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Neuroimaging is critical in the evaluation of patients with transient ischemic attack (TIA) and MRI is the recommended modality to image an ischemic lesion. The presence of a diffusion (DWI) lesion in a patient with transient neurological symptoms confirms the vascular origin of the deficit and is predictive of a high risk of stroke. Refinement of MR studies including high resolution DWI and perfusion imaging using either MRI or CT further improve the detection of ischemic lesions. Rapid etiological work-up includes non-invasive imaging of cervical and intracranial arteries to search for symptomatic stenosis/occlusion associated with an increased risk of stroke., (Copyright © 2015. Published by Elsevier Masson SAS.) more...

Purpose: Type 2 focal cortical dysplasia (FCD2) is one of the main causes of refractory partial epilepsy, but often remains overlooked by MRI. This study aimed to elucidate whether 3T MRI offers better detection and characterization of FCD2 than 1.5T, using similar coils and acquisition time., Methods: Two independent readers reviewed the 1.5T and 3T MR images of 25 patients with histologically proven FCD2. For both magnetic fields, the ability to detect a lesion was analyzed. We compared the identification of each of the five criteria typical of FCD2 (cortical thickening, blurring, cortical signal changes, subcortical signal changes, and "transmantle" sign) and artifacts, using a four-point scale (0-3). Interobserver reliability for lesion detection was calculated., Key Findings: Seventeen lesions (68%) were detected at 3T, two of which were overlooked at 1.5T. Interobserver reliability was better at 3T (κ = 1) than at 1.5T (κ = 0.83). The transmantle sign was more clearly identified at 3T than 1.5T (mean visualization score: 1.72 vs. 0.56; p = 0.002)., Significance: The use of 3T MRI in patients suspected of type 2 FCD improves the detection rate and the lesion characterization owing to the transmantle sign being more clearly seen at 3T. This point is of interest, since this feature is considered as an MR signature of FCD2., (Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.) more...

Background and Purpose: Our aim was to estimate the prevalence of negative diffusion-weighted imaging (DWI) with total perfusion-diffusion mismatch in a large series of anterior circulation stroke patients treated with thrombolysis and to describe the characteristics of these patients., Materials and Methods: From January 2006 to December 2010, a retrospective search was made for total perfusion-diffusion (PWI-DWI) mismatch patterns on pretreatment 1.5-T MRI scans of 166 consecutive thrombolyzed patients taken<4.5 h after onset of anterior stroke. A total mismatch profile corresponded to an absence of initial DWI signal changes with hypoperfusion (T(max)>6 s) on PWI. Clinical and MRI characteristics were compared between DWI+ and DWI- patients., Results: Five (3%) patients had a normal initial DWI. All had stable substantial clinical deficits (NIHSS scores ≥ 6) and large perfusion abnormalities - in other words, 'total mismatch' - and infarcts in the acutely hypoperfused area on follow-up imaging. While DWI- and DWI+ patients did not significantly differ in any of the pretreatment imaging or clinical variables except for the extent of PWI-DWI mismatch, DWI- patients had lower NIHSS scores at 24 h, and were more likely to show early neurological improvement (Δ0-24 h NIHSS ≥ 8) and good outcomes (mRS ≤ 2) at the time of hospital discharge., Conclusion: Total mismatch i.e. failure of DWI to reveal any ischemic tissue despite a large perfusion defect, can be observed before thrombolysis even in stroke patients with stable substantial neurological deficits. However, this rare MRI profile is associated with a favorable outcome after thrombolysis., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.) more...

Background and Purpose: Type 2 FCD is one of the main causes of drug-resistant partial epilepsy. Its detection by MR imaging has greatly improved surgical outcomes, but it often remains overlooked. Our objective was to determine the prevalence of typical MR imaging criteria for type 2 FCD, to provide a precise MR imaging pattern, and to optimize its detection., Materials and Methods: We retrospectively reviewed 1.5T MR imaging of 71 consecutive patients with histologically proved type 2 FCD. The protocol included millimetric 3D T1-weighted, 2D coronal and axial T2-weighted, and 2D or 3D FLAIR images. Two experienced neuroradiologists looked for 6 criteria: cortex thickening, cortical and subcortical signal changes, blurring of the GWM interface, the "transmantle" sign, and gyral abnormalities. The frequency of each sign and their combination were assessed. We compared the delay between epilepsy onset and surgery, taking into account the time of type 2 FCD detection by MR imaging., Results: Only 42 patients (59%) had positive MR imaging findings. In this group, a combination of at least 3 criteria was always found. Subcortical signal changes were constant. Three characteristic signs (cortical thickening, GWM blurring, and transmantle sign) were combined in 64% of patients, indicating that MR imaging can be highly suggestive. However, typical features of type 2 FCD were overlooked on initial imaging in 40% of patients, contributing to a delay in referral for surgical consideration (17 versus 11.5 years when initial MR imaging findings were positive)., Conclusions: A combination of 3 major MR imaging signs allows type 2 FCD to be recognized in clinical practice, thereby enabling early identification of candidates for surgery. more...