OBJECTIVE Typical hemifacial spasm (HFS) commonly initiates from the orbicularis oculi muscle to the orbicularis oris muscle. Atypical HFS (AHFS) is different from typical HFS, in which the spasm of muscular orbicularis oris is the primary presenting symptom. The objective of this study was to analyze the sites of compression and the effectiveness of micro vascular decompression (MVD) for AHFS. METHODS The authors retrospectively analyzed the clinical data for 12 consecutive patients who underwent MVD for AHFS between July 2008 and July 2013. RESULTS Postoperatively, complete remission of facial spasm was found in 10 of the 12 patients, which gradually disappeared after 2 months in 2 patients. No recurrence of spasm was observed during follow-up. Immediate postoperative facial paralysis accompanied by hearing loss occurred in 1 patient and temporary hearing loss with tinnitus in 2. All 3 patients with complications had gradual improvement during the follow-up period. CONCLUSIONS The authors conclude that most cases of AHFS were caused by neurovascular compression on the posterior/rostral side of the facial nerve distal to the root entry zones. MVD is a safe treatment for AHFS, but the incidence of postoperative complications, such as facial paralysis and decrease in hearing, remains high.