[Four cases of abducens palsy caused by a vascular lesion of the vertebrobasilar system].

Several pathological conditions are responsible for abducens palsy, but a lesion of the vertebral artery (VA) has rarely been recognized as one of the causes. It has been reported that a high percentage of cases of abducens palsy are involved with ruptured dissecting aneurysms of the VA. We investigate the vertebrobasilar anatomy in 4 patients, suffering with abducens palsy. One patient revealed a fusiform dilatation of the vertebral artery on the same side as the abducens palsy. Three patients were noted to have stenosis of the vertebral artery from the origin of the posterior inferior cerebellar artery (PICA) to the union. Finally, four patients were found to have abnormal vertebrobasilar anatomy, which was on the same side as the abducens palsy. It is conceivable that changes of vertebrobasilar circulation may cause abducens palsy through direct compression, or ischemic events.