Acute cerebral ischemia: CT and MR findings Bozzao, L; Fantozzi, L M; Bastianello, S
American journal of neuroradiology : AJNR,
03/1992, Letnik:
13, Številka:
2
Journal Article
This study aimed to assess anatomical and functional changes disclosed by magnetic resonance imaging in a patient with suspect normal pressure hydrocephalus following surgical third ventriculostomy ...with placement of a ventriculoperitoneal shunt. The patient was investigated by phase contrast sequences to calculate CSF flow in the Sylvian aqueduct before and after the two surgical procedures. In addition, T1-weighted volumetric MPRAGE images were acquired using voxel-based morphometry to study any changes in size of the ventricular system and CSF in the subarachnoid spaces before and after surgery. CSF flow measurements were closely correlated with the patient's clinical course, increased CSF flow coinciding with worsening symptoms, and a decrease in flow noted after surgery. There were no significant changes in the CSF volumes analyzed. Phase contrast technique proved reliable and effective for the purposes of diagnosis and long-term follow-up in patients with suspect normal pressure hydrocephalus eligible for surgery
Fluid-attenuated inversion recovery (FLAIR) sequence is currently used in clinical practice. Some reports emphasize the possibility that, in pathologic conditions, intravenous injection of gadolinium ...chelates may lead to an increased signal inside the cerebrospinal fluid (CSF). The aim of this study was to evaluate the presence of CSF signal changes in pathologic conditions causing blood-brain barrier disruption or neovascularization when imaging is performed after intravenous injection of gadolinium. We obtained FLAIR sequences after gadolinium injection from 33 patients affected by different intracranial pathologies and 10 control subjects. Patients were affected by ischemic stroke in the subacute phase, from 2 to 7 days from onset of symptoms (12 patients), meningiomas (8 patients), high-grade gliomas (5 patients), previous surgical procedures for intra-axial neoplasms (5 patients), and multiple sclerosis with active plaques (3 patients). Magnetic resonance imaging was performed in patients and controls using a 1.5-T magnet, using T2- and T1-weighted FLAIR sequences. The FLAIR sequence was acquired before and 1-3 h after injection of a standard dose of gadolinium. In those patients affected by ischemic lesions, FLAIR sequences were repeated the next days and 3-4 days later. The CSF signal was visually evaluated by two readers and scored from 0 to 3 depending by the degree of enhancement. The location of CSF signal changes (close to the lesion, hemispheric, or diffuse) was also considered. The CSF signal was markedly increased after 3 h from intravenous injection of gadolinium in all the patients with stroke, in those with previous surgery, and in those with high-grade gliomas whose neoplasm's surface was in contact with the subarachnoid spaces (SAS) or ventricles; a strong enhancement was also evident inside the necrotic component of the tumor. The CSF changes were more evident close to the pathology and/or in the hemisphere involved by the pathology. Moderate CSF enhancement was observed in the SAS close to meningiomas. No signal changes were evident in all the others. In those patients with stroke imaged in the following days, CSF signal showed to be diffuse to both hemispheres the next day and returned to normal values within 2 days. In patients affected by pathologies with blood-brain barrier breakdown or neovascularization close the SAS or the ventricles, CSF changes, related to gadolinium leakage, are likely when FLAIR sequences are acquired 2-24 h after i.v. injection of the contrast. This pattern should be known in order to differentiate it from that of subarachnoid hemorrhage.
Gelastic (laughing) epilepsy, relatively uncommon, is usually associated with hypothalamic hamartomas, pituitary tumors, astrocytomas of the mammillary bodies, and dysraphic conditions. Cases of ...unknown etiology are rare. In three of the four cases reported here, the diagnoses were hamartoma of the tuber cinereum; lobar holoprosencephaly; and lissencephaly type I, grade 2. In the fourth, radiographic investigation gave a normal result; a genetic etiology was suggested because of bilateral familial idiopathic epilepsy. In all patients, EEGs showed both focal spikes and generalized spike-and-wave discharges. The primary underlying neurophysiologic disorder may be provoked by the diffuse hyperexcitability of the cortex and subsequent firing of the thalamocortical networks with which the cortical brain is reciprocally interlinked.
Eighty patients were studied by angiography within 6 h of an ischaemic stroke. Angiography was carried out with digital equipment and was usually limited to the vascular territory responsible for the ...neurological deficits. In 12 of 19 patients with internal carotid occlusion, the contralateral side was also studied. The angiographic abnormalities were classified as extracranial, intracranial, and combined extra and intracranial. The data show a high incidence (66%) of occlusive pathology of intracranial arteries, either isolated or associated with a significant presence of a potential embolic source (85%), and a high incidence of carotid occlusions located at the cervical segment (8 of 19). These observations suggest that most strokes are occlusive in origin.
Two main sedimentary basins can be recognized in southern Somalia, the NE–SW trending Mesozoic-Tertiary Somali coastal basin, and the NNE–SSW Mesozoic Luuq-Mandera basin. The two basins are separated ...by the Bur region where the Proterozoic-Early Paleozoic Metamorphic basement of southern Somalia outcrops. The investigated area covers part of the Metamorphic basement of southern Somalia and of the Luuq-Mandera basin, although this basement is not described in details in this paper.
In the Bur region the basement outcrops discontinuously near inselbergs and monadnocks, which stand out of a blanket of recent sediments. Because of this patchy distribution and the limited areal extent of the outcrops, the structure of the metamorphic basement is difficult to reconstruct. A NW–SE trend of structures prevails and two metamorphic complexes (the Olontole and Diinsor complexes) can be recognized.
The Luuq-Mandera basin is a wide NNE–SSW synclinorium, delimited to the SE by the basement high of the Bur region, and to the west by the crystalline basement high of NE Kenya (Northern Frontier district). The extreme thickness of Triassic sediments in the axial part of the basin, and the thinner and younger succession on both sides of the basin suggest that the Luuq-Mandera basin was a subsiding elongated area that was invaded by the sea in the early Mesozoic, during the dismembering of Gondwana. The Jurassic–Cretaceous succession that followed comprises two main cycles of transgression and regression; the carbonate sediments that lie at the bottom pass up section into shales, evaporites and sandstone deposits.
Since late Cretaceous, continental contition prevaled, with a long phase of peneplanation, and then a general uplift, which brought about the creation of lake depressions and the capture of the Dawa river, with formation of the present Jubba valley.
The main tectonic events in the study area, and throughout SW Somalia, are represented by strike-slip movements along vertical faults in the Sengif and Garbahaarrey belt. Deformation is localized within a narrow belt that extends for more than a 100 km in a NE–SW direction. The near parallelism between the fold axes and the regional orientation of faults indicates a right-lateral movements along faults.
The structure of the Garbahaarrey belt consists of an anastomosing fault system that delimits elongated folded blocks, arranged in anticline–syncline structures, with subvertical axial surfaces and fold axes parallel to the main wrench faults. The orientation of folds and the typical “positive flower structure” profile of the anticlines indicate that shortening was perpendicular to the strike of the wrench, i.e. in a SE–NW direction. In the Garbahaarrey belt, strike-slip and shortening, therefore, occurred contemporaneously and led to a relative transpression between the NW and SE blocks.
The observed parallelism between fold and fault orientation cannot be explained with a simple rotation of pre-existing fold axes during transpression, but can be regarded as an example of folding and strike-slip movements that occurred simultaneously but independently along frictionless faults. The faults delimiting the anticlines accommodated the strike-slip component of transpression only, whereas the compressive component led to the generation of fold axes parallel to the wrench zone.
Results of the field work are summarized in two geological maps of the Gedo, Bakool, and Bay regions (1:250,000) which accompany this report (maps are attached with this issue).
The aim of the present study was to assess the presence of changes in diffusivity in the brains of patients with tuberous sclerosis (TS) in areas free from signal alterations on conventional MR ...sequences. Ten patients and controls were evaluated. ROI were placed on ADC maps in the white matter (frontal, parietal and centrum semiovale) excluding areas with signal alterations on FLAIR images. ADC values of supratentorial white matter turned out to be higher than controls (P < .0001). Our data indicate that TS is more widely diffused than expected in the brains of affected patients.
Parasagittal meningiomas (PSM) may pose a difficult surgical challenge since venous patency and collateral anastomoses have to be clearly defined for correct surgical planning. The aim of this study ...was to assess the diagnostic value of contrast-enhanced (CE) magnetic resonance venography (MRV) in the preoperative evaluation of venous infiltration and collateral venous anastomoses in patients with PSM. CE-MRV was compared with phase-contrast (PC) magnetic resonance (MR) angiography, conventional angiography (when available), and surgery as a reference. Twenty-three patients undergoing surgery for meningiomas located adjacent to the superior sagittal sinus were prospectively evaluated. All the patients underwent both conventional MR examination and MRV. This was performed by means of PC and CE techniques. Both sets of angiograms (CE and PC) were evaluated by two expert neuroradiologists to assess (1) patency of the sinus (patent/occluded), (2) the extent of occlusion (in centimeters), and (3) the number of collateral anastomoses close to the insertion of the meningioma. Eight patients underwent digital subtraction angiography (DSA). All patients were operated on, and intraoperative findings were taken as the gold standard to evaluate the diagnostic value of MRA techniques. PC-MRV showed a flow void inside the sinus compatible with its occlusion in 15 cases, whereas CE-MRV showed the sinus to be occluded in five cases. CE-MRV data were confirmed by surgery, showing five patients to have an occlusion of the superior sagittal sinus. The PC-MRV sensitivity was thus 100% with a specificity of 50%. In those cases in which both MRV techniques documented occlusion of the sinus, the extent of occlusion was overestimated by PC compared with CE and surgery. CE-MRV depicted 87% of collateral venous anastomoses close to the meningioma as subsequently confirmed by surgery, while PC showed 58%. In the preoperative planning for patients with meningiomas located close to a venous sinus, CE-MRV provides additional and more reliable information concerning venous infiltration and the presence of collateral anastomoses compared with PC sequences.
We studied by angiography 80 patients within 6 hours from the onset of symptoms of supratentorial ischaemic stroke. Occlusion of the internal carotid artery in the extracranial segment was found in ...19 patients, at the bifurcation in 11 and at the cervical level in 8. While in the chronic phase of stroke, internal carotid artery occlusion in the cervical segment is an uncommon angiographic finding, we found a high frequency of occlusion at this level (8 out of 19) in our patients. Cervical segment occlusion may be due to a dissecting aneurysm or to an intracranial carotid artery occlusion (embolic or atherothrombotic) with subsequent migration of the clot down to this level. A direct embolic occlusion may be postulated as well.
A study of rock slope stability was performed using geological surveys and Digital Terrestrial Photogrammetry (DTP) integrated by Laser Scanning (LS) and topographic measurements. The use of DTP is ...useful especially in inaccessible sites such as natural cliffs. By obtaining oriented stereo images, accurate digital surface models and orthophotos, useful data can be produced showing geometrical characteristics of joints, blocks and slopes such as planes, attitude, spacing, persistence and rock mass volumes. In order to accomplish the analysis, DTP was combined with LS in order to build the Digital Dense Surface Model (DDSM) of the slope. The conventional method of limit equilibrium was applied to study the slope stability using a deterministic approach and to suggest activities of geo-monitoring and engineering solutions for risk mitigation with respect to the environment.
