Cases reported "Brain Ischemia"

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1/122. Articulatory processes and phonologic dyslexia.

    BACKGROUND-OBJECTIVE: Grapheme-to-phoneme conversion (GPC) allows the pronunciation of nonword letter strings and of real words with which the literate reader has no previous experience. Although cross-modal association between visual (orthographic) and auditory (phonemic-input) representations may contribute to GPC, many cases of deep or phonologic alexia result from injury to anterior perisylvian regions. Thus, GPC may rely upon associations between orthographic and articulatory (phonemic-output) representations. METHOD-RESULTS-CONCLUSION: Detailed analysis of a patient with phonologic alexia suggests that defective knowledge of the position and motion of the articulatory apparatus might contribute to impaired transcoding from letters to sounds.
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ranking = 1
keywords = visual
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2/122. The "thin man" phenomenon: a sign of cortical plasticity following inferior homonymous paracentral scotomas.

    AIM: To investigate an image distortion, experienced by patients with homonymous paracentral scotomas. methods: Two consecutive patients with right inferior homonymous paracentral scotomas resulting from ischaemic brain insults were examined. Neuro-ophthalmological examination included tangent screen and Amsler grid evaluation. In addition, the patients were asked to describe a figure showing two vertical lines, identical in length and symmetrically located on either side of a fixation point. This figure was presented in such a way that when the subject looked at the fixation point the right line crossed the scotoma. Finally, the patients were asked whether, when looking at the face of an interlocutor, both sides of the body looked the same. RESULTS: In both patients field defects were markedly smaller when delineated with Amsler grids than using a tangent screen. With the parallel line test, the right line appeared uninterrupted in patient 1, whereas in patient 2 it looked slightly blurred in a two degree long segment corresponding to the middle of the scotoma. To both subjects the right line appeared shorter than the left line. Finally both subjects indicated that, after steadily fixating their interlocutor's face or neck for 5-10 seconds, the left shoulder appeared narrower than the right one, which made him look surprisingly thin. This perceptual alteration was called the "thin man" phenomenon. CONCLUSIONS: Paracentral homonymous scotomas can be associated with perceptual completion and shape distortion, owing to apparent displacement of images adjacent to the scotoma towards the field defect. Occurrence of such a perceptual change should alert one to the possibility of paracentral homonymous scotomas, which often go undetected when using routine visual field testing procedures.
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keywords = visual
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3/122. Alexia for Braille following bilateral occipital stroke in an early blind woman.

    Recent functional imaging and neurophysiologic studies indicate that the occipital cortex may play a role in Braille reading in congenitally and early blind subjects. We report on a woman blind from birth who sustained bilateral occipital damage following an ischemic stroke. Prior to the stroke, the patient was a proficient Braille reader. Following the stroke, she was no longer able to read Braille yet her somatosensory perception appeared otherwise to be unchanged. This case supports the emerging evidence for the recruitment of striate and prestriate cortex for Braille reading in early blind subjects.
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ranking = 14.182223224143
keywords = cortex
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4/122. Using fMRI to study recovery from acquired dysphasia.

    We have used functional magnetic resonance imaging (fMRI) to characterize brain activations associated with two distinct language tasks performed by a 28-year-old woman after partial recovery from dysphasia due to a left frontal hemispheric ischemic stroke. MRI showed that her ischemic lesion extended posteriorly from the left inferior frontal to the perisylvian cortex. fMRI scans of both language tasks revealed substantial differences in activation pattern relative to controls. The nature of this difference was task-specific. During performance of a verbal semantic decision task, the patient, in contrast to controls, activated a network of brain areas that excluded the inferior frontal gyrus (in either hemisphere). A second task involving rhyme judgment was designed to place a heavier cognitive load on language production processes and activated the left inferior frontal gyrus (Broca's area) strongly in normal controls. During this task, the most prominent frontal activation in the patient occurred in the right homologue of Broca's area. Subsequent analysis of this data by methods able to deal with responses of changing amplitude revealed additional, less sustained recruitment by the patient of cortex adjacent to the infarct in the region inferior to Broca's area during rhyming. These results suggest that in addition to changes in cognitive strategy, recovery from dysphasia could be mediated by both the preservation of neuronal networks in and around the infarct and the use of homologous regions in the contralateral hemisphere.
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ranking = 14.182223224143
keywords = cortex
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5/122. 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.
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ranking = 7.0911116120714
keywords = cortex
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6/122. Homonymous visual field defects in patients without corresponding structural lesions on neuroimaging.

    Homonymous visual field defects usually occur with structural processes affecting retrochiasmal visual pathways. The responsible lesion is usually evident on magnetic resonance imaging or on other neuroimaging studies. When results of neuroimaging are normal, functional illness is often suspected. The authors report four patients with homonymous visual field defects who presented with no evident corresponding lesion on magnetic resonance or computed tomography imaging. Etiologies for the visual field defects included the Heidenhain variant of Creutzfeldt-Jacob disease, degenerative dementia, subtle occipital ischemia demonstrated only on positron-emission tomography scanning, and nonketotic hyperglycemia. Clinicians should be aware of the alternative etiologies of organic homonymous visual field loss in patients with normal neuroimaging.
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ranking = 9
keywords = visual
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7/122. Bilateral and simultaneous ischemic optic neuropathy following hip replacement surgery.

    Ischemic optic neuropathy, is an exceptional complication of surgery. Moreover, bilateral and simultaneous visual deficit in ischemic optic neuropathy is very rare. We describe two patients who suffered bilateral and simultaneous ischemic optic neuropathy after elective total hip replacement. anemia and hypotension are the most likely risk factors.
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ranking = 1
keywords = visual
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8/122. Unusual CT and MRI appearance of carbon monoxide poisoning.

    Unilateral low attenuation areas within the right putamen, globus pallidus and thalamus were observed on CT in a patient after exposure to carbon monoxide. A transient bilateral appearance was found on subsequent CT examinations. Hemorrhagic infarction of the right putamen, and ischemic lesions in both thalami were visualized on MRI 2 weeks later.
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ranking = 1
keywords = visual
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9/122. Hyperacute infarction: early CT findings.

    The aim of our study is to determine how early and reliably ischemic brain infarcts can be detected on CT scanning. We report two cases of an early CT finding of acute ischemic infarcts where CT examination was obtained within the first 3 hours of onset of neurological symptoms. CT examination showed blurred outlines and decreased attenuation of the left lentiform nucleus, loss of the white-gray matter interface in the left insular cortex and left cortical global hypoattenuation with obliteration of left cortical sulci in one patient. In second patient CT showed the following: hyperdense left middle cerebral artery, loss of clear margins of left lentiform nucleus, subtle focal cortical hypodensity in the left fronto-parietal area with signs of mass effect in the form of ventricular compression. CT is still the first choice in the deferential diagnosis of acute stroke. Although older literature positions have suggested that CT was negative during the first 48 hours, modern CT technology can demonstrate positive findings even in the first 3 hours of onset. This is important in patients with acute stroke, as thrombolytic therapy when elected, has to be given within the first 3-6 hours after onset of symptoms. To determine how early and reliably ischemic brain infarcts can be detected on CT scanning, we report two cases of an early CT finding of acute ischemic infarcts where CT examination was obtained within the first 3 hours of onset of neurological symptoms.
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ranking = 7.0911116120714
keywords = cortex
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10/122. Mania caused by a diencephalic lesion.

    We describe the case of a young male patient, SN, who suffered a MR-documented ischaemic lesion of both dorsomedial thalami and presented with a transient maniform syndrome. SN's neuropsychological, structural and functional imaging findings are compared with similar reported cases and are discussed in the framework of fronto-subcortical circuits and their proposed behavioural disorders. SN's mania was characterized by restlessness, mood elevation, a tendency for pleasurable activities, inflated self-esteem and loss of disease awareness. Other symptoms were sexual disinhibition, tactlessness, abnormal discourse, and reduced need for food and sleep. His neuropsychological assessment revealed an anterograde amnesia, and an impairment of frontal-executive functions. A SPECT-study showed diaschisis-related areas of hypoperfusion in both prefrontal regions which were interpreted as equivalents of SN's frontal-dysexecutive syndrome. In addition, there was a perfusion deficit in the right orbitofrontal cortex, which was taken as the imaging correlate of SN's secondary mania and personality disorder. These findings suggest that SN's mania and his other symptoms result from the twofold disruption of fronto-subcortical connections, namely of the right orbitofrontal loop which is concerned with mood regulation and socially appropriate behaviour, and of the dorsolateral prefrontal loop which mediates executive cognitive functions.
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ranking = 7.0911116120714
keywords = cortex
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