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Biomedical subjects

L Mansi

Publications and source records attributed to L Mansi.

At least 73 records · Page 4Linked to original sources
PubMed1985

Positron emission tomography in generalized seizures.

We used 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to study nine patients with clinical absence or generalized seizures. One patient had only absence seizures, two had only generalized tonic-clonic seizures, and six had both seizure types. Interictal scans in eight failed to reveal focal or lateralized hypometabolism. No apparent abnormalities were noted. Two patients had PET scans after isotope injection during hyperventilation-induced generalized spike-wave discharges. Diffusely increased metabolic rates were found in one compared with an interictal scan, and in another compared with control values. Another patient had FDG injected during absence status: EEG showed generalized spike-wave discharges (during which she was unresponsive) intermixed with slow activity accompanied by confusion. Metabolic rates were decreased, compared with the interictal scan, throughout both cortical and subcortical structures. Interictal PET did not detect specific anatomic regions responsible for absence seizure onset in any patient, but the results of the ictal scans did suggest that pathophysiologic differences exist between absence status and single absence attacks.

Adult↗
PubMed1984

Depressed cerebellar glucose metabolism in supratentorial tumors.

Fifty-four patients with supratentorial tumor and one with brainstem tumor were examined with positron emission tomography (PET) using [18F]fluoro-deoxyglucose (FDG). Twenty-one of these cases had satisfactory studies of the cerebellum. Of these, 12 showed significant metabolic asymmetry between the two cerebellar hemispheres, with the rate of glucose utilization in the hemisphere contralateral to the cerebral tumor being 8-34% lower than on the ipsilateral side, as compared with a right-left asymmetry of only--1.6% +/- 2.1% standard deviation for a group of 5 normal subjects. In these 12 cases the tumor involved the sensorimotor cortex and/or the thalamus with varying degrees of hemiparesis being present. For the remaining 9 patients with no significant cerebellar metabolic asymmetry, the tumor involved regions other than the sensorimotor cortex, and unilateral motor dysfunction was not a prominent clinical feature. The correlation between cerebellar metabolic suppression and unilateral motor dysfunction observed in our cases appears to be due to impairment or interruption of the cortico-thalamo-ponto-olivo-cerebellar circuitry by either the tumor itself or by edema. These results illustrate the ability of FDG-PET scans to detect metabolic changes, not apparent on CT scans, in areas of the brain remote from the primary lesion.

Astrocytoma↗
PubMed1984

Wechsler Adult Intelligence Scale performance. Cortical localization by fluorodeoxyglucose F 18-positron emission tomography.

We compared local cerebral glucose metabolism, as determined by positron emission tomography following administration of fluorodeoxyglucose F 18, with Wechsler Adult Intelligence Scale (WAIS) scores in 22 right-handed persons. Five study subjects were normal volunteers and the remainder had Alzheimer's disease. Subtest scores within the verbal IQ group or the performance IQ group were generally highly interrelated; there was usually no correlation between the verbal and performance subtests. The cortical distribution of regions in which glucose metabolism was most closely associated with verbal subtest scores generally centered in the left parasylvian area. In contrast, scores on the performance subtests mainly localized to the right posterior parietal region. Most WAIS subtests thus appeared to evaluate primarily either verbal or visuospatial cognitive functions and either left parasylvian or right posteroparietal cortical activity.

Aged↗
PubMed1984

Issues in the in vivo measurement of glucose metabolism of human central nervous system tumors.

Over 150 cases of central nervous system tumors have been studied with positron emission tomography using fluorine-18-labeled fluorodeoxyglucose (18FDG) as a tracer. From this material 100 consecutive cases of cerebral glioma have been reviewed and analyzed. The results show a strong correlation of tumor grade with glycolytic rate, with visual "hot spots" present in all high-grade neoplasms and in only four low-grade tumors. The quantitative accuracy is limited by three basic factors. First, the measurement of tissue uptake, as compared with the parent technique, autoradiography, is more difficult because detection must be done outside the body. Effects such as scattered radiation and self-attenuation introduce errors unless properly corrected. A more serious problem when measuring small structures, such as a rim-shaped high-grade glioma, is the limited spatial resolution. The most advanced scanner, the Neuro-PET, has a resolution of 6 to 7 mm. Second, corrections are needed for backflow, including free tracer at the time of the scan that will return to the blood and "trapped" tracer that will backflow because of the presence of phosphatase. These corrections are calculated from the blood activity using nominal rate constants for 18FDG. Our study found no significant alteration in rate constants between normal and tumoral tissue. Finally, a lumped constant is needed to correct for kinetic differences between 18FDG and glucose. If there is a change in the mechanism of either membrane transport or the hexokinase reaction, the lumped constant may change. However, measurements of actual glucose utilization in tissue culture lines from six patients support the 18FDG results.

Animals↗
PubMed1984

Regional cortical dysfunction in Alzheimer's disease as determined by positron emission tomography.

Local cerebral glucose metabolism and psychometric function were compared in 17 patients with Alzheimer's disease and 5 healthy age-matched controls. Performance on tests of global intellectual function averaged 30 to 45% lower in the Alzheimer's group. Mean cortical glucose metabolism, as determined by positron emission tomography following fluorine-18-labeled fluorodeoxyglucose administration, was reduced by 30% in the Alzheimer's group. There was a significant positive correlation between the degree of overall dementia and the amount of metabolic reduction. The distribution of cortical hypometabolism was not uniform: the posterior parietal lobes and contiguous portions of the posterior temporal and anterior occipital lobes were most severely involved. The frontal cortex was relatively spared. These findings are compatible with the major clinical deficits found in patients with Alzheimer's disease and may help focus future biochemical probes into the pathophysiology of this disease.

Alzheimer Disease↗
PubMed1984

Cortical abnormalities in Alzheimer's disease.

Regional cerebral glucose metabolism, an index of neuronal activity, was compared in 20 patients with Alzheimer's disease and 8 age-matched normal volunteers by positron emission tomography following [18F]2-fluoro-2-deoxy-D-glucose administration. Overall cortical glucose utilization in the Alzheimer's group was 10 to 49% below that of control individuals. The posterior parietal cortex and contiguous portions of posterior temporal and anterior occipital lobes were most severely affected; frontal cortex was relatively spared. This pattern of cortical involvement is consistent with the major clinical features of Alzheimer's disease. Comparison of patients with early and more advanced dementia suggested that a substantial decline in glucose metabolism occurs before cognitive impairment becomes evident; once the patient is symptomatic, however, small additional metabolic decrements are associated with a marked deterioration in intellectual function.

Aged↗
PubMed1983

Metabolic imaging of the brain stem and spinal cord: studies with positron emission tomography using 18F-2-deoxyglucose in normal and pathological cases.

A new high resolution positron emission scanner (Neuro-PET) has made possible clear visualization and quantitation of glucose metabolism in the brain stem and upper cervical cord (above C4) using 18F-2-deoxyglucose. The following mean measurements of the glucose utilization rate are based on studies of 34 normal volunteers and patients with no apparent pathology in the brain stem or cord: 5.0 +/- 1.0 (SD) mg Glu/100 g/min for the mesencephalon-upper pons, 3.2 +/- 1.0 for the pons-medulla, and 1.7 +/- 0.6 for the upper cervical cord. (The first value also includes studies done with the ECAT-II scanner.) Resolution of white-gray matter within these structures was not possible. Whenever possible, a correlation was made with autoradiographic data in monkeys, and good agreement was found. The glucose utilization in cases showing brain stem and cord pathology was altered, with marked elevation (as high as 8.2 mg/100 g/min) in cases of high-grade gliomas, and reduction in cases of low-grade gliomas and one pontine hematoma.

Adult↗
PubMed1982

Congenital pulmonary arterio-venous fistula in childhood.

Pulmonary arterio-venous fistula is a rare congenital lesion of the pulmonary vasculature, causing cyanosis in children. The lesion can be solitary or multiple, usually involves the lower lobes and is often associated with the Rendu-Osler-Weber syndrome. The case of a 9-year-old boy is reported in whom diagnosis was made on pulmonary angiophotoscintigraphy and confirmed at angiography. The usual treatment of choice of these lesions is lobectomy which promptly relieves the symptoms.

Angiography↗
PubMedDate not supplied

Effect of moderate level x-radiation to brain on cerebral glucose utilization.

The effect of x-radiation in doses used in treatment of brain malignancies has previously been established largely by histologic examination of the tissue or by observation of a deficit in function. At moderate dose levels such effects are usually delayed and are vascular in origin. We have used the 2-[14C]deoxyglucose method for the quantitative measurement of local cerebral glucose utilization to learn whether x-radiation administered to rat brain in a dose below that which is known to result in any histologic change may nevertheless affect the brain's local rates of glucose utilization. Measurements were made 4 days and 4 weeks after exposure of groups of rats to 1,500 rad. Rates of glucose utilization in 54 gray and eight white matter structures in both groups were compared with rates in sham-irradiated controls. Statistically significantly lower rates were found in 16 structures in rats 4 days after radiation and in 25 structures 4 weeks after radiation exposure. A weighted average rate for the brain as a whole was approximately 15% below that of the controls for both radiated groups, but this difference was short of being of statistical significance. It is clear from this study that the metabolic rates of some brain structures are reduced following moderate doses of x-radiation.

Animals↗
PubMedDate not supplied

Simplified, noninvasive PET measurement of blood-brain barrier permeability.

Blood-brain barrier (BBB) permeability to [68Ga]EDTA was measured by positron emission tomography (PET) in four normal volunteers and in 11 patients with brain tumors. A unidirectional transfer constant, Ki, was calculated applying multiple-time graphical analysis (MTGA). This method allows the detection of backflux from brain to blood and, by generalization, the measurement of the constant Kb (brain to blood). Furthermore, the need for an independent measurement of the intravascular tracer is obviated: MTGA itself provides an estimate of the cerebral plasma volume (Vp). In the four normal volunteers the Ki was 3.0 +/- 0.8 X 10(-4) ml g-1 min-1 (mean +/- SD) and the Vp 0.034 +/- 0.007 ml g-1. A net increase in Ki up to a maximum of 121.0 X 10(-4) ml g-1 min-1 (correspondent value of Kb = 0.025 min-1) as well as an increase of Vp was observed in malignant tumors. The input function was calculated using both the [68Ga]EDTA concentration in sequential arterial blood samples and, noninvasively, the activity derived from the superior sagittal sinus image. The values of Ki and Vp from these two calculations were in good agreement. The application of MTGA to PET permits the evaluation of passage of substances across the BBB without making assumptions about the compartments in which the tracer distributes.

Adult↗
PubMedDate not supplied

Cortical motor-sensory hypometabolism in amyotrophic lateral sclerosis: a PET study.

We previously reported generalized cerebral glucose hypometabolism in amyotrophic lateral sclerosis (ALS) patients with upper motor neuron disease, using positron emission tomography (PET) with [18F]2-fluoro-2-deoxy-D-glucose. The present article presents a more detailed regional analysis of the hypometabolism, including measurements of the motor-sensory cortex at higher levels than used earlier. The analysis is based on 19 PET studies of 12 patients with ALS, four of whom had only lower motor neuron involvement, and 11 studies of age-matched control subjects. A brain size correction was included to eliminate differences in metabolism related to brain size but not to pathology. The eight ALS patients with both upper and lower motor neuron disease showed generalized hypometabolism, compared with the normal control subjects, that was greatest in the motor-sensory cortex and putamen. The motor-sensory deficit was strongly correlated with length of disease, and a marked sequential reduction was seen in repeat studies on four of the patients. There was also significant right-left asymmetry in these scans. No cerebral hypometabolism was seen in the four ALS patients without upper motor neuron involvement. Although the observed motor-sensory deficit in ALS is consistent with histopathological findings, the more generalized hypometabolism and the asymmetry suggest more widespread effects.

Adult↗