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13 results

  • Classification of vertebral artery loop formation and association with cervicogenic dizziness

  • A Yenigun, M E Ustun, S Tugrul, R Dogan, O Ozturan
  • Journal:
    The Journal of Laryngology & Otology / Volume 130 / Issue 12 / December 2016
    Published online by Cambridge University Press:
    27 October 2016, pp. 1115-1119
    Print publication:
    December 2016
  • Objective:

    An examination was conducted of the number, level, clinical association and treatment approaches for vertebral arterial loop formation in patients with this condition with and without concurrent cervicogenic dizziness, and classified them according to the vertebral artery segment in which it was present.

    Method:

    A cross-sectional retrospective study.

    Results:

    Thirty-seven patients who had undergone double-sided magnetic resonance angiography were examined; vertebral arterial loop formation was observed at only 1 level in 26 patients and at several levels in 9 patients. Segment one (V1) was involved in 78.3 per cent of cases and segment two (V2) was involved in 21.6 per cent. Symptoms in patients with vertebral arterial loop formation included: positional vertigo, in 100 per cent; and pulsatile tinnitus, in 83.7 per cent.

    Conclusion:

    Loop formation at the vertebral artery was observed most often on the proximal side in patients with cervicogenic dizziness (78.3 per cent). The incidence on the left side was twice as high as on the right side.

  • Chapter 11 - Neuroimaging of wakefulness

  • from Section 2 - Neuroimaging of wakefulness and sleep
  • Edited by Eric Nofzinger, University of Pittsburgh, Pierre Maquet, Université de Liège, Belgium, Michael J. Thorpy
  • Book:
    Neuroimaging of Sleep and Sleep Disorders
    Published online:
    05 March 2013
    Print publication:
    07 March 2013, pp 91-95

  • Summary

    This chapter provides an overview of the fundamental elements of magnetic resonance imaging (MRI). Four terms describe the magnetic properties of materials, such as contrast agents, used in MRI. These terms are diamagnetism, paramagnetism, superparamagnetism, and ferromagnetism. The persistence of magnetization when the external magnetic field is removed distinguishes ferromagnetic materials from paramagnetic materials. To be useful for MRI, the proton must have spin angular momentum, in addition to the nuclear magnetism. Echo time (TE) and repetition time (TR) are basic parameters of image acquisition. Improvement in the magnitude of the MR signal can improve signal-to-noise ratio (SNR). Magnetic resonance angiography (MRA) uses the same MRI system and methods to make images of blood vessels. The most common MRA technique is based on the time-of-flight (TOF) effect, where blood protons flowing into the slice during the acquisition yield very high signal, but signal from stationary protons is suppressed.

  • 36 - Psychotherapy

  • from Section III - Treatments in Behavioral Neurology & Neuropsychiatry
  • Edited by David B. Arciniegas, C. Alan Anderson, Christopher M. Filley
  • Book:
    Behavioral Neurology & Neuropsychiatry
    Published online:
    05 February 2013
    Print publication:
    24 January 2013, pp 587-603

  • Summary

    This chapter focuses on the principles of advanced neuroimaging and their current clinical applications and limitations. Xenon enhanced computed tomography imaging (Xe-CT) is used for the quantification of cerebral blood flow (CBF). Advanced magnetic resonance imaging (MRI) techniques enhance the evaluation of brain structure and/or function. Magnetic resonance angiography (MRA) is used for assessment of the integrity of arteries and veins in the human body. Magnetic resonance spectroscopy data are used to evaluate the composition and metabolic activity of the brain. Diffusion tensor imaging (DTI) is a special form of diffusion-weighted MRI that allows the assessment and visualization of white matter and its constituents on a millimeter-level scale. Arterial spin labeling allows for the characterization and direct visualization of blood low within brain tissue. Information derived from positron emission tomography (PET) data may prove useful in correlating functional and structural abnormalities, and identifying pathophysiological disturbances despite apparently normal brain structure.

  • 71 - OTHER CONDITIONS

  • from PART IX: - OTHER MISCELLANEOUS CONDITIONS
  • Edited by Louis R. Caplan, Julien Bogousslavsky
  • Book:
    Uncommon Causes of Stroke
    Published online:
    06 January 2010
    Print publication:
    09 October 2008, pp 539-544

  • Summary

    The term cervico-cephalic arterial dissection (CAD) encompasses a group of arteriopathies not necessarily with an identical pathogenesis but that have in common an intramural hemorrhage. This most frequently affects the extracranial arterial segments, predominantly the internal carotid artery (ICA), the vertebral artery (VA), or multiple arteries in typical locations. Spontaneous cervico-cephalic arterial dissections (sCAD) have typical predilection sites in the different arteries affected, which in part may be explained by mechanical influences: high cervical segment of extracranial ICA or V2 and V3 segments of VA. In the case of a severe head and/or neck trauma, the pathogenesis is straightforward. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) have replaced angiography as the gold standard, at least in the extracranial segments of ICA and VA. The risk of having a stroke or transient ischemic attack (TIA) after having suffered a CAD in general is very low.

  • 23 - PROGERIA

  • from PART II: - HEREDITARY AND GENETIC CONDITIONS AND MALFORMATIONS
  • Edited by Louis R. Caplan, Julien Bogousslavsky
  • Book:
    Uncommon Causes of Stroke
    Published online:
    06 January 2010
    Print publication:
    09 October 2008, pp 145-148

  • Summary

    Pulmonary arteriovenous malformations (PAVMs) are rare occurrences among the population. These malformations can be acquired in various clinical settings or be congenital. Single PAVMs <2 cm in diameter may be asymptomatic. The severity of symptoms is believed to be proportionally related to the size (diameter) of the PAVMs. The specific anatomy of the vascular malformation must then be analyzed either with helical computed tomography (CT) or magnetic resonance angiography (MRA). Digital subtraction angiography is eventually performed. The aims of treatment are to prevent neurological complications and pulmonary hemorrhage and to improve hypoxemia. Lobectomy or pneumonectomy is performed only in rare situations such as in patients in whom the feeding artery is so short that there is a risk of coil migration. Embolization therapy is applied for PAVMs, and is carried out by transcatheter embolotherapy, which consists in obliterating the feeding artery.

  • 39 - DISSEMINATED INTRAVASCULAR DISEASE

  • from PART IV: - DISORDERS INVOLVING ABNORMAL COAGULATION
  • Edited by Louis R. Caplan, Julien Bogousslavsky
  • Book:
    Uncommon Causes of Stroke
    Published online:
    06 January 2010
    Print publication:
    09 October 2008, pp 275-282

  • Summary

    The characteristic feature of Menkes disease (MD), as expressed in the human infant, is maldistribution of body copper. It is caused by mutation in ATP7A, a gene mapped to the long arm of the X-chromosome (Xq12-q13). This chapter focuses on pathology, clinical manifestations, diagnosis and treatment options for Menkes disease (MD). The clinical history and changes within the brain result from vascular lesions, copper deficiency, or a combination of the two. On angiographic or magnetic resonance (MR) angiographic studies reveal, a striking and progressive intracranial and extracranial vascular tortuosity is apparent. Similar changes are seen in the systemic vasculature. Aneurysms are not unusual. Neuroimaging discloses cerebral atrophy and bilateral ischemic lesions in deep gray matter, or in the cortical areas, the consequence of brain infarcts. Copper supplementation, using daily injections of copperhistidine, appears to be the most promising treatment.

  • 37 - CT Angiography of the Extremities

  • from PART III - COMPUTED TOMOGRAPHY
  • Edited by J. Christian Fox, University of California, Irvine
  • Book:
    Clinical Emergency Radiology
    Published online:
    07 December 2009
    Print publication:
    29 September 2008, pp 506-514

  • Summary

    Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are used instead of conventional angiography for many cases requiring evaluation of the blood vessels. This chapter discusses the indications, diagnostic capabilities, and limitations of CTA of the upper and lower extremities, followed by images of important pathological findings. CTA, like conventional angiography, should be performed after traumatic injuries in patients whose injured extremity is pulseless, has a neurological deficit, has an expanding hematoma, or has a bruit or thrill. It can be used to detect most vascular lesions, including thrombus, aneurysm, arteriovenous fistulas, and injury to the vessel wall. CTA is useful in detecting traumatic injuries, with specificities from 87% to 98%. Suitable images require multidetector scanners and appropriate reconstruction software. Since CTA is not performed in real time but produces static images, it may be difficult to delineate vascular occlusion and other vascular injuries from vasospasm.

  • 11 - Magnetic resonance angiography of the carotid artery

  • from Luminal imaging techniques
  • Edited by Jonathan Gillard, University of Cambridge, Martin Graves, University of Cambridge, Thomas Hatsukami, University of Washington, Chun Yuan, University of Washington
  • Book:
    Carotid Disease
    Published online:
    03 December 2009
    Print publication:
    07 December 2006, pp 140-157

  • Summary

    This chapter summarizes the current state of carotid magnetic resonance angiography (MRA) and deals with the technical aspects of the various types of MRA, including time-of-flight (TOF), phase-contrast (PC) and contrast-enhanced MRA. TOF MRA can be performed as either multiple 2D single slice acquisitions or as a 3D volumetric flow compensated acquisition. Multiple overlapping thin slab acquisition (MOTSA) method aims to reduce the saturation effect by reducing the thickness of the 3D slabs, but maintains the volume coverage by using multiple slabs. Phase-contrast MRA relies on detecting changes in the phase of blood's transverse magnetization as it moves along a magnetic field gradient. Gadolinium-based contrast agents have been used with TOF MRA in order to improve the signal-to-noise ratio (SNR) of carotid angiograms. Amongst the various types of MRA available, 2D TOF and PC techniques are suitable for screening but they suffer from a number of technical limitations.

  • Plaque modelling

  • Edited by Jonathan Gillard, University of Cambridge, Martin Graves, University of Cambridge, Thomas Hatsukami, University of Washington, Chun Yuan, University of Washington
  • Book:
    Carotid Disease
    Published online:
    03 December 2009
    Print publication:
    07 December 2006, pp -

  • Summary

    This chapter concentrates on computational simulation based on magnetic resonance imaging (MRI) and ultrasound imaging. It explores the flow structure and wall shear stress distributions, and describes the relationship with arterial disease patterns. An accurate description of 3D vessel geometry is essential for accurate modelling of blood flow using computational fluid dynamics (CFD), and magnetic resonance angiography (MRA) has been the most popular technique for obtaining the information in vivo. However, for superficial vessels such as the carotid and femoral arteries, extravascular 3D ultrasound can be a cost-effective alternative to MRA. Extravascular 3D ultrasound has potential to become a relatively inexpensive, fast and accurate alternative to MRI for CFD-based hemodynamics studies of superficial arteries. Standardized imaging protocols with high quality images will certainly help to reduce the manpower needed for model reconstruction and preparation, and to minimize operator dependence of the reconstruction process.

  • 12 - Computed tomographic angiography of carotid artery stenosis

  • from Luminal imaging techniques
  • Edited by Jonathan Gillard, University of Cambridge, Martin Graves, University of Cambridge, Thomas Hatsukami, University of Washington, Chun Yuan, University of Washington
  • Book:
    Carotid Disease
    Published online:
    03 December 2009
    Print publication:
    07 December 2006, pp 158-165

  • Summary

    Computerized tomography angiography (CTA) is increasingly used in the diagnosis of carotid artery stenosis, along with other noninvasive tests such as duplex ultrasound (DUS) or magnetic resonance angiography (MRA). The use of intravenous iodinated contrast in CTA allows excellent images of the lumen of the arteries. CTA visualizes the wall of the arteries and the morphology of the atherosclerotic plaque. Each of the different postprocessing techniques used to construct a 3D angiographic display of the artery have their particular strengths and weaknesses in imaging carotid artery stenosis. Maximum intensity projection (MIP) reconstructions are often used in CTA because they can rapidly automatically be generated. The projection, lateral, posteroanterior, or oblique, which shows the most severe stenosis, is used for establishing the degree of stenosis. Multislice CT-scanning together with other technical developments will probably further improve the diagnostic accuracy of CTA.

  • 5 - Technical introduction to MRI

  • Edited by Stephen Davis, Marc Fisher, National Institute of Mental Health, Bethesda, Maryland, Steven Warach, National Institutes of Health, Baltimore
  • Book:
    Magnetic Resonance Imaging in Stroke
    Published online:
    26 August 2009
    Print publication:
    20 March 2003, pp 55-68

  • Summary

    This chapter outlines the basic physical principles of magnetic resonance imaging (MRI), and overviews the MR techniques that have been developed for investigating stroke patients. Magnetic resonance angiography (MRA) is a major advance in application of MRI to imaging of patient blood flow in vessels. The signal intensity in MRI depends on proton density, T1, T2 and T2 relaxation process of any ensemble of the spins. Diffusion- and perfusion-weighted imaging combined with fast imaging capabilities on commercial systems has revolutionized our understanding of the pathophysiological mechanisms involved in the many clinical conditions especially cerebral ischemia and stroke. Another popular technique used for perfusion MR imaging is the arterial spin labelling (ASL). Magnetic resonance spectroscopy (MRS) of the brain is a noninvasive MR technique that gives the relative concentration of certain chemical compounds within 2 to 3 cm3 of tissue.