Displacement of the superior cerebellar artery. A means of distinguishing intra- and extra-axial posterior fossa masses by vertebral arteriography.

Abstract

Numerous studies of vertebral arteriography have established the normal positions of the individual arteries in the posterior fossa.1-3The precise localization of expanding mass lesions by displacement and distortion of these arteries has been more difficult, however, than with displacement and distortion of the supratentorial arteries.4Only rarely are vascular displacements in the posterior fossa of definite localizing value. One example would be the posterior displacement of the basilar artery by a mass in the region of the clivus. Many other displacements which can be noted in the vertebral arteriograms of patients with posterior fossa mass lesions are of less localizing significance. Examples of these would be the anteroposterior or midline displacement of the cranial loop of the posterior inferior cerebellar artery,5and displacements and distortions of the posterior cerebral arteries,6especially when due to tentorial herniation. Downward displacement of the caudal loop of the