Huntington’s disease (HD) is a progressive autosomal dominant inherited neurodegenerative disorder.The primary aim of this thesis is to examine alterations in the cerebral cortex in HD gene... Show moreHuntington’s disease (HD) is a progressive autosomal dominant inherited neurodegenerative disorder.The primary aim of this thesis is to examine alterations in the cerebral cortex in HD gene carriers. Different image modalities and approaches will be used to extent the knowledge on both structural and functional cortical brain changes in early disease. Although striatal atrophy is more extensively present in HD, changes in the cerebral cortex can also be detected in the pre-symptomatic stage. Different methodological approaches used in our studies all showed a consistent pattern of cortical atrophy making volumetric MRI a reliable and effective tool to assess early in-vivo cortical brain changes, even in a rare neurodegenerative disorder such as HD. The influence of cortical changes on other clinical signs that occur in HD should not be overlooked. Our results demonstrate that volume loss and thinning of the cerebral cortex, especially the posterior brain regions, is detectable in early stages and contributes to the presence of specific motor signs and cognitive impairments. We believe that intervention trials could benefit from using cortical volumes as outcome measures, instead of using striatal volumes alone. Show less
With increasing age the prevalence of hypertension rises. High blood pressure at midlife is associated with cognitive impairment. Nevertheless, in older persons a lower rather than a higher... Show more With increasing age the prevalence of hypertension rises. High blood pressure at midlife is associated with cognitive impairment. Nevertheless, in older persons a lower rather than a higher blood pressure is associated with incident dementia. The main purpose of the work in this thesis was to explore the role of blood pressure in relation to cerebral structure, neurocognitive functioning and hemodynamics of the brain in old age. Therefore, we sought to determine whether discontinuation of antihypertensive therapy in persons aged 75 years and over with mild cognitive deficits and using antihypertensive medication (the Discontinuation of ANtihypertensive Treatment in Elderly people [DANTE] population) would improve their cognitive and psychological functioning. The assumption was that the increase in blood pressure after the discontinuation of antihypertensives would lead to a direct increase in cerebral blood flow and, as a consequence, to an improvement in cerebral functioning. An additional objective was to investigate possible underlying mechanisms in the relation between blood pressure and neurocognitive functioning. To enable this, brain MRI was used to determine whether (lower) blood pressure was associated with (micro)structural damage, cerebral small vessel disease and blood flow in the brain, and also whether the presence of cerebral (micro)structural damage was related to neurocognitive functioning. Show less
The aims of this thesis were to gain insight into specific disease processes in Huntington__s Disease (HD) and to identify biomarkers. To achieve these aims, cognitive functioning, structural brain... Show moreThe aims of this thesis were to gain insight into specific disease processes in Huntington__s Disease (HD) and to identify biomarkers. To achieve these aims, cognitive functioning, structural brain characteristics and intrinstic functional brain connectivity of premanifest and early HD subjects were examined. Cortical, subcortical and the intermediate white matter brain tissue shows evidence of structural and functional decline. We found evidence that disease processes, such as altered metabolism, excessive iron accumulation and cell loss, play a role in the changes. We conclude that changes occur throughout the brain from the earliest disease phase onwards. Hence, both premanifest and manifest HD should not be regarded as a disorder of the basal ganglia, but as a disease affecting the whole brain. Candidate biomarkers that have the potential to objectively reflect the early changes and the progressive nature of the disease are measures of subcortical atrophy, integrity of white matter pathways and of intrinsic functional brain connectivity. Iron, creatine, and N-acetylaspartate concentrations in the caudate nucleus and putamen may prove to be useful as markers of disease state for objectifying transitional disease processes from premanifest to manifest HD. Visuospatial working memory could be applied as a state marker for stage two HD. Show less
The general objective of this thesis was to investigate whether early clinical alterations and structural and functional brain markers could be detected in carriers of the Huntington__s disease... Show moreThe general objective of this thesis was to investigate whether early clinical alterations and structural and functional brain markers could be detected in carriers of the Huntington__s disease gene (referred to as carriers) who are still without manifest motor signs. We aimed to detect brain deficits using MRI and found smaller basal ganglia volumes in carriers compared to non carriers. Also, we demonstrated an increased amount of hypointensities in basal ganglia of carriers and suggested this may reflect excessive iron deposition. Furthermore, we showed strong associations between MRI characteristics and clinical variables suggesting that a combination of these measures may shed more light on the contribution of different kinds of pathological processes to the changing phenotype. When using memory activation during EEG registration early funcional brain changes, reflected in reduced alpha power, could be demonstrated in carriers. Furthermore, remarkably strong associations were found between the P3 Event-Related Potential and basal ganglia volumes. Subtle clinical abnormalities in motor function, executive function and memory could be demonstrated in carriers, especially over time. This study showed that several biomarkers provide new and important information on premanifest HD. The mulitfactorial approach offers new insights into the relation between clinical phenomena and abnormalities in the neural substrate Show less
Early dementias are difficult to distinguish from normal age-related memory decline. In the preclinical stages of Alzheimer’s disease and Huntington’s disease, brain functions are already changing... Show moreEarly dementias are difficult to distinguish from normal age-related memory decline. In the preclinical stages of Alzheimer’s disease and Huntington’s disease, brain functions are already changing, but this is not directly visible from the outside. Many research is aimed at discovering early disease markers. However, research using EEG registration during conventional eyes closed conditions revealed little additional information. The yield of EEG research can be improved by probing the weakest spot, which, in case of dementia, is memory. Karin van der Hiele introduced memory tests during EEG registration and found that early abnormalities in brain functioning can then be observed in Alzheimer’s disease and Huntington’s disease. An interesting finding came to light: the EEG in dementia displays a lot of muscle activity which is normally filtered out. However, the researchers decided not to throw this activity away but to measure it. Interestingly, they found that the amount of muscle activity was related to cognition and to the number of depressive complaints. It may pay to keep an open mind regarding the nature of the parameter to be measured. Show less
