Navegando por Autor "Pontes-Neto, Octavio M."
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Artigo Assessing Cerebrovascular Reactivity in Carotid Steno-Occlusive Disease UsingMRI BOLD and ASL Techniques(2012-04-17) Leoni, Renata F.; Mazzetto-Betti, Kelley C.; Silva, Afonso C.; Santos, Antonio C. dos; Araújo, Dráulio Barros de; Leite, João P.; Pontes-Neto, Octavio M.Impaired cerebrovascular reactivity (CVR), a predictive factor of imminent stroke, has been shown to be associated with carotid steno-occlusive disease. Magnetic resonance imaging (MRI) techniques, such as blood oxygenation level-dependent (BOLD) and arterial spin labeling (ASL), have emerged as promising noninvasive tools to evaluate altered CVR with whole-brain coverage, when combined with a vasoactive stimulus, such as respiratory task or injection of acetazolamide. Under normal cerebrovascular conditions, CVR has been shown to be globally and homogenously distributed between hemispheres, but with differences among cerebral regions. Such differences can be explained by anatomical specificities and different biochemical mechanisms responsible for vascular regulation. In patients with carotid steno-occlusive disease, studies have shown that MRI techniques can detect impaired CVR in brain tissue supplied by the affected artery. Moreover, resulting CVR estimations have been well correlated to those obtained with more established techniques, indicating that BOLD and ASL are robust and reliable methods to assess CVR in patients with cerebrovascular diseases. Therefore, the present paper aims to review recent studies which use BOLD and ASL to evaluate CVR, in healthy individuals and in patients with carotid steno-occlusive disease, providing a source of information regarding the obtained results and the methodological difficulties.Artigo Functional versus Nonfunctional Rehabilitation in Chronic Ischemic Stroke: Evidences from a Randomized Functional MRI Study(2016) Pelicioni, Maristela C. X.; Novaes, Morgana M.; Peres, Andre S. C.; Souza, Altay A. Lino de; Minelli, Cesar; Fabio, Soraia R. C.; Pontes-Neto, Octavio M.; Santos, Antonio C.; Araújo, Dráulio Barros deMotor rehabilitation of stroke survivors may include functional and/or nonfunctional strategy. The present study aimed to compare the effect of these two rehabilitation strategies by means of clinical scales and functional Magnetic Resonance Imaging (fMRI). Twelve hemiparetic chronic stroke patients were selected. Patients were randomly assigned a nonfunctional (NFS) or functional (FS) rehabilitation scheme. Clinical scales (Fugl-Meyer, ARA test, and modified Barthel) and fMRI were applied at four moments: before rehabilitation (P1) and immediately after (P2), 1 month after (P3), and three months after (P4) the end of rehabilitation. The NFS group improved significantly and exclusively their Fugl-Meyer scores at P2, P3, and P4, when compared to P1. On the other hand, the FS group increased significantly in Fugl-Meyer at P2, when compared to P1, and also in their ARA and Barthel scores. fMRI inspection at the individual level revealed that both rehabilitation schemes most often led to decreased activation sparseness, decreased activity of contralesional M1, increased asymmetry of M1 activity to the ipsilesional side, decreased perilesional activity, and decreased SMA activity. Increased M1 asymmetry with rehabilitation was also confirmed by Lateralization Indexes. Our clinical analysis revealed subtle differences between FS and NFS.Artigo Quantification of BOLD fMRI Parameters to Infer Cerebrovascular Reactivity of the Middle Cerebral Artery(2013) Mazzetto-Betti, Kelley C.; Leoni, Renata F.; Pontes-Neto, Octavio M.; Sturzbecher, Marcio J.; Santos, Antonio C.; Leite, Joao P.; Silva, Afonso C.; Araújo, Dráulio Barros dePurpose: To quantify the amplitude and temporal aspects of the blood oxygenation level-dependent (BOLD) response to an auditory stimulus during normocapnia and hypercapnia in healthy subjects in order to establish which BOLD parameters are best suited to infer the cerebrovascular reactivity (CVR) in the middle cerebral artery (MCA) territory. Materials and Methods: Twenty healthy volunteers (mean age: 23.6 6 3.7 years, 11 women) were subjected to a functional paradigm composed of five epochs of auditory stimulus (3 sec) intercalated by six intervals of rest (21 sec). Two levels of hypercapnia were achieved by a combination of air and CO2 while the end-tidal CO2 (ETCO2) was continually measured. An autoregressive method was applied to analyze four parameters of the BOLD signal: onset-time, time-to-peak, full-width-at-halfmaximum (FWHM), and amplitude. Results: BOLD onset time (P < 0.001) and full-width at half-maximum (FWHM) (P < 0.05) increased linearly, while BOLD amplitude decreased (P < 0.001) linearly with increasing levels of hypercapnia. Test–retest for reproducibility in five subjects revealed excellent concordance for onset time and amplitude. Conclusion: The robust linear dependence of BOLD onset time, FWHM, and amplitude to hypercapnia suggest future application of this protocol in clinical studies aimed at evaluating CVR of the MCA territory.