RESUMO
OBJECTIVE: Although much tissue damage may occur within the first few hours of ischemic stroke, the duration of tissue injury is not well defined. We assessed the temporal pattern of neuronal loss and ischemia after ischemic stroke using magnetic resonance spectroscopic imaging (MRSI) and diffusion-weighted imaging (DWI). METHODS: We measured N-acetylaspartate (NAA) and lactate in 51 patients with acute ischemic stroke at five time points, from admission to 3 months, in voxels classified as normal, possibly or definitely abnormal (ischemic) according to the appearance of the stroke lesion on the admission DWI. We compared changes in NAA and lactate in different voxel classes using linear mixed models. RESULTS: NAA was significantly reduced from admission in definitely and possibly abnormal (p < 0.01) compared to contralateral normal voxels, reaching a nadir by 2 weeks and remaining reduced at 3 months. Lactate was significantly increased in definitely and possibly abnormal voxels (p < 0.01) during the first 5 days, falling to normal at 2 weeks, rising again later in these voxels. CONCLUSION: The progressive fall in N-acetylaspartate suggests that some additional neuronal death may continue beyond the first few hours for up to 2 weeks or longer. The mechanism is unclear but, if correct, then it is possible that interventions to limit this ongoing subacute tissue damage might add to the benefit of hyperacute treatment, making further improvements in outcome possible.
Assuntos
Ácido Aspártico/análogos & derivados , Isquemia Encefálica/metabolismo , Encéfalo/metabolismo , Ácido Láctico/metabolismo , Espectroscopia de Ressonância Magnética/métodos , Acidente Vascular Cerebral/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Ácido Aspártico/análise , Ácido Aspártico/metabolismo , Biomarcadores/análise , Biomarcadores/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Isquemia Encefálica/patologia , Isquemia Encefálica/fisiopatologia , Mapeamento Encefálico , Morte Celular/fisiologia , Imagem de Difusão por Ressonância Magnética , Progressão da Doença , Regulação para Baixo/fisiologia , Metabolismo Energético/fisiologia , Feminino , Humanos , Ácido Láctico/análise , Modelos Lineares , Masculino , Pessoa de Meia-Idade , Degeneração Neural/diagnóstico , Degeneração Neural/metabolismo , Degeneração Neural/fisiopatologia , Acidente Vascular Cerebral/patologia , Acidente Vascular Cerebral/fisiopatologia , Fatores de TempoRESUMO
BACKGROUND AND PURPOSE: An acute mismatch on diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) may represent the "tissue-at-risk." It is unclear which "semiquantitative" perfusion parameter most closely identifies final infarct volume. METHODS: Acute stroke patients underwent DWI and PWI (dynamic-susceptibility contrast imaging) on admission (baseline), and T2-weighted imaging (T2WI) at 1 or 3 months after stroke. "Semiquantitative" mean transit time (MTTsq=first moment of concentration/time curve), cerebral blood volume (CBVsq=area under concentration/time curve), and cerebral blood flow (CBFsq=CBVsq/MTTsq) were calculated. DWI and PWI lesions were measured at baseline and final infarct volume on T2WI acquired > or =1 month after stroke. Baseline DWI, CBFsq, and MTTsq lesion volumes were compared with final T2WI lesion volume. RESULTS: Among 46 patients, baseline DWI and CBFsq lesions were not significantly different from final T2WI lesion volume, but baseline MTTsq lesions were significantly larger. The correlation with final T2WI lesion volume was strongest for DWI (Spearman rank correlation coefficient rho=0.68), intermediate for CBFsq (rho=0.55), and weakest for MTTsq (rho=0.49) baseline lesion volumes. Neither DWI/CBFsq nor DWI/MTTsq mismatch predicted lesion growth; lesion growth was equally common in those with and without mismatch. CONCLUSIONS: Of the 2 PWI parameters, CBFsq lesions most closely identifies, and MTTsq overestimates, final T2WI lesion volume. "DWI/PWI mismatch" does not identify lesion growth. Patients without "DWI/PWI mismatch" are equally likely to have lesion growth as those with mismatch and should not be excluded from acute stroke treatment.
Assuntos
Imagem de Difusão por Ressonância Magnética/métodos , Isquemia/patologia , Imageamento por Ressonância Magnética/métodos , Acidente Vascular Cerebral/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Circulação Cerebrovascular , Difusão , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Isquemia/diagnóstico , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Perfusão , Estudos Prospectivos , Acidente Vascular Cerebral/diagnóstico , Fatores de TempoRESUMO
OBJECTIVES: Our purpose was to investigate whether differences exist in the values and temporal evolution of mean diffusivity (