ELN and aneurysm: A type A dissection is according to the Stanford classification, a dissection located in the ascending aorta while with a type B dissection the descending thoracic aortic wall is affected.[14] In addition, acute aortic dissections (AADs) are described to be associated with cystic medial necrosis (e.g. reduced SMCs, fragmentation of elastin).[13] As Borges et al.[8] showed for aneurysms, they also observed an overall reduced amount of medial collagen, especially in the media adjacent to the adventitia for AADs.