Positron emission tomography in the study of brain metabolism in psychiatric and neuropsychiatric disorders

Article Abstract:

Positron-emission tomography (PET) measures differences in cerebral blood flow (CBF) of different regions of the brain, by assessing glucose metabolism. The signal measured in PET derives from the decay of injected or inhaled radioactive substances such as carbon-11 and fluorine-18. Unlike computerized tomography (CT), which measures brain structures, PET measures brain function. Studies of normal aging processes using PET have shown an age-related decline in gray matter CBF. However, in Alzheimer's disease (AD) this decline seems to be progressive. In AD, a continuing decline in the rate of oxygen metabolism of both gray and white matter has also been demonstrated. These declines have been shown to be related to the severity of cognitive impairment. In multi-infarct dementia (MID) - a dementia in which brain tissue death is related to impaired blood flow - PET scans demonstrate global reductions in cerebral metabolism. Multiple lesions in the cortex, subcortical white matter and cerebellum have also been shown in MID. The majority of patients with mental illness such as schizophrenia or manic-depressive psychosis have brains which appear to be structurally normal, suggesting the importance of the role of functional abnormalities in psychiatric disorders. However, PET studies of schizophrenia have yielded inconsistent and inconclusive results, and have failed to point to any specific marker dysfunctions. Comparatively few studies have been carried out with PET on patients with major affective (mood) disorders. While PET is potentially the most powerful noninvasive technique available for investigating brain function, finer-grained diagnostic analysis will not be possible until methodological procedures across studies are refined and standardized. (Consumer Summary produced by Reliance Medical Information, Inc.)

Cerebral circulation, PET imaging, Positron emission tomography, Glucose metabolism

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Structure and function in neurology and psychiatry

Article Abstract:

Neurology is an organically based 'structural' discipline, which relies on neuroanatomy and neuropathology to discover causative lesions, while psychodynamic psychiatry is rooted in a 'functional' approach, in which causes are unknown and often cannot be corrected with drugs or surgery. Neuropsychiatry tends to serve as an intermediary science between those two disciplines. Recent developments in psychopharmacology, neurochemistry and brain-imaging techniques have made it more difficult for psychiatrists to adhere to a purely psychodynamic approach or for neurologists to adhere to a strictly structural approach. Specifically, the structural lesions discovered by modern imaging techniques, which can now be linked to specific mental phenomena, are proving difficult to integrate into purely functional terms. As well, nervous system disorders are being shown to be more complex and more related to environmental and psychological stressors than previously thought. Consequences of these recent developments have been that psychiatry has split into psychodynamic and neuropsychiatric branches and that neurology tends to overlook functional disorders of the nervous system which do not fit into their previously established views. However, there has also been a renewal of interest in the localization of structural defects in functional disorders. An area where this integration can be seen is in schizophrenia research, where the focus has been on finding abnormalities in specific brain regions that correspond to particular dysfunctions. It is suggested that while psychological, social and psychodynamic factors play an important part in psychiatric and neurological disorders, a more integrated approach between structural and functional views is required. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Practice, Neurology, Interdisciplinary research, Organic mental disorder, Organic mental disorders

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Correlation between structural and functional changes in brain in an idiopathic headache syndrome

Article Abstract:

An idiopathic headache syndrome has been studied using voxel-based morphometry (VBM). Cluster headache was found to be associated with a brain abnormality, not previously recognized, in the hypothalamic region. Positron emission tomography (PET) showed a co-localization of structural changes and changes in local brain activity in the same area of the brain in the same patients. VBM potentially can change in a fundamental way the concept of primary headache disorders, and it may be that other neurological and psychiatric diseases in which the brain is thought to be structurally normal should be reconsidered. Normal structure, as a tenet, must be reappraised. VBM is an objective, automated analysis method for looking at brain structure.

United Kingdom, Statistical Data Included, Research, Software, Product information, Equipment and supplies, Physiological aspects, Morphology (Biology), Hypothalamus, Automation, Image processing, Image processing equipment industry, Morphology, Image processing software, Brain abnormalities, Diagnostic imaging, Cluster headache, Headache

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