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.