Hemifacial spasm caused by cross type vascular compression

Objectives: The meatal segment of anterior inferior cerebellar artery usually crosses over the gap between cranial nerves VII and VIII, and may compress the cisternal portion (CP) of the facial nerve. This is defined as cross type compression, which is easy to be neglected and thus leads to poor outcome. Here our experience in treating patients of cross type hemifacial spasm (HFS) is reported. Methods: Twenty-one patients of HFS due to cross type compression were treated with microvascular decompression (MVD) surgery with the aid of abnormal muscle response monitoring. Results: In addition to cross type compression at CP, there were typical vascular compressions on the root exit zone and attached segment in 20 cases. After MVD surgery, 17 patients were cured, 3 patients achieved good resolution of spasm, and the other 1 patient got delayed resolution. Three patients had postoperative transient hearing loss and/or tinnitus. Discussion: Even there are apparently typical vascular compressions at proximal portion of the facial nerve, the surgeon should be aware that cross type compression at the CP may co-exist. With the aid of abnormal muscle response (AMR) monitoring, MVD is efficient for patients due to cross type compression.