Background: The diagnosis of horizontal semicircular canal benign paroxysmal positional vertigo (HSC-BPPV) mainly depends on the elicitation of asymmetric horizontal positional nystagmus on rolling head to either side, during the diagnostic supine roll test (SRT). The asymmetry in the strength of the elicited horizontal positional nystagmus during SRT is explained by the Ewald's second law and is crucial for lateralizing the affected ear. Rarely the elicited horizontal positional nystagmus on the head roll to either side during the SRT is of symmetric strength. In such situations, the signs with secondary lateralizing value are useful in management by the repositioning maneuvers that require the affected side to be precisely known. Aim: The submitted article is a case report. Results and Discussion: A 38-year-old male with two days history of vertigo on rolling to either of the lateral recumbent position was seen in the second week of March 2019. His SRT elicited a lying-down nystagmus (LDN) to the right, while the head roll to either side elicited a geotropic horizontal positional nystagmus of symmetric strength. The symmetrical strength of elicited positional nystagmus on SRT to either side led to ascendance of LDN from a lateralizing sign of secondary importance to one that reliably lateralized the involved horizontal semicircular canal. At two short term follow-ups at 1 hour and 24 hours after the therapeutic Gufoni maneuver, patient neither had vertigo nor any nystagmus elicited on the verifying supine roll test Conclusion: In rare instances, LDN, which is a lateralizing sign of secondary importance becomes pivotal in the management of HSC-BPPV especially when the affected side needs to be precisely determined for the execution of the therapeutic repositioning maneuver.


中文翻译：

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卧位眼球震颤 (LDN) – 当次要的侧向体征在水平半规管良性阵发性位置性眩晕 (HSC-BPPV) 的诊断中占优势时


背景：水平半规管良性阵发性位置性眩晕（HSC-BPPV）的诊断主要依赖于在诊断性仰卧滚动试验（SRT）期间诱发不对称水平位置性眼球震颤向两侧滚动。Ewald 第二定律解释了 SRT 期间诱发的水平位置性眼球震颤强度的不对称性，这对于使受影响的耳朵侧向化至关重要。在 SRT 期间，头部向两侧滚动时引发的水平位置性眼球震颤很少具有对称强度。在这种情况下，具有次要侧向价值的体征可用于通过需要准确了解患侧的重新定位操作进行管理。目的：投稿文章为病例报告。结果与讨论： 2019 年 3 月的第二周观察到一名 38 岁男性，在滚动至任一侧卧位时有两天眩晕病史。他的 SRT 引发右侧卧位眼球震颤 (LDN) ，而向任一侧的头部滚动引起了对称强度的向地性水平位置性眼球震颤。SRT 上引起的位置性眼球震颤的对称强度向任一侧导致 LDN 从次要的侧向化标志上升到可靠地将所涉及的水平半规管侧向化的标志。在治疗性 Gufoni 动作后 1 小时和 24 小时的两次短期随访中，患者在验证仰卧滚动试验中既没有眩晕也没有任何眼球震颤结论：在极少数情况下，LDN 是次要的侧向标志，在 HSC-BPPV 的管理中变得至关重要，尤其是当需要精确确定受影响的一侧以执行治疗性重新定位操作时。