The resistance to ischemia of white and gray matter after stroke

Background and Purpose— In acute ischemic stroke, white matter (WM) is considered more resistant to infarction than gray matter (GM). To test this hypothesis, we compared the fate of WM and GM voxels belonging to the acute diffusion-weighted imaging (DWI) lesion, expecting WM voxels to be more prone to reversal after thrombolysis. Methods— Reversible acute DWI (RAD) lesion was defined voxel-wise as an acute lesion on initial DWI (DWI 1 ) with no visible lesion on 24-hour DWI (DWI 2 ). Only patients with RAD lesions >10 mL and >10% of DWI 1 from our previously reported cohort were eligible. The core was defined as voxels hyperintense on DWI 1 and DWI 2 . Semiautomated segmentation of DWI 1 , core, and RAD lesions, normalization into standard space, and WM/GM segmentation allowed calculations of WM/GM proportions in each region of interest using a voxel-counting algorithm. Results— Thirty patients were eligible (RAD lesion median volume [interquartile range], 23.3 mL [19.1–35.0 mL]; onset-to-treatment time, 134 minutes [105–185 minutes]). WM voxels fraction was greater in RAD lesions than in the core (59.4% [52.8%–68.9%] versus 49.6% [43.0%–57.5%]; P =0.011). The proportion of reversibility was greater for WM than for GM voxels (60.8% [25.5%–88.7%] versus 53.5% [21.1%–77.3%]; P =0.02). The percentage of RAD lesions increased with the proportion of WM present in the acute DWI lesion ( P <0.0001; R =0.67). Conclusions— Acute DWI lesions predominantly involving WM may be more prone to reversal and, hence, to respond to therapy than their GM counterparts.

Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Is White Matter More Prone to Diffusion Lesion Reversal After Thrombolysis?

Tisserand

Malherbe

Turc

et al. 2014

“…17 ROIs were placed over the cortex, insula, basal ganglia, and white matter areas in both the affected and unaffected hemispheres across the whole range of axial cuts (Ϸ150 ROIs per subject and side; total number of ROIs across patientsϭ1194). ROIs having a mean PET CBV value Ͼ8.0 mL/100 g were excluded as artifactual.…”

Section: Regions Of Interestmentioning

confidence: 99%

How Reliable Is Perfusion MR in Acute Stroke?

Takasawa

Jones

Guadagno

et al. 2008

180

110

Background and Purpose-Perfusion magnetic resonance imaging (pMR) is increasingly used in acute stroke, but its physiologic significance is still debated. A reasonably good correlation between pMR and positron emission tomography (PET) has been reported in normal subjects and chronic cerebrovascular disease, but corresponding validation in acute stroke is still lacking. Methods-We compared the cerebral blood flow (CBF), cerebral blood volume, and mean transit time (MTT) maps generated by pMR (deconvolution method) and PET ( 15 O steady-state method) in 5 patients studied back-to-back with the 2 modalities at a mean of 16 hours (range, 7 to 21 hours) after stroke onset. We also determined the penumbra thresholds for pMR-derived MTT, time to peak (TTP), and Tmax against the previously validated probabilistic PET penumbra thresholds. Results-In all patients, the PET and pMR relative distribution images were remarkably similar, especially for CBF and MTT. Within-patient correlations between pMR and PET were strong for absolute CBF (average r 2 ϭ0.45) and good for MTT (r 2 ϭ0.35) but less robust for cerebral blood volume (r 2 ϭ0.24). However, pMR overestimated absolute CBF and underestimated MTT, with substantial variability in individual slopes. Removing individual differences by normalization to the mean resulted in much stronger between-patient correlations. Penumbra thresholds of Ϸ6, 4.8, and 5.5 seconds were obtained for MTT delay, TTP delay, and Tmax, respectively. Conclusions-Although derived from a small sample studied relatively late after stroke onset, our data show that pMR tends to overestimate absolute CBF and underestimate MTT, but the relative distribution of the perfusion variables was remarkably similar between pMR and PET. pMR appears sufficiently reliable for clinical purposes and affords reliable detection of the penumbra from normalized time-based thresholds. (Stroke. 2008;39:870-877.)

“…46 White matter appeared to have a higher proportion of hypoxic tissue than gray at the time of imaging, though the volumes of hypoxic tissue eventually surviving infarction were similar in both compartments. This may indirectly suggest that white matter was initially more resistant to ischemia and proceeded more slowly to infarction than gray matter.…”

Section: Takasawa Et Al Hypoxia Imaging In Ischemic Strokementioning

confidence: 91%

Applications of Nitroimidazole In Vivo Hypoxia Imaging in Ischemic Stroke

Takasawa

Moustafa

Baron

2008

104

Background and Purpose-Nitroimidazole imaging is a promising contender for noninvasive in vivo mapping of brain hypoxia after stroke. However, there is a dearth of knowledge about the behavior of these compounds in the various pathophysiologic situations encountered in ischemic stroke. In this article we report the findings from a systematic review of the literature on the use of the nitroimidazoles to map hypoxia after stroke. Summary of Review-We describe the characteristics of nitroimidazoles as imaging tracers, their pharmacology, and results of both animal and clinical studies during and after focal cerebral ischemia. Findings in brain tumors are also presented to the extent that they enlighten results in stroke. Early results from application of kinetic modeling for quantitative measurement of tracer binding are briefly discussed. Conclusions-Based on this literature review, nitroimidazole hypoxia imaging agents are of considerable interest in stroke because they appear, both in animal models and in humans, to specifically detect the severely hypoxic viable tissue, but not the reperfused nor the necrotic tissue. To fully realize this potential in stroke, however, formal validation by concurrent measurement of tissue oxygen tension, together with development of novel ligands with faster distribution kinetics, faster clearance from normal tissue, and well-defined trapping mechanisms, are important goals for future investigations.