Structural brain complexity and cognitive decline in late life : A longitudinal study in the Aberdeen 1936 Birth Cohort

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Cortical Gyrification and Sulcal Spans in Early Stage Alzheimer's Disease

Alzheimer's disease (AD) is characterized by an insidious onset of progressive cerebral atrophy and cognitive decline. Previous research suggests that cortical folding and sulcal width are associated with cognitive function in elderly individuals, and the aim of the present study was to investigate these morphological measures in patients with AD. The sample contained 161 participants, comprising 80 normal controls, 57 patients with very mild AD, and 24 patients with mild AD. From 3D T1-weighted brain scans, automated methods were used to calculate an index of global cortex gyrification and the width of five individual sulci: superior frontal, intra-parietal, superior temporal, central, and Sylvian fissure. We found that global cortex gyrification decreased with increasing severity of AD, and that the width of all individual sulci investigated other than the intra-parietal sulcus was greater in patients with mild AD than in controls. We also found that cognitive functioning, as assessed by Mini-Mental State Examination (MMSE) scores, decreased as global cortex gyrification decreased. MMSE scores also decreased in association with a widening of all individual sulci investigated other than the intra-parietal sulcus. The results suggest that abnormalities of global cortex gyrification and regional sulcal span are characteristic of patients with even very mild AD, and could thus facilitate the early diagnosis of this condition

Physiological and Pathological Changes in Cranial Cerebro-Spinal Fluid Volume in Man, As Defined by Magnetic Resonance Imaging

An accurate and reproducible method for measuring the volume of the cranial CSF spaces was developed in the MRI unit in Glasgow by Dr. B. Condon in 1986. Using this MRI method the total cranial, cortical sulcal, ventricular and posterior fossa CSF volumes could be accurately measured, whereas only ventricular CSF volume could be estimated by previous techniques. The aim of this thesis was firstly to examine the technique critically and to reduce factors that might affect the accuracy or reproducibility of CSF volume measurement; secondly, to determine the normal range of CSF volume; thirdly, to study physiological factors that might influence the cranial CSF volume; and lastly to assess the research and clinical potential of these measurements in conditions where the CSF volumes might be altered. The original technique was modified. The accuracy of the method was improved by using 0.9% sodium chloride as a calibration reference solution, rather than water, as saline was found to produce a signal intensity per unit volume closest to that of anaerobically obtained CSF. The reference phial was sealed, in order to eliminate errors due to phial filling, and placed in an insulated casing that was designed to fit inside the MRI standard head coil. The insulated casing reduced error due to phial cooling during the examination. As the phial was no longer strapped to the head, errors due to phial movement were minimised and the overall examination took leLs time as patient positioning was less critical. The effect of CSF motion on image quality and volume measurement was studied. It was found that CSF motion could result in "background" blurring of the image and errors of approximately 5% could occur. The amount of background blurring was related to the amount of motion within the fluid filled phantom. Background blurring was seen most frequently in patients with obstructive hydrocephalus and in patients with normal pressure hydrocephalus. It is possible that in future the background signal level may be used as an index of CSF motion "in vivo". Cranial CSF volumes increased significantly with age and males had more cranial CSF than females, but there was a wide variation of normal. Total cranial and cortical sulcal CSF volumes increased more significantly than ventricular and posterior fossa volumes reflecting age related cortical atrophy. The normal ratio of ventricular CSF volume to cortical sulcal volume (V:CS ratio) was less than 0.33. The CSF volume measurements were found to be highly reproducible in the short term, but there was a significant increase in CSF volume premenstrually when compared with the mid-cycle CSF volumes. The premenstrual increase may have a hormonal basis or reflect reciprocal changes in intracranial blood volume. Further work is needed to examine intracranial pressure and blood volume changes related to the menstrual cycle and measure CSF volumes in patients with pre-menstrual syndrome, catamenial epilepsy and premenstrual migraine. Total cranial CSF volume decreased during hypercapnia and increased during hypocapnia. This reflected the reciprocal changes in cerebral blood volume and thus provided confirmation of the modified Monro-Kellie Doctrine. Large amounts of CSF were often lost following lumbar puncture and the reduction in CSF volume was related to the presence of headache 24 hours after LP. The preliminary clinical studies included patients with dementia, normal pressure hydrocephalus (NPH), obstructive hydrocephalus and benign intracranial hypertension (BIH). Patients under 70 years of age who had dementia had more cortical sulcal and ventricular CSF than healthy elderly controls, but there was no clear separation between patients over 70 years of age with dementia and healthy elderly subjects. The V:CS ratio separated patients with NPH from patients with dementia of other causes and from healthy volunteers. This measurement may be valuable in the diagnosis of NPH. Patients with a V:CS ratio greater than 1.00 had a significant clinical improvement after V-P shunting but further work is necessary to compare the predictive value of this test with the numerous other tests that claim to be able to predict a good post-operative outcome. The degree of reduction in ventricular CSF volume post-operatively was readily measured and these measurements may be important in the management of patients if a shunt blockage is suspected. (Abstract shortened by ProQuest.)

Development of cortical shape in the human brain from 6 to 24months of age via a novel measure of shape complexity

The quantification of local surface morphology in the human cortex is important for examining population differences as well as developmental changes in neurodegenerative or neurodevelopmental disorders. We propose a novel cortical shape measure, referred to as the ‘shape complexity index’ (SCI), that represents localized shape complexity as the difference between the observed distributions of local surface topology, as quantified by the shape index (SI) measure, to its best fitting simple topological model within a given neighborhood. We apply a relatively small, adaptive geodesic kernel to calculate the SCI. Due to the small size of the kernel, the proposed SCI measure captures fine differences of cortical shape. With this novel cortical feature, we aim to capture comparatively small local surface changes that capture a) the widening versus deepening of sulcal and gyral regions, as well as b) the emergence and development of secondary and tertiary sulci. Current cortical shape measures, such as the gyrification index (GI) or intrinsic curvature measures, investigate the cortical surface at a different scale and are less well suited to capture these particular cortical surface changes. In our experiments, the proposed SCI demonstrates higher complexity in the gyral/sulcal wall regions, lower complexity in wider gyral ridges and lowest complexity in wider sulcal fundus regions. In early postnatal brain development, our experiments show that SCI reveals a pattern of increased cortical shape complexity with age, as well as sexual dimorphisms in the insula, middle cingulate, parieto-occipital sulcal and Broca's regions. Overall, sex differences were greatest at 6 months of age and were reduced at 24 months, with the difference pattern switching from higher complexity in males at 6 months to higher complexity in females at 24months. This is the first study of longitudinal, cortical complexity maturation and sex differences, in the early postnatal period from 6 to 24 months of age with fine scale, cortical shape measures. These results provide information that complement previous studies of gyrification index in early brain development

Dogs with cognitive dysfunction syndrome: a natural model of Alzheimer's Disease

In the search for appropriate models for Alzheimer's disease (AD) involving animals other than rodents, several laboratories are working with animals that naturally develop cognitive dysfunction. Among the animals tested, dogs are quite unique in helping to elucidate the cascade of events that take place in brain amyloid-beta (Aβ)deposition aging, and cognitive deficit. Recent innovative research has validated human methods and tools for the analysis of canine neuropathology and has allowed the development of two different approaches to investigate dogs as natural models of AD. The first approach relates AD-like neuropathy with the decline in memory and learning ability in aged housed dogs in a highly controlled laboratory environment. The second approach involves research in family-owned animals with cognitive dysfunction syndrome. In this review, we compare the strengths and limitations of housed and family-owned canine models, and appraise their usefulness for deciphering the early mechanisms of AD and developing innovative therapies

A comparison of methods to harmonize cortical thickness measurements across scanners and sites

Results of neuroimaging datasets aggregated from multiple sites may be biased by site-specific profiles in participants\u27 demographic and clinical characteristics, as well as MRI acquisition protocols and scanning platforms. We compared the impact of four different harmonization methods on results obtained from analyses of cortical thickness data: (1) linear mixed-effects model (LME) that models site-specific random intercepts (LM

The EEG manifestations of chronic ethanol abuse: Relation to cerebral cortical atrophy

Eleven chronic alcoholic patients without other nonneurological or traumatic disease were evaluated by a simultaneous electroencephalogram and computerized axial tomogram. The findings suggested that chronic abusers of approximately 60 years of age or less may have a normal EEG despite the presence of cerebral cortical atrophy or dementia. In alcoholics over 60 years of age, the greater the severity of cerebral cortical atrophy, the greater the slowing in background frequency of the EEG. Voltage diminution and slow-wave transients also occurred more frequently in the older patients. The incidence of EEG abnormalities was greater than the incidence of CAT scan evidence for cerebral cortical atrophy in alcoholics over 60 years of age with dementia.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50293/1/410030404_ftp.pd