Hemorrhagic arteriovenous malformation (AVM) presentation, increasing age, deep brain location, and exclusive deep venous drainage appear to be independent predictors for AVM hemorrhage during natural history follow-up. The risk of spontaneous hemorrhage may be low in AVMs without these risk factors.

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P rogression to infarction after acute ischemic stroke onset is time-sensitive and has substantial intersubject variability. 1,2 Computed tomographic (CT) perfusion (CTP) measurement of brain parenchyma can be used to estimate ischemic core and penumbra and, therefore, provide immediate information for treatment decision-making. Current CTP thresholds that estimate these tissue states are generally derived either by comparison with magnetic resonance (MR) diffusion-weighted imaging (DWI), often done within an hour of CTP, or with follow-up infarction in patients who have reperfused sometime within 24 hours.3-11 Because infarcts grow over time and final tissue fate depends greatly on what happens in the minutes to hours immediately after this imaging snapshot, CTP thresholds predicting infarction are likely to depend on the time from stroke symptom onset to imaging, time from imaging to reperfusion, and the quality of reperfusion.Background and Purpose-Among patients with acute ischemic stroke, we determine computed tomographic perfusion (CTP) thresholds associated with follow-up infarction at different stroke onset-to-CTP and CTP-to-reperfusion times. Methods-Acute ischemic stroke patients with occlusion on computed tomographic angiography were acutely imaged with CTP. Noncontrast computed tomography and magnectic resonance diffusion-weighted imaging between 24 and 48 hours were used to delineate follow-up infarction. Reperfusion was assessed on conventional angiogram or 4-hour repeat computed tomographic angiography. T max , cerebral blood flow, and cerebral blood volume derived from delayinsensitive CTP postprocessing were analyzed using receiver-operator characteristic curves to derive optimal thresholds for combined patient data (pooled analysis) and individual patients (patient-level analysis) based on time from stroke onset-to-CTP and CTP-to-reperfusion. One-way ANOVA and locally weighted scatterplot smoothing regression was used to test whether the derived optimal CTP thresholds were different by time. Results-One hundred and thirty-two patients were included. T max thresholds of >16.2 and >15.8 s and absolute cerebral blood flow thresholds of <8.9 and <7.4 mL•min −1•100 g −1 were associated with infarct if reperfused <90 min from CTP with onset <180 min. The discriminative ability of cerebral blood volume was modest. No statistically significant relationship was noted between stroke onset-to-CTP time and the optimal CTP thresholds for all parameters based on discrete or continuous time analysis (P>0.05). A statistically significant relationship existed between CTP-to-reperfusion time and the optimal thresholds for cerebral blood flow (P<0.001; r=0.59 and 0.77 for gray and white matter, respectively) and T max (P<0.001; r=−0.68 and −0.60 for gray and white matter, respectively) parameters. Conclusions-Optimal CTP thresholds associated with follow-up infarction depend on time from imaging to reperfusion.

The clinical diagnosis of Marchiafava-Bignami disease (MBD) has considerably changed during recent decades with brain MRI providing the opportunity of a reliable in-vivo diagnosis. However, semiologic and neuroimaging characteristics of the currently known spectrum of MBD have not been investigated systematically, and knowledge of clinicoradiologic associations is sketchy. We report an illustrative case with limited callosal involvement on MRI and a favorable outcome and have reviewed literature on clinical and radiologic features in 50 cases of MBD diagnosed in vivo since 1985. Our reviewed data suggest the differentiation of two clinicoradiologic subtypes: Type A is characterized by major impairment of consciousness, T2-hyperintense swelling of the entire corpus callosum on early MRI and poor outcome. Type B shows at most slight impairment of consciousness, partial callosal lesions on MRI and a favorable outcome. Differentiation of these clinicoradiologic subtypes may help resolve inconsistencies of the established clinical classification resulting from new insights into the clinical course and prognosis of MBD by structural neuroimaging.