RESUMO
BACKGROUND: Mapping high oxygen extraction fraction (OEF) in acute stroke is of considerable interest to depict the at-risk tissue. Being sensitive to deoxyhemoglobin, T2*-weighted MRI has been suggested as a potential marker of high OEF. METHODS: We compared T2*-weighted images from pre-contrast arrival perfusion scans against quantitative positron emission tomography in 5 patients studied 7-21 h after onset of carotid territory stroke. OEF and T2* signal were obtained in the voxels with significantly high OEF. RESULTS: All patients showed increased OEF. No significant relationship between OEF and T2*-weighted signal was found either within or between subjects. CONCLUSION: We found no indication that T2*-weighted MRI in the way implemented in this investigation was sensitive to high OEF in acute stroke.
Assuntos
Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/patologia , Doença Aguda , Idoso , Idoso de 80 Anos ou mais , Artérias Carótidas/diagnóstico por imagem , Artérias Carótidas/patologia , Doenças das Artérias Carótidas/complicações , Doenças das Artérias Carótidas/diagnóstico por imagem , Doenças das Artérias Carótidas/patologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Angiografia por Ressonância Magnética , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Tomografia por Emissão de Pósitrons , Ultrassonografia Doppler TranscranianaRESUMO
Selective neuronal loss (SNL) in the rescued penumbra could account for suboptimal clinical recovery despite effective early reperfusion. Previous studies of SNL used single-photon emission tomography (SPECT), did not account for potential volume loss secondary to collapse of the infarct cavity, and failed to show a relationship with initial hypoperfusion. Here, we obtained acute-stage computerized tomography (CT) perfusion and follow-up quantitative (11)C-flumazenil (FMZ)-PET to map SNL in the non-infarcted tissue and assess its relationship with acute-stage hypoperfusion. We prospectively recruited seven patients with evidence of (i) acute (<6 h) extensive middle cerebral artery territory ischaemia based on clinical deficit (National Institutes of Health stroke scale, NIHSS score range: 8-23) and CT Perfusion (CTp) findings and (ii) early recanalization (spontaneous or following thrombolysis) based on spectacular clinical recovery (DeltaNIHSS > or =6 at 24 h), good clinical outcome (NIHSS < or =5) and small final infarct (6/7 subcortical) on late-stage MRI. Ten age-matched controls were also studied. FMZ image analysis took into account potential post-stroke volume loss. Across patients, clusters of significantly reduced FMZ binding were more prevalent and extensive in the non-infarcted middle cerebral artery cortical areas than in the non-affected hemisphere (P = 0.028, Wilcoxon sign rank test). Voxel-based between-group comparisons revealed several large clusters of significantly reduced FMZ binding in the affected peri-insular, superior temporal and prefrontal cortices (FDR P < 0.05), as compared with no cluster on the unaffected side. Finally, comparing CTp and PET data revealed a significant negative correlation between FMZ binding and initial hypoperfusion. Applying correction for volume loss did not substantially alter the significance of these results. Although based on a small patient sample sometimes studied late after the index stroke, and as such preliminary, our results establish the presence and distribution of FMZ binding loss in ultimately non-infarcted brain areas after stroke. In addition, the data suggest that this binding loss is proportional to initial hypoperfusion, in keeping with the hypothesis that the rescued penumbra is affected by SNL. Although its clinical counterparts remain uncertain, it is tempting to speculate that peri-infarct SNL could represent a new therapeutic target.
Assuntos
Encéfalo/patologia , Circulação Cerebrovascular , Interpretação de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Neurônios/patologia , Acidente Vascular Cerebral/patologia , Idoso , Encéfalo/fisiopatologia , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons , Estudos Prospectivos , Acidente Vascular Cerebral/fisiopatologiaRESUMO
BACKGROUND AND PURPOSE: Evidence now exists for a pathogenic role for neutrophils in acute cerebral ischemia. We have studied the patterns and temporal profile of cerebral neutrophil recruitment to areas of acute ischemic stroke (IS) and have attempted to correlate this with neurological status and outcome. METHODS: Patients with cortical middle cerebral artery (MCA) IS were recruited within 24 hours of clinical onset. Neutrophil recruitment was studied using indium-111 (111In) troponolate-labeled neutrophils, planar imaging, and single-photon emission computed tomography (SPECT). Volume of brain infarction was calculated from concurrent computed tomography (CT). Hematoxylin and eosin sections were obtained postmortem (n=2). Outcome was measured using Barthel, Rankin, and National Institute of Health Stroke (NIHSS) scales. RESULTS: Fifteen patients were studied. Significant 111In-neutrophil recruitment to ipsilateral hemisphere, as measured by asymmetry index (AI), was demonstrated within 24 hours of onset in 9 patients; this response was heterogenous between patients and on repeated measurement attenuated over time. Histologically, recruitment was confirmed within intravascular, intramural, and intraparenchymal compartments. Interindividual heterogeneity in neutrophil response did not correlate with infarct volume or outcome. In an exploratory analysis, neutrophil accumulation appeared to correlate significantly with infarct expansion (Spearman rho=0.66; P=0.03, n=12). CONCLUSIONS: Neutrophils recruit to areas of ischemic brain within 24 hours of symptom onset. This recruitment attenuates over time and is confirmed histologically. While neutrophil accumulation may be associated with either the magnitude or the rate of infarct growth, these results require confirmation in future studies.
Assuntos
Isquemia Encefálica/diagnóstico , Isquemia Encefálica/fisiopatologia , Infarto da Artéria Cerebral Média/diagnóstico , Infarto da Artéria Cerebral Média/fisiopatologia , Infiltração de Neutrófilos , Tropolona/análogos & derivados , Isquemia Encefálica/patologia , Separação Celular , Humanos , Infarto da Artéria Cerebral Média/patologia , Imageamento por Ressonância Magnética , Compostos Organometálicos , Fatores de Tempo , Tomografia Computadorizada de Emissão de Fóton Único , Tomografia Computadorizada por Raios XRESUMO
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.
Assuntos
Encéfalo/irrigação sanguínea , Angiografia Cerebral , Infarto da Artéria Cerebral Média/tratamento farmacológico , Terapia Trombolítica , Idoso , Gânglios da Base/irrigação sanguínea , Gânglios da Base/efeitos dos fármacos , Velocidade do Fluxo Sanguíneo/efeitos dos fármacos , Velocidade do Fluxo Sanguíneo/fisiologia , Técnicas de Apoio para a Decisão , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Infarto da Artéria Cerebral Média/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Prognóstico , Fluxo Sanguíneo Regional/efeitos dos fármacos , Fluxo Sanguíneo Regional/fisiologia , TrombectomiaRESUMO
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.
Assuntos
Encéfalo/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética/efeitos adversos , Metabolismo Energético/efeitos da radiação , Oxigênio/metabolismo , Tomografia por Emissão de Pósitrons , Acidente Vascular Cerebral/metabolismo , Idoso , Idoso de 80 Anos ou mais , Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Encéfalo/patologia , Mapeamento Encefálico , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Espectroscopia de Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Fluxo Sanguíneo Regional/efeitos da radiação , Acidente Vascular Cerebral/diagnósticoRESUMO
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.