[Vertebrobasilar ischemia of thrombotic and embolic origin]

To analyze the mechanisms involved in the appearance of ischemia in vertebro-basilar territory, especially those of embolic or thrombotic characteristics.

The mechanism of vertebro-basilar ischemia had not been adequately studied until a few years ago. This had led to the belief that most were due to a haemodynamic mechanism. However, in recent years studies of large numbers of patients, in whom cardiological and neurovascular evaluation had been systematically carried out, has shown that this is not so. In general, the commonest mechanism is embolism, both of arterial and of cardiac origin. Local thrombosis and a haemodynamic mechanism are less common. The arterial lesions most often associated with intra-arterial embolism have their origins in the intracranial segment of the vertebral artery. The most frequent sites of blockage by emboli are the distal segments of the basilar artery, the superior cerebellar artery, the posterior cerebral artery and the intracranial region of the vertebral artery-posteriorinferior cerebellar artery.

The mechanism of vertebro-basilar ischemia is not homogeneous and can not be taken for granted in any patient in particular. For this reason it is necessary to carry out a full clinical study of patients with these symptoms, similar to that done for patients with carotid ischemia. This permits not only individualized, correct treatment of each patient but also a more complete knowledge of the mechanisms of ischemia in this territory.