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C Degueldre

Publications and source records attributed to C Degueldre.

At least 37 records · Page 2Linked to original sources
PubMed1999

Medial temporal lobe metabolic impairment in dementia associated with motor neuron disease.

In the course of their disease certain patients with frontotemporal dementia (FTD) develop clinical features compatible with a motor neuron disease (FTD-MND). Previous reports have suggested that the functional pattern is similar in FTD and FTD-MND. However, some neuropathological studies suggest greater involvement of medial temporal regions in FTD-MND than in FTD. Using statistical parametric mapping (SPM96), we compared the metabolic patterns obtained at rest with positron emission tomography in 10 FTD patients and three FTD-MND patients with those obtained from 46 healthy subjects (HS). Mean age, duration of illness and dementia stage did not differ statistically between the FTD and FTD-MND groups. In comparison with HS, both groups showed frontal and anterior temporal hypometabolism at P<0.001. When the FTD-MND group was compared to the FTD group, significant hypometabolism was only observed in bilateral amygdala, bilateral hippocampus, and bilateral enthorinal and parahippocampal regions (Brodmann's areas, BA 28/36) at P<0.005. We found no significant differences in regional glucose uptake when FTD patients were contrasted to FTD-MND patients. Our results suggest statistically comparable frontal and lateral temporal hypometabolism in both conditions but greater impairment of medial temporal lobe activity in FTD-MND. Our results and a review of the literature support the hypothesis that there is a functional continuum between classical motor neuron disease (cMND), FTD-MND, and FTD.

Aged↗
PubMed1999

Functional neuroanatomy of hypnotic state.

BACKGROUND: The aim of the present study was to describe the distribution of regional cerebral blood flow during the hypnotic state (HS) in humans, using positron-emission tomography (PET) and statistical parametric mapping. METHODS: The hypnotic state relied on revivification of pleasant autobiographical memories and was compared to imaging autobiographical material in "normal alertness." A group of 9 subjects under polygraphic monitoring received six H215O infusions and was scanned in the following order: alert-HS-HS-HS with color hallucination-HS with color hallucination-alert. PET data were analyzed using statistical parametric mapping (SPM95). RESULTS: The group analysis showed that hypnotic state is related to the activation of a widespread, mainly left-sided, set of cortical areas involving occipital, parietal, precentral, premotor, and ventrolateral prefrontal cortices and a few right-sided regions: occipital and anterior cingulate cortices. CONCLUSIONS: The pattern of activation during hypnotic state differs from those induced in normal subjects by the simple evocation of autobiographical memories. It shares many similarities with mental imagery, from which it differs by the relative deactivation of precuneus.

Adult↗
PubMed1999

Comparison of impaired subcortico-frontal metabolic networks in normal aging, subcortico-frontal dementia, and cortical frontal dementia.

Normal aging, progressive supranuclear palsy (PSP), and frontotemporal dementia (FTD) are characterized by different degrees of decline in frontal lobe functions. We used (18)FDG-PET and statistical parametric mapping (SPM96) to compare relative subcorticofrontal metabolic impairment at rest in 21 healthy elderly subjects (HES), 20 PSP patients, and 6 FTD patients. When HES were compared to 22 healthy young subjects, widespread decrease in metabolism was observed in bilateral medial prefrontal areas including anterior cingulate cortices, in dorsolateral prefrontal areas, in left lateral premotor area, in Broca's area, and in left insula. In PSP compared to the 43 healthy subjects (HS), we observed subcorticofrontal metabolic impairment including both motor and cognitive neural networks. Impairment of functional connections between midbrain tegmentum and cerebellar, temporal and pallidal regions was demonstrated in PSP as compared to HS. When comparing FTD to HS, glucose uptake was primarily reduced in dorsolateral and ventrolateral prefrontal cortices and in frontopolar and anterior cingulate regions. There was also bilateral anterior temporal, right inferior parietal, and bilateral striatal hypometabolism. Finally, FTD showed more severe striatofrontal metabolic impairment than PSP, while mesencephalothalamic involvement was only observed in PSP. Our data suggest that subcorticofrontal metabolic impairment is distributed in distinct subcorticocortical networks in normal aging, PSP, and FTD. Subcorticofrontal dementia in PSP is related to hypometabolism in discrete frontal areas, which are probably disconnected from certain subcortical structures. The concept of subcortical dementia is reinforced by our data, which show disrupted functional connections between mesencephalon and cerebellar cortex, inferior and medial temporal regions, and pallidum.

Adult↗
PubMed1999

Fluorodopa uptake and glucose metabolism in early stages of corticobasal degeneration.

Fluorodopa (FDOPA) and fluorodeoxyglucose (FDG) PET was performed in six patients in early stages of corticobasal degeneration (CBD) and compared to Parkinson's disease (PD) patients with a similar degree of bradykinesia and rigidity and to healthy controls. Statistical parametric mapping analysis comparing CBD to controls showed metabolic decrease in premotor, primary motor, supplementary motor, primary sensory, prefrontal, and parietal associative cortices, and in caudate and thalamus contralateral to the side of clinical signs. Except for the prefrontal regions a similar metabolic pattern was observed when CBD was compared to PD. Putamen FDOPA uptake was decreased in both CBD and PD. Caudate FDOPA uptake in CBD patients was decreased contralateral to clinical signs when compared to controls, but was higher than in PD. In early stages of CBD, FDOPA and FDG PET patterns differed from those observed in PD. In CBD the asymmetry in FDOPA uptake was less pronounced than that of clinical signs or metabolic impairment.

Aged↗
PubMed1999

Regional brain activity during tasks devoted to the central executive of working memory.

Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish precisely the functions of the CE from the storage function of the slave systems. The aim of the present study was to isolate brain areas that subserve manipulation of information by the CE when the influence of storage function was removed. A PET activation study was performed with four cognitive tasks, crossing conditions of temporary storage and manipulation of information. The manipulation of information induced an activation in the right (BA 10/46) and left (BA 9/6) middle frontal gyrus and in the left parietal area (BA7). The interaction between the storage and manipulation conditions did not reveal any significant changes in activation. These results are in agreement with the hypothesis that CE functions are distributed between anterior and posterior brain areas, but could also reflect a simultaneous involvement of controlled (frontal) and automatic (parietal) attentional systems. In the other hand, the absence of interaction between the storage and manipulation conditions demonstrates that the CE is not necessarily related to the presence of a memory load.

Adult↗
PubMed1999

Early thalamic and cortical hypometabolism in adult-onset dementia due to metachromatic leukodystrophy.

A case of early-onset adult dementia with family history of dementia is reported, characterised by neuropsychological deficits, suggesting frontal involvement, with mild non specific white matter abnormalities on CT scan. Familial Alzheimer's disease was suspected but the neuropathological diagnosis on brain biopsy was metachromatic leukodystrophy. 18FDG-PET revealed a very peculiar pattern of metabolic impairment in thalamic areas, in medial and frontopolar regions, and in occipital lobes. Neuropsychological follow-up showed relatively stable difficulties of long-term memory and signs of frontal lobe dysfunction, similar to those observed in subcortical dementias. MRI subsequently showed periventricular leukoencephalopathy. The brain metabolic pattern observed in that case of metachromatic leukodystrophy was quite different from that reported in other types of dementia.

Adult↗
PubMed1998

The role of early measurement of nitrogen-13 ammonia uptake for predicting contractile recovery after acute myocardial infarction.

Previous studies have shown that the maintenance of cell membrane integrity and metabolism requires the persistence of residual myocardial blood flow. The purpose of this study was to assess the role of N-13 ammonia positron emission tomographic (PET) imaging performed early after an acute myocardial infarction for predicting functional recovery. Seventeen patients with an acute myocardial infarction were included in the study. Thirteen received thrombolytic therapy, 2 underwent immediate angioplasty of the infarct-related artery and 2 were treated with heparin. N-13 ammonia imaging was performed 6 +/- 2 days after the acute event and was followed by elective angioplasty in 13 patients. Using a 16-segment polar map display, regional N-13 ammonia uptake was expressed as a percentage of maximal segmental uptake and classified as normal (> 63%), moderately reduced (63-50%) and severely reduced (< 50%) based on values of tracer uptake obtained from healthy subjects. By echocardiographic assessment of regional wall thickening within 96 hours and at 1 month after the infarct, we examined the relationship between blood flow and functional outcome of myocardial segments in the infarct-related area. Regional wall thickening was graded on a 4-point scale: normal (1), hypokinesia (2), akinesia (3) and dyskinesia (4). Of 77 dyssynergic segments at baseline echocardiographic study, 43 had normal flow, 15 moderately reduced flow and 19 severely reduced flow. Segments with N-13 ammonia uptake > or = 50% demonstrated a significant improvement in wall thickening score at follow-up (p < 0.001), whereas segments with N-13 ammonia uptake < 50% showed no improvement in wall thickening scores (p < 0.001). The proportion of segments improving contractility by at least 1 score was significantly higher in the group of segments with N-13 ammonia uptake > 63%. The predictive value for defining functional recovery with segmental N-13 ammonia uptake > 63% was 86%. The predictive value for absence of recovery (uptake < 50%) was 54%. In conclusion, our data showed that early after an acute myocardial infarction N-13 ammonia imaging provides information regarding functional outcome.

Ammonia↗
PubMed1998

Preoperative evaluation of 54 gliomas by PET with fluorine-18-fluorodeoxyglucose and/or carbon-11-methionine.

UNLABELLED: This study evaluates the usefulness of PET for the preoperative evaluation of brain gliomas and methods of quantification of PET results. METHODS: Fifty-four patients with brain gliomas were studied by PET with 18F-fluorodeoxyglucose (FDG) (n = 45) and/or 11C-methionine (MET) (n = 41) before any treatment. Results of visual analysis, calculation of glucose consumption and five tumor-to-normal brain ratios for both tracers were correlated with two histologic grading systems and with follow-up. RESULTS: Visual analysis (for FDG) and tumor-to-mean cortical uptake (T/MCU) ratio proved to be the best tools for the evaluation of PET results. Methionine was proven to be better than FDG at delineating low-grade gliomas. Tumor-to-mean cortical uptake ratios for FDG and MET were clearly correlated (r = 0.78), leading to the equation T/MCU(FDG) = 0.4 x T/MCU(MET). We showed a good correlation between FDG PET and histologic grading. MET uptake could not differentiate between low-grade and anaplastic astrocytomas but was significantly increased in glioblastomas. Low-grade oligodendrogliomas exhibited high uptake of FDG and MET, probably depending more on oligodendroglial cellular differentiation than on proliferative potential. Uptake was decreased in anaplastic oligodendrogliomas, probably due to dedifferentiation. Care must be taken with peculiar histologic subgroups, i.e., juvenile pilocytic astrocytomas and oligodendrogliomas, because of a discrepancy between high PET metabolism and low proliferative potential (good prognosis). Both tracers proved useful for the prediction of survival prognosis. Methionine proved slightly superior to FDG for predicting the histologic grade and prognosis of gliomas, despite the impossibility of differentiation between Grades II and III astrocytomas with MET. This superiority of MET could be explained by patient sampling (low number of Grade III gliomas submitted to examination with both tracers). The combination of both tracers improved the overall results compared to each tracer alone. CONCLUSION: Both tracers are useful for the prediction of the histologic grade and prognosis. The apparent superiority of MET over FDG could be due to the small number of Grade III gliomas studied with both tracers.

Brain↗
PubMed1997

Functional neuroanatomy of human slow wave sleep.

The distribution of regional cerebral blood flow (rCBF) was estimated during sleep and wakefulness by using H215O positron emission tomography (PET) and statistical parametric mapping. A group analysis on 11 good sleepers (8 with steady slow wave sleep, SWS) showed a significant negative correlation between the occurrence of SWS and rCBF in dorsal pons and mesencephalon, thalami, basal ganglia, basal forebrain/hypothalamus, orbitofrontal cortex, anterior cingulate cortex, precuneus, and, on the right side, in a region that follows the medial aspect of the temporal lobe. Given the known decrease in global cerebral blood flow levels during SWS, these negative correlations suggest that rCBF is decreased significantly more in these cerebral areas than in the rest of the brain. The marked rCBF decreases in the pons, mesencephalon, thalamic nuclei, and basal forebrain reflect their close implication in the generation of SWS rhythms. The influence of these rhythms on the telencephalon usually are thought to be global and homogeneous. In contrast, our results show that rCBF is decreased more in some cortical areas (especially in orbitofrontal cortex) than in the rest of the cortex. We hypothesize that cellular processes taking place during SWS might be modulated differently in these regions. Given the functions of the ventromedial frontal areas, we surmise that SWS might be particularly critical for the adaptation of behavior to environmental pressures. This hypothesis is supported indirectly by results of sleep deprivation experiments.

Adult↗
PubMed1997

Functional anatomy of verbal and visuospatial span tasks in Alzheimer's disease.

The aim of the study was to emphasize cerebral regions which subserve the performance of short-term memory tasks in patients with Alzheimer's disease. We correlated scores obtained on span tasks with cerebral metabolism measured at rest with positron emission tomography. Scores obtained on the digit span task correlated with glucose metabolism in a brain area centered on the premotor cortex and extending to the adjacent motor and parietal gyri. There exists some evidence suggesting that this area may subserve the sequential organization of material stored in short-term memory. In a secondary analysis, we also observed significant interregional correlations between left-sided brain areas which are part of the neural network subserving verbal working memory processes in healthy controls. These data suggest that individual performance on verbal span tasks in AD patients may essentially depend on the preservation of their ordination processing capacity. The absence of correlation with prefrontal regions suggests that AD patients might not spontaneously engage central executive resources to reach their maximal span score. For simultaneous visuospatial span task, the performance of patients correlated with posterior brain regions, and not with prefrontal cortices.

Aged↗
PubMed1997

Relation between contractile reserve and positron emission tomographic patterns of perfusion and glucose utilization in chronic ischemic left ventricular dysfunction: implications for identification of myocardial viability.

OBJECTIVES: This study sought to determine the incidence and extent of dobutamine-induced contractile reserve in myocardial regions characterized by classical and new positron emission tomographic (PET) patterns in patients with chronic ischemic left ventricular dysfunction. BACKGROUND: PET is considered the most accurate method for assessment of myocardial viability, which is traditionally identified by perfusion-metabolism mismatch. METHODS: In 23 patients, segmental wall thickening expressed by four echocardiographic scores at rest and during low dose (5 and 10 microg/kg body weight per min) dobutamine infusion and regional myocardial uptake of potassium-38 and fluorine-18 fluorodeoxyglucose (F-18 FDG) during glucose clamp were compared in 16 corresponding segments. RESULTS: Of a total of 368 segments, data analysis focused on 214 (58%) dyssynergic segments at baseline. Contractile reserve was identified with increasing incidence according to the six following PET patterns: 1) diminished perfusion and moderate reduction of F-18 FDG uptake (3 [11%] of 28 segments); 2) proportional reduction of perfusion and F-18 FDG uptake (10 [23%] of 43 segments); 3) perfusion-metabolism mismatch (19 [46%] of 41 segments); 4) preserved perfusion but moderate reduction of F-18 FDG uptake (13 [46%] of 27 segments); 5) preserved perfusion and F-18 FDG uptake (37 [59%] of 63 segments) compared with our normal database; and 6) normal perfusion but absolute increased F-18 FDG uptake (8 [73%] of 11 segments). In the latter category, only 7 of 24 segments had normal rest function. In dyssynergic segments with F-18 FDG uptake > or = 50% supplied by vessels with > or = 75% stenosis, improvement in contractility during dobutamine correlated with the presence of collateral channels. CONCLUSIONS: Myocardial regions with the traditional mismatch pattern of viability show contractile reserve in slightly < 50%. In segments with moderate reduction of F-18 FDG uptake, the contractile response to dobutamine is linked to the level of rest perfusion. Most segments with preserved perfusion and increased F-18 FDG uptake have impaired rest function, but contractile reserve is still present. These data suggest that in chronic ischemic left ventricular dysfunction, myocardial hibernation is a heterogeneous condition.

Dobutamine↗
PubMed1996

Functional neuroanatomy of human rapid-eye-movement sleep and dreaming.

Rapid-eye-movement (REM) sleep is associated with intense neuronal activity, ocular saccades, muscular atonia and dreaming. The function of REM sleep remains elusive and its neural correlates have not been characterized precisely in man. Here we use positron emission tomography and statistical parametric mapping to study the brain state associated with REM sleep in humans. We report a group study of seven subjects who maintained steady REM sleep during brain scanning and recalled dreams upon awakening. The results show that regional cerebral blood flow is positively correlated with REM sleep in pontine tegmentum, left thalamus, both amygdaloid complexes, anterior cingulate cortex and right parietal operculum. Negative correlations between regional cerebral blood flow and REM sleep are observed bilaterally, in a vast area of dorsolateral prefrontal cortex, in parietal cortex (supramarginal gyrus) as well as in posterior cingulate cortex and precuneus. Given the role of the amygdaloid complexes in the acquisition of emotionally influenced memories, the pattern of activation in the amygdala and the cortical areas provides a biological basis for the processing of some types of memory during REM sleep.

Adult↗
PubMed1996

Brain activation induced by estimation of duration: a PET study.

Duration information about a visual stimulus requires processing as do other visual features such as size or intensity. Using positron emission tomography, iterative H215O infusions, and statistical parametric mapping, we investigated the neural correlates of time processing. Nine normal subjects underwent six serial rCBF. Three tasks were studied: (a) A temporal generalization task (D task) in which the subjects had to judge (by pressing one of two keys) whether the duration of the illumination of a green LED was equal to or different from that of a previously presented standard; (b) An intensity generalization task (I task) in which the judgment concerned the intensity of the LED; and (c) A control task (C task) in which the subjects had to press one of the two keys at random in response to LED illumination. A significant increase in rCBF during the D task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, anterior cingulate cortex, vermis, and a region corresponding to the left fusiform gyrus. A significant increase in rCBF during the I task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, right extrastriate cortex, anterior cingulate cortex, left inferior parietal lobule, vermis, and two symmetrical regions corresponding to the fusiform gyri. No significant activation was observed in the D task when compared to that in the I task. We propose that these cortical maps are best explained by the recruitment of visual attention and memory structures, which play a major role in prospective time judgements as indicated by behavioral studies. The data also suggest that the temporal dimension of a visual stimulus is processed in the same areas as other visual attributes.

Adult↗
PubMed1996

Regional brain activity during working memory tasks.

The first aim of our PET study was to replicate previous findings concerning the brain areas activated by a verbal working memory task. The second aim was to specify the neural basis of the central executive, using a task of working memory updating. Our data confirm that the lower left supramarginal gyrus and premotor area are the key regions subserving short-term verbal memory processes. They also suggest that the updating memory task is related to middorsolateral prefrontal activation, most probably responsible for the updating function of the central executive. An unexpected, predominantly right activation occurred in the inferior parietal region during the verbal memory updating task, which we related to a visuospatial strategy used to maintain the information in short-term memory. A third purpose was to explore the brain regions activated by a nonverbal, visual memory task, and our results confirm the importance of the superior occipital gyrus in the visual short-term memory.

Adult↗
PubMed1996

Combined study of cerebral glucose metabolism and [11C]methionine accumulation in probable Alzheimer's disease using positron emission tomography.

There is a characteristic decrease in glucose metabolism in associative frontal and temporo-parietal cortices of patients suffering from Alzheimer's disease (AD). The decrease in metabolism might result from local neuronal loss or from a decrease of synaptic activity. We measured in vivo [11C]methionine accumulation into proteins with positron emission tomography (PET) to assess cortical tissue loss in AD. Both global regional activity and compartmental analysis were used to express [11C]methionine accumulation into brain tissue. Glucose metabolism was measures with [18F]fluorodeoxyglucose and autoradiographic method. Combined studies were performed in 10 patients with probable AD, compared to age-matched healthy volunteers. There was a significant 45% decrease of temporo-parietal glucose metabolism in patients with AD, and frontal metabolism was lowered in most patients. Temporo-parietal metabolism correlated to dementia severity. [11C]methionine incorporation into temporo-parietal and frontal cortices was not significantly decreased in AD. There was no correlation with clinical symptoms. Data suggest that regional tissue loss, assessed by the decrease of [11C]methionine accumulation, is not sufficient to explain cortical glucose hypometabolism, which reflects, rather, reduced synaptic connectivity.

Aged↗
PubMed1996

Frontal lobe dementia presenting as personality disorder.

The early differential diagnosis of frontal lobe dementia is particularly difficult because changes of personality or behaviour overwhelm intellectual and cognitive impairments. We report the case of a patient presenting with paranoid personality disorder who refused to collaborate in neuropsychological testing. Initial functional imaging showed frontal hypometabolism that served as an early marker of frontal lobe dysfunction.

Brain↗
PubMed1996

Anterior cingulate dysfunction in presenile dementia due to progressive supranuclear palsy.

We report neuropsychological and neuroimaging investigations performed in a patient suffering from presenile onset degenerative dementia and subsequent mild extrapyramidal and pyramidal signs. Early neuropsychological testing revealed frontal lobe dysfunction. Neuroanatomical pictures were not contributive. After four years of evolution, the clinical pattern was consistent with progressive supranuclear palsy. Statistical parametric mapping analysis of functional imaging revealed a highly significant metabolic impairment in the anterior cingulate gyrus, that might be a key feature of subcortico-frontal dementia in progressive supranuclear palsy.

Brain↗