Bhandari Anita, Bhandari Rajneesh, Kingma Herman, Strupp Michael
Vertigo and Ear Clinic, Jaipur, India.
NeuroEquilibrium Diagnostic Systems Pvt Ltd., Jaipur, India.
Front Neurol. 2022 May 31;13:881156. doi: 10.3389/fneur.2022.881156. eCollection 2022.
The aim of this study was to show with three-dimensional simulations how the diagnostic supine roll test (SRT) is affected by the initial position of the debris within the horizontal canal (hc) and study the nystagmus patterns on changing the sequence of testing and its impact on the diagnosis of the side of involvement in hc-BPPV.
A 3D dynamic simulation model was developed and applied based on reconstructed MRI images and fluid dynamics. Each semicircular canal was linked to the respective extraocular muscles to visualize nystagmus generated on stimulation of the canal.
The simulations of hc-canalithiasis showed that the nystagmus pattern seen with the SRT is changed by the initial position of the otolith debris within the canal and the sequence of testing. The debris changes position during SRT so that sequential steps do not start at the initial position as previously assumed. The sequence of performing the SRT steps from the right or left side influences the nystagmus pattern generated: bilateral direction-changing, bilateral direction-fixed, and unilateral nystagmus can be seen in different test conditions. The SRT itself may even reposition the debris out of the canal.
Simulations provide a dynamic tool to study the diagnostic SRT in hc-canalithiasis. Starting the SRT from right or left has a major impact on the test outcome (unlike the Dix-Hallpike maneuver). The findings provide a new interpretation for the results of the SRT. The simulations explain the phenomenon of direction-fixed nystagmus as a logical consequence of starting the SRT with the head turned toward the non-affected side in hc-canalithiasis with debris in the ampullary arm. They also show that unilateral nystagmus seen on SRT indicates canalithiasis of the non-ampullary arm of the side opposite to the side of nystagmus. The generation of bilateral direction-changing, bilateral direction-fixed, and unilateral nystagmus can be the cause of misdiagnoses in terms of the affected side and underlying mechanisms. Finally, a recommendation for a standardized protocol for the sequence of positional tests should be established to ensure uniform interpretation of test results.
本研究旨在通过三维模拟展示水平半规管（hc）内耳石碎片的初始位置如何影响诊断性仰卧翻滚试验（SRT），并研究改变测试顺序时的眼震模式及其对hc - BPPV患侧诊断的影响。
基于重建的MRI图像和流体动力学开发并应用了一个三维动态模拟模型。每个半规管与相应的眼外肌相连，以可视化刺激半规管时产生的眼震。
hc管结石症的模拟显示，SRT所见的眼震模式会因管内耳石碎片的初始位置和测试顺序而改变。耳石碎片在SRT过程中会改变位置，因此后续步骤并非如先前假设的那样从初始位置开始。从右侧或左侧执行SRT步骤的顺序会影响所产生的眼震模式：在不同测试条件下可观察到双向变向、双向固定和单向眼震。SRT本身甚至可能将耳石碎片重新移出半规管。
模拟为研究hc管结石症中的诊断性SRT提供了一个动态工具。从右侧或左侧开始SRT对测试结果有重大影响（与Dix - Hallpike手法不同）。这些发现为SRT的结果提供了新的解释。模拟解释了固定方向眼震现象，这是在hc管结石症中壶腹臂有耳石碎片时，头部转向未受影响侧开始SRT的逻辑结果。它们还表明，SRT时出现的单向眼震表明眼震对侧非壶腹臂存在管结石症。双向变向、双向固定和单向眼震的产生可能是患侧和潜在机制误诊的原因。最后，应建立位置测试顺序的标准化方案建议，以确保测试结果的统一解读。
