Hemifacial spasm: neurovascular compressive patterns and surgical significance

Background. The aim of this study was to report further investigation of neurovascular compression as a cause of hemifacial spasm (HFS) and to provide useful surgical guidelines by describing the compression patterns. Material and methods. From January 2004 to February 2006, 236 consecutive patients with HFS underwent microvascular decompression (MVD) in a single centre. Based on the operation and medical records, the intraoperative findings and post-operative outcomes were obtained and analysed. Results. We found that 95.3% of lesions had accompanying causative factors that made the neurovascular compression inevitable. Based on the contributing factors, compression patterns were categorised into six different types including: loop (n = 11: 4.6%), arachnoid (n = 66: 27.9%), perforator (n = 58: 24.6%), branch (n = 18: 7.6%), sandwich (n = 28: 11.9%), and tandem (n = 52: 22.0%). The compression patterns were significantly correlated with the compressing vessels involved. Thirty-two (86.5%) of 37 lesions where the vertebral artery was the compressing vessel involved the tandem type. Anterior inferior cerebellar artery was the compressing vessel involved in 49 (84.5%) of 58 perforator type compressions, while posterior inferior cerebellar artery was the compressing vessel involved in 8 (72.7%) of 11 loop type compressions. Conclusions. Once the compressing vessel responsible for the neurovascular compression are identified, the probable pattern of compression can be anticipated; this knowledge could facilitate the application of the appropriate operative procedures and minimise post-operative complications.