- To test the hypothesis that among patients with symptomatic vertebrobasilar disease (VBD), those with distal blood flow compromise are at higher risk of subsequent posterior circulation stroke than those with normal flow.
Approximately 700,000 strokes occur annually in the U.S. making it the third leading cause of death and the leading cause of permanent disability among adults. Posterior circulation strokes account for 30-40% of all ischemic strokes, resulting in approximately 200,000 cases per year. Atherosclerotic disease of the vertebrobasilar system is an important etiology of posterior circulation stroke. Symptomatic vertebrobasilar disease (VBD) carries a high annual risk of stroke, averaging 10-15% per year despite medical therapy. Vertebrobasilar stroke is particularly prone to resulting in devastating consequences due to the concentrated ‘eloquence’ of brain tissue supplied by the posterior circulation. Consequently, vertebrobasilar stroke can result in high rates of death and disability.
VBD represents a potentially treatable high risk source of stroke. Advances in endovascular angioplasty and stenting have created new options for the treatment of VBD, but the interventions themselves carry significant risks, and the selection criteria for appropriate candidates remains uncertain. Preliminary published retrospective data suggests that the risk of stroke in VBD is affected by the extent to which intracranial blood flow is compromised. Specifically, analysis has indicated that patients with low intracranial flow as assessed by noninvasive quantitative MRA (QMRA) are at significantly higher risk of stroke than those with normal flow. The objective is to conduct a prospective longitudinal study of patients with symptomatic VBD to determine if the level of blood flow compromise assessed by noninvasive MR imaging, consisting of QMRA and MR perfusion, at the baseline examination predicts risk of recurrent ischemic events.
The study is a multi-center prospective observational study of patients with50% stenosis or occlusion of the vertebral or basilar arteries. Once enrolled the patients will undergo hemodynamic assessment with non-invasive MR imaging, the results of which will be kept blinded from the patient and treating physicians. Based upon the results of the imaging, patients will be designated as demonstrating normal or compromised cerebral blood flow as a result of their VBD. Baseline clinical evaluation will be performed, with subsequent clinical follow-up at 6 month intervals for a minimum of 12 months. Patients will receive monthly telephone calls to check on their status, and be re-imaged at 6 month intervals for a minimum of 12 months. The primary endpoint will be the incidence of stroke in the vertebrobasilar territory at 12 months.