A 65-year-old male with acute chest
pain. Chest radiograph shows a left sided pleural effusion.MRI of the chest was performed.
MR findings reveal a large ruptured, dissecting aneurysm in the descending thoracic aorta, with a peri-aneurysmal hematoma, and left hemothorax.
Dissecting aneurysms are mainly encountered in the aorta and hypertension is the main predisposing cause. Men are mostly affected, usually aged between 50-70 years. Rare causes include Marfans syndrome, or in women with pregnancy, aortic stenosis, or coarctation.
De Bakey classification is as follows:
Type I starts in the ascending aorta and extends throughout the arch and descending aorta to the iliacs
Type II starts in the ascending aorta but does not extend beyond the arch
Type III starts in the distal arch and extends down to the iliacs
Type II is least common and is associated with Marfans syndrome.
Clinical features include acute chest pain, or symptoms due to involvement of aortic branches, such as hemiplegia and vertebral symptoms (cerebral branches), paraplegia following occlusion of intercostal or lumbar vessels, mesenteric ischemia or pancreatitis, retrograde spread to pericardium could lead to cardiac tamponade, anuria due to renal artery occlusion, or lower limb ischaemia due to iliac occlusion.
Widening of the mediastinum, localized dilatation of the aortic knuckle (hump sign), pleural effusion, lateral displacement of the trachea
Catheter tip needs to be placed in the aortic root so that the whole of the ascending aorta can be visualized and the contrast medium can enter the false lumen if the tear is a proximal one. Usually both the false and true lumen will fill with the displaced intima appearing as a linear band separating the two. Sometimes, only the true lumen may fill, but it may be compressed by the false lumen, giving rise to the twisted tape sign.
CT & MRI
Are both useful in confirming a diagnosis of dissection. Intravenous contrast is required for CT, and both modalities reveal the dilated aorta, with true and false lumens separated by the intimal flap. MRI does have the added advantage of saggital and coronal imaging.
Dr. Deepak Patkar, MRI Nanavati, Mumbai