Influence of mental activity upon regional cerebral blood flow in man. A preliminary study.
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Adult↗
Biomedical subjects
J Risberg
Publications and source records attributed to J Risberg.
Regional cerebral blood flow measurements in the clinical evaluation of demented patients.
The clinical usefulness of two-dimensional measurements of regional cerebral blood flow (rCBF) for diagnosis of dementia is discussed on the basis of data from 150 patients with autopsy-based diagnosis. The specificity of Alzheimer's disease is found to be very good but the sensitivity only in the order of 75-80%, the majority of the mislabelled cases having selective incomplete white matter infarcts in addition to their Alzheimer pathology. Frontal lobe dementia is recognized by rCBF with high sensitivity but fairly low specificity due to the fact that frontal flow decreases are shared with several other disorders. Regarding cerebrovascular dementia the sensitivity is rather good (95%) while specificity is somewhat lower (70-75%). It is argued that rCBF should be interpreted diagnostically only when clear-cut findings are made preferably in a series of measurements. The noninvasiveness, repeatability, low radiation dose and low cost makes the present method an excellent tool for research as well as for clinical routine use.
Aged↗
Oral tetrahydroaminoacridine treatment of Alzheimer's disease evaluated clinically and by regional cerebral blood flow and EEG.
Neurochemical evidence indicates that cognitive impairment in dementia of Alzheimer type (DAT) is related to degeneration of cholinergic neurons in the brain. A pharmacological approach is treatment with a cholinesterase inhibitor such as tetrahydroaminoacridine (THA). THA treatment of 17 patients with DAT was studied with a double-blind crossover design with three types of treatment, THA + lecithin, THA + placebo and placebo + placebo. Each treatment period was 6 weeks with wash out periods of 2 weeks. The treatment was evaluated with clinical ratings, psychometric testing, EEG and regional cerebral blood flow (rCBF) measurements. No significant clinical differences between treatment periods were found in the total sample, but marked individual differences were observed. The patients were subdivided into three outcome groups based on four clinical measures: 6 patients improved (responders), 5 patients were mainly unchanged, and 6 patients showed further deterioration during the trial period of 26 weeks. Pretreatment rCBF in responders differed significantly from that of the deteriorated patients. EEG showed more high frequency activity among responders. Hepatotoxic side effects were observed in several cases. Three subjects showed marked increases of liver enzymes, with normalization following dose reduction. The majority of patients who improved or remained unchanged during the study chose to continue THA treatment in an open trial.
Aged↗
Multichannel EEG frequency analysis and somatosensory-evoked potentials in patients with different types of organic dementia.
Thirty-five patients with organic dementia were investigated with multichannel FFT analysis of EEG. In 21 of them, somatosensory-evoked potentials (SEPs) with stimulation of the median nerves were also recorded. Based on clinical and psychometric data and regional cerebral blood flow measurements, the patients were subdivided into Alzheimer-type dementia (DAT) of moderate (n = 10) and severe (n = 11) degree, multi-infarct dementia (MID) (n = 7), and frontotemporal degeneration (FTD) (n = 7). The FTD patients showed mild EEG abnormality and the MID patients showed increases of low frequency activity in combination with a well-preserved posterior dominant activity. The DAT patients showed the most pronounced abnormalities with deterioration of the posterior activity combined with a large increase of low frequency activity. The SEPs of the DAT group showed an amplitude enhancement of the parietal response components. The FTD group showed only a moderate delay of the precentral N30 component. The MID group showed individually varying abnormalities, including a delay of the primary cortical response. It is concluded that the different distributions of pathology in the different organic dementia disorders are reflected in the quantified EEG and SEPs as studied with multichannel technique.
Aged↗
Regional cerebral blood flow in frontal lobe dementia of non-Alzheimer type.
Twenty-five out of 26 cases of autopsy-verified frontal lobe degeneration of non-Alzheimer type (FLD) were found to have focal frontal or frontotemporal blood flow reductions involving both hemispheres. The deviant case had an asymmetric frontal pathology only apparent on the right side. Focal reduction of blood flow in the frontal lobes is, however, a common and unspecific flow abnormality found in e.g. Pick's disease. Creutzfeldt-Jakob's disease, and in some cases of Alzheimer's disease. Low frontal flow has also been reported in schizophrenia and in toxic encephalopathy. Since a characteristic feature of FLD is a steady progress of the pathology, serial flow measurements extending over several years are especially informative.
Cerebrovascular Circulation↗
Neuropsychological findings in frontal lobe dementia.
Neuropsychological investigations were performed on 18 patients with a clinical diagnosis of frontal lobe dementia supported by regional cerebral blood flow measurements. Nature and degree of cognitive impairment were examined with a comprehensive test battery. The results of the neuropsychological assessment could be described as three levels of cognitive impairment. The increasing levels of cognitive impairment were accompanied by corresponding levels of reduced cerebral blood flow in frontotemporal areas. No apparent relationship emerged between impairment level and illness duration, indicating a considerable individual variation in the clinical course of frontal lobe dementia.
Adult↗
Monitoring regional cerebral blood flow in normal man with a computer-controlled 32-dector system.
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Cerebrovascular Circulation↗
Increase of blood flow in cortical association areas during memorization and abstract thinking.
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Adult↗
Cerebral hemodynamic response to mental activation in normo- and hypercapnia.
Changes of regional cerebral blood flow from rest to mental activation by a visually presented spatial reasoning test were measured during normo- and hypercapnia in 10 healthy subjects. Hypercapnia, elicited by inhalation of 6% CO2, resulted in similar flow increases in all 32 cortical regions measured. Increases of flow during testing were seen in post-central regions of the brain whether the resting level was augmented by hypercapnia or not. The results show that an elevated local functional level in the cortex causes an automatic local vasodilatory response which is totally independent of the basal level of perfusion and availability of metabolic substrates.
Adult↗
Prediction of hemispheric blood flow from carotid velocity measurements. A study with the Doppler and 133Xe inhalation techniques.
Doppler carotid velocity determinations were related to hemispheric blood flow measurements by the 133Xe inhalation method in 28 patients with psychiatric disorders without arterial pathology and in 2 normal subjects. Results from 39 double determinations showed a product-moment correlation of 0.88 (p < 0.001) between right hemispheric blood flow and right internal carotid end-diastolic velocity. The correlation for the left side was slightly lower (r = 0.83), while the common carotid end-diastolic velocity showed a considerably lower correlation of 0.71 (rt) and 0.69 (lt) respectively. The peak-systolic velocity values (internal carotids) showed a less close relationship to hemispheric flow (r = 0.71 (rt) and r = 0.61 (lt)). It is concluded that a fairly accurate (15-20% maximum error) prediction of hemispheric blood flow from Doppler internal carotid end-diastolic velocity values is possible in patients without abnormalities in these arterial systems. The high correlations found, in spite of the fact that arterial diameters were not taken into account, are further proof of the accuracy and validity of both methods.
Adult↗
rCBF in patients with carotid occlusion. Resting and hypercapnic flow related to collateral pattern.
rCBF was measured by 133Xenon inhalation technique in 39 patients with unilateral carotid artery occlusion in a subacute-chronic stage. Resting flow values (ISI) varied between 23.7 and 52.4 ml/100 g/min. An almost constant finding was interhemispheric asymmetry, the degree of which was correlated with the severity of the initial symptoms. An ischemic focus was an insignificant finding. The CO2 response was normal in patients with angiographic signs of circle of Willis collateral flow and without significant contralateral carotid stenosis, whereas it was impaired in patients with a retrograde ophthalmic flow or collateral flow via the circle of Willis and contralateral carotid stenosis greater than or equal to 50%. It is concluded that the CO2 response in useful rCBF variable and may be applied for analysis of collateral flow capacity in patients with carotid artery occlusion considered for bypass surgery.
Adult↗
Regional cerebral blood flow by 133xenon inhalation.
Repeated measurements of regional cerebral blood flow (rCBF) were made by the short (ten minutes) 133Xenon inhalation technique and bicompartmental analysis in 11 patients with cerebrovascular disorders, mainly acute cerebral infarction. rCBF was measured 3 to 11 times during one to two weeks. The blood flow of the fast compartment (f1) was calculated as well as the relative weight of this compartment (w1, assumed to correspond to gray matter). In addition a new flow index, the Initial Slope Index (ISI) modified for the inhalation technique, was used. This index of predominantly gray matter flow was calculated from a one-minute epoch of the early part of the clearance curve corrected for recirculation. In three of the patients the f1 and ISI varied in parallel and the w1 showed generally only minor variations from one measurement to the other. However, in the other eight patients fluctuation of the w1 and f1 values were seen which often showed no meaningful relation to the clinical course. The observed w1 changes indicated that some tissues (slowly perfused gray matter and/or rapidly perfused white extracerebral tissues) fluctuate between the fast and the slow compartment. In such cases the f1 values obtained cannot be used for comparison between measurements, since they represent flow rates of varying tissues and do not always represent a true gray matter blood flow. In these patients the ISI, which is independent of such weight changes, showed moderate and clinically likely variations.
Adult↗
133Xenon inhalation method. Analysis of reproducibility: some of its physiological implications.
Regional cerebral blood flow (rCBF) was simultaneously measured at seven locations in each hemisphere by the Obrist 133Xenon inhalation method. In each of 35 healthy right-handed subjects two rest measurements were performed on consecutive days. The data analysis comprises the two-compartmentally derived parameters for flow (f1), relative tissue weight (w1), and fractional flow (FF1) respectively of the first compartment, and in addition the initial slope index (ISI). At each detector location the coefficient of variation (C.V.) of the change from first to second measurement was on average 10.4% (ISI), 14.2% (f1), 7.2% (w1), and 2.9% (FF1) respectively. However, when each regional measurement was expressed as a percentage of its hemispheric mean, the C.V. of the intermeasurement change was on average 4.4% (ISI), 7.0% (f1), 7.7% (w1), and 1.9% (FF1) respectively; that of the hemispheric means of ISI, f1, and FF1 was found to be distinctly larger, whereas that of w1 was about equal in size. The interhemispheric coefficient of variation for the change of the hemispheric means from first to second measurement was only 2.3% (ISI), 4.4% (f1), 1.6% (w1), and 1.1% (FF1) respectively. The findings suggest that (1) the variability of rCBF from subject to subject and in consecutive measurements in the same subject is to a substantial degree of physiological origin, and that (2) there are two determinants of rCBF which may operate independently: a determinant of the hemispheric mean level, probably a single determinant for both hemispheres, and a set of determinants for each separate regions superimposed on the hemispheric mean level.
Adolescent↗
Spectrum subtraction technique for minimizing extracranial influence on cerebral blood flow measurements by 133xenon inhalation.
Estimates of regional cerebral blood flow (rCBF) by the 133Xe inhalation method are influenced by isotope contamination from slow clearing extracerebral tissues. Subtraction of x-ray (31 kev) from gamma-ray counts (81 kev) has been suggested as a means of yielding clearance curves that are relatively free of such contamination. In the present study, rCBF measurements based on the total 133Xe spectrum (x-ray plus gamma) were compared with those derived from the subtracted spectrum (x-ray minus gamma) in 20 young controls, using a two-compartmental analysis of the clearance curves. In comparison with addition, the subtraction data gave substantially higher estimates of blood flow for the slow (second) compartment. This, along with a shift in the relative weights of the two compartments, indicated a decreased contribution of slow tissue components, consistent with a reduction in extracerebral contamination. Blood flow values obtained by subtraction were in good agreement with those reported for the intracarotid injection method. A limitation of the subtraction technique, however, is the relatively high dose of isotope required for adequate signal-to-noise ratios.
Adult↗
Electroencephalography and magnetic resonance imaging in neurological decompression sickness.
The purpose of this study was to evaluate the use of electroencephalography (EEG) and magnetic resonance imaging (MRI) in the clinical evaluation of acute decompression sickness (DCS) in the central nervous system (CNS). Twenty-one patients treated because of acute DCS in the CNS during 1999-2001 were included, 15 patients with clinical cerebral DCS and five with clinical spinal cord DCS. Seven patients had abnormalities in their EEG, five with cerebral DCS and two with spinal cord DCS. MRI showed high intensity lesions in the spinal cord in four patients with clinical spinal cord DCS and in one with clinical cerebral DCS. Cerebral lesions were not identified by MRI in any patient. In conclusion, EEG showed unspecific abnormalities in only one third of the cases. Conventional MRI with a 1.5 T scanner may be of help in the diagnosis of DCS in the spinal cord, but not in the brain. EEG and MRI have low sensitivity in the diagnosis of acute DCS in the CNS. Recompression treatment of DCS should still be guided by clinical neurological examination and assessment of symptoms.
Adolescent↗