Mechanisms of early Recurrence in Intracranial Atherosclerotic Disease (MyRIAD): Rationale and design.

RATIONALE: Intracranial atherosclerotic disease (ICAD) is the most common cause of ischemic stroke with the highest rate of recurrence, despite aggressive medical management. Diverse mechanisms may be responsible for ICAD-related cerebral ischemia, with potential therapeutic implications. Here we present the rationale, design and methods of the Mechanisms of Early Recurrence in Intracranial Atherosclerotic Disease (MyRIAD) study. The aim of MyRIAD is to determine the mechanisms of stroke in ICAD through physiologic imaging biomarkers that evaluate impaired antegrade flow, poor distal perfusion, abnormal vasoreactivity, artery to artery embolism, and their interaction. METHODS AND DESIGN: This is a prospective observational study of patients with recently symptomatic (<21 days) ICAD with 50-99% stenosis treated medically and monitored for up to 1 year. An estimated 110 participants are recruited at 10 sites to identify the association between the presence of each mechanism of ischemia and recurrent stroke. The primary outcome is ischemic stroke in the territory of the symptomatic artery. Secondary outcomes include new cerebral infarction on MRI at 6-8 weeks and recurrent TIA in the territory of the symptomatic artery. DISCUSSION: MyRIAD is positioned to define the role of specific mechanisms of recurrent ischemia in patients with symptomatic ICAD. This knowledge will allow the development and implementation of effective and specific treatments for this condition.

Measuring Cerebral Blood Flow in Moyamoya Angiopathy by Quantitative Magnetic Resonance Angiography Noninvasive Optimal Vessel Analysis.

BACKGROUND: Moyamoya disease causes progressive occlusion of the supraclinoidal internal carotid artery, and middle, anterior, and less frequently the posterior cerebral arteries, carrying the risk of stroke. Blood flow is often partially reconstituted by compensatory moyamoya collaterals and sometimes the posterior circulation. Cerebral revascularization can further augment blood flow. These changes to blood flow within the cerebral vessels, however, are not well characterized. OBJECTIVE: To evaluate blood flow changes resulting from the disease process and revascularization surgery using quantitative magnetic resonance angiography with noninvasive optimal vessel analysis (NOVA). METHODS: We retrospectively analyzed 190 preoperative and postoperative imaging scans in 66 moyamoya patients after revascularization surgery. Images were analyzed for blood flow using NOVA and compared with preoperative angiographic staging and postoperative blood flow. Blood flow rates within superficial temporal artery grafts were compared based on angiographic evidence of patency. RESULTS: Diseased vessels had lower blood flow, correlating with angiographic staging. Flow in posterior cererbal and basilar arteries increased with disease severity, particularly when both the anterior and middle cerebral arteries were occluded. Basilar artery flow and ipsilateral internal carotid artery flow decreased after surgery. Flow rates were different between angiographically robust and poor direct bypass grafts, as well as between robust and patent grafts. CONCLUSION: Preoperative changes in cerebral vessel flow as measured by NOVA correlated with angiographic disease progression. NOVA demonstrated that preoperative augmentation of the posterior circulation decreased after surgery. This report is the first to quantify the shift in collateral supply from the posterior circulation to the bypass graft.

Hemispheric revascularization in the setting of carotid occlusion and subclavian steal: a diagnostic and management role for quantitative magnetic resonance angiography?

OBJECTIVE: Advances in phase contrast magnetic resonance imaging have facilitated the noninvasive assessment of blood flow rates and flow direction in patients with complex cerebrovascular disorders. METHODS: We describe a case of right hemispheric hypoperfusion in which, on noninvasive assessment with quantitative magnetic resonance angiography, the patient was found to harbor an occult subclavian steal with flow reversal in the left vertebral artery. RESULTS: The presence of posterior communicating arteries noted on quantitative magnetic resonance angiography suggested that normalization of flow in the vertebral arteries by treating the subclavian occlusion could improve flow in the anterior circulation. Angiography confirmed the noninvasive findings, and the subclavian occlusion was treated with angioplasty and stenting. Postintervention quantitative magnetic resonance angiography documented quantitative improvement in right middle cerebral artery flow and restoration of antegrade flow in the left vertebral artery. CONCLUSION: This case illustrates the potential role of noninvasive assessment of blood flow rates and flow direction in the diagnosis, treatment planning, and follow-up of patients with complex cerebrovascular disease.