String sign in angiography is suggestive of:

Traditional angiography remains the basis of diagnosis and characterization of aerial dissection. Angiographic abnormalities include stenosis of the true lumen, or "string-sign," visible intimal flaps, and the appearance of contrast in the false lumen. Four-vessel cerebral angiography should be performed when suspicion of dissection exists. Ref: Schwaz's principle of surgery 9th edition, chapter 42.