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OBJECTIVE: For stroke patients with unknown time of onset, mismatch between diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) can guide thrombolytic intervention. However, access to MRI for hyperacute stroke is limited. Here, we sought to evaluate whether a portable, low-field (LF)-MRI scanner can identify DWI-FLAIR mismatch in acute ischemic stroke. METHODS: Eligible patients with a diagnosis of acute ischemic stroke underwent LF-MRI acquisition on a 0.064-T scanner within 24 h of last known well. Qualitative and quantitative metrics were evaluated. Two trained assessors determined the visibility of stroke lesions on LF-FLAIR. An image coregistration pipeline was developed, and the LF-FLAIR signal intensity ratio (SIR) was derived. RESULTS: The study included 71 patients aged 71 ± 14 years and a National Institutes of Health Stroke Scale of 6 (interquartile range 3-14). The interobserver agreement for identifying visible FLAIR hyperintensities was high (κ = 0.85, 95% CI 0.70-0.99). Visual DWI-FLAIR mismatch had a 60% sensitivity and 82% specificity for stroke patients <4.5 h, with a negative predictive value of 93%. LF-FLAIR SIR had a mean value of 1.18 ± 0.18 <4.5 h, 1.24 ± 0.39 4.5-6 h, and 1.40 ± 0.23 >6 h of stroke onset. The optimal cut-point for LF-FLAIR SIR was 1.15, with 85% sensitivity and 70% specificity. A cut-point of 6.6 h was established for a FLAIR SIR <1.15, with an 89% sensitivity and 62% specificity. INTERPRETATION: A 0.064-T portable LF-MRI can identify DWI-FLAIR mismatch among patients with acute ischemic stroke. Future research is needed to prospectively validate thresholds and evaluate a role of LF-MRI in guiding thrombolysis among stroke patients with uncertain time of onset. ANN NEUROL 2024;96:321-331.
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Imagem de Difusão por Ressonância Magnética , AVC Isquêmico , Humanos , Idoso , Masculino , Imagem de Difusão por Ressonância Magnética/métodos , Feminino , Pessoa de Meia-Idade , Idoso de 80 Anos ou mais , AVC Isquêmico/diagnóstico por imagem , Acidente Vascular Cerebral/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodosRESUMO
In this episode of the AJR Podcast Series on Training and Education, Pamela Schaefer, MD, joins host Monica Cheng, MD, to discuss incorporating education into radiology careers. Dr. Schaefer shares her journey, the role of leadership, and advice for aspiring educators.
In this episode of the AJR Podcast Series on Training and Education, Pamela Schaefer, MD, joins host Monica Cheng, MD, to discuss incorporating education into radiology careers. Dr. Schaefer shares her journey, the role of leadership, and advice for aspiring educators.
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Liderança , Radiologia , Radiologia/educação , Humanos , Webcasts como Assunto , Publicações Periódicas como AssuntoRESUMO
OBJECTIVES: High-resolution post-contrast T1-weighted imaging is a workhorse sequence in the evaluation of neurological disorders. The T1-MPRAGE sequence has been widely adopted for the visualization of enhancing pathology in the brain. However, this three-dimensional (3D) acquisition is lengthy and prone to motion artifact, which often compromises diagnostic quality. The goal of this study was to compare a highly accelerated wave-controlled aliasing in parallel imaging (CAIPI) post-contrast 3D T1-MPRAGE sequence (Wave-T1-MPRAGE) with the standard 3D T1-MPRAGE sequence for visualizing enhancing lesions in brain imaging at 3 T. METHODS: This study included 80 patients undergoing contrast-enhanced brain MRI. The participants were scanned with a standard post-contrast T1-MPRAGE sequence (acceleration factor [R] = 2 using GRAPPA parallel imaging technique, acquisition time [TA] = 5 min 18 s) and a prototype post-contrast Wave-T1-MPRAGE sequence (R = 4, TA = 2 min 32 s). Two neuroradiologists performed a head-to-head evaluation of both sequences and rated the visualization of enhancement, sharpness, noise, motion artifacts, and overall diagnostic quality. A 15% noninferiority margin was used to test whether post-contrast Wave-T1-MPRAGE was noninferior to standard T1-MPRAGE. Inter-rater and intra-rater agreement were calculated. Quantitative assessment of CNR/SNR was performed. RESULTS: Wave-T1-MPRAGE was noninferior to standard T1-MPRAGE for delineating enhancing lesions with unanimous agreement in all cases between raters. Wave-T1-MPRAGE was noninferior in the perception of noise (p < 0.001), motion artifact (p < 0.001), and overall diagnostic quality (p < 0.001). CONCLUSION: High-accelerated post-contrast Wave-T1-MPRAGE enabled a two-fold reduction in acquisition time compared to the standard sequence with comparable performance for visualization of enhancing pathology and equivalent perception of noise, motion artifacts and overall diagnostic quality without loss of clinically important information. KEY POINTS: ⢠Post-contrast wave-controlled aliasing in parallel imaging (CAIPI) T1-MPRAGE accelerated the acquisition of three-dimensional (3D) high-resolution post-contrast images by more than two-fold. ⢠Post-contrast Wave-T1-MPRAGE was noninferior to standard T1-MPRAGE with unanimous agreement between reviewers (100% in 80 cases) for the visualization of intracranial enhancing lesions. ⢠Wave-T1-MPRAGE was equivalent to the standard sequence in the perception of noise in 94% (75 of 80) of cases and was preferred in 16% (13 of 80) of cases for decreased motion artifact.
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Imageamento Tridimensional , Imageamento por Ressonância Magnética , Humanos , Imageamento por Ressonância Magnética/métodos , Imageamento Tridimensional/métodos , Encéfalo/diagnóstico por imagem , Artefatos , Movimento (Física)Assuntos
Acidentes por Quedas , Dor nas Costas , Rigidez Muscular Espasmódica , Adulto , Feminino , Humanos , Dor nas Costas/etiologia , Diagnóstico Diferencial , Perna (Membro) , Rigidez Muscular Espasmódica/complicações , Rigidez Muscular Espasmódica/diagnóstico , Rigidez Muscular Espasmódica/imunologia , Rigidez Muscular Espasmódica/terapia , Espasmo/etiologiaRESUMO
PURPOSE: To evaluate the impact of magnetization transfer (MT) on brain tissue contrast in turbo-spin-echo (TSE) and EPI fluid-attenuated inversion recovery (FLAIR) images, and to optimize an MT-prepared EPI FLAIR pulse sequence to match the tissue contrast of a clinical reference TSE FLAIR protocol. METHODS: Five healthy volunteers underwent 3T brain MRI, including single slice TSE FLAIR, multi-slice TSE FLAIR, EPI FLAIR without MT-preparation, and MT-prepared EPI FLAIR with variations of the MT-preparation parameters, including number of preparation pulses, pulse amplitude, and resonance offset. Automated co-registration and gray matter (GM) versus white matter (WM) segmentation was performed using a T1-MPRAGE acquisition, and the GM versus WM signal intensity ratio (contrast ratio) was calculated for each FLAIR acquisition. RESULTS: Without MT preparation, EPI FLAIR showed poor tissue contrast (contrast ratio = 0.98), as did single slice TSE FLAIR. Multi-slice TSE FLAIR provided high tissue contrast (contrast ratio = 1.14). MT-prepared EPI FLAIR closely approximated the contrast of the multi-slice TSE FLAIR images for two combinations of the MT-preparation parameters (contrast ratio = 1.14). Optimized MT-prepared EPI FLAIR provided a 50% reduction in scan time compared to the reference TSE FLAIR acquisition. CONCLUSION: Optimized MT-prepared EPI FLAIR provides comparable brain tissue contrast to the multi-slice TSE FLAIR images used in clinical practice.
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Imageamento por Ressonância Magnética , Substância Branca , Encéfalo/diagnóstico por imagem , Imagem Ecoplanar/métodos , Substância Cinzenta/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética/métodos , Neuroimagem , Substância Branca/diagnóstico por imagemRESUMO
OBJECTIVES: Wave-CAIPI (Controlled Aliasing in Parallel Imaging) enables dramatic reduction in acquisition time of 3D MRI sequences such as 3D susceptibility-weighted imaging (SWI) but has not been clinically evaluated at 1.5 T. We sought to compare highly accelerated Wave-CAIPI SWI (Wave-SWI) with two alternative standard sequences, conventional three-dimensional SWI and two-dimensional T2*-weighted Gradient-Echo (T2*w-GRE), in patients undergoing routine brain MRI at 1.5 T. METHODS: In this study, 172 patients undergoing 1.5 T brain MRI were scanned with a more commonly used susceptibility sequence (standard SWI or T2*w-GRE) and a highly accelerated Wave-SWI sequence. Two radiologists blinded to the acquisition technique scored each sequence for visualization of pathology, motion and signal dropout artifacts, image noise, visualization of normal anatomy (vessels and basal ganglia mineralization), and overall diagnostic quality. Superiority testing was performed to compare Wave-SWI to T2*w-GRE, and non-inferiority testing with 15% margin was performed to compare Wave-SWI to standard SWI. RESULTS: Wave-SWI performed superior in terms of visualization of pathology, signal dropout artifacts, visualization of normal anatomy, and overall image quality when compared to T2*w-GRE (all p < 0.001). Wave-SWI was non-inferior to standard SWI for visualization of normal anatomy and pathology, signal dropout artifacts, and overall image quality (all p < 0.001). Wave-SWI was superior to standard SWI for motion artifact (p < 0.001), while both conventional susceptibility sequences were superior to Wave-SWI for image noise (p < 0.001). CONCLUSIONS: Wave-SWI can be performed in a 1.5 T clinical setting with robust performance and preservation of diagnostic quality. KEY POINTS: ⢠Wave-SWI accelerated the acquisition of 3D high-resolution susceptibility images in 70% of the acquisition time of the conventional T2*GRE. ⢠Wave-SWI performed superior to T2*w-GRE for visualization of pathology, signal dropout artifacts, and overall diagnostic image quality. ⢠Wave-SWI was noninferior to standard SWI for visualization of normal anatomy and pathology, signal dropout artifacts, and overall diagnostic image quality.
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Imageamento por Ressonância Magnética , Neuroimagem , Artefatos , Encéfalo/diagnóstico por imagem , Humanos , Imageamento Tridimensional/métodos , Imageamento por Ressonância Magnética/métodosRESUMO
PURPOSE: To assess the utility of ASL in evaluating patients presenting to the ED with stroke-like symptoms. METHODS: ASL and DWI images from 526 consecutive patients presenting to the ED with acute stroke symptoms were retrospectively reviewed. DWI images were evaluated for volume of restricted diffusion using ABC/2. ASL maps were evaluated for decreased, normal, or increased signal. The volume of decreased ASL signal was calculated using the same ABC/2 technique. The volume of decreased ASL signal was correlated with the volume of DWI signal abnormality to identify cases of mismatch (DWI:ASL ratio > 1.8) and to correlate this mismatch with infarct growth on imaging follow-up. NIHSS, length of hospital stay, mRS, and future admission for acute stroke-like symptoms were recorded. Correlations between ASL abnormalities and clinical parameters were evaluated using a two-tailed t-test. RESULTS: Of the 526 patients presenting with acute stroke symptoms, 136 patients had an abnormal ASL scan and 388 patients had a normal ASL scan. Of the 136 patients with abnormal ASL, 84 patients had low ASL signal with 79 of these being related to acute infarcts. Elevated ASL signal was seen in 52 patients, of which 30 of these patients had reperfusion hyperemia related to acute infarctions. ASL had a negative predictive value of 94% for evaluating patients with acute ischemic stroke. A subset of patients with abnormal ASL scans with a discharge diagnosis of acute infarction were found to have an ASL:DWI mismatch (ratio > 1.8) and demonstrated significant lesion growth on follow-up imaging (57%). This included some patients who exhibited low ASL signal before development of diffusion restriction (infarction). CONCLUSION: In patients presenting to the ED with acute stroke symptoms, ASL provides information not available with DWI alone. The NPV of ASL for evaluating patients with acute ischemia was 94%.
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Isquemia Encefálica , AVC Isquêmico , Acidente Vascular Cerebral , Imagem de Difusão por Ressonância Magnética/métodos , Serviço Hospitalar de Emergência , Humanos , Infarto , Perfusão , Estudos Retrospectivos , Marcadores de SpinRESUMO
Many patients with severe coronavirus disease 2019 (COVID-19) remain unresponsive after surviving critical illness. Although several structural brain abnormalities have been described, their impact on brain function and implications for prognosis are unknown. Functional neuroimaging, which has prognostic significance, has yet to be explored in this population. Here we describe a patient with severe COVID-19 who, despite prolonged unresponsiveness and structural brain abnormalities, demonstrated intact functional network connectivity, and weeks later recovered the ability to follow commands. When prognosticating for survivors of severe COVID-19, clinicians should consider that brain networks may remain functionally intact despite structural injury and prolonged unresponsiveness. ANN NEUROL 2020;88:851-854.
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Encéfalo/diagnóstico por imagem , Coma/diagnóstico por imagem , Infecções por Coronavirus/fisiopatologia , Estado Vegetativo Persistente/diagnóstico por imagem , Pneumonia Viral/fisiopatologia , Recuperação de Função Fisiológica , Betacoronavirus , Encéfalo/fisiopatologia , COVID-19 , Coma/fisiopatologia , Infecções por Coronavirus/terapia , Eletroencefalografia , Neuroimagem Funcional , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Vias Neurais , Pandemias , Estado Vegetativo Persistente/fisiopatologia , Pneumonia Viral/terapia , Prognóstico , Insuficiência Renal/fisiopatologia , Respiração Artificial , Síndrome do Desconforto Respiratório/fisiopatologia , Síndrome do Desconforto Respiratório/terapia , SARS-CoV-2 , Choque/fisiopatologiaRESUMO
The development of reperfusion therapies has profoundly impacted stroke care, initially with the advent of IV thrombolytic treatment and, more recently, with the development and refinement of endovascular treatment (EVT). Progress in neuroim-aging has supported the paradigm shift of stroke care, and advanced neuroimaging now has a fundamental role in triaging patients for both IV thrombolytic treatment and EVT. As the standard of care for acute ischemic stroke (AIS) evolves, controversies remain in certain clinical scenarios. This article explores the use of multimodality imaging for treatment selection of patients with AIS in the context of recent guidelines, highlighting controversial topics and providing guidance for clinical practice. The results of major randomized trials supporting EVT are reviewed. The advantages and disadvantages of CT, CTA, MRI, and MRA in stroke diagnosis are summarized with attention to level 1 evidence supporting the role of vascular imaging and perfusion imaging. Patient selection is compared between approaches based on time thresholds and physiologic approaches based on infarct core measurement using imaging. Moreover, various imaging approaches to core measurement are described. As ongoing studies push treatment boundaries, advanced imaging is expected to help identify a widening range of patients who may benefit from therapy.
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AVC Isquêmico/diagnóstico por imagem , Imagem Multimodal , Neuroimagem , Procedimentos Endovasculares , Humanos , AVC Isquêmico/fisiopatologia , AVC Isquêmico/terapia , Trombectomia , Terapia Trombolítica , Tempo para o TratamentoAssuntos
Confusão , Febre , Cefaleia , Adulto , Confusão/etiologia , Febre/etiologia , Cefaleia/etiologia , Humanos , MasculinoAssuntos
Acidentes por Quedas , Encéfalo/patologia , Síndrome de Creutzfeldt-Jakob/genética , Debilidade Muscular/etiologia , Proteínas Priônicas/genética , Idoso , Síndrome de Creutzfeldt-Jakob/complicações , Síndrome de Creutzfeldt-Jakob/diagnóstico , Diagnóstico Diferencial , Família , Evolução Fatal , Feminino , Aconselhamento Genético , Humanos , Imageamento por Ressonância Magnética , Debilidade Muscular/genética , MutaçãoAssuntos
Mycobacterium bovis , Tuberculose/diagnóstico , Idoso , Falso Aneurisma/diagnóstico por imagem , Aorta Torácica/diagnóstico por imagem , Doenças da Aorta/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Delírio/etiologia , Diagnóstico Diferencial , Evolução Fatal , Humanos , Pulmão/diagnóstico por imagem , Pulmão/patologia , Imageamento por Ressonância Magnética , Masculino , Mycobacterium bovis/isolamento & purificação , Insuficiência Renal/etiologia , Tuberculose/complicaçõesRESUMO
Head and neck imaging is an intimidating subject for many radiologists because of the complex anatomy and potentially serious consequences of delayed or improper diagnosis of the diverse abnormalities involving this region. The purpose of this article is to help radiologists to understand the intricate anatomy of the head and neck and to review the imaging appearances of a variety of nontraumatic head and neck conditions that bring patients to the emergency department, including acute infectious and inflammatory diseases and acute complications of head and neck neoplasms. These conditions are presented in five sections on the basis of their primary location of involvement: the oral cavity and pharynx, neck, sinonasal tract, orbits, and ears. Important anatomic landmarks are reviewed briefly in each related section.Online supplemental material is available for this article.©RSNA, 2019.
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Cabeça/diagnóstico por imagem , Imageamento por Ressonância Magnética , Pescoço/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Idoso , Criança , Emergências , Feminino , Neoplasias de Cabeça e Pescoço/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Pescoço/anatomia & histologia , Adulto JovemAssuntos
Borrelia/isolamento & purificação , Febre Recorrente/diagnóstico , Borrelia/genética , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Infarto Cerebral/diagnóstico por imagem , Infarto Cerebral/etiologia , Líquido Cefalorraquidiano/microbiologia , Confusão/etiologia , Diagnóstico Diferencial , Fadiga/etiologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Febre Recorrente/complicações , Febre Recorrente/microbiologia , Distúrbios da Fala/etiologia , Tomografia Computadorizada por Raios XAssuntos
Transtorno Bipolar/etiologia , Encéfalo/diagnóstico por imagem , Função Executiva , Lobo Frontal , Comportamento Impulsivo , Acidente Vascular Cerebral/diagnóstico por imagem , Antidepressivos/efeitos adversos , Transtorno Bipolar/induzido quimicamente , Transtorno Bipolar/diagnóstico , Encéfalo/patologia , Diagnóstico Diferencial , Lobo Frontal/patologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Transtornos da Personalidade/etiologia , Transtornos do Sono-Vigília/etiologia , Acidente Vascular Cerebral/complicaçõesAssuntos
Confusão/etiologia , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , Herpesvirus Humano 6/isolamento & purificação , Hospedeiro Imunocomprometido , Meningoencefalite/diagnóstico , Infecções por Roseolovirus/diagnóstico , Antivirais/uso terapêutico , Autopsia , Diagnóstico Diferencial , Evolução Fatal , Foscarnet/uso terapêutico , Reação Enxerto-Hospedeiro , Humanos , Leucemia Linfocítica Crônica de Células B/terapia , Masculino , Meningoencefalite/complicações , Meningoencefalite/virologia , Pessoa de Meia-Idade , Infecções por Roseolovirus/complicações , Infecções por Roseolovirus/tratamento farmacológico , Transplante HomólogoRESUMO
BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) can reliably identify critically ischemic tissue shortly after stroke onset. We tested whether thresholded computed tomographic cerebral blood flow (CT-CBF) and CT-cerebral blood volume (CT-CBV) maps are sufficiently accurate to substitute for DWI for estimating the critically ischemic tissue volume. METHODS: Ischemic volumes of 55 patients with acute anterior circulation stroke were assessed on DWI by visual segmentation and on CT-CBF and CT-CBV with segmentation using 15% and 30% thresholds, respectively. The contrast:noise ratios of ischemic regions on the DWI and CT perfusion (CTP) images were measured. Correlation and Bland-Altman analyses were used to assess the reliability of CTP. RESULTS: Mean contrast:noise ratios for DWI, CT-CBF, and CT-CBV were 4.3, 0.9, and 0.4, respectively. CTP and DWI lesion volumes were highly correlated (R(2)=0.87 for CT-CBF; R(2)=0.83 for CT-CBV; P<0.001). Bland-Altman analyses revealed little systemic bias (-2.6 mL) but high measurement variability (95% confidence interval, ±56.7 mL) between mean CT-CBF and DWI lesion volumes, and systemic bias (-26 mL) and high measurement variability (95% confidence interval, ±64.0 mL) between mean CT-CBV and DWI lesion volumes. A simulated treatment study demonstrated that using CTP-CBF instead of DWI for detecting a statistically significant effect would require at least twice as many patients. CONCLUSIONS: The poor contrast:noise ratios of CT-CBV and CT-CBF compared with those of DWI result in large measurement error, making it problematic to substitute CTP for DWI in selecting individual acute stroke patients for treatment. CTP could be used for treatment studies of patient groups, but the number of patients needed to identify a significant effect is much higher than the number needed if DWI is used.
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Infarto Cerebral/diagnóstico , Infarto Cerebral/epidemiologia , Imagem de Difusão por Ressonância Magnética/normas , Acidente Vascular Cerebral/diagnóstico , Acidente Vascular Cerebral/epidemiologia , Tomografia Computadorizada por Raios X/normas , Doença Aguda , Idoso , Circulação Cerebrovascular , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Estudos Retrospectivos , Método Simples-CegoRESUMO
BACKGROUND AND PURPOSE: Acute infarct volume, often proposed as a biomarker for evaluating novel interventions for acute ischemic stroke, correlates only moderately with traditional clinical end points, such as the modified Rankin Scale. We hypothesized that the topography of acute stroke lesions on diffusion-weighted magnetic resonance imaging may provide further information with regard to presenting stroke severity and long-term functional outcomes. METHODS: Data from a prospective stroke repository were limited to acute ischemic stroke subjects with magnetic resonance imaging completed within 48 hours from last known well, admission NIH Stroke Scale (NIHSS), and 3-to-6 months modified Rankin Scale scores. Using voxel-based lesion symptom mapping techniques, including age, sex, and diffusion-weighted magnetic resonance imaging lesion volume as covariates, statistical maps were calculated to determine the significance of lesion location for clinical outcome and admission stroke severity. RESULTS: Four hundred ninety subjects were analyzed. Acute stroke lesions in the left hemisphere were associated with more severe NIHSS at admission and poor modified Rankin Scale at 3 to 6 months. Specifically, injury to white matter (corona radiata, internal and external capsules, superior longitudinal fasciculus, and uncinate fasciculus), postcentral gyrus, putamen, and operculum were implicated in poor modified Rankin Scale. More severe NIHSS involved these regions, as well as the amygdala, caudate, pallidum, inferior frontal gyrus, insula, and precentral gyrus. CONCLUSIONS: Acute lesion topography provides important insights into anatomic correlates of admission stroke severity and poststroke outcomes. Future models that account for infarct location in addition to diffusion-weighted magnetic resonance imaging volume may improve stroke outcome prediction and identify patients likely to benefit from aggressive acute intervention and personalized rehabilitation strategies.
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Isquemia Encefálica/patologia , Avaliação de Resultados em Cuidados de Saúde , Índice de Gravidade de Doença , Acidente Vascular Cerebral/patologia , Idoso , Idoso de 80 Anos ou mais , Isquemia Encefálica/fisiopatologia , Imagem de Difusão por Ressonância Magnética , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Acidente Vascular Cerebral/fisiopatologia , Fatores de TempoAssuntos
Encéfalo/patologia , Transtornos da Consciência/etiologia , Febre do Nilo Ocidental/diagnóstico , Idoso , Encéfalo/diagnóstico por imagem , Neoplasias Encefálicas/diagnóstico , Diagnóstico Diferencial , Eletroencefalografia , Encefalite/diagnóstico , Evolução Fatal , Febre/etiologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Debilidade Muscular/etiologia , Redução de Peso , Febre do Nilo Ocidental/complicações , Febre do Nilo Ocidental/fisiopatologia , Vírus do Nilo OcidentalRESUMO
BACKGROUND AND PURPOSE: Major anterior circulation ischemic strokes caused by occlusion of the distal internal carotid artery or proximal middle cerebral artery or both account for about one third of ischemic strokes with mostly poor outcomes. These strokes are treatable by intravenous tissue-type plasminogen activator and endovascular methods. However, dynamics of infarct growth in these strokes are poorly documented. The purpose was to help understand infarct growth dynamics by measuring acute infarct size with diffusion-weighted imaging (DWI) at known times after stroke onset in patients with documented internal carotid artery/middle cerebral artery occlusions. METHODS: Retrospectively, we included 47 consecutive patients with documented internal carotid artery/middle cerebral artery occlusions who underwent DWI within 30 hours of stroke onset. Prospectively, 139 patients were identified using the same inclusion criteria. DWI lesion volumes were measured and correlated to time since stroke onset. Perfusion data were reviewed in those who underwent perfusion imaging. RESULTS: Acute infarct volumes ranged from 0.41 to 318.3 mL. Infarct size and time did not correlate (R2=0.001). The majority of patients had DWI lesions that were <25% the territory at risk (<70 mL) whether they were imaged <8 or >8 hours after stroke onset. DWI lesions corresponded to areas of greatly reduced perfusion. CONCLUSIONS: Poor correlation between infarct volume and time after stroke onset suggests that there are factors more powerful than time in determining infarct size within the first 30 hours. The observations suggest that highly variable cerebral perfusion via the collateral circulation may primarily determine infarct growth dynamics. If verified, clinical implications include the possibility of treating many patients outside traditional time windows.