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Purpose: To develop an imaging prediction model for patients with embolic stroke of undetermined source (ESUS), we investigated the association of topographic diffusion-weighted imaging (DWI) patterns with potential embolic sources (PES) identified by transesophageal echocardiography., Methods: From a total of 992 consecutive patients with embolic stroke, 366 patients with the ESUS group were selected. ESUS was defined as no atrial fibrillation (Af) within 24h from admission and no PES after general examination. Clinical variables include age (> 80years, 70-80 years), sex, vascular risk factors and left atrial diameter > 4 cm. Age, sex and vascular risk factors adjusted odds ratio of each DWI for the different PESs were calculated. DWI was determined based on the arterial territories. Middle cerebral arteries were divided into 4 segments, i.e., M1-M4. Moreover, M2 segments were subdivided into superior and inferior branches., Results: The 366 patients consisted of 168 with paroxysmal Af (pAf), 77 with paradoxical embolism, 71 with aortic embolism and 50 with undetermined embolism after transesophageal echocardiography. The variables adjusted odds ratio (OR) of internal carotid artery (OR: 12.1, p = 0.037), M1 (4.2, p = 0.001), inferior M2 (7.5, p = 0.0041) and multiple cortical branches (12.6, p < 0.0001) were significantly higher in patients with pAf. Striatocapsular infarction (12.5, p < 0.0001) and posterior inferior cerebellar artery infarcts (3.6, p = 0.018) were significantly associated with paradoxical embolism. Clinical variables adjusted OR of multiple small scattered infarcts (8.3, p < 0.0001) were significantly higher in patients with aortic embolism., Conclusion: The associations of DWI with different PES have their distinctive characteristics and DWI along with clinical variables may help predict PES in patients with ESUS., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)

Diffusion-weighted imaging (DWI) is commonly used to assess irreversibly infarcted tissue but its accuracy is challenged by reports of diffusion lesion reversal (DLR). We investigated the frequency and implications for mismatch classification of DLR using imaging from the EPITHET (Echoplanar Imaging Thrombolytic Evaluation Trial) and DEFUSE (Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution) studies. In 119 patients (83 treated with IV tissue plasminogen activator), follow-up images were coregistered to acute diffusion images and the lesions manually outlined to their maximal visual extent in diffusion space. Diffusion lesion reversal was defined as voxels of acute diffusion lesion that corresponded to normal brain at follow-up (i.e., final infarct, leukoaraiosis, and cerebrospinal fluid (CSF) voxels were excluded from consideration). The appearance of DLR was visually checked for artifacts, the volume calculated, and the impact of adjusting baseline diffusion lesion volume for DLR volume on perfusion-diffusion mismatch analyzed. Median DLR volume reduced from 4.4 to 1.5 mL after excluding CSF/leukoaraiosis. Visual inspection verified 8/119 (6.7%) with true DLR, median volume 2.33 mL. Subtracting DLR from acute diffusion volume altered perfusion-diffusion mismatch (T(max)>6 seconds, ratio>1.2) in 3/119 (2.5%) patients. Diffusion lesion reversal between baseline and 3 to 6 hours DWI was also uncommon (7/65, 11%) and often transient. Clinically relevant DLR is uncommon and rarely alters perfusion-diffusion mismatch. The acute diffusion lesion is generally a reliable signature of the infarct core.

Background and Purpose: The ischemic penumbra may be classical, with complete annular configuration around the infarct core, or nonclassical with a more fragmented pattern. We tested the hypotheses that these penumbral patterns may: be associated with specific predictive factors, influence infarct growth and clinical outcome, and influence the effect of tissue plasminogen activator (t-PA)., Methods: Using the EPITHET/DEFUSE data set, in which patients received alteplase or placebo 3 to 6 hours poststroke, perfusion-weighted imaging and diffusion-weighted imaging images were analyzed. These mismatch patterns were defined as "classical" or "nonclassical." Multivariate analysis was used to identify variables associated with mismatch patterns, the effect of t-PA, as well as the relationship between mismatch patterns, infarct growth, and clinical outcomes., Results: We included 158 patients (median age, 74 years; median National Institute of Health Stroke Scale score, 12). Multivariate analysis indicated that the factors associated with classical mismatch pattern type were large mismatch volume (P<0.001) and cortical infarct location (P=0.036). Infarct growth, clinical outcome, and the efficacy of t-PA were not statistically different between patterns., Conclusions: Coregistered mismatch volume and cortical location of infarction were the important factors associated with presence of the classical mismatch pattern. The lack of effect of the type of mismatch patterns on infarct growth, clinical outcomes, or the benefit of t-PA would suggest that mismatch topography is less important during the hyperacute phase of ischemic stroke than during subacute phase.

Background and Purpose: the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET) was a prospective, randomized, double-blinded, placebo-controlled, phase II trial of alteplase between 3 and 6 hours after stroke onset. The primary outcome of infarct growth attenuation on MRI with alteplase in mismatch patients was negative when mismatch volumes were assessed volumetrically, without coregistration, which underestimates mismatch volumes. We hypothesized that assessing the extent of mismatch by coregistration of perfusion and diffusion MRI maps may more accurately allow the effects of alteplase vs placebo to be evaluated., Methods: patients were classified as having mismatch if perfusion-weighted imaging divided by coregistered diffusion-weighted imaging volume ratio was >1.2 and total coregistered mismatch volume was ≥ 10 mL. The primary outcome was a comparison of infarct growth in alteplase vs placebo patients with coregistered mismatch., Results: of 99 patients with baseline diffusion-weighted imaging and perfusion-weighted imaging, coregistration of both images was possible in 95 patients. Coregistered mismatch was present in 93% (88/95) compared to 85% (81/95) with standard volumetric mismatch. In the coregistered mismatch patients, of whom 45 received alteplase and 43 received placebo, the primary outcome measure of geometric mean infarct growth was significantly attenuated by a ratio of 0.58 with alteplase compared to placebo (1.02 vs 1.77; 95% CI, 0.33-0.99; P=0.0459)., Conclusions: when using coregistration techniques to determine the presence of mismatch at study entry, alteplase significantly attenuated infarct growth. This highlights the necessity for a randomized, placebo-controlled, phase III clinical trial of alteplase using penumbral selection beyond 3 hours.

Introduction: It is often clinically difficult to assess the severity of aphasia in the earliest stage of cerebral infarction. A method enabling objective assessment of verbal function is needed for this purpose. We examined whether diffusion tensor (DT) tractography is of clinical value in assessing aphasia., Methods: Thirteen right-handed patients with left middle cerebral artery infarcts who were scanned within 2 days after stroke onset were enrolled in this study. Magnetic resonance data of ten control subjects were also examined by DT tractography. Based on the severity of aphasia at discharge, patients were divided into two groups: six patients in the aphasic group and seven in the nonaphasic group. Fractional anisotropy (FA) and number of arcuate fasciculus fibers were evaluated. Asymmetry index was calculated for both FA and number of fibers., Results: FA values for the arcuate fasciculus fibers did not differ between hemispheres in either the patient groups or the controls. Number of arcuate fasciculus fibers exhibited a significant leftward asymmetry in the controls and the nonaphasic group but not in the aphasic group. Asymmetry index of number of fibers was significantly lower (rightward) in the aphasic group than in the nonaphasic (P = 0.015) and control (P = 0.005) groups. Loss of leftward asymmetry in number of AF fibers predicted aphasia at discharge with a sensitivity of 0.83 and specificity of 0.86., Conclusions: Asymmetry of arcuate fasciculus fibers by DT tractography may deserve to be assessed in acute infarction for predicting the fate of vascular aphasia.

Background and Aims: The apparent diffusion coefficient (ADC) and anisotropy (eg, fractional anisotropy (FA)) of ischaemic tissue evolve over time. A reduction in diffusivity (ie, lambda(2) and lambda(3)) is an important marker for characterising hyperacute-stage infarction, as these parameters may reflect axonal membrane status. The study examines whether transverse diffusivity could be useful in assessing white matter infarcts of various ages., Methods: Diffusion tensor imaging data from 44 adult patients (34 men, 10 women, aged 46 to 89 years, mean = 70.3) with acute white matter infarction (1-168 h) of the internal capsule were analysed. Relative eigenvalues were calculated as: (lambda(ipsi)-lambda(contra))/lambda(contra). Lesions were classified based on theoretically expected evolution of diffusivity over time as follows: stage I, FA higher than the contralesional region of interest (ROI); stage II, diffusivity lower than the contralesional side for all eigenvalues; stage III, one of two transverse eigenvalues (lambda(2) or lambda(3)) higher than the contralesional ROI., Results: Stage I infarcts (n = 5) were found primarily within 24 h of the onset of symptoms, with one case found on the third day. Stage II infarcts were found most commonly within 24 h (n = 18), and fewer after 24 h. After the first day, the ratio of stage III infarcts increased significantly. Thus, diffusivity-based classification of white matter infarcts seems to show a chronological trend., Conclusions: Diffusion anisotropy may be useful for defining the biological tissue clock of white matter infarctions.

We present two patients (case 1: a 78-year-old right-handed woman, case 2: a 66-year-old right-handed woman) with suspected transient global amnesia. Both patients showed sudden onset amnesia that appeared to resolve within 24 hours, and they showed no abnormal findings on electroencephalography or single photon emission tomography. However, the results of the Wechsler Memory Scale-Revised (WMS-R) on the ninth (case2) or tenth day (case1) after the onset indicated memory impairment. And diffusion-weighted magnetic resonance imaging (DWI) revealed a unilateral high-intensity area in the hippocampus, leading to the diagnosis of hippocampal infarction in both patients. Case 1 had a left hippocampal lesion and exhibited impairment of predominantly verbal memory, while case 2 had a right hippocampal lesion and demonstrated impairment of predominantly visual memory. When evaluating a patient with suspected transient global amnesia, imaging of the hippocampus and tests on memory function after an appropriate interval from the onset are often helpful in establishing a correct diagnosis.

Background and Purpose: Pathogenesis of leukoaraiosis is incompletely understood and accumulation of small infarctions may be one of the possible sources of such white matter lesions. Thus, the purpose of this study was to identify the rate of incident infarction as depicted on diffusion-weighted images (DWIs) obtained from a general patient population., Materials and Methods: During the 4-year study period, a total of 60 patients (36 men and 24 women) had an incidental DWI-defined infarction without overt clinical symptoms suggestive of a stroke or a transient ischemic attack. All of the MR images were obtained by using a similar protocol on 2 identical 1.5T whole-body scanners. The patient's vascular risk factors, as well as the presence of white matter lesions (WMLs) on MR imaging and atheromatous changes on MR angiography, were assessed retrospectively. The incidental DWI-defined infarcts were also characterized in terms of their lateralization, lobe, and specific location., Results: A total of 16,206 consecutive brain MR images were done during the study period; the overall incidence of incidental infarcts was 0.37%. Most of these patients with an incidental infarct had vascular risk factors and WMLs on MR images. Most of these patients (80%) had a single lesion on DWI. A total of 88 lesions were identified; most were located in the white matter of the supratentorial brain, primarily in the frontoparietal lobes. There were also lesions involving the brain stem (n = 2). The lesions involving cerebrum were more commonly located in the right side (right to left = 52:34)., Conclusion: Small, DWI-defined acute brain infarctions can be found incidentally in an asymptomatic population; this finding may account, at least in part, for the pathogenesis of WMLs identified on MR imaging.

Purpose: To prospectively evaluate the course of sensory fibers through the supratentorial brain with diffusion-tensor-based tractography., Materials and Methods: This study was approved by the institutional review board. Informed consent was obtained. Seven healthy volunteers (five men, two women; age range, 20-55 years) underwent 1.5-T magnetic resonance imaging. Diffusion-tensor images with isotropic voxels (2 x 2 x 2 mm) were obtained by using a single-shot echo-planar imaging technique, with a motion-probing gradient in 15 orientations, a b value of 1000 sec/mm(2), and nine signals acquired. The total imaging time was approximately 30 minutes. Fiber tracking of the sensorimotor pathways was performed with the fiber assignment by continuous tracking method., Results: All the pyramidal tracts rotated anteriorly as they traveled through the centrum semiovale. On the other hand, the sensory tracts rotated posteriorly as they coursed through the centrum semiovale toward the cortex. When the sensorimotor tracts were viewed as a unit, the tracts of the lower extremity formed the axis of rotation around which the other parts of the pyramidal and sensory homunculus rotated., Conclusion: Sensorimotor fibers of the lower extremity form an axis of rotation, around which the pyramidal fibers rotate anteriorly and the sensory fibers rotate posteriorly.