Animal models of cervical artery dissection.

We developed a canine model of arterial dissection and serially observed morphological changes angiographically and histopathologically to clarify the causes and mechanisms resulting in dissecting aneurysm formation or arterial occlusion. Intimal defects of various sizes and shapes were made on the arterial walls to provide an entry zone for dissection, so as to simulate the extent of arterial wall injury. Our experimental model showed angiographic and histopathological changes similar to those in clinical cases. As for our initial findings immediately after lesioning, either a double shadow (pseudolumen) or stenosis of the affected artery, due to compression from the subadventitial hematoma, was observed in the angiograms of all lesions. In some lesions with a pseudolumen, a dissecting aneurysm developed subsequently. Some arteries showing focal occlusion recanalized, and stenosis spontaneously improved. Very small dissections resulted in spontaneous healing, while a large intimal entry zone caused stenotic lesions. However, a medium-sized entry zone (4-6 mm) may induce aneurysm formation. The different features of dissection may be caused by the characteristics of flow into the subadventitial cavity and by thrombogenesis. Morphological changes after arterial dissection were closely related to the extent of intimal injury, suggesting that the size of the intimal entry zone may determine whether or not a dissecting aneurysm is formed.