrast, T2 and dynamic susceptibility contrast scans of 74 glioma patients with histologically confirmed grade were acquired. For each patient, a set of statistical features was obtained from the parametric maps derived from the original images, in a region-of-interest encompassing the tumor volume. A forward stepwise selection procedure was used to find the best combinations of features for grade prediction with a cross-validated logistic model and survival time prediction with a cox proportional-hazards regression.
Presence/absence of enhancement paired with kurtosis of the FM (first moment of the first-pass curve) was the feature combination that best predicted tumor grade (grade II vs. grade III-IV; median AUC = 0.96), with the main contribution being due to the first of the features. A lower predictive value (median AUC = 0.82) was obtained when grade IV tumors were excluded. Presence/absence of enhancement alone was the best predictor for survival time, and the regression was significant (P < 0.0001).
Presence/absence of enhancement, reflecting transendothelial leakage, was the feature with highest predictive value for grade and survival time in glioma patients.
Acta Radiologica 11/2011; 52(9):1052-60. · 1.37 Impact Factor
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ABSTRACT: Distributed brain areas support intellectual abilities in adults. How structural maturation of these areas in childhood enables development of intelligence is not established. Neuroimaging can be used to monitor brain development, but studies to date have typically considered single imaging modalities. To explore the impact of structural brain maturation on the development of intelligence, we used a combination of cortical thickness, white matter (WM) volume and WM microstructure in 168 healthy participants aged 8-30 years. Principal component analyses (PCAs) were conducted separately for cortical thickness, WM volume, fractional anisotropy (FA) and mean diffusivity (MD) in 64 different brain regions. For all four parameters, the PCAs revealed a general factor explaining between 40% and 53% of the variance across regions. When tested separately, negative age-independent relationships were found between intellectual abilities and cortical thickness and MD, respectively, while WM volume and FA were positively associated with intellectual abilities. The relationships between intellectual abilities and brain structure varied with age, with stronger relationships seen in children and adolescents than in young adults. Multiple regression analysis with the different imaging measures as simultaneous predictors, showed that cortical thickness, WM volume and MD all yielded unique information in explaining intellectual abilities in development. The present study demonstrates that different imaging modalities and measures give complementary information about the neural substrates of intellectual abilities in development, emphasizing the importance of multimodal imaging in investigations of neurocognitive development.
Neuropsychologia 09/2011; 49(13):3605-11. · 3.64 Impact Factor
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ABSTRACT: To explore white matter (WM) and gray matter tissue integrity in the apparently unaffected hemisphere of patients with herpes simplex encephalitis (HSE) who have gross unilateral medial temporal lobe (MTL) lesions and both verbal and visuospatial memory deficits.
This study had institutional ethics committee approval and included written informed consent. Magnetic resonance (MR) imaging was performed in five patients who had recovered from HSE (one woman, four men; median age, 32 years; interquartile range, 28.5-37 years) and 51 age-matched controls (30 women, 21 men; median age, 32 years; interquartile range, 28-37 years). As markers of microstructural WM integrity, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity (RD) derived from diffusion-tensor (DT) imaging were used. An automated regional brain segmentation approach yielded estimates of subcortical volumes, including hippocampus, and cortical thickness. Group differences were evaluated by using permutation tests.
Examination of standard MR images found unilateral lesions in all patients. The patients with HSE showed reduced FA and increased MD and RD in several WM tracts contralateral to lesions (P < .05, corrected for multiple comparisons). Affected tracts included connections between the MTLs and other parts of the brain. No significant group differences were observed in subcortical volume or cortical thickness.
These results suggest that patients with HSE have reduced microstructural integrity of normal-appearing WM contralateral to grossly visible lesions. These subtle lesions, detectable at DT imaging, probably contribute to the memory impairment manifested by these patients.
http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100179/-/DC1.
Radiology 10/2010; 257(3):774-81. · 5.73 Impact Factor
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ABSTRACT: Magnetic resonance imaging volumetry studies report inverted U-patterns with increasing white-matter (WM) volume into middle age suggesting protracted WM maturation compared with the cortical gray matter. Diffusion tensor imaging (DTI) is sensitive to degree and direction of water permeability in biological tissues, providing in vivo indices of WM microstructure. The aim of this cross-sectional study was to delineate age trajectories of WM volume and DTI indices in 430 healthy subjects ranging 8-85 years of age. We used automated regional brain volume segmentation and tract-based statistics of fractional anisotropy, mean, and radial diffusivity as markers of WM integrity. Nonparametric regressions were used to fit the age trajectories and to estimate the timing of maximum development and deterioration in aging. Although the volumetric data supported protracted growth into the sixth decade, DTI indices plateaued early in the fourth decade across all tested regions and then declined slowly into late adulthood followed by an accelerating decrease in senescence. Tractwise and voxel-based analyses yielded regional differences in development and aging but did not provide ample evidence in support of a simple last-in-first-out hypothesis of life-span changes.
Cerebral Cortex 09/2010; 20(9):2055-68. · 6.54 Impact Factor
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ABSTRACT: An autostereoscopic display with image quality comparable to ordinary 2D displays has recently been developed. The purpose of our study was to evaluate whether the visualization of static 3D models from intracranial time-of-flight (TOF) MR angiography (MRA) was improved by this display.
Maximum Intensity Projection (MIP) and Volume Rendering (VR) 3D models of intracranial arteries were created from ten TOF MRA datasets. Thirty-one clinically relevant intracranial arterial segments were marked in the TOF source images. A total of 217 markings were used. The markings were displayed in the 3D models as overlying red dots. Three neuroradiologists viewed the static 3D models on the autostereoscopic display, with the display operating either in autostereoscopic mode or in 2D mode. The task of the neuroradiologists was to correctly identify the marked artery. A paired comparison was made between arterial identification in autostereoscopic and 2D display mode.
In 314 MIP 3D models, 233 arterial markings (74%) were correctly identified with the display operating in autostereoscopic mode versus 179 (57%) in 2D mode. Odds ratio for correct identification with autostereoscopic mode versus 2D mode was 2.17 (95% confidence interval 1.55-3.04, P < 0.001). In 337 VR 3D models, 256 markings (76%) were correctly identified using autostereoscopic mode and 229 (68%) using 2D mode (odds ratio 1.49, 95% confidence interval 1.06-2.09, P = 0.021).
The visualization of intracranial arteries in static 3D models from TOF MRA can be improved by the use of an autostereoscopic display.
International Journal of Computer Assisted Radiology and Surgery 09/2010; 5(5):549-54. · 1.48 Impact Factor
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ABSTRACT: A range of cognitive abilities improves in childhood and adolescence. It has been proposed that the protracted development of executive functions is related to the relatively late maturation of the prefrontal cortex. However, this has rarely been directly investigated. In this cross-sectional study, 98 healthy children and adolescents (8-19 years old) were tested with six tasks considered to index three frequently postulated executive functions; updating (Keep track and Letter memory), inhibition (Antisaccade and Stroop) and shifting (Plus minus and Trail making). Task performance was then related to magnetic resonance imaging (MRI) measures of cortical thickness. The behavioral results did not indicate any clear organization of the executive function measures in the domains updating, inhibition and shifting. Limitations associated with the use of speed-based scores from the tasks considered to index shifting ability were also indicated. Independently of the effects of age, performance on the Keep track task was associated with thinner cortex bilaterally in clusters encompassing parietal and frontal regions, including the left inferior frontal gyrus, while performance on the Antisaccade task was associated with thinner cortex bilaterally in occipital and parietal regions. Further, levels of performance on the Antisaccade and Stroop tasks were related to estimated rates of cortical maturation in posterior brain regions, but not in the prefrontal cortex. The results from the present study add to previous knowledge about the cortical correlates of executive functions by indicating an important role of posterior cerebral areas in executive development.
Neuropsychologia 04/2010; 48(9):2496-508. · 3.64 Impact Factor
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ABSTRACT: Cortical thickness decreases from childhood throughout life, as estimated by magnetic resonance imaging (MRI). This monotone trajectory does not reflect the fundamentally different neurobiological processes underlying morphometric changes in development versus aging. We hypothesized that intracortical gray matter (GM) and subjacent white matter (WM) T1-weighted signal intensity would distinguish developmental and age-related changes in the cortex better than thickness. Intracortical GM and subjacent WM signal intensity and cortical thickness was measured across the brain surface in a healthy life span sample (n=429, 8-85 years). We also computed the relaxation rate of T2* (R2*) from multiecho sequences and mapped intracortical GM and subjacent WM values to the surface to delineate age-related variability in R2* and to adjust the T1 signal intensity for possible confounds of accumulated iron. While monotone age-related reductions in thickness were found, both intracortical GM and subcortical WM signal intensity showed inverted U patterns with peaks from eight to approximately 30 years of age. The spatial pattern of intracortical neurodevelopment followed a posterior-anterior gradient, with earliest maturation of occipital visual cortices and most protracted in superior frontal regions. From 50s and 60s, substantial signal reductions were observed in several regions, including the insula, cingulate, and inferior temporal gyrus. R2* showed similar patterns but peaked much later than the T1-weighted signal intensity measures. The results are presented as animations yielding detailed depictions of the dynamic regional variability in cortical neurodevelopment and aging and demonstrate that cortical thickness and T1-weighted signal intensity are sensitive to different cortical maturational and aging-related processes.
NeuroImage 03/2010; 52(1):172-85. · 5.89 Impact Factor
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ABSTRACT: Higher-order cognitive functions are supported by distributed networks of multiple interconnected cortical and subcortical regions. Efficient cognitive processing depends on fast communication between these regions, so the integrity of the connections between them is of great importance. It is known that white matter (WM) development is a slow process, continuing into adulthood. While the significance of cortical maturation for intellectual development is described, less is known about the relationships between cognitive functions and maturation of WM connectivity. In this cross-sectional study, we investigated the associations between intellectual abilities and development of diffusion tensor imaging (DTI) derived measures of WM microstructure in 168 right-handed participants aged 8-30 years. Independently of age and sex, both verbal and performance abilities were positively related to fractional anisotropy (FA) and negatively related to mean diffusivity (MD) and radial diffusivity (RD), predominantly in the left hemisphere. Further, verbal, but not performance abilities, were associated with developmental differences in DTI indices in widespread regions in both hemispheres. Regional analyses showed relations with both FA and RD bilaterally in the anterior thalamic radiation and the cortico-spinal tract and in the right superior longitudinal fasciculus. In these regions, our results suggest that participants with high verbal abilities may show accelerated WM development in late childhood and a subsequent earlier developmental plateau, in contrast to a steadier and prolonged development in participants with average verbal abilities. Longitudinal data are needed to validate these interpretations. The results provide insight into the neurobiological underpinnings of intellectual development.
Human Brain Mapping 02/2010; 31(10):1609-25. · 5.88 Impact Factor
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ABSTRACT: Brain development during late childhood and adolescence is characterized by decreases in gray matter (GM) and increases in white matter (WM) and ventricular volume. The dynamic nature of development across different structures is, however, not well understood, and the present magnetic resonance imaging study took advantage of a whole-brain segmentation approach to describe the developmental trajectories of 16 neuroanatomical volumes in the same sample of children, adolescents, and young adults (n = 171; range, 8-30 years). The cerebral cortex, cerebral WM, caudate, putamen, pallidum, accumbens area, hippocampus, amygdala, thalamus, brainstem, cerebellar GM, cerebellar WM, lateral ventricles, inferior lateral ventricles, third ventricle, and fourth ventricle were studied. The cerebral cortex was further analyzed in terms of lobar thickness and surface area. The results revealed substantial heterogeneity in developmental trajectories. GM decreased nonlinearly in the cerebral cortex and linearly in the caudate, putamen, pallidum, accumbens, and cerebellar GM, whereas the amygdala and hippocampus showed slight, nonlinear increases in GM volume. WM increased nonlinearly in both the cerebrum and cerebellum, with an earlier maturation in cerebellar WM. In addition to similarities in developmental trajectories within subcortical regions, our results also point to differences between structures within the same regions: among the basal ganglia, the caudate showed a weaker relationship with age than the putamen and pallidum, and in the cerebellum, differences were found between GM and WM development. These results emphasize the importance of studying a wide range of structural variables in the same sample, for a broader understanding of brain developmental principles.
Journal of Neuroscience 09/2009; 29(38):11772-82. · 7.11 Impact Factor
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ABSTRACT: The development of cortical gray matter, white matter (WM) volume, and WM microstructure in adolescence is beginning to be fairly well characterized by structural magnetic resonance imaging (sMRI) and diffusion tensor imaging (DTI) studies. However, these aspects of brain development have rarely been investigated concurrently in the same sample and hence the relations between them are not understood. We delineated the age-related changes in cortical thickness, regional WM volume, and diffusion characteristics and investigated the relationships between these properties of brain development. One hundred and sixty-eight healthy participants aged 8-30 years underwent sMRI and DTI. The results showed regional age-related cortical thinning, WM volume increases, and changes in diffusion parameters. Cortical thickness was the most strongly age-related parameter. All classes of measures showed unique associations with age. The results indicate that cortical thinning in adolescence cannot be explained by WM maturation in underlying regions as measured by volumetry or DTI. Moderate associations between cortical thickness and both volume and diffusion parameters in underlying WM regions were also found, although the relationships were not strong. It is concluded that none of the measures are redundant and that the integration of the 3 will yield a more complete understanding of brain maturation.
Cerebral Cortex 07/2009; 20(3):534-48. · 6.54 Impact Factor
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ABSTRACT: Diffusion tensor imaging (DTI) and CSF biomarkers are useful diagnostic tools to differentiate patients with mild cognitive impairment (MCI) from normal controls, and may help predict conversion to dementia. Total Tau protein (T-tau) and DTI parameters are both markers for axonal damage, thus it is of interest to determine if DTI parameters are associated with elevated CSF T-tau levels in patients with cognitive impairment. For this purpose, patients with subjective cognitive impairment (SCI) and MCI were recruited from a university based memory clinic. Regions of interest were used to determine fractional anisotropy (FA), radial diffusivity (DR) and axial diffusivity (DA) in known white matter tracts in patients with MCI (n=39) and SCI (n=8) and 26 cognitively healthy controls. Significant lower FA and higher DR values were observed in patients with pathological vs. patients with normal CSF T-tau levels and vs. controls in left posterior cingulum fibers. T-tau values were negatively correlated with FA and positively correlated with DR values in the posterior cingulum fibers. Cingulum fiber diffusivity was related to T-tau pathology in SCI/MCI patients and altered DR may suggest that loss of myelin contributes to early white matter changes in patients at risk of developing Alzheimer's disease (AD).
Neurobiology of aging 06/2009; 32(4):581-9. · 5.94 Impact Factor
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ABSTRACT: There is still limited knowledge about the relationship between different structural brain parameters, despite huge progress in analysis of neuroimaging data. The aim of the present study was to test the relationship between fractional anisotropy (FA) from diffusion tensor imaging (DTI) and regional white matter (WM) volume. As WM volume has been shown to develop until middle age, the focus was on changes in WM properties in the age range of 40 to 60 years. 100 participants were scanned with magnetic resonance imaging (MRI). Each hemisphere was parcellated into 35 WM regions, and volume, FA, axial, and radial diffusion in each region were calculated. The relationships between age and the regional measures of FA and WM volume were tested, and then FA and WM volume were correlated, corrected for intracranial volume, age, and sex. WM volume was weakly related to age, while FA correlated negatively with age in 26 of 70 regions, caused by a mix of reduced axial and increased radial diffusion with age. 23 relationships between FA and WM volume were found, with seven being positive and sixteen negative. The positive correlations were mainly caused by increased radial diffusion. It is concluded that FA is more sensitive than volume to changes in WM integrity during middle age, and that FA-age correlations probably are related to reduced amount of myelin with increasing age. Further, FA and WM volume are moderately to weakly related and to a large extent sensitive to different characteristics of WM integrity.
NeuroImage 07/2008; 42(4):1654-68. · 5.89 Impact Factor
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ABSTRACT: White matter (WM) is critical to cognitive function and brain activity. The objective of the present study was to test whether diffusion tensor imaging (DTI) derived WM measures are related to the cognitive event-related potential error-related negativity (ERN). Eighty-seven healthy middle-aged adults underwent DTI scanning and electrophysiological recordings while doing a version of the Eriksen flanker task. ERN was elicited in error trials. Fractional anisotropy (FA) was calculated based on the DTI scans. FA indexes degree of anisotropic diffusion in every voxel, and is assumed related to the integrity of myelinated fiber bundles. The principal neuronal generator for ERN is located in the anterior cingulate cortex (ACC). Hence, the relationship between FA in the cingulum bundle and ERN amplitude was tested. It was found that FA in the left posterior cingulate correlated with ERN. Eigenvalue analyses revealed that radial diffusivity was responsible for the FA effect. ERN amplitude predicted response accuracy in the Flanker task, suggesting that electrophysiological measures are intermediate explanatory variables connecting DTI indices of WM organization, synchronization of large cell assemblies, and behavior.
Cerebral Cortex 06/2008; 19(2):293-304. · 6.54 Impact Factor
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Kirsten E Stabell,
Søren J Bakke,
Sverre Andresen,
Helge Bjørnaes,
Hans M Borchgrevink, Paulina Due-Tønnessen,
Einar Heminghyt,
Terje Nome,
Hans-Kristian Pedersen,
Jon Ramm-Pettersen,
Geir K Røste,
Bjørn Tennøe
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ABSTRACT: To evaluate the efficacy and risk of complications of selective posterior cerebral artery (PCA) amobarbital anesthesia in memory assessment of patients with epilepsy under consideration for temporal lobe resection.
Thirty-two candidates for temporal lobectomy in whom conclusive memory assessment could not be obtained by the standard intracarotid amobarbital procedure were submitted to a selective PCA amobarbital test. A mean dose of 75 mg amobarbital was injected via microcatheter into the P2 segment of the PCA. Ten common objects were presented for naming and remembering while the anesthesia was judged efficient. After return to neurologic baseline, recall and recognition memory were assessed.
In all of the 32 patients, angiography and PCA anesthesia were successfully accomplished without serious adverse events. All but one of the patients remained alert and cooperative for memory testing under the anesthesia, and 28 of these patients showed adequate memory capacity of the hemisphere contralateral to the side targeted for surgery. So far, 19 patients have proceeded to surgery, and no case of global amnesia or serious, material-specific memory impairment has resulted. Three patients failed the PCA test (fewer than 67% items correctly recognized) and were excluded from surgery, partly on the basis of the PCA test results, but also supported by an overall evaluation of all the diagnostic procedures used.
The selective PCA amobarbital test appears justifiable when performed by interventional neuroradiologists and may significantly reduce the risk of erroneously excluding patients with epilepsy from temporal resection. Further corroboration of the safety of the procedure seems warranted.
Epilepsia 08/2004; 45(7):817-25. · 3.96 Impact Factor
