FIG 1. Images obtained in a 53-year-old woman with a sudden onset of occipital pain and unsteady gait. a, Conventional angiogram of the left VA in an oblique projection shows alternating regions of luminal narrowing and dilatation at the V4 segment (arrows). b and c, Axial source CT angiograms show a target appearance (narrowed eccentric lumen surrounded by crescent-shaped mural thickening and an enhanced wall) at the bilateral intracranial VAs (arrows). An associated increased external diameter of the dissected artery is noted. d, MIP CT angiogram demonstrates the same picture of an alternatively narrowed and dilated lumen (black arrows) and the intramural hematoma (white arrows)