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PubMed2006

Reliabilities of and correlations among five standard methods of assessing the sagittal alignment of the cervical spine.

STUDY DESIGN: The reliabilities of and correlations among 5 standard methods of assessing cervical sagittal alignment were evaluated. OBJECTIVE: To investigate the reliabilities of and correlations among 5 standard methods of assessing cervical sagittal alignment. SUMMARY OF BACKGROUND DATA: Although various cervical sagittal alignment assessment methods are widely used, their relative reliability and intercorrelation have not been reported. METHODS: From 442 lateral cervical radiographs, 40 with lordotic, 40 with straight or sigmoid, and 40 with kyphotic alignment were selected. Two orthopedic surgeons independently evaluated the sagittal alignment in each group twice using CCL, C1-C7 Cobb, C2-C7 Cobb, sagittal tangent, and the Ishihara methods. Intraobserver and interobserver reliabilities were confirmed and the correlations among the 5 methods were measured. RESULTS: Intraobserver and interobserver reliabilities for all 5 methods were good. In the lordotic group, the correlations among all 5 methods were consistently strong (r = 0.731 to 0.922). In the straight or sigmoid group, the correlations were weak to moderate among the CCL, C2-C7 Cobb, sagittal tangent, and Ishihara methods but tended to be weak between these 4 methods and the C1-C7 Cobb method (r = -0.245 to 0.777). In the kyphotic group, the correlations were also weak to moderate among the same 4 methods, and were statistically insignificant between them and the C1-C7 Cobb. CONCLUSIONS: The correlations among the CCL, C1-C7 Cobb, C2-C7 Cobb, sagittal tangent, and Ishihara methods are strong when lordosis is retained; otherwise, they are moderate to poor. In the kyphotic group, C1-C7 Cobb has no significant correlation with the other 4 methods.

Adolescent↗

PubMed1997

Correlated evolution and independent contrasts.

The use of the independent contrast method in comparative tests is studied. It is assumed that: (i) the traits under investigation are subject to natural selection; (ii) closely related species are similar because they share many characteristics of their niche, inherited from a common ancestor; and (iii) the current adaptive significance of the traits is the focus of investigation. The main objection to the use of species values in this case is that third variables which are shared by closely related species confound the relationship between the focal traits. In this paper, I argue that third variables are largely not controlled by the contrast methods, which are designed to estimate correlated evolution. To the extent that third variables also show correlated evolution, the true relationship among the traits of interest will remain obscured. Although the independent contrast method does not resolve the influence of third traits it does, in principle, provide a greater resolution than the use of the species mean values. However, its validity depends on the applicability of an evolutionary model which has a substantial stochastic component. To illustrate the consequences of relaxing this assumption I consider an alternative model of an adaptive radiation, where species come to fill a fixed niche space. Under this model, the expected value for the contrast correlation differs from that for the species correlation. The two correlations differ because contrasts reflect the historical pattern of diversification among species, whereas the species values describe the present-day relationships among the species. If the latter is of interest, I suggest that assessing significance based on the species correlations can be justified, providing that attention is paid to the role of potentially confounding third traits. Often, differences between contrast and species correlations may be biologically informative, reflecting changes in correlations between traits as an adaptive radiation proceeds; contrasts may be particularly useful as a means of investigating past history, rather than current utility of traits.

Animals↗

PubMed2000

Velocity cross-correlations and atomic momentum transfer in simple liquids with different potential cores

Time correlation functions between the velocity of a tagged particle and velocities of particles within specified ranges of initial separations have been obtained by molecular dynamics simulation. These correlation functions have allowed us to analyze the momentum transfer between particles in different coordination shells. Two simple liquids at very different densities and two purely repulsive potentials with very different softnesses have been considered. The longitudinal correlations, which are the velocity cross-correlations along the initial direction defined by the centers of two given particles, have been calculated separately. It has been proven that these correlations should be attributed to particles both in front of and behind the central one. As with propagating longitudinal modes, they are strongly dependent on the softness of the potential core. Some characteristic features of the velocity correlation functions after the initial rise should be related to nonlongitudinal correlations. It has been shown that velocity cross-correlations between distinct particles cannot only be attributed to the direct interactions among particles, but also to the motions induced by the movement of a tagged particle on their neighbors.

Journal Article↗

PubMed2002

Large scale cross-correlations in Internet traffic.

The Internet is a complex network of interconnected routers, and the existence of a collective behavior such as congestion suggests that the correlations between the different connections play a crucial role. It is thus critical to measure and quantify these correlations. We use methods of random matrix theory (RMT) to analyze the cross-correlation matrix C of information flow changes of 650 connections between 26 routers of the French scientific network "Renater." We find that C has the universal properties of the Gaussian orthogonal ensemble of random matrices: The distribution of eigenvalues-up to a rescaling that exhibits a typical correlation time of the order of 10 min-and the spacing distribution follow the predictions of RMT. There are some deviations for large eigenvalues which contain network-specific information and which identify genuine correlations between the connections. The study of the most correlated connections reveals the existence of "active centers" that are exchanging information with a large number of routers thereby inducing correlations between the corresponding connections. These strong correlations could be a reason for the observed self-similarity in the world-wide web traffic.

Journal Article↗

PubMed2006

Generation of long-range correlations in large systems as an optimization problem.

We propose an efficient method of generating long-range correlations in large systems. The development of this method was motivated by the problem of constructing an optimal model for a large-scale porous medium. There are typically long-range correlations in the properties of such porous media, such as their permeability and porosity, for which there are usually only limited data. The optimal model must not only honor (preserve) the available data and their correlation function, but also accurately predict the future behavior of fluid flow in the media. We formulate the problem of generating the long-range correlations as one of optimization, and utilize simulated annealing to generate a d-dimensional array which contains the correlations and honors the existing data. The optimization process is based on the data's correlation function. The method is, therefore, free of the many numerical difficulties and/or limitations that most previous techniques suffer from. It is completely general and may be used for generating long-range correlations with any type of correlation function, in both isotropic and anisotropic media. Representative examples are presented, and the method's efficiency and accuracy are discussed.

Journal Article↗

PubMed1996

Correlated phasing of multiple isomorphous replacement data.

Substantial highly correlated differences sometimes exist between a series of heavy-atom derivatives of a macromolecule and the native structure. Use of such a series of derivatives for phase determination by multiple isomorphous replacement (MIR) has been difficult because MIR analysis has treated errors as independent. A simple Bayesian approach has been used to derive probability distributions for the phase in the case where a group of MIR derivatives have correlated errors. The utility of the resulting 'correlated-phasing' method has been examined by applying it to both simulated and real MIR data sets that contain sizeable correlated errors and it has been found that it can dramatically improve MIR phase estimates in these cases. Correlated phasing is applicable to situations where derivatives exhibit substantial correlated changes in protein conformation or crystal packing or where correlated errors in heavy-atom models are large. Correlated phasing does not substantially increase the complexity of phase computation and is suitable for routine use.

Journal Article↗

PubMed2004

Object detection by correlation coefficients using azimuthally averaged reference projections.

A method of computing correlation coefficients for object detection that takes advantage of using azimuthally averaged reference projections is described and compared with two alternative methods-computing a cross-correlation function or a local correlation coefficient versus the azimuthally averaged reference projections. Two examples of an application from structural biology involving the detection of projection views of biological macromolecules in electron micrographs are discussed. It is found that a novel approach to computing a local correlation coefficient versus azimuthally averaged reference projections, using a rotational correlation coefficient, outperforms using a cross-correlation function and a local correlation coefficient in object detection from simulated images with a range of levels of simulated additive noise. The three approaches perform similarly in detecting macromolecular views in electron microscope images of a globular macrolecular complex (the ribosome). The rotational correlation coefficient outperforms the other methods in detection of keyhole limpet hemocyanin macromolecular views in electron micrographs.

Algorithms↗

PubMed2003

Phylogenetic analysis of correlation structure in stalk-eyed flies (Diasemopsis, Diopsidae).

Morphological divergence among species may be constrained by the pattern of genetic variances and covariances among traits within species. Assessing the existence of such a relationship in nature requires information on the stability of intraspecific correlation and covariance structure and the correspondence of this structure to the pattern of evolutionary divergence within a lineage. Here, we investigate these issues for nine morphological traits and 15 species of stalk-eyed flies in the genus Diasemopsis. Within-species matrices for these traits were generated from phenotypic data for all the Diasemopsis species and from genetic data for a single Diasemopsis species, D. dubia. The among-species pattern of divergence was assessed by calculating the evolutionary correlations for all pairwise combinations of the morphological traits along the phylogeny of these species. Comparisons of intraspecific matrices reveal significant similarity among all species in the phenotypic correlations matrices but not the covariance matrices. In addition, the differences in correlation structure that do exist among species are not related to their phylogenetic placement or change in the means of the traits. Comparisons of the phenotypic and phylogenetic matrices suggest a strong relationship between the pattern of evolutionary change among species and both the intraspecific correlation structure and the stability of this structure among species. The phenotypic and the phylogenetic matrices are significantly similar, and pairs of traits whose intraspecific correlations are more stable across taxa exhibit stronger coevolution on the phylogeny. These results suggest either the existence of strong constraints on the pattern of evolutionary change or a consistent pattern of correlated selection shaping both the phenotypic and phylogenetic matrices. The genetic correlation structure for D. dubia, however, does not correspond with patterns found in the phenotypic and phylogenetic data. Possible reasons for this disagreement are discussed.

Animals↗

PubMed1995

Differential correlation between interleukin patterns in disseminated and chronic human paracoccidioidomycosis.

In an attempt to understand better the immunoregulatory disorders in paracoccidioidomycosis (PCM), the possible correlation between interleukin pattern, lymphoproliferation, C-reactive protein (CRP) and specific antibody levels was investigated in the polarized clinical forms of this disease. We studied 16 PCM patients, eight with the disseminated disease (four under treatment and four non-treated) and eight with the chronic disease. The patients with disseminated disease exhibited high antibody titres specific to Paracoccidioides brasiliensis antigen compared with patients with the chronic form of disease. Tumour necrosis factor (TNF), IL-1, IL-6 and CRP in the serum of non-treated disseminated PCM patients were increased, which correlated positively with the low mitogenic response of peripheral blood mononuclear cells (PBMC) to phytohaemagglutinin (PHA) (P < 0.01) and with the high antibody titres (P < 0.001) of these patients. Moreover, we found in the disseminated PCM patients positive correlations between IL-1 and IL-6 (P = 0.0007); IL-1 and TNF (P = 0.0045); IL-1 and IL-6 with the high antibody titres (P = 0.0834 and P = 0.0631, respectively); IL-1, IL-6 and TNF with CRP levels. By contrast, no correlations were found with those interleukins in the treated disseminated and chronic patients or in controls. It was interesting to find an inverse correlation between IL-4 and antibody production in non-treated disseminated PCM (r = -0.4770); moreover, a significant correlation (P = 0.0820) was found in chronic PCM patients with respect to the low level of either IL-4 and antibody titres against fungus antigen. Chronic PCM patients also had IL-2 levels inversely correlated with antibody production (r = -0.6313; P = 0.0628). Inverse correlations were also observed between IL-2 and IL-6 levels in non-treated disseminated patients (P = 0.0501) and between IL-2 and IL-4 in chronic patients (P = 0.0131). The inflammatory cytokines might have a pivotal role in the genesis and in control of some aspects of the disease, such as granulomatous reaction, hypergammaglobulinaemia and depression of T cell-mediated immunity in PCM.

Adult↗

PubMed1991

Correlation of plasma insulin and insulin-like growth factor-I with indices of androgen transport and metabolism in women with polycystic ovary syndrome.

OBJECTIVE: Polycystic ovary syndrome (PCOS) is said to be associated with hyperinsulinaemia. Insulin stimulates androgen production by ovarian tissue in vitro and previous studies have identified a positive correlation of insulin with androstenedione. The aim of the present study was to discover whether insulin levels correlate with clinical presentation and with markers of androgen transport and metabolism in women with PCOS. DESIGN: Within-group analysis of clinical and biochemical characteristics of a consecutive series of women with PCOS, focusing on correlations of plasma insulin with clinical presentation and androgens. Insulin levels were also compared with a control group of normal women. PATIENTS: Forty-seven women who presented with hirsutism, cycle abnormalities or both, with ultrasound proven PCOS, were recruited. Mean age was 26.6 +/- 0.7 years (mean +/- SEM), BMI 27.3 +/- 1.2 kg/m2. MEASUREMENTS: Plasma insulin levels were measured at 30-minute intervals for 3 hours following a 75 g glucose load. Blood was also taken for measurement of testosterone (T), androstenedione (A), free testosterone (fT), sex hormone binding globulin (SHBG) and insulin-like growth factor-I (IGF-I). Androsterone glucoronide (AG), a marker of peripheral androgen metabolism, was also measured. RESULTS: Neither basal insulin nor the sum of insulin measurements during the glucose tolerance test (sumINS) in women with PCOS were significantly different from a control group with normal ovaries. Within the PCOS group, basal insulin was greater in women with irregular cycles or amenorrhoea than in those with regular ovulatory menses (8.0 +/- 1.1 vs 3.1 +/- 1.5 mU/l, P less than 0.01) despite similarly raised androgen levels. Both basal insulin and sumINS correlated with BMI in women with PCO (r = 0.37, P less than 0.05 and r = 0.64, P less than 0.01 respectively) but not in controls. There was no significant correlation between insulin or IGF-I levels and T, A or AG despite a positive correlation of AG (but no other androgen) with BMI. SHBG showed an inverse correlation and fT correlated positively with sumINS (r = -0.51, P less than 0.01; r = 0.39, P less than 0.05). Regression analysis of each of the androgens on the other variables demonstrated no significant relationship between insulin and androgens. CONCLUSIONS: These data suggest that, in vivo, the major effect of insulin on androgen secretion is mediated by changes in SHBG rather than by direct stimulation of ovarian androgen production. Higher insulin concentrations in anovulatory compared with ovulatory women with hyperandrogenaemia may indicate that insulin resistance in the ovary contributes to the mechanism of anovulation in PCOS.

Adult↗

PubMed2004

Correlations of adiponectin level with insulin resistance and atherosclerosis in Japanese male populations.

OBJECTIVE: Adiponectin, which is secreted specifically by adipose tissue, has been shown to have an anti-atherosclerotic effect and to improve insulin resistance. The aim of this study was to determine the correlations of plasma adiponectin concentration with insulin resistance and atherosclerosis. DESIGN AND METHODS: We investigated the relationships of adiponectin concentration with insulin sensitivity, high-sensitivity C-reactive protein (hCRP) and pulse wave velocity (PWV) in male inhabitants of rural communities in Japan. hCRP and PWV were used as an indexes of atherosclerosis. RESULTS: A negative correlation was found between homeostasis model assessment (HOMA) as an index of insulin resistance and adiponectin concentration. Results of stepwise regression analysis for adiponectin showed that age, HOMA and serum triglyceride (TG) were independently correlated with adiponectin. Multiple regression analysis for lipid profile was also performed and revealed that adiponectin and HOMA were independently correlated with TG and serum high density lipoprotein (HDL)-cholesterol but not with serum total cholesterol. A significant negative correlation was found between adiponectin and hCRP in all subjects, and a significant negative correlation between adiponectin and PWV was also found in subjects equal or less than 70 years old. When HOMA was added to this analysis, HOMA was found to be independently correlated with hCRP and PWV, but the adiponectin level did not appear to be a significant predictor of hCRP or PWV. CONCLUSIONS: The results suggest that adiponectin plays a role in lipid metabolism and correlates with atherosclerosis either directly or through insulin resistance.

Adiponectin↗

PubMed2005

Tracking quasi-stationary flow of weak fluorescent signals by adaptive multi-frame correlation.

We have developed a novel cross-correlation technique to probe quasi-stationary flow of fluorescent signals in live cells at a spatial resolution that is close to single particle tracking. By correlating image blocks between pairs of consecutive frames and integrating their correlation scores over multiple frame pairs, uncertainty in identifying a globally significant maximum in the correlation score function has been greatly reduced as compared with conventional correlation-based tracking using the signal of only two consecutive frames. This approach proves robust and very effective in analysing images with a weak, noise-perturbed signal contrast where texture characteristics cannot be matched between only a pair of frames. It can also be applied to images that lack prominent features that could be utilized for particle tracking or feature-based template matching. Furthermore, owing to the integration of correlation scores over multiple frames, the method can handle signals with substantial frame-to-frame intensity variation where conventional correlation-based tracking fails. We tested the performance of the method by tracking polymer flow in actin and microtubule cytoskeleton structures labelled at various fluorophore densities providing imagery with a broad range of signal modulation and noise. In applications to fluorescent speckle microscopy (FSM), where the fluorophore density is sufficiently low to reveal patterns of discrete fluorescent marks referred to as speckles, we combined the multi-frame correlation approach proposed above with particle tracking. This hybrid approach allowed us to follow single speckles robustly in areas of high speckle density and fast flow, where previously published FSM analysis methods were unsuccessful. Thus, we can now probe cytoskeleton polymer dynamics in living cells at an entirely new level of complexity and with unprecedented detail.

Actins↗

PubMed2006

Lesson from performing SCORADs in children with atopic dermatitis: subjective symptoms do not correlate well with disease extent or intensity.

BACKGROUND: Atopic dermatitis (AD) is a distressing disease associated with pruritus and sleep disturbance. It is not known how well these symptoms correlate with the extent and intensity of eczematous involvement. We evaluated whether: (i) the level of sleep loss correlates with pruritus and (ii) the level of pruritus correlates with the extent or severity of AD in children according to the SCORing Atopic Dermatitis (SCORAD) index. METHOD: Patients with AD younger than 18 years old were recruited from the pediatric dermatology clinic of a university teaching hospital, and AD severity was evaluated by the SCORAD index. RESULTS: One hundred and eighty-two Chinese children with AD (107 boys and 75 girls) [mean (SD) age of 9.6 (4.2) years] were recruited. Their mean (SD) overall SCORAD was 30.1 (19.2). Sleep loss was strongly correlated with pruritus (r = 0.57, P < 0.001). However, the two subjective symptoms were only weakly correlated with the objective signs (extent and intensity) of AD. The correlations between pruritus and extent and intensity were 0.42 (P < 0.001) and 0.38 (P < 0.001), respectively, and the correlations between sleep loss and extent and intensity were 0.38 (P < 0.001) and 0.34 (P < 0.001), respectively. CONCLUSION: We speculate that the lack of a better correlation was either because pruritus and sleep loss as reported by parents were imprecise, or that mechanisms other than disease extent or severity are responsible for the pathogenesis of these subjective symptoms.

Adolescent↗

PubMed1993

Correlates of cognitive function scores in elderly outpatients.

OBJECTIVE: To determine medical, ophthalmologic, and demographic predictors of cognitive function scores as measured by the Telephone Interview for Cognitive Status (TICS), an adaptation of the Folstein Mini-Mental Status Exam. A secondary objective was to perform an item-by-item analysis of the TICS scores to determine which items correlated most highly with the overall scores. DESIGN: Cross-sectional cohort study. SETTING: The Glaucoma Consultation Service of the Massachusetts Eye and Ear Infirmary. SUBJECTS: 472 of 565 consecutive patients age 65 and older who were seen at the Glaucoma Consultation Service between November 1, 1987 and October 31, 1988. MEASUREMENTS: Each subject had a standard visual examination and review of medical history at entry, followed by a telephone interview that collected information on demographic characteristics, cognitive status, health status, accidents, falls, symptoms of depression, and alcohol intake. RESULTS: A multivariate linear regression model of correlates of TICS score found the strongest correlates to be education, age, occupation, and the presence of depressive symptoms. The only significant ocular condition that correlated with lower TICS score was the presence of surgical aphakia (model R2 = .46). Forty-six percent (216/472) of patients fell below the established definition of normal on the mental status scale. In a logistic regression analysis, the strongest correlates of an abnormal cognitive function score were age, diabetes, educational status, and occupational status. An item analysis using step-wise linear regression showed that 85 percent of the variance in the TICS score was explained by the ability to perform serial sevens and to repeat 10 items immediately after hearing them. Educational status correlated most highly with both of these items (Kendall Tau R = .43 and Kendall Tau R = .30, respectively). CONCLUSION: Education, occupation, depression, and age were the strongest correlates of the score on this new screening test for assessing cognitive status. These factors were stronger correlates of the TICS score than chronic medical conditions, visual loss, or medications. The Telephone Interview for Cognitive Status is a useful instrument, but it may overestimate the prevalence of dementia in studies with a high prevalence of persons with less than a high school education.

Accidental Falls↗

PubMed1985

Intraclass correlations of periodontal measurements.

Components of variance and intraclass correlation coefficients were computed for changes in attachment level, pocket depth, gingival and plaque index scores for 5 groups of treated periodontal disease patients and 1 group of untreated subjects with periodontal disease. The intraclass correlation coefficients for attachment level change ranged from 0.011 to 0.165 (median 0.067), while intraclass correlation coefficients for pocket depth changes ranged from -0.009 to 0.178 (median 0.071). These intraclass correlation coefficients were much lower than those computed for changes in measurements of plaque which ranged from 0.086 to 0.568 (median 0.268) or gingival inflammation which ranged from 0.119 to 0.522 (median 0.264). Intraclass correlation coefficients at baseline for pocket depths ranged from 0.000 to 0.199 (median 0.053), for plaque accumulation from 0.121 to 0.531 (median 0.222) and for gingival inflammation from 0.229 to 0.596 (median 0.391). The differences in the intraclass correlation coefficients between pocket depth and attachment level on the one hand and plaque accumulation or gingival inflammation on the other could not be explained on the basis of differences in the measurement scale employed, since collapsing measurement scales had little effect on the intraclass correlation coefficients. The observed larger intraclass correlation coefficients for changes in plaque and gingival indices suggest a larger rôle for host contribution to these measurements. In contrast, the data suggest that the major but by no means the sole factor determining the variability of attachment level or pocket depth changes is the nature of the local factors.

Chlorhexidine↗

PubMed2006

Dopamine-dependent non-linear correlation between subthalamic rhythms in Parkinson's disease.

The basic information architecture in the basal ganglia circuit is under debate. Whereas anatomical studies quantify extensive convergence/divergence patterns in the circuit, suggesting an information sharing scheme, neurophysiological studies report an absence of linear correlation between single neurones in normal animals, suggesting a segregated parallel processing scheme. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys and in parkinsonian patients single neurones become linearly correlated, thus leading to a loss of segregation between neurones. Here we propose a possible integrative solution to this debate, by extending the concept of functional segregation from the cellular level to the network level. To this end, we recorded local field potentials (LFPs) from electrodes implanted for deep brain stimulation (DBS) in the subthalamic nucleus (STN) of parkinsonian patients. By applying bispectral analysis, we found that in the absence of dopamine stimulation STN LFP rhythms became non-linearly correlated, thus leading to a loss of segregation between rhythms. Non-linear correlation was particularly consistent between the low-beta rhythm (13-20 Hz) and the high-beta rhythm (20-35 Hz). Levodopa administration significantly decreased these non-linear correlations, therefore increasing segregation between rhythms. These results suggest that the extensive convergence/divergence in the basal ganglia circuit is physiologically necessary to sustain LFP rhythms distributed in large ensembles of neurones, but is not sufficient to induce correlated firing between neurone pairs. Conversely, loss of dopamine generates pathological linear correlation between neurone pairs, alters the patterns within LFP rhythms, and induces non-linear correlation between LFP rhythms operating at different frequencies. The pathophysiology of information processing in the human basal ganglia therefore involves not only activities of individual rhythms, but also interactions between rhythms.

Adult↗

PubMed2003

Correlation of a scanning laser derived oedema index and visual function following grid laser treatment for diabetic macular oedema.

AIM: To correlate change of an oedema index derived by scanning laser tomography with change of visual function in patients undergoing grid laser photocoagulation for clinically significant diabetic macular oedema (DMO). METHODS: The sample comprised 24 diabetic patients with retinal thickening within 500 micro m of the fovea. Inclusion criteria included a logMAR visual acuity of 0.25, or better. Patients were assessed twice before a single session of grid laser treatment and within 1 week of, and at 1, 2, 4, and 12 weeks after, treatment. At each visit, patients underwent logMAR visual acuity, conventional and short wavelength automated perimetry (SWAP), and scanning laser tomography. Each visual function parameter was correlated with the mean oedema index. The mean oedema index represented the z-profile signal width divided by the maximum reflectance intensity (arbitrary units). A Pearson correlation coefficient (Bonferroni corrected) was undertaken on the data set of each patient. RESULTS: 13 patients exhibited significant correlation of the mean oedema index and at least one measure of visual function for the 10 degrees x 10 degrees scan field while 10 patients correlated for the 20 degrees x 20 degrees scan field. Seven patients demonstrated correlation for both scan fields. Laser photocoagulation typically resulted in an immediate loss of perimetric sensitivity whereas the oedema index changed over a period of weeks. Localised oedema did not impact upon visual acuity or letter contrast sensitivity when situated extrafoveally. CONCLUSIONS: Correlation of change of the oedema index and of visual function following grid laser photocoagulation was not found in all patients. An absence of correlation can be explained by the localised distribution of DMO in this sample of patients, as well as by differences in the time course of change of the oedema index and visual function. The study has objectively documented change in the magnitude and distribution of DMO following grid laser treatment and has established the relation of this change to the change in visual function.

Aged↗

PubMed2004

Diffusion tensor MRI correlates with executive dysfunction in patients with ischaemic leukoaraiosis.

BACKGROUND: Cerebral small vessel disease is a common cause of vascular dementia. Both discrete lacunar infarcts and more diffuse ischaemic changes, seen as confluent high signal (leukoaraiosis) on T2 weighted magnetic resonance imaging (MRI), occur. However, there is a weak correlation between T2 lesion load and cognitive impairment. Diffusion tensor MRI (DTI) is a new technique that may provide a better index of white matter damage. OBJECTIVES: To determine whether DTI measures are correlated more strongly with cognitive performance than lesion load on T2 weighted images, and whether these correlations are independent of conventional MRI parameters. METHODS: 36 patients with ischaemic leukoaraiosis (leukoaraiosis plus a previous lacunar stroke) and 19 healthy volunteers underwent DTI, conventional MRI, and neuropsychological assessment. RESULTS: On DTI, diffusivity was increased both within lesions and in normal appearing white matter. Mean diffusivity of normal appearing white matter correlated with full scale IQ (r = -0.46, p = 0.009) and tests of executive function. These correlations remained significant after controlling for age, sex, brain volume, and T1/T2 lesion volumes. No significant correlation was identified between T2 lesion load and IQ or neuropsychological scores. Of conventional measures, brain volume correlated best with cognitive function. CONCLUSIONS: Diffusion tensor measurements correlate better with cognition than conventional MRI measures. They may be useful in monitoring disease progression and as a surrogate marker for treatment trials. The findings support the role of white matter damage and disruption of white matter connections in the pathogenesis of cognitive impairment in cerebral small vessel disease.

Aged↗