Three cases of a basilar/middle meningeal artery anastomosis are demonstrated angiographically. No reference to previous angiographic demonstration of this vascular anomaly has been found in the literature, and only one similar case with an anatomical description has been located. An embryological explanation of this rare anastomosis is presented.

The anatomy and angiographic appearance of the great horizontal fissure is seen on most vertebral angiograms of excellent quality and is best shown on the lateral and AP (transfacial) projections. Identification of the fissure may provide an additional angiographic landmark for precise localization of peripherally situated masses, either within or adjacent to the cerebellum.