AICA loops in the cerebellopontine cistern have been implied in causing auditory and vestibular symptoms, as well as hemifacial spasm, resulting from compression of the VII and VIII cranial nerves.

The vessels can be classified according to their anatomic location: 

• type I: lying only in the CPA, but not entering the internal auditory canal (IAC)
• type II: entering, but not extending >50% of the length of the IAC
• type III: entering and extending >50% of the length of the IAC

In addition, it is important to evaluate the presence of vascular contact and the angulation of eighth cranial nerve at the contact point, as specific signs of vascular compression.