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Biomedical subjects

E Salmon

Publications and source records attributed to E Salmon.

At least 37 records · Page 2Linked to original sources
PubMed2001

Positron emission tomography in evaluation of dementia: Regional brain metabolism and long-term outcome.

CONTEXT: Deficits in cerebral glucose utilization have been identified in patients with cognitive dysfunction attributed to various disease processes, but their prognostic and diagnostic value remains to be defined. OBJECTIVE: To assess the sensitivity and specificity with which cerebral metabolic patterns at a single point in time forecast subsequent documentation of progressive dementia. DESIGN, SETTING, AND PATIENTS: Positron emission tomography (PET) studies of [(18)F]fluorodeoxyglucose in 146 patients undergoing evaluation for dementia with at least 2 years' follow-up for disease progression at the University of California, Los Angeles, from 1991 to 2000, and PET studies in 138 patients undergoing evaluation for dementia at an international consortium of facilities, with histopathological diagnoses an average of 2.9 years later, conducted from 1984 to 2000. MAIN OUTCOME MEASURES: Regional distribution of [(18)F]fluorodeoxyglucose in each patient, classified by criteria established a priori as positive or negative for presence of a progressive neurodegenerative disease in general and of Alzheimer disease (AD) specifically, compared with results of longitudinal or neuropathologic analyses. RESULTS: Progressive dementia was detected by PET with a sensitivity of 93% (191/206) and a specificity of 76% (59/78). Among patients with neuropathologically based diagnoses, PET identified patients with AD and patients with any neurodegenerative disease with a sensitivity of 94% and specificities of 73% and 78%, respectively. The negative likelihood ratio of experiencing a progressive vs nonprogressive course over the several years following a single negative brain PET scan was 0.10 (95% confidence interval, 0.06-0.16), and the initial pattern of cerebral metabolism was significantly associated with the subsequent course of progression overall (P<.001). CONCLUSION: In patients presenting with cognitive symptoms of dementia, regional brain metabolism was a sensitive indicator of AD and of neurodegenerative disease in general. A negative PET scan indicated that pathologic progression of cognitive impairment during the mean 3-year follow-up was unlikely to occur.

Aged↗
PubMed2001

Neural and cognitive bases of upper limb apraxia in corticobasal degeneration.

OBJECTIVE: To investigate the neural and cognitive bases of upper limb apraxia in corticobasal degeneration (CBD). METHODS: Eighteen patients with CBD underwent a cognitive neuropsychological assessment of apraxia and resting [(18)F]-fluorodeoxyglucose PET scanning. Two complementary measures of apraxia were computed for each modality of gesture production. First, a performance score measured error frequency during gesture execution. Second, as a more stringent test of the integrity of the praxis system, the correction score measured the patient's ability to correct his or her errors on a second attempt. For each measure type, a cut-off score for the presence of apraxia was defined with regard to healthy controls. Using each cut-off score, the regional cerebral glucose metabolism of patients with CBD with apraxia (i.e., performing below cut-off score) was compared with that of patients with CBD without apraxia. RESULTS: Mean performance scores were below normal values in all modalities. Anterior cingulate hypometabolism predominated in patients with CBD who performed below the cut-off performance score. At variance, mean correction scores were below normal values for gesture imitation only. Hypometabolism in superior parietal lobule and supplementary motor area characterized patients with CBD who were unable to correct their errors at the same rate as control subjects did. CONCLUSIONS: Distinct neural networks underlie distinct aspects of the upper limb apraxic deficits in CBD. Extending previous findings of gesture production deficits in CBD, the use of complementary measures of apraxic behavior discloses a visuoimitative upper limb apraxia in CBD, underlain by a metabolic decrease in a parietofrontal neural network.

Aged↗
PubMed2001

The neural substrate of orientation working memory.

We have used positron emission tomography (PET) to identify the neural substrate of two major cognitive components of working memory (WM), maintenance and manipulation of a single elementary visual attribute, i.e., the orientation of a grating presented in central vision. This approach allowed us to equate difficulty across tasks and prevented subjects from using verbal strategies or vestibular cues. Maintenance of orientations involved a distributed fronto-parietal network, that is, left and right lateral superior frontal sulcus (SFSl), bilateral ventrolateral prefrontal cortex (VLPFC), bilateral precuneus, and right superior parietal lobe (SPL). A more medial superior frontal sulcus region (SFSm) was identified as being instrumental in the manipulative operation of updating orientations retained in the WM. Functional connectivity analysis revealed that orientation WM relies on a coordinated interaction between frontal and parietal regions. In general, the current findings confirm the distinction between maintenance and manipulative processes, highlight the functional heterogeneity in the prefrontal cortex (PFC), and suggest a more dynamic view of WM as a process requiring the coordinated interaction of anatomically distinct brain areas.

Adult↗
PubMed2001

The functional anatomy of inhibition processes investigated with the Hayling task.

The cortical areas involved in inhibition processes were examined with positron emission tomography (PET). The tasks administered to subjects were an adaptation of the Hayling test. In the first condition (response initiation), subjects had to complete sentences with a word clearly suggested by the context, whereas in the second condition (response inhibition), subjects had to produce a word that made no sense in the context of the sentence. Results indicated that the response initiation processes were associated to increases of activity in the left inferior frontal gyrus (BA 45/47), whereas response inhibition processes led to increases in a network of left prefrontal areas, including the middle (BA 9 and BA 10) and inferior (BA 45) frontal areas.

Adult↗
PubMed2001

Acquisition of a novel vocabulary in an amnesic patient.

This study explored the ability of a severe amnesic patient (AC) to acquire new vocabulary words. We compared AC's knowledge of words entered into the French lexicon during three different periods: before 1920, between 1965 and 1985, and after 1986 (i.e. after the onset of his amnesia). AC's knowledge was assessed by asking him to give, for each word, its definition (word-definition task), the general domain to which the word belonged ("domain" task), and to generate a sentence containing the word (sentence-generation task). Finally, we administered a recognition task in which AC had to select, for each word, its correct definition amongst four definitions. For all of these tasks, the results showed that AC's performance was similar to that of four control subjects matched for age, education, and profession. In particular, there was no difference with regard to AC's knowledge of words entered into the language after the onset of his amnesia. Therefore, these results indicate that, despite his profound amnesia, AC was able to learn normally new vocabulary words. More generally, they confirm that, at least is some cases, semantic learning can be spared in amnesia.

Adult↗
PubMed2001

[A day care center for management of early stage Alzheimer's disease].

Alzheimer's disease represents an important problem for our societies, both in social and economical dimensions. Built in July 1997, the day care center of Liège aims at practicing strategic cognitive interventions in early Alzheimer patients or when pathological memory impairments occur. By means of an interdisciplinary work (by neuropsychologists and occupational therapists), the ultimate goal of the interventions is to facilitate the patient's autonomy in activities of daily living. Because of the variability of clinical symptoms of the disease, the goal of these cognitive interventions is to optimize the performance of each patient by making the most of its preserved abilities. Moreover, another goal of the day care center is also to support the caregivers, by giving them advices in order to adequately face with difficulties presented by the patient.

Activities of Daily Living↗
PubMed2001

[Dementia in Belgium: prevalence in aged patients consulting in general practice].

Early detection of dementia is an important element for the efficacy of therapies currently proposed to slow down disease progression. This detection mainly relies on general practitioners. In order to estimate the impact of dementia on health services, we have estimated from the data of the NAtional Dementia Economic Study (NADES) the prevalence rate of dementia in patients aged > or = 65 years living at home and consulting in general practice. The study population was based on the sampling of consecutive patients consulting a general practitioner, irrespective of the reason and location of the consultation. The diagnosis of dementia was based on the CAMDEX performed at home in patients presenting > or = 3 warning signs of dementia. The prevalence rate of dementia among 2.234 registered patients living at home was 14.3% (CI95: 12.6-16.0). In age groups 65-74, 75-84 and > or = 85 years, it was 7.0%, 17.5% and 18.5%, respectively, in men, and 6.1%, 15.8% and 25.2%, respectively, in women. The percentage of demented with mild, mild to moderate, moderate and severe dementia was 35.0%, 38.8%, 13.1% and 13.1%, respectively. After adjusting for the age and sex distribution of the Belgian population, the prevalence rate in patients aged > or = 65 years was estimated at 11.3%. A diagnosis of dementia had already been made by a specialist in 41.5% of patients with dementia, with figures of 19.3%, 34.3%, 41.9% and 60.9% according to the severity of disease (mild, mild to moderate, moderate, severe). The onset of first symptoms had preceded the diagnosis by an average of 1 year. Our results show a high prevalence rate of dementia in the elderly living at home consulting in general practice, and less than half of the patients had previously been diagnosed. It is possible that a systematic detection will not be performed as long as specific treatments are not made widely available.

Aged↗
PubMed2001

Guidelines for brain radionuclide imaging. Perfusion single photon computed tomography (SPECT) using Tc-99m radiopharmaceuticals and brain metabolism positron emission tomography (PET) using F-18 fluorodeoxyglucose. The Belgian Society for Nuclear Medicine.

The purpose of these guidelines is to assist nuclear medicine practitioners in recommending, performing, interpreting, and reporting the results of brain perfusion SPECT studies using Tc-99m radiopharmaceuticals and brain metabolism PET studies using F-18 fluorodeoxyglucose (FDG). These guidelines have been adapted and extended from those produced by the Society of Nuclear Medicine (Juni et al., 1998) and the European Association of Nuclear Medicine by a Belgian group of experts in the field trained in neurology and/or nuclear medicine. Some indications are not universally approved (e.g. brain death), but largely supported by the literature. They have been included in these guidelines in order to provide recommendations and a standardised protocol.

Acetazolamide↗
PubMed2000

Correlation of intellectual impairment in Parkinson's disease with FDG PET scan.

This study investigated the relationship between regional glucose metabolism with intellectual impairment in patients with Parkinson's disease using statistical parametric mapping. Regional cerebral glucose metabolism using [18F]deoxyglucose (FDG) PET scans were performed on 10 patients with Parkinson's disease. We used the intellectual impairment score from the UPDRS. PET scans were analyzed with SPM96. Patients showed significant positive correlations with left limbic structures such as the cingulate gyrus, parahippocampal gyrus, and medial frontal gyrus. Patients showed significant negative correlations with associative neocortical posterior structures such as bilateral parietal and occipital gyrus. There were significant relationships between regional glucose metabolism and intellectual impairment.

Aged↗
PubMed2000

Voxel-based analysis of confounding effects of age and dementia severity on cerebral metabolism in Alzheimer's disease.

Alzheimer's disease is characterized by early hippocampal lesions, but neuropathological and functional imaging studies have also demonstrated involvement of associative cortices in patients suffering from this illness. New image-processing technologies have led to demonstration of predominant posteromedial cortical metabolic impairment in the disease. Confounding effects of both age and dementia severity on brain metabolism were assessed using categorical and correlational analyses performed with Statistical Parametric Mapping. Posterior cingulate and precuneus metabolism, assessed by positron emission tomography, was significantly correlated with age in a population of 46 patients with probable Alzheimer's disease. Metabolism in posterior cingulate and precuneus was higher in elderly than in younger patients with a diagnosis of Alzheimer's disease, even when dementia severity was taken as a confounding covariate. The data suggest that the sensitivity of positron emission tomography for the diagnosis of Alzheimer's disease is reduced in elderly cases, where less severe pathology is sufficient to induce clinical symptoms of dementia. Conversely, higher posteromedial metabolic impairment in early onset cases may reflect greater density of regional cerebral lesions or major decrease of functional afferences in a richly connected multimodal associative area. Posterior cingulate metabolism was also correlated to dementia severity, even when age was taken as a confounding covariate, whereas metabolism in the hippocampal formation was not shown to correlate with global cognitive deficit. Functional correlation was maintained between posterior cingulate and middle frontal cortex in demented patients as in elderly controls. The key role of posteromedial cortex in cognitive dysfunction assessed in Alzheimer's disease is probably related to its highly integrated position within attentional, visuospatial and memory neuronal networks.

Age Factors↗
PubMed2000

Voxel-based distribution of metabolic impairment in corticobasal degeneration.

This report emphasizes the precise topographic distribution of cerebral metabolic impairment in corticobasal degeneration (CBD) and the pathophysiological differences between CBD and progressive supranuclear palsy (PSP). Statistical parametric mapping (SPM96) analysis of 18FDG positron emission tomography (PET) data was performed in 22 patients with CBD compared with 46 healthy subjects (HS) and 21 patients with PSP who were studied at rest. A statistical threshold of p <0.001 was fixed, further corrected for multiple or independent comparisons (p <0.05). In comparison with HS, the metabolic impairment in CBD was asymmetrically distributed in the putamen, thalamus, precentral (Brodmann's area, BA 4), lateral premotor (BA 6/44) and supplementary motor areas (SMA, BA 6), dorsolateral prefrontal (8/9/46) cortex, and the anterior part of the inferior parietal lobe (BA 40) including the intraparietal sulcus (BA 7/40). A similar hypometabolic pattern was observed for most individual analyses. When PSP was compared with CBD, metabolic impairment predominated in the midbrain, anterior cingulate (BA 24/32), and orbitofrontal regions (BA 10). The reverse contrast showed more posterior involvement in CBD (BA 6 and 5/7/40) including SMA. Our data suggest that multiple components of neural networks related to both movement execution and production of skilled movements are functionally disturbed in CBD compared with both HS and PSP.

Adult↗
PubMed2000

The role of lateral occipitotemporal junction and area MT/V5 in the visual analysis of upper-limb postures.

Humans, like numerous other species, strongly rely on the observation of gestures of other individuals in their everyday life. It is hypothesized that the visual processing of human gestures is sustained by a specific functional architecture, even at an early prelexical cognitive stage, different from that required for the processing of other visual entities. In the present PET study, the neural basis of visual gesture analysis was investigated with functional neuroimaging of brain activity during naming and orientation tasks performed on pictures of either static gestures (upper-limb postures) or tridimensional objects. To prevent automatic object-related cerebral activation during the visual processing of postures, only intransitive postures were selected, i. e., symbolic or meaningless postures which do not imply the handling of objects. Conversely, only intransitive objects which cannot be handled were selected to prevent gesture-related activation during their visual processing. Results clearly demonstrate a significant functional segregation between the processing of static intransitive postures and the processing of intransitive tridimensional objects. Visual processing of objects elicited mainly occipital and fusiform gyrus activity, while visual processing of postures strongly activated the lateral occipitotemporal junction, encroaching upon area MT/V5, involved in motion analysis. These findings suggest that the lateral occipitotemporal junction, working in association with area MT/V5, plays a prominent role in the high-level perceptual analysis of gesture, namely the construction of its visual representation, available for subsequent recognition or imitation.

Adult↗
PubMed2000

[(18)F]p-MPPF: aA radiolabeled antagonist for the study of 5-HT(1A) receptors with PET.

This paper summarizes the present status of the researches conducted with [(18)F]4-(2'-methoxyphenyl)-1-[2'-[N-(2"-pyridinyl)-p-fluorobenzamido ]ethyl]-piperazine known as [(18)F]p-MPPF, a new 5-HT(1A) antagonist for the study of the serotonergic neurotransmission with positron emission tomography (PET). This includes chemistry, radiochemistry, animal data (rats, cats, and monkeys) with autoradiography and PET, human data with PET, toxicity, and metabolism.

Aminopyridines↗
PubMed2000

[A neuropsychological and functional brain imaging study of visuo-imitative apraxia].

We describe the case of a 58-years-old right-handed women suffering from an occipital-parietal lesion. The administration of a cognitively based assessment tool for limb praxis (Batterie d'Evaluation des Praxies, B.E.P., Peigneux and Van der Linden, 1998) demonstrated bilateral visuo-imitative apraxia. Gesture production was mainly characterised by spatial, errors, and imitation of meaningful gestures was worse than their pantomime on verbal command. Moreover, the imitation of meaningless gestures and their reproduction on a manikin were worse than imitation of their matched meaningful gestures. In a cognitive perspective, adapted from the Rothi et al. (1997) and Goldenberg (1995) contributions to our understanding of limb praxis, this configuration of performance suggests deficits occurring at multiple levels. On one hand, it suggests either access difficulties or alteration of the output praxicon, i.e., the lexicon for visuo-kinesthetic engrams of meaningful gestures. On the other hand, the simultaneous deficit for meaningless gesture reproduction on the subject's own body and on a manikin favors an alteration of the structural descriptions of the human body (i.e., human body knowledge), underlying the mental transposition processes occurring between the visual analysis of a meaningless gestural configuration and its effective reproduction on oneself or on a manikin, thus contradicting the classic view of a direct pathway linking visual analysis and motor planning in meaningless gesture imitation. Finally, due to the output praxicon deficit, imitation of meaningful gestures is partly processed in the same way as meaningless gestures (also impaired in this case), leading to an interference effect between both degraded memory-based and visually-transposed traces, which account for imitation of meaningful gestures being worse than their pantomime on verbal command. We also assess regional cerebral metabolism using positron emission tomography (PET). Comparison with 41 healthy subjects (SPM96) demonstrated a statistically significant hypometabolism in the left intraparietal sulcus and superior parietal lobule, and in the right dorsal prestriate cortex. These results, together with a review of the other studies of visuo-imitative apraxia, suggest that the left intraparietal sulcus may be associated with access or integration of information from the output praxicon. The left superior parietal and the right dorsal prestriate deficits functionally impaired a bilateral dorsal network implied in the mental transformations of the body, thus suggesting that these mental transformations are underlined by knowledge of the human body, which may subsequently explain the deficit for the reproduction of meaningless and meaningful configurations.

Aged↗
PubMed2000

[An update of diagnostic and therapeutic procedures in Alzheimer disease].

Early diagnosis of Alzheimer's disease is difficult, but neuropsychological tests become quite sensitive, and neuroimaging gives useful information. Criteria for differential diagnosis appear in the literature, but vascular dementia remains an ill-defined concept. There are ongoing researches on possible therapeutic interferences with formation of histological brain lesions. Meanwhile, treatments are symptomatic and should be started as early as possible. Both inhibitors of acetylcholinesterase and cognitive rehabilitation in day-care centres fulfill therapeutic criteria for dementia, i.e. improvement or stabilization of cognitive impairment and daily life activities.

Activities of Daily Living↗
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

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↗