Cobweb sign in aortic dissection are slender linear areas of low attenuation seen occasionally in the false lumen in contrast enhanced computerized tomographic (CT) scans. They are specific for the false lumen and help in the identification of the false lumen . The slender linear areas correspond to incompletely dissected aortic media.
It is thought to be a specific sign for the false lumen, but with low sensitivity as it is not seen very frequently.
D M Williams, A Joshi, M D Dake, G M Deeb, D C Miller and G D Abrams studied aortic cobwebs by multiple modalities . They studied 23 pathological specimens, 27 magnetic resonance (MR) studies, 5 intravascular ultrasound scans (IVUS), 3 transesophageal ultrasound images from and 43 patients with aortic dissection. Cobwebs were found in 17 of the 23 pathological specimens, while it was found only in 6 of the 27 MR images. They were noted in 2 of the 5 IVUS images and 1 of the 3 transesophageal ultrasound scans.