Fig 1. Examples of types of AICA loops and eighth CN-AICA relationships. Axial 3D-FIESTA MR images through the eighth CN show the following: AICA loop within the IAC (arrow) but not >50% of its depth (Type II) (A); vascular loop extending into >50% of the IAC (arrow) (Type III) (B); and contact of AICA (arrow) with the eighth CN, not resulting (C) and resulting (D) in angulation on the eighth CN (arrow) in the CPA.