MR Angiography and Imaging for the Evaluation of Middle Cerebral Artery Atherosclerotic Disease

Abstract

SUMMARY:Intracranial atherosclerotic disease may constitute the most common cause of ischemic stroke worldwide; yet, in the developed world, imaging research has largely focused on extracranial atherosclerosis. Many studies in populations of Asian, African, and Hispanic descent demonstrate the preponderance of intracranial stenosis compared with carotid stenosis. This review examines the clinical presentations of MCA atherosclerosis and stenosis and the use of noninvasive MR imaging in the assessment of intracranial vasculature. MRA is a well-validated technique that offers great advantage over traditional angiography. Advances in high-resolution MR imaging of MCA stenosis have the potential to yield excellent visualization of plaque. Future developments in high-resolution MR imaging to depict intracranial atherosclerosis are explored in this review; these advances will guide endovascular therapy and the comparison of novel interventions.ABBREVIATIONS: TOF ϭ time-of-flight; TCD ϭ transcranial Doppler S troke is a common cause of morbidity and mortality, with cerebrovascular disease constituting the second most frequent cause of death worldwide.1 While the burden of cerebrovascular disease in the developing world is receiving greater attention, its importance is underestimated.2 Intracranial atherosclerotic disease is reaching greater clinical prominence as potentially the greatest contributor to the burden of cerebrovascular disease worldwide.3 Previously, atherosclerotic disease within intracranial vessels was not well-appreciated clinically, perhaps due to the inability to visualize the MCA noninvasively or the greater emphasis on the more easily imaged carotid arteries. In an early study of MCA syndromes, Lhermitte et al 4 alleged that "atherosclerotic thrombosis of MCA is probably a rare event and the primary cause . . . lies in the proximal ICA . . . for an almost inaccessible artery appears to be of little significance." Thus, early investigations established a precedent of emphasizing extracranial atherosclerosis at the expense of investigation of other manifestations of cerebrovascular disease.In examining only extracranial disease, investigators may be detecting only advanced atherosclerosis. Some argue that MCA disease may precede extracranial atherosclerosis; this sequence is suggested by the lack of substantial carotid stenosis in a group of patients with intracranial atherosclerosis, while nearly all those with extracranial stenosis also had concomitant intracranial stenosis.5 Therefore, detecting intracranial atherosclerosis may enable clinicians to intervene earlier.There is much controversy about the degree of MCA stenosis responsible for stroke, with some groups arguing that MCA stenosis is not important in the white population on the basis of a small TCD sonography study.6 Yet a host of postmortem and imaging studies implicate MCA atherosclerosis as a likely cause of stroke.7-9 Further investigation is necessary to evaluate the prevalence and importance of MCA disease as an etiology of ischemic...

Isolated MCA Disease in Patients Without Significant Atherosclerotic Risk Factors

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Reversible Cerebral Vasoconstriction Syndrome, Part 2: Diagnostic Work-Up, Imaging Evaluation, and Differential Diagnosis

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