Journal of neuroimaging : official journal of the American Society of Neuroimaging
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Imaging techniques as confirmatory tests may add safety to the diagnosis of brain death, but are partly not accepted either because they are too invasive, such as conventional arterial angiography, or because there is still lack of evidence of its reliability, such as magnetic resonance angiography. In this study the reliability of diffusion weighted imaging for the diagnosis of brain death was evaluated according in terms of its sensitivity and specificity. The apparent diffusion coefficients (ADC) of 18 brain dead patients were registered from 14 distinct brain areas. ⋯ Despite a highly significant decrease of the mean ADC value in 16 patients, two patients showed mean ADC values that were within normal physiological range. An explanation may be the pseudonormalization of ADC values seen in stroke patients that depends on the time of the onset of the brain damage. We conclude, diffusion-weighted imaging may provide additional information on damage of the brain tissue but is not a practicable confirmatory test for the reliable diagnosis of brain death.
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Flow diversion techniques are increasingly used to treat cerebral aneurysms. The optimal stent porosity to achieve aneurysm obliteration would allow clinicians to treat aneurysms more effectively. We sought to determine the optimal porosity threshold in an in vitro flow model that would lead to stagnation of flow in an aneurysm. ⋯ The current model demonstrates a method to evaluate the optimal porosity threshold to achieve thrombosis of an aneurysm as a primary modality. Moreover, a gap may occur between the stent and the aneurysm that may create unfavorable circulatory conditions by increasing flow into the aneurysm.
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Posterior reversible encephalopathy syndrome (PRES) is a clinicoradiologic entity not yet understood, that is present with transient neurologic symptoms and particular radiological findings. The most common imaging pattern in PRES is the presence of edema in the white matter of the posterior portions of both cerebral hemispheres. The cause of PRES is unclear. ⋯ Numerous factors can trigger this syndrome, most commonly: acute elevation of blood pressure, abnormal renal function, and immunosuppressive therapy. There are many cases described showing the relationship between PRES and eclampsia, transplantation, neoplasia and chemotherapy treatment, systemic infections, renal disease acute, or chronic. However, this is the first case of PRES following a scorpion sting.
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The cerebellum, basal ganglia (BG), and other cortical regions, such as supplementary motor area (SMA) have emerged as important structures dealing with various aspects of timing, yet the modulation of functional connectivity between them during motor timing tasks remains unexplored. ⋯ Our findings indicate that although early PD subjects and controls use similar functional circuits to maintain a successful outcome in predictive motor timing behavior, the type and strength of EC and its modulation by behavioral performance differ between these two groups. These functional differences might represent the first step of cortical reorganization aimed at maintaining a normal performance in the brain affected by early Parkinson's disease and may have implications for the neuro-rehabilitation field.
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In transcranial sonography (TCS), hypoechogenic signal of mesencephalic raphe structures has been described as a frequent finding in unipolar depression. It remains unclear if raphe hypoechogenicity represents a correlate for an altered serotonergic system. The loudness dependence of auditory evoked potentials (LDAEP) has been proposed as an indirect indicator of central serotonergic activity. ⋯ There were no significant correlations with the psychometric assessments. At least in healthy subjects, our findings do not support the hypothesis that abnormal structural finding of hypoechogenic BR in TCS is accompanied by a functional impairment of serotonergic system as assessed by LDAEP. Further multimodal studies on patients with depressive disorders are needed to elucidate the impact of the hypoechogenic raphe signal in the pathophysiology of depression.