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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Excluding vascular involvement, vertigo due to a central vestibular syndrome reflects a median or paramedian lesion of the brain stem or the cerebellum. Recurrent attacks of vertigo usually occur with peripheral lesions. Persistent acute vertigo with peripheral destruction can reveal ischemia of the brain stem. Central positional vertigo is rare and has symptomatology that is different from that of benign positional vertigo. Persistent instability has a symptomatology that is more difficult to analyse and is usually associated with a central vestibular syndrome when it is organic. Diagnosis of a central vestibular syndrome is based on detection of well-defined clinical or electronystagmographic signs of which abnormal nystagmus is primordial. Some of them such as inferior vertical nystagmus or dissociated nystagmus can localise the site. MRI has become the diagnostic procedure which is best adapted for identifying the most frequent aetiologies such as tumors, congenital malformations and multiple sclerosis.
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PMID:[Vertigo in non-vascular diseases of the central nervous system]. 817 98

The concept of vascular origin in vertigo and equilibrium disorders is only a pragmatic clinical tool used to initiate and direct complex, complementary clinical investigation to determine the location (peripheral, central or mixed), the pathophysiological mechanisms and the multiple etiologies of the vestibular disorder. The concept includes focal and systemic ischemic processes and haemorrhagic processes of the posterior fossa. If the vertigo is associated with central neurological signs, the method can lead to certain diagnosis. If such signs are not detected by neurological screening of all the intra-axial signs of the vertebrobasilar regions, the diagnosis is uncertain clinical. Screening associated CT scan and MRI is more reliable than neuro-otological quantification. The major diagnostic difficulty involves TIA. Vertebrobasilar appears to be more heterogeneous than carotid ischemia. Schematic distinction is possible to differentiate thrombo-embolic from hemodynamic TIA. It is based on methodic clinical analysis and complementary investigations that are of unequal value.
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PMID:[Vertigo of vascular origin]. 817 99

Seven patients who received epidural anesthesia for gynecological (5 cases), cosmetic (1 case) or general surgery (1 case) developed spinal arachnoiditis leading to subarachnoid cyst in all 7 and cord cavitation in 5. MRI was useful to show the subarachnoid and intramedullary cysts, as well as to monitor lesion extent and progress. Associated MRI findings were a Chiari anomaly in one case, a tethered cord in another and spinal cord atrophy in a third. One patient refused surgery but improved spontaneously while the other six were treated by a shunting procedure, with a satisfactory outcome in three. Meningeal inflammation may have left scars which later induced ischemia and subsequent cavitation. Alternatively, CSF circulation blockade may have dilated the central spinal canal causing ischemia by compression, followed by myelomalacia and cavitation. Careful handling of this procedure is urged in order to avoid such severe complications.
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PMID:[Spinal arachnoiditis as a complication of peridural anesthesia]. 799 43

A sensitive radiotracer technique was used to measure transfer constants (Kis) for blood to brain diffusion of the MR contrast reagent gadolinium diethylenetriaminepentaacetate (GdDTPA2-) and the MR shift reagent dysprosium triethylenetetraminehexaacetate (DyTTHA3-) across the normal and the ischemically injured blood-brain barrier (BBB) of rats. In rats with a normal BBB mean Kis (nL/g/s) for these reagents ranged from 0.3 to 1.4 across eight brain regions and were significantly lower in each region than Kis for sucrose (1.5-3.2), a substance known to be a poor permeant of the intact BBB. Kis measured 6 h after a 10 min period of normothermic forebrain ischemia were increased to 4.0-6.2 (reagents) and 6.6-7.5 (sucrose) in two brain regions, striatum and hippocampus, known to be especially vulnerable to ischemic injury. Measurements of BBB permeability to DyTTHA3- after osmotic opening of the barrier with hypertonic arabinose gave Kis of 25-30 in forebrain regions. Estimates of reagent concentrations in brain interstitial fluid 30 min after dosing the animals indicated that both an extremely high dose of DyTTHA3- and severe disruption of the BBB would be required to shift the resonance frequency of extracellular Na+ appreciably. With the moderate degrees of BBB injury produced by short-term ischemia, a dose of GdDTPA2- about 25 times the usual clinical dose of 0.1 mmol/kg would be required to quantify the injury by dynamic MRI.
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PMID:Diffusion into rat brain of contrast and shift reagents for magnetic resonance imaging and spectroscopy. 826 67

Cerebral infarction is the result of cerebrovascular insufficiency and itself creates complex changes in cerebral hemodynamics. To allow recognition of patterns of change in regional cerebral blood flow (r-CBF) caused by cerebral infarction, the authors present an atlas of Tc-99m hexamethylpropyleneamine oxime (Tc-99m HMPAO) SPECT brain scan sections for a variety of strokes demonstrating typical vascular territorial involvements and evolution of morphologic and r-CBF change. Sections from MRI or CT are shown with SPECT images of the stroke lesion for comparison of the complementary information provided by regional cerebroperfusion and by morphology. Examples of SPECT during acute, subacute, and chronic stages of stroke are provided. To illustrate the temporal evolution of stroke and accompanying changes in the "stroke penumbra," case examples of acute tissue necrosis, luxury perfusion, ischemia, and diaschisis are presented. Methods for semiquantitative analysis of morphologic versus r-CBF defect size after acute stroke are described. How brain SPECT scans conducted during Diamox initiated cerebrovascular stress tests can complement the information obtained from baseline studies and assist in the interpretation of r-CBF abnormalities is also demonstrated.
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PMID:Regional cerebral blood flow changes in stroke imaged by Tc-99m HMPAO SPECT with corresponding anatomic image comparison. 829 29

Cortical laminar necrosis is a histopathological entity, related to conditions of cerebral energy depletion. Clinical correlates are supposed to be spastic motor deficits, decreased intellectual capacity and epilepsy. A study was performed in 45 children with cortical laminar abnormalities in signal intensity on MRI. The purpose of the study was to evaluate causes and clinical consequences of these cortical abnormalities on MRI in order to find indirect evidence for the hypothesis that they may represent cortical laminar necrosis. In view of the frequently present concomitant white matter damage, two contrast groups were formed: one group of 40 children with periventricular white matter abnormalities, part of them with subcortical extensions of the white matter damage; and another group of 53 children without abnormalities on MRI. Data concerning history, present clinical condition and final diagnosis were collected. The presence of cortical laminar abnormalities on MRI was found to be strongly associated with a history of cerebral energy depletion, especially hypoxia-ischemia, either in the perinatal period or later in life. Whereas white matter abnormalities tended to be more frequent in premature children, cortical laminar abnormalities tended to occur more frequently in term neonates and older children. The presence of cortical laminar abnormalities on MRI was correlated with an increased risk of spasticity in children without concomitant white matter abnormalities. In children with white matter lesions, cortical laminar abnormalities did not contribute to the risk of spasticity, which was already highly increased by the presence of white matter damage. No association was found between cortical abnormalities on MRI and epilepsy or psychomotor retardation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cortical laminar abnormalities--occurrence and clinical significance. 835 19

Twenty-seven patients were studied with MRI between 3 and 40 days following partial liver resection. Twenty-four patients had undergone major hepatectomy (three to six segments) and three had undergone minor hepatectomy (tumorectomy, one; bisegmentectomy, two). Indications for surgery were as follows: metastases (n = 16), hepatocellular carcinoma (n = 5), hemangioma (n = 3), focal nodular hyperplasia (n = 2), and cholangiocarcinoma (n = 1). A total of 36 MR examinations were performed using a 1.5 T superconducting unit. Three patients were studied three times and three patients were studied twice. The MR images were evaluated to detect and to characterize liver parenchymal abnormalities and intraabdominal fluid or blood collections as well as to assess vascular and/or graft patency. The MR images showed hepatic ischemia in two cases and allowed differentiation between intraabdominal hemorrhagic (n = 30 and nonhemorrhagic (n = 4) fluid collections. Gradient echo images allowed assessment of polytetrafluoroethylene graft patency as well as demonstration of iliac vein (one case) and portal vein (one case) thrombosis. The presence of surgical clips at the resection margins did not affect image quality.
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PMID:Early MR follow-up of partial hepatectomy. 845 55

Brain ischemia is now possible to trace through the multiple facets of MRI, morphological as well as functional. Experimental studies have been conducted for many years and clinical feasibility is reached. Although the initial decrease in blood flow does not influence morphological imaging, this early phase is shown with functional MRI, either with diffusion imaging or with cerebral blood volume imaging. The later is achieved either with the calculation of the integral of the first passage of a bolus of a diffusible paramagnetic agent or with the circulation of positive or negative blood pool contrast agents. This may serve to confirm an early diagnosis before inclusion in therapeutic trials. Immediate metabolic changes are reflected on phosphorus and proton spectroscopy achievable during the same session as imaging. This type of information may at this stage serve as a reference. It allows observation of the turnover of lactate over time in the lesion and the neuronal loss shown by decreased N-acetyl-aspartate. Edema, as a reaction to ischemia, builds up over time and has already been described for long as it modifies T1- and T2- weighted sequences. Similarly the breakdown of the blood-brain barrier is well known on conventional sequences because it produces contrast enhancement.
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PMID:[Results of magnetic resonance imaging in the acute phase of cerebral infarction]. 854 99

Purpose. To determine whether gadolinium-enhanced MR imaging can detect early reversible ischemia of the capital femoral epiphysis and physis induced by hip hyperabduction in piglets. Materials and methods. Thirteen 1- to 3-week-old piglets were placed in maximal abduction of both hips and studied with dynamic gadolinium-enhanced MR imaging 1-6 h later to assess ischemia of the 26 femoral heads. They were then allowed to ambulate freely for 1 or 7 days, and reimaged in neutral position to assess reperfusion. Enhancement was evaluated on MR images and compared with histologic findings.Results. Ischemia after hyperabduction developed in all 26 cartilaginous epiphyses and in 85 % of the physes. The most frequent abnormality was a sharply marginated nonenhancing area in the anterior part of the femoral head. A smaller area of ischemia developed in the posterior part of the femoral head, adjacent to the acetabular rim. The secondary center of ossification was ischemic in 56 % of the hips after 1 h of abduction and in all hips after 4 or 6 h (p = 0.02). The overall severity of ischemia was greater with increasing abduction time (p < 0.001) and increasing degree of abduction (p < 0.01). There was partial reperfusion in 83 % of the hips after 1 day of ambulation and complete reperfusion in all 26 hips (100 %) after 1 week.Conclusion. Enhanced MRI detects early ischemia of the epiphyseal and physeal cartilage and the epiphyseal marrow. In piglets, ischemia due to hyperabduction is reversible if corrected within 6 h.
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PMID:Gadolinium-enhanced MR imaging demonstrates abduction-caused hip ischemia and its reversal in piglets. 857 Mar 10

Two magnetization transfer (MT) contrast effects, a T2-like effect and the improved contrast observed when gadolinium is used with MT, are combined in a single sequence. Forty patients (22 males:18 females; mean age, 45 years (23-87)) with suspected intracranial pathology underwent MRI on a 1.5 Tesla system. Of 46 lesions; seven were ischemic, five infective, seven neoplastic, four hemorrhagic, four multiple sclerosis, seven human immunodeficiency virus (HIV) leukoencephalopathy, nine normal/miscellaneous, and three gliosis. A conventional spin-echo sequence (TR 900 TE 15) was used with on-resonance binomial MT pulses. The sequence was performed postgadolinium +/- MT. The signal intensity ratios +/- MT were: white matter, 0.62 +/- 0.03; gray matter, 0.75 +/- 0.04; ischemia, edema, and demyelination, 0.75 (0.57-0.86); and gadolinium/methemoglobin, 0.85 (0.81-0.98). Areas which exhibited MT had T2-like contrast and those that did not maintained expected contrast for the given parameters. The result was a combination of T2-like contrast, gadolinium enhancement, and dark cerebrospinal fluid (CSF) providing both increased sensitivity to lesions which exhibited both contrast features and improved delineation of periventricular lesions. Furthermore, the differential signal between T2-like contrast of edema and gadolinium enhancement in neoplastic or infective lesions was maintained.
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PMID:Clinical utility of a new contrast option from magnetization transfer contrast. 857 39


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