Journal of neuroimaging : official journal of the American Society of Neuroimaging
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Transcranial Doppler (TCD) sonography combines the advantages of real-time hemodynamic information, cost-effectiveness, and bedside application. However, measurements can be difficult to reproduce because the spatial resolution and the determination of insonation angles are limited. The purpose of this study was to use the high anatomic resolution of three-dimensional (3D) magnetic resonance angiography (MRA) images for the stereotactic guidance of TCD in order to improve the accuracy and reproducibility of TCD examinations. ⋯ Without navigation the reproducibility of vessel segment insonation dropped to 4.7 mm for the middle cerebral artery and to 4.84 mm for all vessels. The authors conclude that 3D MRA, acquired as an initial procedure in patients with intracranial vascular disorders, can be used to provide stereotactic guidance for repeated TCD examinations. This facilitates the reproducible insonation of specific vessel segments.
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In 1996, a survey of the members of the American Academy of Neurology revealed the following facts and opinions: (1) On an average month, each respondent ordered 15 computed tomography, 22 magnetic resonance imaging, 13 ultrasound and 1 single-photon emission computerized tomography studies. (2) Most respondents did not read their own studies for reimbursement, but relied on their own reading for patient management. (3) Respondents felt that neurologists are appropriate specialists to read imaging studies; however, they favored certification for neurologists credentialed in neuroimaging. (4) Organized neurology should provide certification in neuroimaging for neurologists with appropriate training and defend their right and their need to practice neuroimaging, including endovascular procedures.
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Case Reports
Internal carotid artery dissection causes hypoglossal nerve palsy: CT, MRI, and angiographic findings.
A case of unilateral XIIth nerve palsy due to the dissection of the internal carotid artery is reported. The clinical and radiological features are described. ⋯ Diagnosis is discussed with emphasis on magnetic resonance imaging findings. Magnetic resonance imaging is also useful for follow-up of arterial lesions.
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Comparative Study
Power Doppler compared to color-coded duplex sonography in the assessment of the basal cerebral circulation.
Power-based transcranial duplex sonography (p-TDS) is a new promising ultrasound technique that generates intravascular color signals from the amplitude of the echo signal. The present investigation was undertaken to determine the advantages and limitations of power Doppler in the assessment of the basal cerebral circulation compared with transcranial color-coded real-time sonography (TCCS) and contrast-enhanced transcranial color-coded real-time sonography (CE-TCCS). Thirty-eight patients without cerebrovascular diseases were examined with p-TDS and TCCS, and in 11 patients CE-TCCS studies were performed. ⋯ In comparison with CE-TCCS, p-TDS had no important advantages in the detection of intracranial vessels. In conclusion, p-TDS and CE-TCCS were superior to TCCS with regard to identification of the basal arterial circulation. Both methods permit noninvasive and reliable identification of the basal cerebral circulation.
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Comparative Study
Transcranial Doppler in 178 patients before, during, and after carotid endarterectomy.
From July 1991 to March 1995, 178 patients who underwent 198 carotid surgical repairs were investigated preoperatively, intraoperatively, and postoperatively by transcranial Doppler sonography (TCD). Preoperative TCD evaluation showed stenosis of the middle cerebral artery (MCA) in 4 patients (2.2%), siphon stenosis in 3 (1.6%), incomplete circle of Willis in 23 (12.9%), a decrease of mean blood flow velocity more than 70% of the basal value during digital common carotid compression in 31 (17.9%), and a critical reduction of vasomotor reactivity (no significant increase of mean blood flow velocity in the MCA during breath-holding test) in 34 (19.1%). Nine patients (5%) had surgery without preoperative angiography. ⋯ Intraoperative TCD monitoring showed a decrease of mean blood flow velocity in the MCA due to shunt malfunction in (8.3%) of 36 surgeries, turbulence of blood flow during declamping in 79 procedures (39.8%), and microembolic events in 10 patients (5%) that were related to one transient and one permanent neurological deficit. Another permanent deficit occurred in a patient without TCD signs. After surgery, TCD reliably detected an early asymptomatic occlusion of the carotid artery, hyperperfusion syndrome in 12 (6.0%), and an increase of vasomotor reactivity in 10 (29.4%) of 34 surgeries.