Supplementary Material for: Flip-Flop Phenomenon: Swallowing-Induced Arterial Displacement as an Indicator of Carotid Artery Disease

Background and purpose: The dynamic displacement of the carotid arteries with interference of the hyoid bone during swallowing, named as “flip-flop” phenomenon (FFP), may be associated with ischemic stroke. However, the extent to which FFP is prevalent in carotid artery disease remains unknown. We aimed to investigate its exact prevalence to explore the relationship between FFP and carotid artery disease. Methods: We examined 202 consecutive patients who were affected by neurological diseases including cerebrovascular diseases. Using carotid ultrasound, we evaluated carotid intima-media thickness, internal carotid artery stenosis (ICS), and FFP during swallowing with neck rotation. Results: FFP was observed in 39 of the 202 patients (19.3%). Patients with FFP showed significantly higher prevalence of ICS than those without FFP (12/39 [30.8] vs. 21/163 [12.9%]; p = 0.007). Among those with ICS (n = 33; 36 vessels), FFP was associated with symptomatic ICS more frequently than with asymptomatic ICS (6/11 [54.5] vs. 5/25 [20.0%]; p = 0.038). Among those with unilateral FFP (n = 37), the prevalence of ipsilateral ICS was higher than that of contralateral ICS (9/37 [24.3] vs. 2/37 [5.4%]; p = 0.035). Conclusions: FFP accompanies the swallowing movement in some neurological patients, and more frequently in patients with ICS. FFP may thus be a novel indicator of stroke.

背景与目的：吞咽过程中受舌骨干扰的颈动脉动态移位现象，被命名为“翻转型现象（flip-flop phenomenon, FFP）”，该现象或与缺血性脑卒中相关。但目前尚不明确FFP在颈动脉疾病人群中的患病率。本研究旨在明确其确切患病率，以探讨FFP与颈动脉疾病之间的关联。
方法：本研究纳入202例连续入组的、罹患包括脑血管疾病在内的神经系统疾病的患者。采用颈动脉超声检查，评估受试者的颈动脉内膜中层厚度、颈内动脉狭窄（internal carotid artery stenosis, ICS）以及颈部旋转时吞咽过程中的FFP表现。
结果：202例患者中共39例（19.3%）观察到FFP。合并FFP的患者，其颈内动脉狭窄患病率显著高于未合并FFP的患者（12/39 [30.8%] vs 21/163 [12.9%]；p=0.007）。在合并颈内动脉狭窄的患者中（n=33，共累及36支血管），FFP与症状性颈内动脉狭窄的关联显著多于无症状性颈内动脉狭窄（6/11 [54.5%] vs 5/25 [20.0%]；p=0.038）。在单侧FFP患者中（n=37），患侧颈内动脉狭窄患病率显著高于对侧（9/37 [24.3%] vs 2/37 [5.4%]；p=0.035）。
结论：部分神经系统疾病患者在吞咽运动过程中可出现FFP，且颈内动脉狭窄患者的FFP检出率更高。因此，FFP或可成为脑卒中的新型预测指标。