Regional Cerebral Blood Flow Data Research Articles

The contribution of single photon emission tomography to the clinical differentiation of degenerative cortical brain disorders.

The accurate clinical diagnosis of degenerative cortical brain disorders is a necessary prerequisite for patient management and the critical evaluation of new treatments. This study has evaluated the ability of single photon emission tomography (SPET) to differentiate between Alzheimer's disease (AD) and different forms of non-Alzheimer lobar atrophy (LA), using a multi-purpose system in widespread routine clinical use. 99mTc-HMPAO SPET was carried out in patients with AD and three clinical syndromes associated with LA: frontotemporal dementia (FTD), progressive non-fluent aphasia (PA) and semantic dementia (SD). Principal component (PC) analysis was performed on regional cerebral blood flow (rCBF) data and inter-group comparisons were performed for PC scores using multiple t-tests. Three PCs explained 86.5% of the variation in rCBF values between individual patients and normal controls. The first PC reflected the average rCBF value and separated patient groups from normal controls but failed to distinguish between patient groups. The second PC reflected anterior-posterior asymmetry and separated AD from all three forms of LA. This PC also separated FTD and SD from controls but failed to distinguish between FTD, PA and SD. The third PC reflected left-right asymmetry and separated PA from all other groups. 99mTc-HMPAO SPET is able to differentiate between degenerative cortical brain disorders in a simple and physiological meaningful way, thereby showing considerable potential as a routine tool in the clinical evaluation and differentiation of AD and LA.

Single Photon Emission Computed Tomography of the Brain in Patients with Chemical Sensitivities

Chemical sensitivities display a recurrent pattern on scintigraphic examinations of the brain. The pattern can include mismatching between early and late imaging, multiple hot and cold foci distributed throughout the cortex without regard to lobar distribution (salt and pepper pattern), temporal asymmetries, and sometimes increased activity in the basal ganglia. This study used Desert Shield/Desert Storm veterans who present with abnormal neurological and psychological symptoms as a model to exhibit abnormalities by brain scintigraphy. These are typical of those seen in patients with documented exposure to neurotoxic compounds who develop a clinical syndrome that has been termed "chemical sensitivity." Exposure to cocaine, alcohol, and other substances of abuse can result in abnormal scintigrams of the brain using tracers such as [technetium-99m]hexamethylpropyleneoxime. This study used techniques combining regional cerebral blood flow data with delayed distributional data after the intracellular conversion of the tracer into a hydrophilic molecule. In addition to delayed image abnormalities, a mismatch occurs in the regional activity between the two image sets of the veterans. This degree of mismatch was not seen in control subjects who were screened for avoidance of neurotoxic agents. Patterns identified from examinations performed on patients with known exposure to petroleum distillates, pesticides and other materials linked with neurotoxicity were identified in some veterans of the Desert Shield/Desert Storm operation. A single case of repeated examinations on a veteran showed a reversion of these patterns toward normal after therapy. This reversion followed independent assessments of clinical improvement.

Data analysis in behavioral cerebral blood flow activation studies using xenon-133 clearance.

Three mainstream strategies exist to detect the responses of regional cerebral blood flow to functional activation. We tested the significance of changes in raw regional cerebral blood flow data, regional cerebral blood flow data normalized by division by global cerebral blood flow (dependent model of the regional-to-global cerebral blood flow relation), and regional cerebral blood flow data treating global cerebral blood flow as a covariate (independent model). Both latter models attempt to enhance regional sensitivity by removing global effects. We examined the sensitivity and pitfalls of these three strategies in behavioral activation studies. These three strategies of data analysis were applied to changes in regional cerebral blood flow induced by a visuospatial problem-solving task in 38 healthy subjects as measured by the intravenous xenon-133 method with 32 stationary detectors. Mental activation increased blood flow in all regions of interest. Raw data were most sensitive and reliable to detect responses to mental stimulation. Both the independent and dependent models to remove global effects were less sensitive and falsely indicated deactivation in regions that were clearly stimulated. In behavioral activation paradigms, safe data analysis should be restricted to using raw regional cerebral blood flow increases without normalization or separation of global from regional effects. Studies using complex stimulation tasks should be scrutinized for global cerebral blood flow effects confounding regional responses.

Regional Cerebral Blood Flow and Cognitive Function in Huntington's Disease and Schizophrenia

Matching patients with etiologically distinct but clinically overlapping cognitive disorders on performance of a regionally specific neuropsychological task is a novel and potentially powerful approach to highlighting differences in the pathophysiological mechanisms of impaired cognition. We used this strategy to compare patients with Huntington's disease (HD) and schizophrenia (SC), disorders that share similarities in cognitive impairment. Patients were matched on the basis of performance on the Wisconsin Card Sorting test of "prefrontal" function, after which neuropsychological test data and regional cerebral blood flow data were determined while patients who performed the Wisconsin Card Sorting test were examined. Patients with HD performed worse on visuospatial tasks and recall memory than did patients with SC, although Wechsler Adult Intelligence Scales-Revised IQ and Wechsler Memory Scale memory quotients were equivalent. These differences could not be attributed to differences on the index task, the Wisconsin Card Sorting Test. Patients with HD and SC exhibited a double dissociation in regional cerebral blood flow. The patients with SC had relatively low frontal and high parietal flows, while patients with HD exhibited the reverse of this pattern. Thus, the regional cerebral blood flow and neuropsychological findings in this study appeared to demonstrate that the single final common cognitive impairment of executive function in HD and SC is associated with two markedly dissimilar pathophysiological states.

Measurements of regional cerebral blood flow and cognitive performance in Alzheimer's disease.

Single photon emission computed tomography (SPECT) with 99mTc-HMPAO was used to image 26 patients with dementia of the Alzheimer type (DAT) and 10 healthy controls. Regional cerebral blood flow (rCBF) data indicated a relative sparing of the occipital regions in DAT. Normalisation to occipital flow illustrated highly significant CBF deficits in a number of cortical regions, particularly in the left and right posterior--temporal cortex in DAT compared to controls. The cognitive performance of DAT patients was measured using a clinical cognitive assessment procedure (CAMCOG) and numerous correlations between these scores and rCBF were obtained. The implications and value of this investigative technique are discussed.

Correlation between regional cerebral blood flow and anatomicopathological data.

Correlation between regional cerebral blood flow and anatomicopathological data.