C. Oppenheim

Prediction of Malignant Middle Cerebral Artery Infarction by Diffusion-Weighted Imaging

Background and Purpose This study was designed to analyze whether early diffusion-weighted imaging (DWI) provides reliable quantitative information for the prediction of stroke patients at risk of malignant brain infarct. Methods We selected 28 patients with a middle cerebral artery (MCA) infarct and proven MCA or carotid T occlusion on DWI and MRI angiography performed within 14 hours after onset (mean 6.5±3.5 hours, median 5.2 hours). Of these, 10 patients developed malignant MCA infarct, whereas 18 did not. For the 2 groups, we compared the National Institutes of Health Stroke Scale (NIHSS) score at admission, site of arterial occlusion, standardized visual analysis of DWI abnormalities, quantitative volume measurement of DWI abnormalities (volumeDWI), and apparent diffusion coefficient values. Univariate and multivariate discriminant analysis was used to determine the most accurate predictors of malignant MCA infarct. Results Univariate analysis showed that an admission NIHSS score >20, total versus partial MCA infarct, and volumeDWI >145 cm3 were highly significant predictors of malignant infarct. The best predictor was volumeDWI >145 cm3, which achieved 100% sensitivity and 94% specificity. Prediction was further improved by bivariate models combining volumeDWI and apparent diffusion coefficient measurements, which reached 100% sensitivity and specificity in this series of patients. Conclusions Quantitative measurement of infarct volume on DWI is an accurate method for the prediction of malignant MCA infarct in patients with persistent arterial occlusion imaged within 14 hours of onset. This may be of importance for early management of severe stroke patients.

Usefulness of Magnetic Resonance–Derived Quantitative Measurements of Cerebral Blood Flow and Volume in Prediction of Infarct Growth in Hyperacute Stroke

Background and Purpose The identification of the tissue at risk for infarction remains challenging in stroke patients. In this study, we evaluated the value of quantitative cerebral blood flow (CBF) and cerebral blood volume (CBV) measurements in the prediction of infarct growth in hyperacute stroke. Methods Fluid-attenuated inversion recovery (FLAIR), diffusion-weighted (DW), and gradient-echo echo-planar perfusion-weighted (PW) sequences were obtained in 66 patients within 6 hours of stroke onset; ischemia was confirmed on follow-up FLAIR images. We delineated the following: (1) the initial infarct on DW images, (2) the area of hemodynamic disturbance on mean transit time (MTT) maps, and (3) the final infarct on follow-up FLAIR images. MTT, CBF, and CBV were calculated in the following areas: area of initial infarct (INF), area of infarct growth (IGR, final minus initial infarct), the hemodynamically disturbed area that remained viable (OLI, hemodynamic disturbance minus final infarct), and all contralateral mirror regions. Results Compared with mirror regions, the MTT in abnormal areas was always prolonged. The respective mean±SD CBF and CBV values were as follows: for INF, 28±16 mL/min per 100 g and 6.9±2.7%; for IGR, 36±20 mL/min per 100 g and 8.9±3.1%; for OLI, 50±17 mL/min per 100 g and 11.2±3%; and for mirror regions, 64±23 mL/min per 100 g and 8.7±2.5%. The CBV and CBF values were significantly different between all abnormal areas (except for the CBF between INF and IGR). In the area of DW/PW mismatch, a combined CBF or CBV threshold of 35 or 8.2, respectively, predicted evolution to infarction with a sensitivity of 81% and a specificity of 76%. Conclusions Quantitative measurements of CBF and CBV in hyperacute stroke may help to predict infarct growth and to select the subjects who will benefit from thrombolysis.

Can diffusion weighted magnetic resonance imaging help differentiate stroke from stroke-like events in MELAS?

The precise mechanism of neurological symptoms in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is still controversial. The diffusion weighted MR findings at the acute phase of a neurological event in MELAS are described and the pathophysiology of stroke-like lesion in the light of diffusion changes is discussed. Brain MRI was performed 2 days after the sudden onset of cortical blindness in a 25 year old patient with MELAS. Fluid attenuated inversion recovery (FLAIR) images showed multifocal cortical and subcortical hyperintensities located bilaterally in the frontobasal and the temporo-occipital lobes. Diffusion weighted images showed normal to increased apparent diffusion coefficient values in the acute left temporooccipital lesion and increased values in the older stroke-like lesions. These diffusion weighted findings support the metabolic rather than the ischaemic pathophysiological hypothesis for stroke-like episodes occurring in MELAS. Normal or increased apparent diffusion coefficient values within 48 hours of a neurological deficit of abrupt onset should raise the possibility of MELAS, especially if conventional MR images show infarct-like lesions.

Diffusion-Weighted Magnetic Resonance Imaging in a Case of Cerebral Venous Thrombosis

BACKGROUNDnDiffusion-weighted imaging (DWI) is the most sensitive MR sequence in acute arterial ischemic stroke but has not yet been evaluated in venous cerebral ischemia. We describe a patient with DWI performed at the acute phase of a venous ischemic stroke.nnnCASE DESCRIPTIONnA rapid cerebral MRI including DWI and fast fluid-attenuated inversion recovery (FLAIR) sequences was performed at the acute phase of a venous stroke confirmed by conventional angiography. DWI showed a slight decrease in apparent diffusion coefficient values 3 hours after onset (0.53+/-0.07x10(-3) mm2/s) and was normal 48 hours later (0.064+/-0.15x10(-3) mm2/s). Fast FLAIR sequences showed large left frontoparietal hyperintensities. The lack of a clear decrease in apparent diffusion coefficient values associated with marked FLAIR abnormalities may suggest prominent or early associated vasogenic edema. Physiopathological differences between arterial and venous ischemia may explain the different type of DWI FLAIR abnormalities during the acute phase as well as the better recovery of neurological deficit in venous stroke than in arterial ischemic stroke.nnnCONCLUSIONSnIn the context of an acute stroke, the contrast between marked FLAIR and subtle DWI abnormalities on MRI may reflect the venous mechanism of cerebral ischemia.

Added Value of High-Resolution MR Imaging in the Diagnosis of Vertebral Artery Dissection

BACKROUND AND PURPOSE: The optimal imaging method for the diagnosis of VAD remains undefined. Our aim was to evaluate the added value of HR-MR imaging for the diagnosis of VAD. MATERIALS AND METHODS: We retrospectively extracted 35 consecutive patients suspected of having acute VAD who had the following: 1) a focal lumen abnormality of the VA on CE-MRA, 2) HR-MR imaging during the initial hospital stay, and 3) clinical and imaging follow-up within 6 months. Two neurologists classified patients as either VAD (group A) or non-VAD (group B) by reviewing all the available data at hospital discharge, except HR-MR imaging data. On HR-MR imaging, 2 radiologists searched for signs of acute VAD. The 2 classifications were compared. In case of discordance, CE-MRA follow-up and axial fat-suppressed T1WI, used to obtain supportive evidence for or against VAD, were considered as the standard of reference. RESULTS: In 4/18 patients in group A, HR-MR imaging did not demonstrate any signs of acute VAD and perivertebral signal-intensity changes were attributed to venous plexus, with an unchanged lumen on follow-up. In 4/17 patients in group B, HR-MRI demonstrated a mural hematoma, with lumen normalization on follow-up CE-MRA. CONCLUSIONS: Our results encourage the use of HR-MR imaging as a second-line diagnostic tool in the event of suspicion of acute VAD and doubtful findings on standard imaging.

Diagnosis of acute ischaemic stroke with fluid-attenuated inversion recovery and diffusion-weighted sequences

Abstract We evaluated the feasibility and use of diffusion-weighted and fluid-attenuated inversion-recovery pulse sequences performed as an emergency for patients with acute ischaemic stroke. A 5-min MRI session was designed as an emergency diagnostic procedure for patients admitted with suspected acute ischaemic stroke. We reviewed routine clinical implementation of the procedure, and its sensitivity and specificity for acute ischaemic stroke over the first 8 months. We imaged 91 patients (80 min to 48 h following the onset of stroke). Clinical deficit had resolved in less than 3 h in 15 patients, and the remaining 76 were classified as stroke (59) or stroke-like (17) after hospital discharge. Sensitivity of MRI for acute ischaemic stroke was 98 %, specificity 100 %. MRI provided an immediate and accurate picture of the number, site, size and age of ischaemic lesions in stroke and simplified diagnosis in stroke-like episodes. The feasibility and high diagnostic accuracy of emergency MRI in acute stroke strongly support its routine use in a stroke centre.

Pulsed arterial spin labeling applications in brain tumors: Practical review

Few institutions use MRI perfusion without contrast injection called arterial spins labeling (ASL) routinely in clinical setting. After general considerations concerning the different ASL techniques and quantitative issues, we will detail a pulsed sequence that can be used on a clinical 1.5-T MR unit. We will discuss and illustrate the use of ASL in tumoral diseases for diagnosis, gliomas grading, stereotactic biopsy guidance and for follow-up after treatment.

MR Imaging-Based Decision in Thrombolytic Therapy for Stroke on Awakening : Report of 2 Cases

SUMMARY: Patients with stroke on awakening are denied the potential benefit of thrombolysis on the grounds that the onset time is unknown. Relying on clinical and MR imaging to indicate the most appropriate treatment could be more rational. We report 2 cases of stroke with unknown onset time. In both cases, anamnesis and MR imaging indicated that we might still be within 6 hours from stroke onset, with salvageable tissue. Arterial recanalization was successfully performed in both cases.

Suprasellar paraganglioma: a case report and review of the literature

Paragangliomas arising in the suprasellar region are extremely rare. We report a case of suprasellar paraganglioma in a 47-year-old man who presented with amnesia and impaired visual acuity without any endocrine dysfunction. Magnetic resonance imaging (MRI) showed a large enhancing tumour in the suprasellar area. Following subtotal surgical excision, the diagnosis of paraganglioma was confirmed by pathology. In this case report we describe the MRI pattern of suprasellar paraganglioma and review the literature of this uncommon lesion.

Magnetic Resonance-Guided Stereotactic Biopsies: Results in 100 Consecutive Cases

Summary¶u2003Background. We present the results of 100 consecutive magnetic resonance (MR)-guided biopsies in cases where computerised tomography (CT) guiding was considered dangerous or impossible.nMethod. MR guiding was preferred to CT guiding for cases where lesions were located in the central area, or were not clearly visible on CT scan, or where the visualization of vessels was considered necessary. For most of the patients, calculation of target co-ordinates was performed using dedicated software enabling trajectory previsualization. There were 62 cases of contrast enhanced lesions, 32 cases of lesions without contrast enhancement, and 6 cases of very small lesions appearing hyperintense on T2-weighted images.nFindings. Biopsies allowed a histological diagnosis in 92 cases. In 8 cases, the biopsy was negative (necrosis, gliosis or normal brain tissue). Three patients had a transient worsening of their neurological disturbances. Two patient had a non-regressive loss of motor function. No patient died.nInterpretation. MR guiding for stereotactic biopsies was effective for CT-invisible or ill-defined lesions, lesions located in functional or densely vascularized areas and in the brain stem. The rate of postoperative complications was equivalent to or less than that reported in series of CT-guided biopsies.