Anatomical deviations of vertebral artery in hemifacial spasm: a quantitative study

Purpose There exist different opinions on whether the anatomical laterality of vertebral artery (VA) is related to the unilateral onset of hemifacial spasm (HFS). In this study, we intended to qualitatively explore the potential correlation between the anatomical deviations of VA and the clinical characteristics of HFS. Methods Two hundred and forty patients who underwent microvascular decompression for HFS between January 2018 and December 2019 were recruited. Clinical data including medical records and preoperative MRI images were retrospectively reviewed. A score system was specially designed for VAs to illustrate their distribution, and a score-weighted cross-sectional area of VA was proposed to represent the relative thickness of VA on each side. Then, the anatomical deviations of VA were comparatively analyzed between the symptomatic side and asymptomatic side and between VA-involved cases and non-VA-involved cases. Results The score and weighted cross-sectional area (WCSA) of VA in symptomatic side were significantly greater than those in asymptomatic side (P = 0.000, P = 0.000). And in symptomatic side, the score and WCSA of VA in VA-involved cases were significantly greater than those in non-VA-involved cases (P = 0.000). Moreover, with higher score (P = 0.000) and greater WCSA (P = 0.001) on the left side, the VA-involved cases showed a preference (74%) of left HFS. Conclusions In HFS, the symptomatic side tends to have an ipsilaterally deviated and relatively larger VA, especially in VA-involved cases. And it is the VA-involved cases that are prone to have a prevalence of left HFS, but not the non-VA-involved cases.