Recently, a young woman presented acutely with a left hemispheric stroke and differing blood pressures in the arms as her initial manifestation of Takayasu's arteritis. Helical CT angiography, performed to rule out aortic dissection, revealed a thickened wall of the aortic arch with stenoses and occlusions of the great vessels, suggesting the diagnosis. The sequence of imaging studies and findings in this unusually catastrophic presentation of a typically insidious disease are highlighted
