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J-C Baron

Publications and source records attributed to J-C Baron.

16 recordsLinked to original sources
PubMed2006

How affected is oxygen metabolism in DWI lesions?: A combined acute stroke PET-MR study.

OBJECTIVE: To use back-to-back diffusion-weighted imaging (DWI) and PET to obtain quantitative measures of the cerebral metabolic rate of oxygen (CMRO(2)) within DWI lesions, and to assess the perfusion-metabolism coupling status by measuring the cerebral blood flow and the oxygen extraction fraction within DWI lesions. METHODS: Six prospectively recruited acute carotid-territory stroke patients completed the imaging protocol, which was commenced 7 to 21 hours from onset and combined DWI derived from state-of-the-art diffusion tensor imaging sequencing using a 3-T magnet and fully quantitative (15)O-PET. The PET variables were obtained in individual DWI lesions in each patient. RESULTS: Across patients, the CMRO(2) was reduced in the DWI lesion relative to mirror (mean reduction 39.5%; p = 0.028). Examining individual DWI lesions, however, revealed considerable variability in the extent of this CMRO(2) reduction. The flow-metabolism coupling pattern underlying the DWI lesion was also variable, including ongoing ischemia, mild oligemia, and partial or complete reperfusion. DISCUSSION: Diffusion-weighted imaging (DWI) lesions generally reflect substantial disruption of energy metabolism. However, the degree of metabolic disruption is variable, indicating DWI lesions may not always represent irreversibly damaged tissue. Finally, because DWI lesions can persist despite reperfusion, assessment of perfusion is necessary for interpretation of DWI changes in acute stroke.

Aged↗
PubMed2006

Does healthy aging affect the hemispheric activation balance during paced index-to-thumb opposition task? An fMRI study.

Normal aging is generally associated with declining performance in cognitive and fine motor tasks. Previous functional imaging studies have been inconsistent regarding the effect of aging on primary motor cortex (M1) activation during finger movement, showing increased, unchanged or decreased activation contralaterally, and more consistently increased activation ipsilaterally. Furthermore, no study has addressed the effect of age on M1 hemispheric activation balance. We studied 18 optimally healthy right-handed subjects, age range 18-79 years (mean +/- SD: 47 +/- 17) using 3 T fMRI and right index finger-thumb tapping auditory-paced at 1.25 Hz. The weighted Laterality Index (wLI) for M1 was obtained according to Fernandez et al. (2001) [Fernandez, G., de Greiff, A., von Oertzen, J., Reuber, M., Lun, S., Klaver, P., et al. 2001. Language mapping in less than 15 min: real-time functional MRI during routine clinical investigation. Neuroimage 14 585-594], with some modifications. The wLI, as well as the total activation on each side, were assessed against age using non-parametric correlation. There was a highly significant negative correlation between age and wLI such that the older the subjects, the lower the wLI. Furthermore, there was a highly significant positive correlation between total activation for ipsilateral M1 and age, and a nearly significant trend for contralateral M1. This study documents that during execution of a simple paced motor task, the older the subject the less lateralized the M1 activation balance as a result of increasing amount of activation on both sides, more significantly so ipsilaterally. Thus, in aging, enhanced M1 recruitment bilaterally is required to produce the same motor performance, suggesting a compensatory process. These findings are in line with cognitive studies indicating a tendency for the aging brain to reduce its functional lateralization, perhaps from less efficient transcallosal connections.

Acoustic Stimulation↗
PubMed2006

Perfusion CT helps decision making for thrombolysis when there is no clear time of onset.

Current guidelines on thrombolysis post stroke with recombinant tissue plasminogen activator (rt-PA) exclude its use where time of onset is unknown, thus denying some patients potentially beneficial treatment. Contrast enhanced perfusion computed tomography (pCT) imaging can be used together with plain CT and information on clinical deficits to decide whether or not thrombolysis should be initiated even though the exact time of stroke onset is unknown. Based on the results of pCT and CT, rt-PA was administered to two patients with unknown time of stroke onset; one of the patients also underwent suction thrombectomy. Results in both cases were excellent.

Aged↗
PubMed2005

How healthy is the acutely reperfused ischemic penumbra?

Because it is the main determinant of clinical recovery, early reperfusion of the ischemic penumbra has become the mainstay of acute stroke therapy. Although early permanent recanalization can be associated with spectacular and complete recovery, some patients in fact exhibit delayed or incomplete recovery, even despite small infarcts on late structural imaging. This might result from tissue inflammation and selective neuronal death/damage, two probably inter-related cellular events well described in the animal literature, precluding full functional restoration in the salvaged penumbra. However, impact of these processes on recovery may be complex because of the interplay with ongoing plasticity and the possible promoting effect of inflammation on the latter. Preliminary results from imaging studies of inflammation and selective neuronal loss after middle cerebral artery territory stroke, using radioligands of the central benzodiazepine receptor and the activated microglia, respectively, reviewed here, suggest these phenomena also exist in man, although their relationship with acute-stage hypoperfusion and their impact on clinical recovery, if any, remain poorly understood. Furthermore, their inter-relationships in the salvaged penumbra have not been addressed. Better understanding of these potentially harmful processes might help to maximize benefits from thrombolysis, and could also have implications for patients who enjoy spontaneous recanalization.

Animals↗
PubMed2005

Using voxel-based morphometry to map the structural changes associated with rapid conversion in MCI: a longitudinal MRI study.

Capturing the dynamics of gray matter (GM) atrophy in relation to the conversion from mild cognitive impairment (MCI) to clinically probable Alzheimer's disease (AD) would be of considerable interest. In this prospective study we have used a novel longitudinal voxel-based method to map the progression of GM loss in MCI patients over time and compared converters to non-converters. Eighteen amnestic MCI patients were followed-up for a predefined fixed period of 18 months and conversion was judged according to NINCDS-ADRDA criteria for probable AD. Each patient underwent a high-resolution T1-weighted volume MRI scan both at entry in the study and 18 months later. We used an optimal VBM protocol to compare baseline imaging data of converters to those of non-converters. Moreover, to map GM loss from baseline to follow-up assessment, we used a modified voxel-based morphometry (VBM) procedure specially designed for longitudinal studies. At the end of the follow-up period, seven patients had converted to probable AD. Areas of lower baseline GM value in converters mainly included the hippocampus, parahippocampal cortex, and lingual and fusiform gyri. Regions of significant GM loss over the 18-month follow-up period common to both converters and non-converters included the temporal neocortex, parahippocampal cortex, orbitofrontal and inferior parietal areas, and the left thalamus. However, there was significantly greater GM loss in converters relative to non-converters in the hippocampal area, inferior and middle temporal gyrus, posterior cingulate, and precuneus. This accelerated atrophy may result from both neurofibrillary tangles accumulation and parallel pathological processes such as functional alteration in the posterior cingulate. The ability to longitudinally assess GM changes in MCI offers new perspectives to better understand the pathological processes underlying AD and to monitor the effects of treatment on brain structure.

Aged↗
PubMed2005

Utility of an ultrafast magnetic resonance imaging protocol in recent and semi-recent strokes.

OBJECTIVE: To evaluate the technical feasibility of an integrated ultrafast head magnetic resonance (MR) protocol using a sensitivity encoding (SENSE) technique for depicting parenchymal ischaemia and vascular compromise in patients with suspected recent stroke. METHODS: 23 patients were evaluated with the ultrafast MR protocol using T2, T1, fluid attenuated inversion recovery (FLAIR), 3D time of flight magnetic resonance angiography (MRA), and diffusion weighted imaging (DWI) sequences. These were compared with routine conventional MR sequences. RESULTS: One patient could not tolerate conventional imaging, although imaging using the three minute head SENSE protocol was diagnostic. Both conventional and ultrafast protocols were of similar diagnostic yield in the remaining patients. There were no significant differences in clinical diagnostic quality for the T1, T2, FLAIR, and DWI sequences. One MRA examination was of better quality when SENSE was used, owing to reduced motion artefacts and shorter imaging time. CONCLUSIONS: It is possible to undertake a comprehensive MR examination in stroke patients in approximately three to five minutes. Ultrafast imaging may become a useful triage tool before thrombolytic therapy. It may be of particular benefit in patients unable to tolerate longer sequences. Further work is necessary to confirm these findings in hyperacute stroke.

Adult↗
PubMed2004

MCI conversion to dementia and the APOE genotype: a prediction study with FDG-PET.

OBJECTIVES: To investigate whether the combination of fluoro-2-deoxy-d-glucose (FDG) PET measures with the APOE genotype would improve prediction of the conversion from mild cognitive impairment (MCI) to Alzheimer disease (AD). METHOD: After 1 year, 8 of 37 patients with MCI converted to AD (22%). Differences in baseline regional glucose metabolic rate (rCMRglc) across groups were assessed on a voxel-based basis using a two-factor analysis of variance with outcome (converters [n = 8] vs nonconverters [n = 29]) and APOE genotype (E4 carriers [E4+] [n = 16] vs noncarriers [E4-] [n = 21]) as grouping factors. Results were considered significant at p < 0.05, corrected for multiple comparisons. RESULTS: All converters showed reduced rCMRglc in the inferior parietal cortex (IPC) as compared with the nonconverters. Hypometabolism in AD-typical regions, that is, temporoparietal and posterior cingulate cortex, was found for the E4+ as compared with the E4- patients, with the E4+/converters (n = 5) having additional rCMRglc reductions within frontal areas, such as the anterior cingulate (ACC) and inferior frontal (IFC) cortex. For the whole MCI sample, IPC rCMRglc predicted conversion to AD with 84% overall diagnostic accuracy (p = 0.003). Moreover, ACC and IFC rCMRglc improved prediction for the E4+ group, yielding 100% sensitivity, 90% specificity, and 94% accuracy (p < 0.0005), thus leading to an excellent discrimination. CONCLUSION: Fluoro-2-deoxy-d-glucose-PET measures may improve prediction of the conversion to Alzheimer disease, especially in combination with the APOE genotype.

Aged↗
PubMed2004

Guidance for the preparation of neurological management guidelines by EFNS scientific task forces--revised recommendations 2004.

Since the publication of the first EFNS task force reports in 1997, a total of 20 evidence-based guidelines for the treatment and management of neurological diseases have been published by the EFNS (http://www.efns.org/guidelines). In 2001, recommendations for the preparation of neurological guidelines were issued by the EFNS Scientific Committee (Eur J Neurol 2001; 8: 549-550). These have now been updated and revised. More unified criteria for standards of reporting are set up which include classes of scientific evidence and predefined levels of recommendation. These criteria as well as others listed below should be used for all working groups that aim at recommending treatment, diagnostic procedures or other interventions within the framework of the EFNS.

Consensus↗
PubMed2003

Mild cognitive impairment: Can FDG-PET predict who is to rapidly convert to Alzheimer's disease?

Patients with mild cognitive impairment (MCI) were assessed, and a metabolic profile associated with conversion to AD at 18-month follow-up was sought. As compared with nonconverters (n = 10), converters (n = 7) had lower fluorodeoxyglucose uptake in the right temporoparietal cortex (p = 0.02, corrected for cluster size), without individual overlap. Awaiting replication in an independent sample, these findings suggest that among patients with MCI, fluorodeoxyglucose PET may accurately identify rapid converters.

Alzheimer Disease↗
PubMed2003

Hemorrhagic stroke associated with the Iowa amyloid precursor protein mutation.

The authors searched for mutations in the beta-amyloid precursor protein in a Spanish family with a hereditary syndrome of hemorrhagic stroke, dementia, leukoencephalopathy, and occipital calcifications. DNA from two affected members demonstrated the Iowa amyloid precursor protein mutation previously identified as a cause of severe amyloid angiopathy without hemorrhagic stroke. These data point to other genetic or environmental factors that may determine the occurrence of symptomatic hemorrhage in amyloid angiopathy.

Age of Onset↗
PubMed2003

Progress in imaging stroke: emerging clinical applications.

Recent years have seen major advances in the imaging of cerebrovascular disease. Although quantitative positron emission tomography (PET) has continued to be the gold standard in acquiring functional imaging data, with recent developments continuing to bear fruit, it remains a complex, costly, and not readily available technique. The emphasis in this overview is in the development of the newer magnetic resonance (MR) techniques, such as diffusion-weighted (DWI) and perfusion-weighted imaging (PWI), which allow rapid assessment of the underlying pathophysiology in acute ischaemic stroke. This is of major importance in classifying patients according to pathophysiology rather than clinical and structural imaging data, which may be essential in deciding therapy such as thrombolysis (which has proven benefit within 3-6 h of clinical onset, but can also lead to harmful haemorrhagic transformation) and/or neuroprotection, as well as patient selection in clinical trials. In conjunction with magnetic resonance angiography (MRA), DWI-PWI has been shown to improve the diagnosis and clinical management of stroke. Other novel MR techniques which have yet to reach the clinician, such as spectroscopic imaging, diffusion tensor imaging (DTI) and blood oxygenation level-dependent functional MRI (BOLD-fMRI), are currently established research tools which provide data about infarct evolution, fibre disruption and the mechanisms of stroke recovery. Electrophysiological methods including transcranial magnetic stimulation (TMS) and magneto-encephalography (MEG) will not be addressed here.

Brain Ischemia↗
PubMed2002

Transient global amnesia: concomitant episodic memory and positron emission tomography assessment in two additional patients.

Transient global amnesia (TGA) is characterized by a profound but transient deficit of episodic memory. The study of cerebral blood flow and oxygen metabolism with positron emission tomography (PET) provides relevant pathophysiologic data, but only three patients have been reported so far and in only one was concomitant neuropsychological testing performed. We report here the concomitant neuropsychological and PET assessment of two additional patients. Episodic disturbance was characterized by a storage disturbance for one case and an incapacity to learn episodic associations in the other, illustrating cognitive heterogeneity despite similar neurological presentation. PET findings disclosed mild but significant changes in the amygdala (right or left) and left posterior hippocampus, which could account for both the storage disturbance and the inability to associate episodic components. The PET findings also argued in favor of a vascular disturbance accompanying TGA.

Aged↗
PubMed2002

The metabolic substrates of bradykinesia and tremor in uncomplicated Parkinson's disease.

The pathophysiological mechanisms of bradykinesia and resting tremor, i.e., two major features of Parkinson's disease (PD), remain incompletely understood despite extensive studies, including functional imaging investigations. Using high-resolution positron emission tomography (PET) and [(18)F]fluoro-2-deoxyglucose (FDG) in 17 nondemented patients with uncomplicated PD on a stable therapeutic regimen, we measured the resting-state cerebral metabolic rate of glucose (CMRGlc), a validated marker of synaptic density/activity. Following formulation of distinct a priori hypotheses about potentially involved brain regions based on previous experimental and clinical literature, correlations between CMRGlc and objective scores of bradykinesia and tremor were searched in a voxel-based fashion using SPM99. Bradykinesia scores were significantly positively correlated with bilateral putamen and globus pallidum CMRGlc, while tremor scores were negatively correlated with bilateral putamen and cerebellar vermis CMRGlc. There was a large overlap of putamenal voxels significantly but inversely correlated with both extrapyramidal features. For both bradykinesia and tremor, the observed patterns of subcortical correlations largely concurred with our a priori hypotheses, and point to the major role of disruption of the striatofrontal and corticocerebellar pathways in the genesis of these extrapyramidal features. The direction of these correlations was not entirely expected, however, which may be due to the patients' being studied on medication, contrary to most studies performed to date. The observation that overlapping portions of the putamen inversely correlated with bradykinesia and tremor was a novel and striking finding which points to the complexity of the underlying pathophysiology of PD. Because it allows greater control of the neurological status, studying patients on medication may partly explain our findings. Voxel-based analysis of resting FDG-PET holds considerable potential for assessing the neural substrates of motor impairment in PD.

Aged↗