From the case:
Hemifacial spasm
Axial FIESTA

This patient suffered from left hemifacial spasm. Note the left vertebral artery contacting the facial nerve at the nerve root entry zone, making it the likely culprit.
From the case:
Hemifacial spasm
Axial

Annotate image demonstrating the relationship between facial nerve and left vertebral artery.
Case Discussion
The challenge with cranial nerve compression syndromes is not just identifying a small vessel contacting the nerve root entry zone but also, possibly more importantly, that many many asymptomatic individuals have similar anatomy.