Journal of neuroimaging : official journal of the American Society of Neuroimaging
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Transcranial color-coded real-time sonography (TCCS) was applied to 26 patients with ventricular enlargement to quantify the ventricular size and to estimate intracranial pressure. Intracranial pressures, as determined by lumbar, epidural, or ventricular tonometry, ranged from 6.5 to 55 cm H2O (8 patients had pressures > 18 cm H2O). The widths of the third ventricle and the frontal horns of both lateral ventricles depicted by TCCS were compared to corresponding computed tomography data: TCCS and computed tomography findings correlated well for the third ventricle (r = 0.96) and for the right (r = 0.86) and left (r = 0.92) frontal horns. ⋯ In all patients with intracranial pressure below 17 cm H2O, rotatory head movements induced septum pellucidum undulation; no lateral deflection of the septum pellucidum was found in patients with an intracranial pressure above 21 cm H2O. Therefore, TCCS may be employed to quantify and follow-up ventricular enlargement. Dynamic neurosonographic tests may allow a gross estimation of intracranial pressure.
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Comparative Study
In vitro validation of color velocity imaging and spectral Doppler for velocity determination.
Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow imaging. Using information contained in the two-dimensional B-mode, gray-scale image to determine velocity, CVI offers potential advantages over Doppler color flow imaging methods. In order to be used clinically, velocity determination with CVI must be validated by other current methods. ⋯ At all string speeds tested, the averaged estimated and the actual velocities for both methods were within the 95% confidence estimates. The range for the CVI 95% confidence limits from the regression line varied from +/-1.07 cm/sec at the lowest speed of 10 cm/sec (11.6%) to +/-7.72 cm/sec at 200 cm/sec (3.87%). Based on in vitro testing, CVI is as accurate as Doppler spectral analysis for the estimation of flow velocity.
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Magnetic resonance imaging (MRI) findings in a group of 60 ambulatory elderly individuals (average age, 75.8 yr) were characterized as normal (grade 0), periventricular changes only (grade 1 ). small punctate lesions (grade 2), and confluent or large (> 2 mm) punctate lesions (grade 3). Patients were characterized by stroke risk factors, cardiolipin antibodies, coagulation factors (fibrinogen and plasminogen activator inhibitor-1 ). and Doppler ultrasound findings in the carotid and middle cerebral arteries. ⋯ There was no significant association between variables and MRI grade. These findings suggest that ischemia is not a major cause of MRI signal abnormalities in neurologically asymptomatic elderly individuals.
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Tha pathophysiology of brain injury in patients undergoing cardiopulmonary bypass remains unclear despite several decades of inquiry. The advent of noninvasive high-resolution brain and cerebrovascular imaging by magnetic resonance, computed tomography, and pulsed Doppler ultrasonography now permits in vivo assessment of pathophysiological mechanisms. Neuroradiographic and carotid duplex studies were performed in patients who developed neurological deficits following cardiopulmonary bypass. ⋯ Watershed injury was the predominant finding in a single patient, while findings consistent with global anoxia were present in another patient. Carotid atheroemboli were excluded as a possible source of embolism in 11 patients whose carotid duplex studies were unremarkable preoperatively as well as in 3 further patients whose neuroradiographic findings did not correspond with their moderate carotid disease. It is concluded that infarction due to noncarotid embolism is the primary pathophysiology of neurological deterioration following cardiopulmonary bypass.
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Atrial fibrillation and congestive heart failure are risk factors for ischemic stroke usually attributed to cardiac embolism. To define potential alternative mechanisms, patients with atrial fibrillation and congestive heart failure were investigated by transcranial Doppler. Middle cerebral artery (MCA) blood flow velocities were analyzed in neurologically asymptomatic patients with nonvalvular (n = 10) and valvular (n = 13) atrial fibrillation, patients in normal sinus rhythm with congestive heart failure (n = 13), and control subjects (n = 11). ⋯ Peak, mean, and diastolic MCA velocities in patients with atrial fibrillation and those with congestive heart failure were significantly less than those in control subjects. Patients with nonvalvular atrial fibrillation had a higher pulsatility index compared to each of the other three groups. These findings demonstrate substantial nonemboligenic alterations of the intracranial circulation associated with atrial fibrillation and congestive heart failure, and also provide an intracranial hemodynamic profile that may distinguish valvular from nonvalvular atrial fibrillation.