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PubMed2001

Abnormal brain white matter in schizophrenia: a diffusion tensor imaging study.

Fractional anisotropy and the mean diffusion coefficient were measured in the cerebral volume in 20 schizophrenic and 24 healthy subjects, men and women, using diffusion tensor imaging. In addition, 3D SPGR was used for segmentation of brain tissue into grey and white matter and cerebrospinal fluid. In schizophrenic patients, fractional anisotropy was reduced in the splenium of the corpus callosum and in adjacent occipital white matter. The segmentation revealed no tissue deficits in the volume of reduced fractional anisotropy. The mean diffusion was increased in the total white and grey matter volume of the schizophrenic patients compared with the healthy subjects. The findings support the view that global and regional white matter abnormalities occur in chronic schizophrenia.

Adult↗
PubMed2002

Investigating regional white matter in schizophrenia using diffusion tensor imaging.

Diffusion tensor imaging (DTI) was used to investigate regional white matter in vivo in patients with schizophrenia. DTI is capable of providing information about the organization of white matter tracts and has only recently been used to study schizophrenia. In this study, a voxel based analysis of DTI maps in 14 patients and 19 controls did not reveal any areas of significant differences in DTI measures in white matter. The findings suggest that the structural integrity of white matter in these patients was not disrupted. These results are discussed in relation to previous studies reporting positive findings. It is concluded that further studies using DTI in larger samples, improved and standardised methods of data acquisition and analysis are needed.

Adult↗
PubMed2002

Mapping gray matter loss with voxel-based morphometry in mild cognitive impairment.

We used voxel-based morphometry to comprehensively and objectively map gray matter loss in 22 patients with amnestic mild cognitive impairment, defined as progressive isolated episodic memory decline. Compared with 22 age-matched healthy controls, patients had highly significant gray matter loss predominantly affecting the hippocampal region and cingulate gyri (posterior and subcallosal part of the anterior), and extending into the temporal neocortex. Compared with 16 age-matched patients with mild Alzheimer's disease, gray matter density was significantly preserved in mild cognitive impairment in the posterior association cortex. This pattern of gray matter loss in mild cognitive impairment agrees with but considerably expands upon previous region-of-interest based MRI studies, and is highly consistent with the course of neurofibrillary tangles across aging and Alzheimer's disease.

Aged↗
PubMed1993

Influence of tutors' subject-matter expertise on student effort and achievement in problem-based learning.

PURPOSE: To investigate the effects of tutors' subject-matter expertise on students' levels of academic achievement and study effort in a problem-based health sciences curriculum. Also, to study differences in tutors' behaviors and the influences of these differences on students' performances. METHOD: Data were analyzed from 336 staff-led tutorial groups involving student participants in seven four-year undergraduate programs at the University of Limburg Faculty of Health Sciences in 1989-90. Overall, 1,925 data records were studied, with each student participating in an average of 1.7 groups led by either content experts or non-experts. The basic analyses were of (1) students' achievement scores as a function of tutors' expertise levels and students' curriculum year; (2) students' estimates of self-study time as a function of tutors' expertise levels and students' curriculum year; and (3) the average ratings of the tutors' behaviors as a function of tutors' expertise levels. Statistical methods included analysis of variance and Pearson correlations. RESULTS: The students guided by subject-matter experts were shown to spend more time on self-directed study, and they achieved somewhat better than did the students guided by non-expert tutors. The effect of subject-matter expertise on achievement was strongest in the first curriculum year, suggesting that novice students are more dependent on their tutors' expertise than are more advanced students. Also, the content-expert tutors made more extensive use of their subject-matter knowledge to guide students. However, in addition to the tutors' knowledge-related behaviors, the tutors' process-facilitation skills affected student achievement. Moreover, these two sets of behaviors were correlated, indicating that both are necessary conditions for effective tutoring. CONCLUSION: The results indicate that, at least for the curriculum studied, the assumption in the literature that tutors do not necessarily need content knowledge so long as they are skilled in the tutoring process is not entirely justified: the students who were guided by content experts achieved somewhat better and spent more time on self-directed learning. More important, tutoring skill and content knowledge seemed to be necessary and closely related conditions for effective tutoring.

Achievement↗
PubMed1995

Rarefied white matter in patients with Alzheimer disease.

Magnetic resonance head scans of 94 patients with probable Alzheimer disease (AD) and 45 patients with possible AD were examined prospectively to determine the prevalence and significance of rarefied cerebral white matter (leukoaraiosis) in patients with AD. Only 8.7% of patients with probable AD and 11.1% of patients with possible AD exhibited large confluent areas of subcortical leukoaraiosis. The remaining patients had variable degrees of leukoaraiosis surrounding the lateral ventricles. The magnitude of leukoaraiosis correlated with the patient's age but not with the Hachinski Ischemic and Mini Mental Status scores. Postmortem studies of two Alzheimer patients showed that their large confluent areas of subcortical leukoaraiosis consisted of rarefied white matter, gliosis, and arteriosclerotic small arteries. Eight additional Alzheimer patients who underwent autopsy had similar but less pronounced white matter changes limited to the periventricular regions of the cerebral hemispheres. Large confluent areas of rarefied subcortical white matter occur in a small minority of Alzheimer patients and are probably not caused by AD.

Aged↗
PubMed1980

Predominant white matter involvement in subcortical arteriosclerotic encephalopathy (Binswanger disease).

Fifteen of 605 examinations of patients aged 60 to 85 years showed symmetrical white matter hypodensity on computed tomography (CT). Six of these showed severe white matter hypodensity, low grade atrophy, and dilated ventricles. A diagnosis of encephalopathia subcorticalis chronica progressiva, or Binswanger disease, featuring the typical clinical course of neurological and psychiatric symptoms was reached. In one case, the diagnosis was confirmed by postmortem anatomopathological findings. The etiology is considered to be vascular and to represent a special course of arteriosclerosis. In some elderly patients, both white and gray matter involvement is seen on CT, but white matter hypodensity is not a common finding in severe vascular brain atrophy.

Aged↗
PubMed1983

Nuclear magnetic resonance (NMR) imaging in white matter disease of the brain using spin-echo sequences.

Attention is drawn to the use of nuclear magnetic resonance (NMR) spin-echo sequences in the recognition of white matter disease of the brain. In 5 patients with multiple sclerosis, 8 lesions were seen with postcontrast x-ray computed tomography (CT) (37.5 g of iodine), 33 with inversion-recovery (IR) scans, and 47 with spin-echo (SE) scans. Partial volume effects were less of a diagnostic difficulty with SE scans than with IR scans. Extensive areas of abnormal white matter were seen with CT, IR, and SE scans in a patient with leucodystrophy associated with congenital muscular dystrophy. In a patient with adrenoleucodystrophy focal lesions were seen with CT, IR, and SE scans. In addition, loss of gray-white matter contrast was seen in both occipital lobes with IR scans. Extensive areas of white matter involvement were also seen in a case of Binswangers disease.

Adrenoleukodystrophy↗
PubMedDate not supplied

Segmentation of MR brain images into cerebrospinal fluid spaces, white and gray matter.

An interactive computer method for quantifying CSF, white matter, and gray matter in magnetic resonance (MR) axial brain scans is presented. A stripping algorithm is used to remove the skull and scalp from each axial section. The images are then filtered to correct for radiofrequency inhomogeneity image artifacts. Late echo images are subtracted from or added to early echo images to enhance fluid/tissue and gray/white tissue contrast, respectively. Thresholds for fluid/tissue and gray/white separation are set interactively. A boundary pixel locking algorithm is used to handle ambiguities due to partial voluming between the fluid and tissue compartments. The MR brain scans from five healthy, young, normal men were obtained using a standard neuroanatomical reference technique. These data were processed and percentages computed for fluid, gray matter and white matter compartments. The gray/white ratios compare favorably with those determined in a published postmortem brain study.

Algorithms↗
PubMedDate not supplied

Magnetization transfer measurements in normal-appearing cerebral white matter in patients with chronic obstructive hydrocephalus.

PURPOSE: The purpose of this work was to assess the presence of subtle changes in normal-appearing white matter on T2-weighted MR images in patients with chronic obstructive hydrocephalus using magnetization transfer (MT) measurements. METHOD: In 12 patients with chronic obstructive hydrocephalus, MT ratios (MTRs) of normal-appearing rostral (PR) and caudal (PC) periventricular white matter, of the genu (CG) and the splenium (CS) of the corpus callosum, and of the thalamus (TH) were measured and compared with those of 16 healthy control subjects. RESULTS: We found a significantly lower MTR in chronic obstructive hydrocephalus than in the normal group for PR, PC, CG, and CS but not for TH. CONCLUSION: Our study shows that MT measurements give additional information that cannot be gained by conventional SE MRI, suggesting that chronic obstructive hydrocephalus is associated with diffuse white matter damage that also affects normal-appearing cerebral white matter.

Adult↗
PubMedDate not supplied

Comparison of multishot echo-planar fluid-attenuated inversion-recovery imaging with fast spin-echo fluid-attenuated inversion-recovery and T2-weighted imaging in depiction of white matter lesions.

PURPOSE: To compare a multishot echo-planar fluid-attenuated inversion-recovery (EPI-FLAIR) sequence with fast spin-echo FLAIR (F-FLAIR) and fast spin-echo T2-weighted (FSE-T2W) sequences in depiction of white matter lesions. METHODS: Thirty-five patients with various white matter lesions were included in this prospective study. Two independent readers for lesion detection (lesion size, >2 mm) compared sequences quantitatively. In 22 patients, contrast was calculated between periventricular hyperintensity (PVH) and the cerebrospinal fluid (CSF). RESULTS: EPI-FLAIR revealed more lesions than FSE-T2W (p < 0.01). However, F-FLAIR revealed more lesions than EPI-FLAIR (p < 0.01). For PVH-to-CSF contrast, EPI-FLAIR demonstrated significantly higher contrast than FSE-T2W. There were no differences in PVH-to-CSF contrast between EPI-FLAIR and F-FLAIR. CONCLUSIONS: This study shows that EPI-FLAIR has distinct advantages over FSE-T2W in the depiction of white matter lesions. Although EPI-FLAIR reduces imaging time by more than 60% relative to F-FLAIR, it cannot replace F-FLAIR for the detection of lesions in the cerebral white matter.

Aged↗
PubMed1978

Laminar scars in cerebral white matter: a perinatal injury due to edema.

Branched plate-like demyelinated lesions were present in the gyral and central white matter of two individuals, 3 and 54 years of age. The degenerated areas contained very few axons and were densely gliotic, and in the older case, contained connective tissue fibers and were continuous with a large parenchymal cyst. The lesions were covered on both sides by normally myelinated white matter, often representing only the subcortical arcuate white matter, occasionally being considerably broader. In some of the latter zones, there was a central area of less severe degeneration which, however, spared the arcuate zone which remained normal. It is suggested that these lesions represent the effects of edema induced by birth injury, under circumstances which permitted the continued formation and maturation of white matter after the edema had subsided. The edema is thought due for the most part to diffuse hypoxia and acidosis, but other mechanisms, such as infection, venous stasis and trauma, may have contributed to the pathogenesis of the edema, and to the lesions directly.

Birth Injuries↗
PubMed1994

CD44-hyaluronate interaction mediates in vitro lymphocyte binding to the white matter of the central nervous system.

The cell adhesion molecule CD44 is expressed in the central nervous system, especially on glial cells in the white matter, the extracellular matrix of which also contains one of its ligands, hyaluronate. We investigated the role of CD44 and hyaluronate in the adhesion of human peripheral blood lymphocytes to myelinated areas of cerebellum by an in vitro binding assay. Hermes-1 epitope, which recognizes the hyaluronate binding site of CD44, and Hermes-3 epitope, involved in lymphocyte binding to mucosal high endothelial venules, were both immunohistochemically expressed in the white matter. No immunoreactivity was observed with mAb Var3.1, which sees variant forms of CD44 containing the exon v6 encoding region. The molecular weight analysis showed that CD44 of the white matter was identical to the major 90 kD form of CD44 present on lymphocytes. The binding of both T and B lymphocytes was significantly inhibited by pretreatment of both cells and sections with mAb Hermes-1 but not with Hermes-3. Digestion of the sections and/or lymphocytes with hyaluronidase also reduced lymphocyte binding. These findings implicate that CD44-hyaluronate mediates lymphocyte adhesion to the white matter and this interaction may be involved in the pathogenesis of inflammations and lymphomas of the central nervous system.

Antibodies, Monoclonal↗
PubMed1994

Vascular architecture in white matter of neonates: its relationship to periventricular leukomalacia.

Arterial and venous structures in the deep white matter of the developing brain were examined by postmortem angiography. About the anterior horn, body and trigon of the lateral ventricle, ventriculopetal arteries reached the deep white matter and branched out to form an abundant network of small arterioles (hypervascular zone) particularly in premature brain, thus indicating the tentative border zone between ventriculofugal and petal arteries not to be hypovascular. A deep draining group of medullary veins converged at different zones in the deep white matter, becoming large to form a large converging zone, and finally drained into a subependymal vein. A fan-shaped draining area of the converging group of veins corresponded well to the area of periventricular leukomalacia (PVL) with the edema and hemorrhage. About the occipital horn and inferior horn of the lateral ventricle, transcerebral veins were abundant and PVL was rarely seen. The pathogenesis of PVL could not be fully explained by border zone infarct. An alternative pathogenesis of PVL is considered the following: 1) circulatory disturbance of the deep draining group of veins occurs, 2) edema with or without venous hemorrhage follows, 3) edema fluid and hemorrhage compress abundant arterioles in the deep white matter with 4) consequent coagulation necrosis.

Brain↗
PubMed2004

White matter hyperintensities and their associations with suicidality in psychiatrically hospitalized children and adolescents.

OBJECTIVE: Increasingly, researchers and clinicians are recognizing that there may be biological markers associated with increased risk of suicide. The objective of this study was to compare white matter hyperintensities in psychiatrically hospitalized children and youth with and without a history of suicide attempt while controlling for other variables. METHOD: White matter hyperintensities of 153 child and adolescent psychiatry inpatients were rated on T2-weighted magnetic resonance imaging scans using a modified Coffey scale. DSM-IV diagnosis, history of suicide attempt, and control variables such as gender, age, comorbid medical illnesses, developmental disorder, substance abuse, severity of mental illness, head injury, and possible cerebral hypoxia were obtained from discharge medical records. RESULTS: Within the unipolar depression group (n = 48), white matter hyperintensities were significantly associated with a higher prevalence of past suicide attempts (Fisher exact test, p =.03). Logistic regression analysis confirmed this relationship, indicating that none of the control variables confounded our results and suggesting a specificity of 0.94. CONCLUSIONS: This is the first report of an increased prevalence of white matter hyperintensities in children and youth with unipolar depression and a history of suicide attempt. Replication and expansion of our preliminary findings could be of great clinical interest.

Adolescent↗
PubMed2005

Potential role for white matter lysosome expansion in HIV-associated dementia.

Expansion of the lysosomal apparatus occurs in subcortical white matter in brains from persons with AIDS. This study examined whether HIV-associated subcortical dementia (HAD) is significantly related to this lysosomal anomaly. Brain cortex and adjacent white matter from the middle frontal gyrus were obtained from the National NeuroAIDS Tissue Consortium. Lysosomal hydrolase activity was assayed in 57 subjects who underwent neuropsychological testing within 6 months prior to autopsy. Decedents were evaluated from 4 geographical sites in the United States: Galveston/Houston, Texas (n = 36), Los Angeles, California (n = 5), New York, New York (n = 5), and San Diego, California (n = 11). Increased beta-glucuronidase activity, a representative lysosomal glycosidase, was correlated with the amount of neurocognitive impairment. Significant correlation was present in 5 of 7 functional testing domains, including some that draw upon frontal lobe output (r = 0.419; P < 0.002). The biochemical anomaly was negligible in cerebral cortex and cerebrospinal fluid and was not correlated with brain dysfunction in those compartments. Glycosidase activation was associated significantly with increased HIV RNA concentration in brain tissue (r = 0.469; P < 0.021) and possibly with HIV RNA in cerebrospinal fluid (r = 0.266; P < 0.067). HIV RNA in blood plasma was not correlated. These results support the suggestion that abnormal metabolism in white matter glial cells contributes to cognitive slowing in persons with HAD. Because membrane turnover is routed through the endosome-lysosome apparatus, these data are in agreement with brain spectroscopic data that have suggested that there is an increase in membrane turnover in white matter glia.

AIDS Dementia Complex↗
PubMed2005

In vivo visualization of white matter fiber tracts of preterm- and term-infant brains with diffusion tensor magnetic resonance imaging.

OBJECTIVE: The goal of this study was to test the feasibility of visualizing a 3-dimensional structure of cerebral white matter fiber tracts in preterm infants, postconceptional age (PCA) 28 weeks to term, by using volumetric diffusion tensor magnetic resonance imaging (DTI) data. MATERIALS AND METHOD: We combined tractography algorithms and visualization methods, currently available for adult DTI data, to trace the pixelated principal direction of a diffusion tensor originating from regions-of-interest with high fractional anisotropy. Consequently, white matter fiber bundles from the genu and the splenium of corpus callosum, the corticospinal tracts, the inferior fronto-occipital fasciculi, and optic radiations were visualized. RESULTS: Our results suggest that major white matter tracts of preterm infant brains, with PCAs ranging from 28 weeks to term (40 weeks old), can be successfully visualized despite the small brain volume and low anisotropy. CONCLUSION: The feasibility of fiber tractography in preterm neonates with DTI may add a new dimension in detection and characterization of white matter injuries of preterm infants.

Algorithms↗
PubMed2004

Epidemiology of white matter lesions.

This is an overview of the prevalence of, and risk factors for white matter lesions in older persons. The prevalence of white matter lesions is high and increases with age. Most risk factors that have been examined in association with white matter lesions are similar to those for cardiovascular disease, including elevated blood pressure, diabetes atherosclerosis, homocysteine levels, and markers of oxidative stress. The genetic contributions to white matter lesions are also reviewed.

Age Factors↗
PubMed2005

Current concepts of analysis of cerebral white matter hyperintensities on magnetic resonance imaging.

Cerebrovascular disease is common and associated with cognitive deficits and increased risk for dementia. Until recently, only limited attention has focused on advances in imaging techniques to better define and quantify the spectrum of asymptomatic cerebrovascular disease commonly seen on magnetic resonance imaging, such as abnormal white matter signals. Abnormal signals in cerebral white matter, although nonspecific, are increased in prevalence and severity in association with aging and cerebrovascular risk factors among older individuals. The ubiquitous occurrence of these abnormal white matter signals commonly referred to as white matter hyperintensities (WMHs) and the association with cerebrovascular risk and cognitive impairment among older individuals make scientific evaluation of WMHs an important and much needed avenue of research. In this section, we review current methods of WMH analysis. Strengths and limitation of both quantitative and qualitative methods are discussed initially, followed by a brief review of current magnetic resonance imaging segmentation and mapping techniques that make it possible to assess the anatomical location of WMHs. We conclude by discussing future analytic methods designed to better understand the pathophysiology and cognitive consequences of WMHs.

Brain↗