Background: The compression of 7th cranial nerve by arteries is one of the various causes of hemifacial spasm (HFS).A few previous studies were revealed the relation between the compression of 7th cranial nerve and common trunkanomaly. We evaluated the common trunk anomalies in patients with HFS using MRI and MRA.Methods: From January 2001 to December 2005, 41 consecutive patients (9 men, mean age 54.5