Intraoperative Measuring of the Offending Vessel's Pressure on the Facial Nerve at Root Exit Zone in Patients with Hemifacial Spasm During Microvascular Decompression: A Prospective Study.

Objective: The compression of the offending vessel on the facial nerve at root exit zone is considered as the leading cause of hemifacial spasm (HFS). However, the correlation between the severity of spasm and the pressure of neurovascular compression (NVC) has not yet been investigated. The aim of this study was to investigate the clinical correlation between the severity of HFS and the pressure of NVC.

Methods: A prospective study was performed, which included 52 of 151 patients who underwent microvascular decompression. We classified the preoperative spasm severity according to the Cohen scores. Codman intracranial pressure monitoring system was used to measure the NVC pressure at the root exit zone during microvascular decompression. All patients were followed up for 12-24 months.

Results: Herein, the intraoperative pressure readings of NVC were in the range of 21-63 mmHg. The means of the pressure of NVC that corresponded to the Cohen scores (1-4) were 23.00 ± 1.83, 34.91 ± 12.42, 46.50 ± 9.40, and 55.40 ± 3.03 mmHg, respectively. The Spearman's rank correlation established a strong positive correlation between the pressure and the Cohen scores (r = 0.689, P < 0.0001). The simple linear analysis indicated that sex (P = 0.132), duration (P = 0.304), and delayed relief (P = 0.158) were not significantly associated with the pressure. However, a substantial correlation was determined between the pressure values and the time until the complete recovery (r = 0.949, P < 0.0001) of the delayed healing population.

Conclusions: The severity of HFS exhibited a strong positive correlation with the intraoperative offending vessel's pressure values. Thus, the neurovascular pressure is a significant factor in the pathogenesis of HFS.