High riding basilar

High riding basilar is a normal anatomical variation.
The term ectatic basillar is often overused for this finding as the term Ectasia is confined to abnormal dilatation of an artery.

Clinical significance: 

The position of the basilar tip in relation to the posterior clinoid and less importantly to the petrous apex is critical in pre-surgical assessment for those who still clip basilar tip aneurysms.
An aneurysm neck below the posterior clinoid tip is difficult or impossible to reach and clip even with a subtemporal approach.

This is simply a high riding tip of basilar. The term ectatic basillar is often overused for this finding as the term Ectasia is confined to abnormal dilatation of an artery.