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ABSTRACT: BACKGROUND AND PURPOSE: Bilateral paramedian thalamic infarction is a rare subtype of stroke the etiology of which still remains undetermined in many patients. METHODS: From a computed tomography (CT)/magnetic resonance imaging report database, we identified and analyzed 48 patients with bilateral paramedian thalamic infarction on diffusion-weighted imaging. Vascular pathologies were noted on CT angiography (CTA)/magnetic resonance angiography (MRA) and the P1 segments of the posterior cerebral artery (PCA) described as normal, hypoplastic, or absent. RESULTS: Vascular imaging revealed top of the basilar artery (BA) occlusion in 6 (12.5%), BA occlusion in 4 (8.3%), BA stenosis in 1 (2.1%), and BA hypoplasia in 3 (6.3%), PCA occlusion in 4 (8.3%), and PCA stenosis in 4 (8.3%) patients. In 18 (37.5%) patients, one or both P1 segments of the PCA were hypoplastic or absent. Patients with hypoplastic/absent P1 segments were more likely to have exclusively bilateral paramedian thalamic lesions (P < .001). An embolic source could be identified in 25 (55.6%) patients; there were no significant differences between both groups. CONCLUSIONS: Vascular imaging is useful to determine underlying vascular pathologies and may support the diagnosis of small vessel disease in those patients with isolated bilateral paramedian thalamic infarction, hypoplastic/absent P1 segment of the PCA, and lack of vascular pathology.
Journal of neuroimaging: official journal of the American Society of Neuroimaging 04/2013; · 1.72 Impact Factor
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ABSTRACT: Object Reliable visualization of the subthalamic nucleus (STN) is indispensable for accurate placement of electrodes in deep brain stimulation (DBS) surgery for patients with Parkinson disease (PD). The aim of the study was to evaluate different promising new MRI methods at 3.0 T for preoperative visualization of the STN using a standard installation protocol. Methods Magnetic resonance imaging studies (T2-FLAIR, T1-MPRAGE, T2*-FLASH2D, T2-SPACE, and susceptibility-weighted imaging sequences) obtained in 9 healthy volunteers and in 1 patient with PD were acquired. Two neuroradiologists independently analyzed image quality and visualization of the STN using a 6-point scale. Interrater reliability, contrast-to-noise ratios, and signal-to-noise ratios for the STN were calculated. For illustration of the anatomical accuracy, coronal T2*-FLASH2D images were fused with the corresponding coronal section schema of the Schaltenbrand and Wahren stereotactic atlas. Results The STN was best and reliably visualized on T2*-FLASH2D imaging (in particular, the coronal view). No major artifacts in the STN were observed in any of the sequences. Susceptibility-weighted, T2-SPACE, and T2*-FLASH2D imaging provided significantly higher contrast-to-noise ratio values for the STN than standard T2-weighted imaging. Fusion of the coronal T2*-FLASH2D and the digitized coronal atlas view projected the STN clearly within the boundaries of the STN found in anatomical sections. Conclusions For 3.0-T MRI, T2*-FLASH2D (particularly the coronal view) provides optimal delineation of the STN using a standard installation protocol.
Journal of Neurosurgery 10/2012; · 2.96 Impact Factor
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ABSTRACT: To assess the feasibility of dual energy (DE)-CTA images with DE-bone removal (DEBR) for visualization of extra- to intracranial (EC/IC) arterial bypass compared to digital subtraction angiography (DSA).
Prospectively, 24 patients underwent DE-CTA and DSA for evaluation of EC/IC-bypass. Using 5-point scales (0=poor to 4=excellent) two examiners rated image quality, quality of bone removal, and vessel integrity of bypass for three segments (extracranial, trepanation, intracranial) in CTA images with and without DEBR in comparison to DSA. Scores were evaluated by Friedmann's- and post-hoc Wilcoxon rank test.
Image quality was high in CTA with and without DEBR and DSA (3.78 ± 0.36, 3.78 ± 0.36, 3.27 ± 0.46). No significant bone remnants were present using DEBR. Mean scores of bypass visualization were not significantly different for the extra- and intracranial segments. However, in the trepanation segment pseudo-lesions of the bypass were present in DEBR-CTA (6 out 24 cases) with a negative effect on visualization scores compared to DSA (p < 0.05).
CTA with DEBR for assessment of EC/IC-bypass is feasible with reliable removal of cranial bones. Readers should be aware of a potential pitfall showing focal pseudostenosis/-occlusion of the bypass close to bone at the trepanation margin.
European Radiology 10/2010; 21(4):750-6. · 3.22 Impact Factor
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ABSTRACT: Glioblastoma multiforme is the most common and most malignant primary brain tumour. Prognosis after diagnosis remains poor despite recent advances in adjuvant therapy. Treatment of choice is gross surgical resection and combined radio-chemotherapy with temozolomide as chemotherapeutic agent. Experimental continuous low-dose chemotherapy with temozolomide in combination with a cyclooxygenase-2 inhibitor has shown encouraging effects on progression-free survival and overall survival in patients, but leads to a high proportion of distant recurrences. Here, we describe extreme far-distant metastases along the neural axis of glioblastoma multiforme in four patients receiving metronomic antiangiogenic chemotherapy and review the literature to discuss possible mechanisms.
Neurosurgical Review 03/2010; 33(3):375-81; discussion 381. · 2.04 Impact Factor
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ABSTRACT: To correlate pineal parenchyma volume (PP) to circadian melatonin profiles and to determine the 24-hour melatonin per volume of pineal tissue (MLPV). Furthermore, we compared melatonin profiles of cystic and solid glands.
In 15 healthy male subjects (20-27 years) the PP was determined using high-resolution magnetic resonance imaging (trueFISP, isotropic voxel: 0.8 mm(3)). Melatonin plasma concentrations (MC) were determined every 2 hours for 24 hours.
Mean PP was 125 +/- 54 mm(3). PP correlated linearly to maximum MC and to 24-hour melatonin (r = 0.61 and r = 0.64, P < 0.05) but not to minimum MC. The 24-hour melatonin was 653 +/- 242.6 pg/mL, MLPV was 5.8 +/- 2.3 pg/mL*ml(-1). Nine pineal glands were solid and six were cystic. PP of solid glands showed higher linear correlations to maximum melatonin, to 24-hour melatonin, and to the slope of the melatonin increase of the curve (P < 0.05).
PP correlates linearly to melatonin plasma concentrations in humans. MLPV displays similar interindividual differences as 24-hour melatonin. PP of solid glands show better correlation to melatonin profiles than cystic.
Journal of Magnetic Resonance Imaging 07/2009; 30(3):499-505. · 2.70 Impact Factor
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ABSTRACT: Magnetic resonance imaging (MRI) is a powerful tool to assess brain lesions, but currently available contrast agents are limited in the assessment of cellular and functional alterations. By use of the novel MRI contrast agent gadofluorine M (Gf) we report on imaging of transient and widespread changes of blood-brain barrier (BBB) properties as a consequence of focal photothrombotic brain lesions in rats. After i.v. application, Gf led to bright contrast in the lesions, but also the entire ipsilateral cortex on T1-weighted MRI. In contrast, enhancement after application of gadolinium diethylenetriamine-pentaacetic acid (Gd-DTPA), a common clinical indicator of BBB leakage was restricted to the lesions. Remote Gf enhancement was restricted in time to the first 24 h after photothrombosis and corresponded to a transient breakdown of the BBB as revealed by extravasation of the dye Evans blue. In conclusion, our study shows that Gf can visualize subtle disturbances of the BBB in three dimensions not detectable by Gd-DTPA. Upon entry into the central nervous system Gf most likely is locally trapped by interactions with extracellular matrix proteins. The unique properties of Gf hold promise as a more sensitive contrast agent for monitoring BBB disturbances in neurologic disorders, which appear more widespread than anticipated previously.
Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 10/2008; 29(2):331-41. · 5.46 Impact Factor
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ABSTRACT: Models of photochemically-induced thrombosis are widely used in cerebrovascular research. Photothrombotic brain infarctions can be induced by systemic application of photosensitizing dyes followed by focal illumination of the cerebral cortex. Although the ensuing activation of platelets is well established, their contribution for thrombosis and tissue damage has not formally been proved.
Infarction to the cerebral cortex was induced in mice by Rose Bengal and a cold light source. To assess the functional role of platelets, animals were platelet-depleted by anti-GPIbalpha antibodies or treated with GPIIb/IIIa-blocking F(ab)(2) fragments. The significance of the plasmatic coagulation cascade was determined by using blood coagulation factor XII (FXII)-deficient mice or heparin. Infarct development and infarct volumes were determined by serial MRI and conventional and electron microscopy.
There was no difference in development and final size of photothrombotic infarctions in mice with impaired platelet function. Moreover, deficiency of FXII, which initiates the intrinsic pathway of coagulation and is essential for thrombus formation, or blockade of FXa, the key protease during the waterfall cascade of plasmatic coagulation, by heparin likewise did not affect lesion development.
Our data demonstrate that platelet activation, factor XII-driven thrombus formation, and plasmatic coagulation pathways downstream of FX are not a prerequisite for ensuing tissue damage in models of photothrombotic vessel injury indicating that other pathomechanisms are involved. We suggest that this widely used model does not depend on platelet- or plasmatic coagulation-derived thrombosis.
Stroke 05/2008; 39(4):1262-8. · 5.73 Impact Factor
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ABSTRACT: Parallel imaging techniques such as GRAPPA have been introduced to optimize image quality and acquisition time. For spinal imaging in a clinical setting no data exist on the equivalency of conventional and parallel imaging techniques. The purpose of this study was to determine whether T1- and T2-weighted GRAPPA sequences are equivalent to conventional sequences for the evaluation of degenerative lumbar spine disease in terms of image quality and artefacts.
In patients with clinically suspected degenerative lumbar spine disease two neuroradiologists independently compared sagittal GRAPPA (acceleration factor 2, time reduction approximately 50%) and non-GRAPPA images (25 patients) and transverse GRAPPA (acceleration factor 2, time reduction approximately 50%) and non-GRAPPA images (23 lumbar segments in six patients). Comparative analyses included the minimal diameter of the spinal canal, disc abnormalities, foraminal stenosis, facet joint degeneration, lateral recess, nerve root compression and osteochondrotic vertebral and endplate changes. Image inhomogeneity was evaluated by comparing the nonuniformity in the two techniques. Image quality was assessed by grading the delineation of pathoanatomical structures. Motion and aliasing artefacts were classified from grade 1 (severe) to grade 5 (absent).
There was no significant difference between GRAPPA and non-accelerated MRI in the evaluation of degenerative lumbar spine disease (P>0.05), and there was no difference in the delineation of pathoanatomical structures. For inhomogeneity there was a trend in favour of the conventional sequences. No significant artefacts were observed with either technique.
The GRAPPA technique can be used effectively to reduce scanning time in patients with degenerative lumbar spine disease while preserving image quality.
Neuroradiology 02/2008; 50(5):403-9. · 2.82 Impact Factor
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New England Journal of Medicine 11/2007; 357(17):e18. · 53.30 Impact Factor
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ABSTRACT: The aim of our study was to visualize developing vessel occlusion in focal cerebral ischemia in vivo. Cortical photothrombosis (PT) was induced in rats, which in addition received superparamagnetic iron oxide (SPIO) particles intravenously. When SPIO particles were applied simultaneously during illumination of the brain for induction of PT, animals showed a markedly hypointense cortical lesion on T2-weighted (T2-w) magnetic-resonance images (MRI). At 3 h after PT, this hypointense area was surrounded by a small hyperintense rim. At 48 h after PT the hyperintense rim had further extended, whereas the hypointense lesion core did not change in size or signal. On histological sections areas of signal loss on T2-w MRI corresponded to local accumulation of iron particles, which were trapped within vessel thrombi. When SPIO particles were applied at 2 h after PT, the lesion appeared hyperintense on T2-w MRI, but was surrounded by a small hypointense rim indicating ongoing vessel occlusion at its outer margins. In contrast, delayed SPIO application at 24 h after completion of PT produced a merely hyperintense cortical lesion on T2-w MRI. Correspondingly, no iron deposits were seen on tissue sections. In conclusion, early SPIO-enhanced MRI provides a reliable in vivo tool to delineate areas of developing vessel occlusion in experimental cerebral ischemia and identifies vessel thrombosis as one mechanism of secondary infarct growth in the PT paradigm. This new imaging technique may aid to evaluate antithrombotic treatment strategies in the future.
Journal of Cerebral Blood Flow & Metabolism 12/2005; 25(11):1548-55. · 5.01 Impact Factor
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Journal of Neurology 02/2005; 252(1):108-10. · 3.47 Impact Factor
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ABSTRACT: Preoperative embolization of meningiomas is frequently used to facilitate surgery and to reduce intraoperative blood loss. The purpose of this study was to evaluate the frequency of procedure-related neurologic complications during and after particle embolization of intracranial meningiomas.
Between 1996 and 2004, 185 consecutive patients underwent particle embolization of an intracranial meningioma. Devascularization was performed by means of superselective probing of the tumor-feeding vessels and ensuing free-flow embolization with spherical particles. All procedures were performed with systemic heparinization.
Six patients (3.2%) had ischemic events with neurologic deficit. Two had amaurosis, and four patients presented with hemiparesis. Hemorrhage occurred in six patients (3.2%). In five of these patients, rapid microsurgical tumor removal resulted in a favorable outcome without persistent neurologic deficit. In one patient, massive intratumoral, subarachnoid, and subdural hemorrhage was lethal.
Particle embolization of meningiomas is associated with a substantial risk of ischemic and hemorrhagic events. The individual risk-to-benefit ratio of embolization should be thoroughly considered.
American Journal of Neuroradiology 26(6):1413-9. · 2.93 Impact Factor
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Ingo Nölte
