Biomedical subjects

W D Heiss

Publications and source records attributed to W D Heiss.

At least 19 recordsLinked to original sources

PubMed1995

Planum temporale and Brodmann's area 22. Magnetic resonance imaging and high-resolution positron emission tomography demonstrate functional left-right asymmetry.

OBJECTIVE: To describe the registered analysis of magnetic resonance imaging and glucose metabolic data acquired with positron emission tomography to determine the relationship between structure and function of temporal lobe cortical structures between the left and right hemispheres. BACKGROUND: The dominance of the left cerebral hemisphere is associated with a preponderance of the left planum temporale. SUBJECTS AND METHODS: Fifteen subjects without signs or symptoms of a neurological disorder. Three-dimensional-registered magnetic resonance imaging and positron emission tomography with the use of fludeoxyglucose F18 and a high-resolution positron emission tomography scanner. Analysis of regional metabolic activation during single-word repetition on matched parasagittal magnetic resonance imaging and positron emission tomography. RESULTS: The planum temporale was bilaterally activated without left-right asymmetry. The metabolic increase was asymmetric within the left Brodmann's area (BA) 22. The part of the left BA 22 that was buried in the superior temporal sulcus was significantly less activated than the part of BA 22 on the surface of the superior temporal gyrus. The metabolic activation in the sulcal part of the left BA 22 had a significant inverse correlation with the anatomical predominance of the left planum temporale (r = .71, P = .003) and a significant direct correlation with the metabolic activation in the surface aspects of the right BA 22 (r = .82, P < .001). CONCLUSION: Brodmann's area 22 is a critical feature of language dominance and is also important with regard to the exchange of information between the two hemispheres.

Adult↗

PubMed1995

Neurological sequelae of cyanide intoxication--the patterns of clinical, magnetic resonance imaging, and positron emission tomography findings.

We report 2 patients with neurological sequelae of oral cyanide intoxication who were evaluated clinically and neuropsychologically, with high-resolution magnetic resonance imaging and one of them with positron emission tomography. The clinical syndrome was characterized by extrapyramidal motor and cerebellar symptoms such as bradykinesia, hypomimia, slowed speech, anteropulsion, and marked retropulsion, but little tremor. The sensory and pyramidal motor systems were normal or relatively spared. On neuropsychological testing the intellectual capacity and memory functions were normal, whereas the speed of motor reaction and verbal fluency were reduced. Magnetic resonance imaging showed damage of the globus pallidus, putamen, substantia nigra, subthalamic nucleus, and cerebellum in both patients, whereas the sensory-motor cortex and hippocampus were relatively spared. 18F-6-Fluoro-dopa positron emission tomography revealed a symmetrical reduction of striatal dopa uptake by 42% on average that was similar in the putamen and caudate. 18F-2-Fluoro-2-deoxyglucose positron emission tomography showed a regional reduction of the glucose metabolism in the posterior putamen and temporo-parieto-occipital and cerebellar cortex.

Adult↗

PubMed1995

Cognitive impairment in Alzheimer's disease correlates with ventricular width and atrophy-corrected cortical glucose metabolism.

We compared the correlation of PET and MRI with neuropsychological tests in 26 patients with probable Alzheimer's disease (AD). The width of the temporal horns and the third ventricle, regional metabolic rates of glucose (rCMRGlu) and the proportion of cerebrospinal fluid space in mesial temporal and temporoparietal cortical regions were measured with three-dimensionally coregistered PET and MRI in two planes perpendicular to the Sylvian fissure. Highly significant correlations between rCMRGlu and neuropsychological tests were found mainly in the temporoparietal cortex, with and without correction for atrophy. Correlations of similar magnitude were seen also between most tests and the width of the temporal horns and third ventricle. Changes in the third ventricle and mesial temporal lobe were best seen with MRI, whereas PET most clearly depicted alterations in neocortical association areas. These two aspects of the disease correlated with the severity of dementia to a similar degree.

Aged↗

PubMed1995

P300 in Alzheimer's disease: relationships to dementia severity and glucose metabolism.

In 45 patients (aged 48-85 years) with probable Alzheimer's disease (AD) according to current research criteria (NINCDS-ADRDA) with different stages of dementia severity (Mini Mental Status Examination (MMSE) 7-27) the auditory evoked P300 waves were mapped and regional cerebral metabolic rates of glucose were measured by positron emission tomography of 2-[18F]fluoro-2-deoxy-D-glucose. Age adjusted P300 latency was significantly correlated to dementia severity (r = -0.33, p = 0.028), but no significant relationships were found for P300 amplitudes. Dependencies existed among cortical glucose metabolic rates and MMSE with the highest correlation coefficient for the metabolic ratio of regions typically affected and non-affected in AD (r = 0.75, p = 0.0001). A significant correlation was also calculated between P300 latency and metabolic ratio (r = -0.44, p = 0.002), but no relationships were observed among P300 amplitudes and glucose metabolic rates of individual brain regions. These results indicate that P300 latency and metabolic rates but not P300 amplitudes qualify as measures of severity in AD. The lack of regional correlations among P300 amplitudes and glucose metabolism is not consistent with a cortical contribution to P300 generation.

Aged↗

PubMed1995

Regional cerebral blood flow and metabolism in Sturge-Weber disease.

A 50-year-old man with Sturge-Weber syndrome (SWS) and left cerebral hemisphere atrophy was studied using PET with O-15 oxygen and O-15 water in order to evaluate regional cerebral blood flow and energy metabolism in this condition. PET demonstrated decreased perfusion and increased oxygen extraction fraction in the affected left cerebral hemisphere and ipsilateral cerebellum. These findings suggest that a chronic state of reduced perfusion may be the etiology for the cerebral hemiatrophy seen in some patients with SWS.

Cerebrovascular Circulation↗

PubMed1995

Dysfunction of visual cortex contributes to disturbed processing of visual information in Alzheimer's disease.

The relation between visual impairment and regional cerebral metabolic rate of glucose (rCMRGl) was studied in 31 patients with probable Alzheimer's disease (AD) by using positron emission tomography with 18F-2-fluoro-2-deoxy-D-glucose. To exclude any precortical cause of visual dysfunction only patients were included who had amplitudes and latencies of visually evoked potentials (flash and pattern reversal) within the normal range. Visual information processing was evaluated psychometrically by a fragmented picture test (FPT), which is a combined perception (identification score) and memory (reidentification score) task and refers to Gollin's incomplete pictures. The identification and reidentification scores were significantly worse than in normals. Reductions of the rCMRGl in the primary visual fields, and in the secondary visual fields were found. A significant partial correlation with adjustment for age between the reidentification score of the FPT and the rCMRGl of the secondary visual fields (r = -.39, p < .05) in AD patients was found, indicating involvement of the secondary visual cortex in the pathological changes in AD.

Aged↗

PubMed1994

Quantitative topographical EEG compared to FDG PET for classification of vascular and degenerative dementia.

Quantitative topographical EEG was compared with regional glucose metabolism measured by PET with respect to the sensitivity in the classification of mild to moderate dementia. In 24 patients with probable Alzheimer's disease (DAT), 19 patients with vascular dementia (VD) and 15 age-matched healthy controls, global and regional EEG and PET data were analyzed. The metabolic ratio between typically affected and non-affected regions differentiated between DAT and VD (P < 0.001) as well as between DAT and normal controls (P < 0.001) even for the subgroup of mild dementia. In contrast to PET, global EEG changes were more sensitive than regional alterations for the classification into the respective groups. Relative theta power was most sensitive for the differentiation of demented patients irrespective of type of normal controls (P < 0.01), whereas OCC/FR alpha ratio (occipital divided by frontal power) separated between dementia types (P < 0.01) as well as between DAT and normals (P < 0.05). Additionally, EEG may help to grade severity especially in DAT. Combined use of EEG and PET was more discriminative and reached higher diagnostic specificity than each test individually. These results suggest that EEG and PET are complementary diagnostic procedures for the differentiation and classification of dementias.

Aged↗

PubMed1992

Flow thresholds for extracellular purine catabolite elevation in cat focal ischemia.

Ischemic glutamate excitotoxicity may be counteracted by adenosine which appears extracellularly during ischemia as an intermediate purine catabolite and has the potential to modulate glutamate release and its receptor action. The present study was conducted to evaluate the flow threshold for purine catabolite accumulation in relation to that for glutamate elevation in focal ischemia which was induced by middle cerebral artery (MCA) occlusion in halothane anesthetized cats. Assemblies of platinum electrodes and microdialysis probes were inserted into the somatosensory (SF, n = 13) and the auditory (A, n = 9) cortices to assess local cerebral blood flow (CBF) using hydrogen clearance and purine catabolite (adenosine, inosine and hypoxanthine) as well as glutamate concentrations in the dialysate using high-performance liquid chromatography (HPLC). In both investigated areas, purine catabolites were elevated if CBF fell below 25 ml/100 g/min, while glutamate increased at a flow threshold below 20 ml/100 g/min. Maximum elevations of adenosine, inosine and hypoxanthine were 76-, 29- and 11-fold, respectively, that of glutamate was 24-fold. In the range between 20 and 25 ml/100 g/min, significant increases of adenosine (5-15-fold) were measured, while glutamate did not markedly increase. The elevation of adenosine was transient whereas that of inosine, hypoxanthine and glutamate persisted over an ischemic period of 3 h. The higher flow threshold for adenosine may reflect an inherent but time limited protective mechanism against glutamate excitotoxicity.

Adenosine Triphosphate↗

PubMed1992

Severity of vascular dementia is related to volume of metabolically impaired tissue.

The relation between dementia severity and regional cerebral metabolic rate of glucose was studied in 28 patients with vascular dementia (VD) in comparison with 20 age-matched patients who were suffering from Alzheimer's disease (AD) and 24 normal subjects by using positron emission tomography with fludeoxyglucose F 18. Similar metabolic impairment was found in the temporoparietal and frontal association cortex in patients with VD and in those with AD. Metabolism of the basal ganglia, thalamus, and cerebellum was reduced significantly in patients with VD only. The total volume of regions with metabolism below the 95% confidence interval of control values was significantly related to the severity of dementia but did not differ between patients with VD and those with AD. A metabolic ratio of regional cerebral glucose metabolism of association areas divided by regional cerebral glucose metabolism of structures that were typically not affected by AD was significantly lower in patients with AD than in those with VD. This ratio was also related to dementia severity in both types of dementia.

Aged↗

PubMed1992

In vivo imaging of glucose consumption and lactate concentration in human gliomas.

Twenty patients with histologically confirmed gliomas were studied with positron emission tomography (PET) and proton magnetic resonance spectroscopy (1H-MRS). PET with 18F-2-fluoro-2-deoxy-D-glucose (FDG) provided tomograms of the metabolic rate of glucose. MRS images were obtained by combining volume-selective excitation with phase-encoded acquisition. With 32 x 32 gradient phase-encoding steps, an in-plane resolution of 7 x 7 mm was achieved. From this set of spectra, lactate maps were created and compared with PET maps of glucose metabolism. Maximum glucose metabolic rates within tumors (relative to metabolic rates of glucose in contralateral regions of the brain) were correlated significantly with maximum lactate concentrations (relative to N-acetyl aspartate peaks in the contralateral part of the brain). In 8 tumors, no lactate was detected, and in 7 of these the maximum glucose metabolic rate was below the median value. The tumor with the highest lactate concentration also had the highest glucose metabolic rate. The topographic relation between glucose metabolic rate and lactate concentration could be analyzed in 9 patients by three-dimensional alignment of the PET and MRS images. In that analysis, maximum lactate concentrations were often not found in the same location as maximum glucose metabolism, but lactate tended to accumulate in tumor cysts, necrotic areas, and the vicinity of the lateral ventricles. The combination of FDG PET and 1H-MRS imaging demonstrates details of the spatial relation between the two poles of nonoxidative glycolysis, glucose uptake and lactate deposition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

FDG transport and phosphorylation in human gliomas measured with dynamic PET.

Twenty-six patients with gliomas of WHO-grades two to four were examined with dynamic positron emission tomography (PET) and 18F-2-fluoro-2-deoxy-D-glucose (FDG). FDG rate constants and derived glucose metabolic rates (MRdyn) were determined in solid tumor tissue and in tumor-free brain tissue. In addition, glucose metabolism was also calculated from single scans recorded 30 to 40 min after injection (MRstat). All three rate constants, K1, k2, and k3, were significantly correlated with MRdyn in tumor-free brain. In contrast, in gliomas only k3 was significantly correlated with MRdyn. The ratio of k3 in tumors to k3 in tumor-free brain was also significantly related to histological tumor grade. The results indicate that FDG uptake in brain tumors is governed by FDG phosphorylation and is rather independent from the variation of FDG transport. A comparison between glucose metabolic rates calculated by an autoradiographic approach (MRstat) with the calculation based on individually fitted rate constants (MRdyn) revealed a very close correlation in spite of a moderate systematic difference in absolute values.

Adult↗

PubMed1992

Changing patterns of glucose metabolism during the course of subacute sclerosing panencephalitis as measured with 18FDG-positron-emission tomography.

18FDG-positron emission tomography performed at different stages in the course of subacute sclerosing panencephalitis revealed a changing pattern of metabolic disturbance. In clinical stage II patients the inflammation in the basal ganglia appeared to lead to neuronal excitation accompanied by hypermetabolism. Widespread cortical functional inhibition of metabolism followed. The striatal inflammation ended with necrosis and hypometabolism, with resulting functional cortical disinhibition; later, deep midbrain structures and brain stem became hypermetabolic. A patient clinically in remission showed no such changes in cerebral glucose metabolism.

Adolescent↗

PubMed1992

Subcortical damage and cortical dysfunction in progressive supranuclear palsy demonstrated by positron emission tomography.

Regional cerebral glucose metabolism was studied in nine patients with progressive supranuclear palsy (PSP). (18F)-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) revealed general cerebral hypometabolism in all PSP patients in comparison with an age-matched reference group. When comparing the degree of regional metabolic deterioration, a consistent pattern of the most affected brain regions became obvious: the strongest significant alteration of cerebral glucose metabolism was observed in subcortical regions, e.g. in caudate nucleus, lentiform nucleus and upper mid-brain, which showed nerve cell loss in previous pathological studies. Less severe, but still significant hypometabolism was observed in frontal cortex. This pattern of hypometabolism was distinctly different from that typically seen in dementias of Alzheimer's type. The present data show that PET findings agree with histopathological studies: PSP is a primarily subcortical disease with secondary inactivation of cortical, especially of frontal brain regions.

Aged↗

PubMed1992

Positron emission tomography in degenerative disorders of the dopaminergic system.

21 patients who had Parkinson's disease (PD), PD plus dementia of Alzheimer type (PDAT) or progressive supranuclear palsy (PSP), were studied with positron emission tomography (PET) using (18F)-2-fluoro-2-deoxy-D-glucose (FDG). In one patient with strictly unilateral PD side differences in striatal dopa uptake were studied with 6-(18F)fluoro-L-dopa (F-dopa). In patients with PD PET with FDG did not show any significant change in regional cerebral metabolic rates for glucose (rCMR(Glu)). In PDAT glucose metabolism was generally reduced, the most severe decrease was found in parietal cortex. The metabolic pattern was similar to that typically found in patients with Alzheimer's disease (AD). In the patient with strictly unilateral PD rCMR(Glu) was normal, F-dopa PET, however, revealed a distinct reduction of dopa uptake in the contralateral putamen. In PSP glucose metabolism was significantly decreased in subcortical regions (caudatum, putamen and brainstem) and in frontal cortex. Thus PET demonstrated a clear difference of metabolic pattern between PDAT and PSP.

Adult↗

PubMed1992

Quantitative EEG mapping and PET in Alzheimer's disease.

Quantitative analysis of topographical EEG was studied in comparison with measurement of regional glucose metabolism by PET in 42 patients with clinical diagnosis of probable dementia of Alzheimer type (AD) and in 15 age-matched normal controls. Measures analyzed included global and regional data from areas typically affected and not affected by AD pathology. While disturbance of metabolism followed a typical regional pattern, relative alpha, theta and delta power were more globally altered without selectivity for specific regions. Separation between AD and age matched controls by relative theta power was correct in 86% and was close to that by temporo-parietal glucose metabolism (correct classification 87%). Relative theta power as well as temporo-parietal glucose metabolism were significantly correlated (tau B = 0.54 and -0.53, respectively) to severity of AD assessed by the global deterioration scale. These results indicate that EEG measures may be used with an accuracy close to metabolic values from PET for the assessment of severity of AD.

Aged↗

PubMed1992

Progressive derangement of periinfarct viable tissue in ischemic stroke.

Sixteen patients were studied by multitracer positron emission tomography (PET) within 6-48 (mean of 23) h of onset of a hemispheric ischemic stroke and again 13-25 (mean of 15.6) days later. Cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO2), oxygen extraction fraction (OEF), and cerebral metabolic rate of glucose (CMRglc) were measured each time by standard methods, and the sets of brain slices obtained at the two studies were matched using a three-dimensional alignment procedure. On matched brain slices, regions of interest (ROIs) for infarct and peri-infarct tissue, contralateral mirror regions, and major brain structures were outlined. In the core of infarction, blood flow and metabolism were significantly lower than in the corresponding contralateral regions at the first study, and did not change during the observation period. In the peri-infarct tissue, CMRO2 was moderately decreased at the first measurement; over time, the CMRO2 deteriorated progressively while flow did not change. When peri-infarct regions were selected on the basis of increased OEF (25 +/- 29.8% above corresponding contralateral regions) on the early scans, the CBF was significantly decreased (23 +/- 6.6%) while the CMRO2 showed only a slight difference from the mirror region. Within the observation period, the CBF improved but the CMRO2, OEF, and CMRglc deteriorated. Only in a few regions with increased OEF and slightly impaired CMRO2 was metabolism preserved close to normal values. These data from repeat PET studies in reproducibly defined tissue compartments furnish evidence of viable tissue in the border zone of ischemia up to 48 h after stroke. While this viable peri-infarct tissue exhibits some potential for effective treatment of ischemic stroke, therapeutic routines available today cannot prevent subsequent metabolic derangement and progression to necrosis. Multitracer PET studies identifying viable tissue could be of value in the development of effective treatment of ischemic stroke.

Adolescent↗

PubMed1992

Functional and morphological imaging of small striato-capsular infarction by CT, MRI and multitracer PET.

Regional cerebral blood flow, oxygen consumption, blood volume and glucose metabolism were studied by positron emission tomography (PET) in 16 patients with striato-capsular infarction during the acute phase. Visual evaluation of tomograms and quantitative analysis of PET data detected in all patients severe flow disturbances and metabolic derangement within the territory of the penetrating branches of the middle cerebral artery. Additionally remote effects were observed. The correspondence of early PET changes with the diagnosis of striato-capsular infarction was verified later on by computerized three-dimensional alignment of PET scans and MRI. These results demonstrate that PET allows localization of small striato-capsular infarction with high accuracy in the acute phase by demonstrating both severe local flow disturbances and metabolic derangement, as well as remote effects.

Brain↗

PubMed1992

Metabolic derangement in viable periinfarct tissue in the course of acute ischaemic infarction: a multitracer positron emission tomography (PET) study.

We used a multitracer positron emission tomography (PET) approach to assess metabolic changes in infarcted and periinfarct tissue in acute ischaemic stroke. 16 patients were studied within 6-48 hours (mean, 23 h) after onset of symptoms from a first hemispheric stroke and again 13-25 days later (mean, 15.6 days). Regional cerebral metabolic rates of oxygen (CMRO2) and glucose (CMRGlc), blood flow (CBF) and blood volume (CBV) were measured and oxygen extraction (OEF) as well as glucose extraction (GEF) and microvascular transit time were calculated. PET images were three-dimensionally aligned using serial CT or MRI scans. Regions of interest on the side of the infarction were individually compared to contralateral mirror regions. In the infarction core CBF, CMRO2 and CMRGlc were significantly lower than on the contralateral side and did not change during time. In the periinfarct regions there was a decreased CMRO2 with progressive deterioration over time while CBF slightly increased. Only in a few ischaemic regions with initially increased OEF oxygen metabolism was preserved during the course of time.

Blood Volume↗