Browsing by Author "Valenzuela, Marcela"
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Item Accuracy of diffusion-weighted imaging in the diagnosis of stroke in patients with suspected cerebral infarct(American Heart Association, 2013) Brunser, Alejandro; Hoppe, Arnold; Illanes, Sergio; Díaz, Violeta; Muñoz, Paula; Cárcamo, Daniel; Olavarría, Verónica; Valenzuela, Marcela; Lavados, PabloBACKGROUND AND PURPOSE: The accuracy of diffusion-weighted imaging (DWI) for the diagnosis of acute cerebral ischemia among patients with suspected ischemic stroke arriving to an emergency room has not been studied in depth. METHODS: DWI was performed in 712 patients with acute or subacute focal symptoms that suggested an acute ischemic stroke (AIS), 609 of them with AIS. RESULTS: DWI demonstrated a sensitivity of 90% and specificity of 97%, a positive likelihood ratio of 31 and a negative likelihood ratio of 0.1 for detecting AIS. The overall accuracy was 95%. Of those patients who demonstrated abnormal DWI studies, 99.5% were AIS patients, and of those patients with normal DWI studies 63% were stroke mimics. CONCLUSIONS: DWI is accurate in detecting AIS in unselected patients with suspected AIS; a negative study should alert for nonischemic conditions.Item Validez del Doppler transcraneal en el diagnóstico de muerte encefálica(2010) Brunser, Alejandro; Hoppe, Arnold; Cárcamo, Daniel; Lavados, Pablo; Roldán, AndrésS; Rivas, Rodrigo; Valenzuela, Marcela; Montes, José MiguelThe clinical diagnosis of brain death is complex. Aim: To evaluate the diagnostic accuracy of transcranial Doppler (TCD) for brain death. Patients and Methods: Patients seen on the intensive care unit of a private hospital between January 2004 to December 2008, were included if they were in structural coma, had no craniectomy and had a blind evaluation by a neurologist and TCD done in less than three hours. The diagnosis of brain death was based on a clinical evaluation that considered the absence of sedative drugs, median blood pressure >60 mmHg, body temperature over 35º Celsius and complete absence of brainstem reflexes. An expert neurosonologist, with a TCD-PMD-100, 2 Mhz transducer, used an institutional protocol that considers the examination as positive for brain circulatory arrest when there is presence of reverberating, small systolic peaks or the disappearance of a previous signal present on both middle cerebral arteries and intracranial vertebral arteries. Results: Fifty three patients were evaluated, 25 with clinical brain death. On 45 cases (84.9%), the interval between both evaluations was less than one hour. The sensitivity, specificity, positive and negative predictive values for the diagnosis of brain death with TCD were 100, 96, 96.1 and 100% respectively. Positive and negative likelihood ratios for brain death were 28 and 0, respectively. Conclusions: TCD is a valid and useful technique for the diagnosis of brain death and can be used on complicated cases.