1/9. Vascular and metabolic reserve in Alzheimer's disease.Vascular and metabolic reserve were analyzed in probable Alzheimer's disease (AD) and vascular dementia (VaD). Cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO(2)), and oxygen extraction fraction (OEF) were measured quantitatively with positron emission tomography (PET). Vascular reactivity (VR) was also calculated by comparing the CBF during 5% CO(2) inhalation with the CBF during normal breathing. Vascular transit time (VTT) that was calculated as a ratio of CBV/CBF and VR reflect vasodilating capacity of the small resistance vessels, whereas OEF designates metabolic (oxygen-extraction) reserve in threatening brain ischemia. Significant increase in OEF was seen in the parieto-temporal cortex and both VTT and VR were preserved in AD patients. By constrast, there was no significant increase in OEF whereas VTT was prolonged and VR was markedly depressed in VaD patients. The increase of OEF and preserved VTT and VR seen in AD patients indicate the possible participation of vascular factors in the pathogenesis of AD perhaps at the capillary level.- - - - - - - - - - ranking = 1keywords = extraction (Clic here for more details about this article) |
2/9. Endovascular mechanical thrombectomy of an occluded superior division branch of the left MCA for acute cardioembolic stroke.Cardiac embolism accounts for a large proportion of ischemic stroke. Revascularization using systemic or intra-arterial thrombolysis is associated with increasing risks of cerebral hemorrhage as time passes from stroke onset. We report successful mechanical thrombectomy from a distal branch of the middle cerebral artery (MCA) using a novel technique. A 72-year old man suffered an acute ischemic stroke from an echocardiographically proven ventricular thrombus due to a recent myocardial infarction. Intraarterial administration of 4 mg rt-PA initiated at 5.7 hours post-ictus failed to recanalize an occluded superior division branch of the left MCA. At 6 hours, symptomatic embolic occlusion persisted. Mechanical extraction of the clot using an Attracter-18 device (Target therapeutics, Freemont, CA) resulted in immediate recanalization of the MCA branch. Attracter-18 for acute occlusion of MCA branches may be considered in selected patients who fail conventional thrombolysis or are nearing closure of the therapeutic window for use of thrombolytic agents.- - - - - - - - - - ranking = 0.5keywords = extraction (Clic here for more details about this article) |
3/9. Significance of low perfusion with increased oxygen extraction fraction in a case of internal carotid artery stenosis.BACKGROUND AND PURPOSE: Decreased cerebral blood flow with an increased oxygen extraction fraction, the so-called misery perfusion syndrome, suggests a vulnerability to reduction in cerebral perfusion pressure and a tendency to develop cerebral infarction. It is uncertain, however, whether the infarct would occur in the brain region specifically exhibiting this condition. CASE DESCRIPTION: We report the case of a patient with right intracranial internal carotid artery stenosis who presented with mild left hemiparesis resulting from a right frontal watershed infarct. Positron emission tomography 2 months after the stroke showed decreased cerebral blood flow with an increased oxygen extraction fraction in noninfarcted areas of the affected hemisphere. Maximal changes were detected in the watershed area between the middle cerebral artery and the posterior cerebral artery. Three months later, while on antiplatelet therapy, he suffered a new infarct in the right temporo-occipital watershed area that had shown the highest oxygen extraction fraction value on the first positron emission tomographic study. One month after the recurrence of stroke, a second study showed that low perfusion with increased oxygen extraction fraction persisted in the affected hemisphere to a lesser degree than in the first study. CONCLUSIONS: This observation suggests that the area of low perfusion exhibiting the highest oxygen extraction fraction has the highest risk for infarction. Increased oxygen extraction fraction may be an important factor in the development of hemodynamic infarction.- - - - - - - - - - ranking = 5keywords = extraction (Clic here for more details about this article) |
4/9. Tentorial hemorrhage associated with vacuum extraction.The clinical and radiologic descriptions of three neonates with tentorial hemorrhage after vacuum extraction are reported. All patients were full term, with Apgar scores of 8 or more; one patient experienced fetal distress during delivery. Within 36 hours after birth, the neonates had multiple generalized seizures; computed tomography or magnetic resonance imaging outlined distinctive tentorial hemorrhages with extension over the superior surface of the cerebellum or inferior surface of the occipital lobe. One patient had diffuse hypoxic-ischemic injury, and another had bilateral temporal lobe infarcts. Treatment included medical control of seizures and intracranial hypertension; one patient had surgical evacuation of bilateral subdural hematomas. Follow-up from 1 to 5 years showed significant developmental delays in two patients. These cases demonstrate that the forces generated on the fetal cranium by vacuum extraction are similar to those produced by forceps and result in tentorial laceration, venous rupture, and subdural hemorrhage. Because these hemorrhages may be associated with significant ischemic injury, serial radiologic evaluation is recommended for the detection of persistent structural abnormalities.- - - - - - - - - - ranking = 3keywords = extraction (Clic here for more details about this article) |
5/9. brain ischemia and infarction positively visualized by pyruvate-1-11C using positron-emission tomography.We describe positron-emission tomography (PET) scintigraphic findings obtained using pyruvate-1-11C in eight patients with cerebral ischemic hypoxia or infarction. The extraction of 11C by brain tissue from blood after an i.v. injection of 11C-pyruvate was very rapid, being almost complete after a single circulatory passage. Most ischemic lesions were found to be more or less deficient with regard to 11C-extraction capacity. With time, however, the ratio of 11C in ischemic tissue to that in normal tissue was inverted, and the ischemic lesion appeared as a 'hot' area in the scintigram. Very old infarcts did not exhibit this phenomenon. These observations indicate the usefulness of an 11C-pyruvate PET scan for the diagnosis of therapeutically restorable brain damage.- - - - - - - - - - ranking = 1keywords = extraction (Clic here for more details about this article) |
6/9. herpes zoster ophthalmicus with contralateral hemiparesis. A case report and review of the literature.An 80-year-old man developed right herpes zoster ophthalmicus complicated by contralateral hemiparesis after right cataract extraction. Although herpes zoster ophthalmicus is a frequent occurrence among the elderly, the association with contralateral hemiparesis is probably overlooked by many ophthalmologists. A review of the literature has been made to outline the etiology of this problem and to make diagnosis more likely. The varicella virus probably spreads in a retrograde fashion from the gasserian ganglion toward the cavernous sinus to involve cranial nerves 3, 4, or 6. Involvement of the ipsilateral carotid arterial system by the progressive inflammatory reaction can result in the contralateral hemiparesis. Standard therapy includes topical steroids and topical antibiotics for the ocular and surface lesions. The efficacy of systemic steroids to minimize the hemiparesis is still in question.- - - - - - - - - - ranking = 0.5keywords = extraction (Clic here for more details about this article) |
7/9. Reversal of focal "misery-perfusion syndrome" by extra-intracranial arterial bypass in hemodynamic cerebral ischemia. A case study with 15O positron emission tomography.Tomographic images of cerebral blood flow (CBF) and oxygen extraction fraction (OEF) using the 15O continuous inhalation technique, and positron emission tomography, were obtained from a patient with cerebral ischemia distal to an occluded left internal carotid artery. There was a focal mismatch between CBF and oxygen metabolism in the brain supplied by the middle cerebral artery where CBF was decreased and OEF increased ("misery-perfusion syndrome" as opposed to "luxury-perfusion syndrome"). These abnormalities were most marked in the parieto-occipital watershed area. After left superficial temporal to middle cerebral artery anastomosis, the clinical attacks ceased and a repeat study did not demonstrate the previous CBF and OEF abnormalities. This suggests that this pattern of abnormalities indicates potential viable tissue. The concept of "misery-perfusion" may be of some importance in the pathophysiological mechanisms of hemodynamic cerebral ischemia and serve as a rational basis for revascularization procedures.- - - - - - - - - - ranking = 0.5keywords = extraction (Clic here for more details about this article) |
8/9. Cerebral extraction of oxygen, lactate production, and perfusion pressure in gunshot wound to the head: case report.A case of gunshot wound to the head is presented, in which the patient made a satisfactory recovery after a prolonged period of elevated intracranial pressure and increased cerebral extraction of oxygen. Even though cerebral extraction of oxygen was increased in the most acute phase, the arteriojugular lactate difference was never abnormally decreased (ischemic). This finding indicated that, in this patient, increased cerebral extraction of oxygen was not sufficient to result in global cerebral ischemia (increased cerebral lactate production). To our knowledge, this is the first report on frequent serial assessment of cerebral extraction of oxygen and lactate production in severe penetrating head injury.- - - - - - - - - - ranking = 4keywords = extraction (Clic here for more details about this article) |
9/9. Simultaneous intracerebral microdialysis and positron emission tomography in the detection of ischemia in patients with subarachnoid hemorrhage.Intracerebral microdialysis (MD) was applied in patients with subarachnoid hemorrhage. The regional CBF, the CMRO2, and oxygen extraction ratio (OER) were measured with simultaneous positron emission tomography (PET). The aim was to directly correlate alterations in dialysate levels of energy-related metabolites (lactate, lactate/pyruvate ratio, hypoxanthine) and excitatory amino acids (EAAs) (glutamate and aspartate) to the energy state in the MD probe region as determined by PET. Regional ischemia was defined according to Heiss et al. and Lassen (Heiss et al., 1992; Lassen, 1966). Whole-brain ischemia was considered present when the OER for the whole brain exceeded the mean whole-brain OER 2 SD of six reference patients. In general, the presence of whole-brain ischemia and/or regional ischemia within the region of the MD probe was associated with increased levels of energy-related metabolites and EAAs retrieved by MD. Increased levels of energy-related metabolites and EAAs were only occasionally seen when PET did not show any signs of ischemia or when signs of regional ischemia were found remote from the MD probe region. Thus, the energy-related metabolites and EAAs may be used as extracellular "markers" of ischemia. PET may be of use in defining critical ischemic regions (tissue at risk) where the MD probe can be inserted for chemical monitoring.- - - - - - - - - - ranking = 0.5keywords = extraction (Clic here for more details about this article) |