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Biomedical subjects

M Reivich

Publications and source records attributed to M Reivich.

At least 91 records · Page 5Linked to original sources
PubMed1987

The effect of anxiety on cortical cerebral blood flow and metabolism.

The relation between anxiety and cortical activity was compared in two samples of normal volunteers. One group was studied with the noninvasive xenon-133 inhalation technique for measuring cerebral blood flow (CBF) and the other with positron emission tomography (PET) using 18Flurodeoxyglucose (18FDG) for measuring cerebral metabolic rates (CMR) for glucose. The inhalation technique produced less anxiety than the PET procedure, and for low anxiety subjects, there was a linear increase in CBF with anxiety. For higher anxiety subjects, however, there was a linear decrease in CBF with increased anxiety. The PET group manifested a linear decrease in CMR with increased anxiety. The results indicate that anxiety can have systematic effects on cortical activity, and this should be taken into consideration when comparing data from different procedures. They also suggest a physiologic explanation of a fundamental behavioral law that stipulates a curvilinear, inverted-U relationship between anxiety and performance.

Adolescent↗
PubMed1987

The effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants.

The effects of hematocrit and systolic blood pressure on cerebral blood flow were measured in 15 stable, low birth weight babies. CBF was measured with a modification of the xenon-133 (133Xe) clearance technique, which uses an intravenous bolus of 133Xe, an external chest detector to estimate arterial 133Xe concentration, eight external cranial detectors to measure cephalic 133Xe clearance curves, and a two-compartmental analysis of the cephalic 133Xe clearance curves to estimate CBF. There was a significant inverse correlation between hematocrit and CBF, presumably due to alterations in arterial oxygen content and blood viscosity. Newborn CBF varied independently of systolic blood pressure between 60 and 84 mm Hg, suggesting an intact cerebrovascular autoregulatory mechanism. These results indicate that at least two of the factors that affect newborn animal CBF are operational in human newborns and may have important clinical implications.

Blood Pressure↗
PubMed1987

Sequential computerized tomography and positron emission tomography studies in a patient with malignant glioma.

Computerized tomography (CT) and positron emission tomography (PET) using fluorine-18-deoxyglucose were performed in a patient with malignant glioma over a one-year period. Postoperatively and during radiation therapy, there was slight improvement in metabolic activity in the hemisphere ipsilateral to the tumor. After radiation therapy and during chemotherapy, there was a rapid and then gradual decline in whole brain metabolic rate by 39%. This might have been explained by radiation effect on brain. The tumor area was metabolically similar to the adjacent brain until one year after diagnosis, when an area of abnormal increased activity was noted. Even though CT scans showed minimal evidence of tumour growth, a large glioblastoma multiforme was found at autopsy at the site of the increased activity. Radiation leukoencephalopathy was also observed at autopsy. It is concluded that PET studies may offer new information regarding the metabolic effects of anti-tumor therapy, and may demonstrate regrowth of tumor prior to CT.

Brain↗
PubMed1987

[14C]iodoantipyrine and microsphere blood flow estimates in cat brain.

A comparison of local cerebral blood flow estimates with the microsphere and the 4-[N-methyl-14C]iodoantipyrine ([14C]IAP) techniques has been performed in cats. Good correlation of [14C]IAP with microsphere flow estimates in the gray matter was found. In the white matter, however, [14C]IAP flow estimates were consistently lower than microsphere flow estimates. Error analysis of both techniques and comparison with previous studies suggest that peculiarities of white matter arterial vasculature with preferential microsphere accumulation may lead to this discrepancy. Microspheres did not interfere with flow as shown by the normal appearance of subsequent [14C]IAP autoradiograms. The number of microspheres seen on autoradiograms was used for an estimate of microvessels blocked by spheres and found to be negligible. The study also demonstrates that [14C]IAP is not diffusion limited up to the observed flow values of 2 ml.g-1.min-1. Both techniques might be used together for a combination of their respective advantages, which are temporal and spatial resolution for microsphere and [14C]IAP, respectively.

Animals↗
PubMed1987

Local cerebral metabolic changes in acute ischemic strokes.

Positron emission tomography (PET) studies with 18F deoxyglucose were completed in 35 patients with acute ischemic strokes. Twelve cases were studied within 72 h, 23 between 4 and 14 days. Results indicate the functional and prognostic significance of early tomography studies of metabolism, and anticipate possible use of metabolic imaging in the evaluation of treatment.

Brain↗
PubMed1987

Regional variation in cerebral perfusion during acute hypertension.

Regional cerebral blood flow (rCBF) was measured in rats to define the autoregulatory response at different levels of hypertension. Mean arterial blood pressure (MABP) was raised with IV metaraminol. rCBF was measured using 14C-iodoantipyrine. Autoregulation was intact in normotensive animals and those with MABP of 152 to 158 mm Hg. At higher pressures, autoregulation was abnormal and heterogeneous. Hyperperfusion was most prominent in cerebellum, parietal gray matter, thalamus, striatum, and pons. These anatomic sites are recognized sites of hypertensive hemorrhage in humans.

Animals↗
PubMed1987

Cerebral blood flow in systemic lupus erythematosus with or without cerebral complications.

We measured mean cerebral blood flow (CBF) in 25 lupus patients using the xenon-133 method. The CBF was normal in lupus patients without cerebral disease and also in CNS lupus patients in remission. The CBF was lower than normal during bouts of cerebral lupus (p less than 0.001). Repeat studies showed a stereotyped pattern consisting of depressed CBF during exacerbation of CNS disease and normalization of CBF during remission (p less than 0.01). These results show that CBF is a sensitive indicator of activity of CNS disease and that the direction of change in CBF reflects the clinical course of CNS lupus.

Brain Diseases↗
PubMed1987

Metabolic and clinical correlates of acute ischemic infarction.

We studied cerebral metabolism, anatomy, and clinical status in 36 patients with acute cerebral ischemia. Results from FDG-PET were compared with CT to find the relationships between the metabolic, anatomic, and clinical findings. Metabolic abnormalities seen on PET frequently were more extensive than the corresponding CT findings. The pattern of metabolic abnormality was significantly related to both the type of clinical syndrome and the degree of eventual recovery. No such relationships were found for the CT results. We conclude that studies of cerebral metabolism are of value in establishing prognosis after acute cerebral ischemia. Also, knowledge of the patterns of cerebral dysmetabolism provides a powerful means for the localization of clinical function.

Aged↗
PubMed1987

Positron emission tomography in aging and dementia: effect of cerebral atrophy.

The spatial resolution of current positron emission tomography (PET) scanners does not allow a distinction between cerebrospinal fluid (CSF) containing spaces and contiguous brain tissue. Data analysis strategies which therefore purport to quantify cerebral metabolism per unit mass brain tissue are in fact measuring a value which may be artifactually reduced due to contamination by CSF. We studied cerebral glucose metabolism (CMRglc) in 17 healthy elderly individuals and 24 patients with Alzheimer's dementia using [18F]fluorodeoxyglucose and PET. All subjects underwent x-ray computed tomography (XCT) scanning at the time of their PET study. The XCT scans were analyzed volumetrically, in order to determine relative areas for ventricles, sulci, and brain tissue. Global CMRglc was calculated before and after correction for contamination by CSF (cerebral atrophy). A greater increase in global CMRglc after atrophy correction was seen in demented individuals compared with elderly controls (16.9% versus 9.0%, p less than 0.0005). Additional preliminary data suggest that volumetric analysis of proton-NMR images may prove superior to analysis of XCT data in quantifying the degree of atrophy. Appropriate corrections for atrophy should be employed if current PET scanners are to accurately measure actual brain tissue metabolism in various pathologic states.

Aged↗
PubMed1987

Cerebellar glucose consumption in normal and pathologic states using fluorine-FDG and PET.

We studied cerebellar metabolism in 118 subjects including young and elderly controls and patients suffering from stroke, supratentorial brain tumor and Alzheimer's disease using fluorine-18 fluorodeoxyglucose ([18F]FDG) and position emission tomography (PET). Alzheimer's disease and normal aging did not alter mean cerebellar metabolism. In stroke and tumor mean cerebellar metabolism was lower in the hemisphere contralateral to the supratentorial lesion. In tumor bilaterally significant reductions in absolute cerebellar metabolism also were noted, unlike stroke. Primary sensory stimulation did not alter absolute or relative cerebellar metabolism. These results show that absolute and relative values for cerebellar metabolism vary depending on the process under study. Thus analysis schemes employing normalization of regional metabolic data to cerebellar values may be subject to error.

Adult↗
PubMed1986

Slowly progressive aphasia without generalized dementia: studies with positron emission tomography.

Slowly progressive aphasia without generalized dementia is a degenerative syndrome selectively affecting dominant hemisphere language areas. We report changes in regional glucose metabolism measured by positron emission tomography in two patients with this condition. Striking abnormalities of glucose utilization in the left cerebral cortex were demonstrated in both patients. The findings of other neurodiagnostic studies were relatively unremarkable. The first patient had a 3-year history of progressive anomia and impaired auditory verbal recall. An electroencephalogram was normal, and computed tomography showed mild left perisylvian atrophy. Positron emission tomography revealed profound hypometabolism in the left temporal regions. The second patient also had a 3-year history of progressive anomia. Electroencephalography, computed tomography, and magnetic resonance imaging scans were normal. Positron emission tomography showed a major reduction in left parietal glucose utilization, with a lesser decrement in left temporal metabolism. Neither patient demonstrated significant contralateral or global abnormalities such as those reported in positron emission tomographic studies of Alzheimer's disease with or without focal clinical features. These observations support the concept of adult-onset progressive aphasia without dementia as a clinical syndrome distinct from Alzheimer's disease.

Aphasia↗
PubMed1986

Kinetics of microcirculatory, NAD/NADH, and electrocorticographic changes in cat brain cortex during ischemia and recirculation.

Changes in microcirculation, the NAD/NADH redox state, and electrical activity during 2 hours of ischemia and 4 hours of reperfusion produced by middle cerebral artery occlusion and release were studied in cats. Twelve animals were classified into three groups of ischemia (mild, moderate, and severe) based on the severity of electrocorticographic (ECoG) depression at the end of the recovery period. Four animals were studied as controls. Occlusion of the middle cerebral artery (MCAO) resulted in a marked but similar degree of reduction in cerebral blood flow (CBF) in all three groups. After this initial change, CBF increased continuously during occlusion in the mild group. CBF in the moderate and severe groups remained at the same low level during the entire period of MCAO. Immediately after MCAO, NAD reduction was increased by approximately 50% in all groups. At the end of MCAO, while the NAD/NADH redox state returned to its pre-ischemic reference level in the severe group, it remained markedly reduced in the mild and moderate groups. Removal of the clip led to slight reactive hyperemia in the mild and severe groups but not in the moderate group. Immediately after recirculation, NAD/NADH redox was shifted toward oxidation in all groups. However, this reoxidation of NADH was only partial in the mild and moderate groups, and a pronounced hyperoxidation occurred in the severe group. In spite of the similar behavior of CBF in the recovery period, a marked secondary NAD reduction occurred in the moderate group during the recirculation period. It is suggested that this represents cessation of mitochondrial electron transport in the dying cells, accompanied by stimulated anaerobic glycolysis in other cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Positron emission tomography imaging of regional cerebral glucose metabolism.

The (F-18) fluorodeoxyglucose (FDG) technique to measure local cerebral metabolic rate for glucose (LCMRglu) is well accepted and widely used by many institutions around the world. A large number of studies has been carried out in normal volunteers and patients with a variety of CNS disorders. Several investigators have noted that no significant age-related changes in cerebral glucose use occur with normal aging. Some important and interesting findings have been revealed following sensory, motor, visual, and auditory stimulations. Functional imaging with FDG in certain neurologic disorders has dramatically improved our understanding of their underlying pathophysiologic phenomena. Some abnormalities detected on the positron emission tomography (PET) images have no corresponding changes on either x-ray computed tomograms (XCT) or magnetic resonance images (MRI). In patients with Alzheimer's disease, primary sensorimotor, visual, and cerebellar metabolic activity appears relatively preserved. In contrast, parietal, temporal, and to some degree, frontal glucose metabolism is significantly diminished even in the early stages of the disease. Patients with Huntington's disease and those at risk of developing this disorder have a typical pattern of diminished CMRglu in the caudate nuclei and putamen. In patients with stroke, PET images with FDG have demonstrated abnormal findings earlier than either XCT or MRI and with a wider topographic distribution. FDG scans have revealed interictal zones of decreased LCMRglu in approximately 70% of patients with partial epilepsy. The location of the area of hypometabolism corresponds to the site of the epileptic focus as determined by electroencephalography and microscopic examination of the resected tissue. Ictal scans during partial seizures demonstrate areas of hypermetabolism corresponding to the sites of seizure onset and spread. Several investigators have reported relative hypofrontal CMRglu in patients with schizophrenia. In our center, FDG scans from patients with schizophrenia were successfully differentiated from those obtained in normal controls. Finally, our preliminary data (using PET, XCT, and MRI) in patients with CNS disorders indicate that MRI provides excellent delineation of the structural abnormalities. It may prove to be superior to XCT in the evaluation of certain diseases such as cerebral ischemia and infarcts, head injury, tumors, and white matter lesions. Metabolic imaging with FDG provides functional information not obtainable with either MRI or NMR spectroscopy. Therefore, PET studies will play a complementary role to the anatomic imaging in the management of patients with CNS disorders.

Aging↗
PubMed1986

Computerized tomography, magnetic resonance imaging, and positron emission tomography in the study of brain trauma. Preliminary observations.

Results of computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), xenon-133 measurement of cerebral blood flow (CBF), and neuropsychological assessments are described in three head-injured patients. The patients were selected because they presented with intracranial hemorrhage diagnosed by CT. Two of the patients were studied acutely and again approximately 6 months later. In the acute stage, MRI was superior to CT in identifying the precise location and extent of intracranial hemorrhage and associated edema. Small subdural hematomas diagnosed on MRI were missed with CT scanning. The extent of apparent encephalomalacia in the chronic stages of injury was also better defined with MRI. Positron emission tomography showed disturbances of glucose metabolism that extended beyond the structural abnormalities demonstrated by MRI and CT; anterior temporal lobe dysfunction was particularly evident in all three patients. Regional CBF studies failed to detect a number of the abnormalities seen on MRI and CT, and even ignored the metabolic dysfunction evident on PET that should have been accompanied by changes in regional CBF. The neuropsychological studies localized frontal lesions, but did not reveal abnormalities attributable to the structural lesions and the reduced metabolism in the anterior temporal lobes.

Adult↗
PubMed1985

Brain function in psychiatric disorders. III. Regional cerebral blood flow in unmedicated schizophrenics.

Regional cerebral blood flow (rCBF) was measured during resting baseline and the performance of a verbal and a spatial task in 19 unmedicated schizophrenics and 19 matched controls. Abnormalities in rCBF were evident in schizophrenics both for resting and activated measures. Resting flows were higher in the left hemisphere for schizophrenics, supporting the hypothesis of left hemispheric overactivation. This effect was stronger in the more severely disturbed patients. The pattern of rCBF changes during activation with the verbal and spatial tasks was also different in schizophrenics. Laterality of flow changes further supported the hypothesis of left hemispheric overactivation. Furthermore, whereas normals had greater increase in flow for the spatial than the verbal task, schizophrenics showed the reverse pattern. This effect also was more pronounced in the severely disturbed patients. Comparison with an earlier sample of medicated schizophrenics suggested that neuroleptics restore symmetry of resting flows before they produce symptomatic relief. Medication did not affect the abnormalities in pattern of rCBF changes during activation with cognitive tasks.

Adolescent↗
PubMed1985

Glucose metabolic rate kinetic model parameter determination in humans: the lumped constants and rate constants for [18F]fluorodeoxyglucose and [11C]deoxyglucose.

The rate constants and lumped constants (LCs) for [18F]fluorodeoxyglucose ([18F]FDG) and [11C]deoxyglucose ([11C]DG) were determined in humans for the glucose metabolic rate kinetic model used to measure local cerebral glucose consumption. The mean values (+/- SE) of the LCs for [18F]FDG and [11C]DG are 0.52 +/- 0.028 (n = 9) and 0.56 +/- 0.043 (n = 6), respectively. The mean values (+/- SE) of the rate constants k*1, k*2, k*3, and k*4 for [18F]FDG for gray matter are 0.095 +/- 0.005, 0.125 +/- 0.002, 0.069 +/- 0.002, and 0.0055 +/- 0.0003, respectively. The corresponding values for white matter are 0.065 +/- 0.005, 0.126 +/- 0.003, 0.066 +/- 0.002, and 0.0054 +/- 0.0006, respectively. Using these values and previously published values for the rate constants for [11C]DG, the average whole-brain metabolic rates for glucose in normal subjects measured with [18F]FDG and [11C]DG are 5.66 +/- 0.37 (n = 6) and 4.99 +/- 0.23 (n = 6) mg/100 g/min, respectively. These values are not significantly different (t = 1.56, p greater than 0.10) and agree well with reported values in the literature determined by means of the Kety-Schmidt technique.

Adolescent↗