Newman-Toker D E, Sharma P, Chowdhury M, Clemons T M, Zee D S, Della Santina C C
Department of Neurology, The Johns Hopkins Hospital, Pathology Building 2-210, 600 North Wolfe Street, Baltimore, MD 21287, USA.
J Neurol Neurosurg Psychiatry. 2009 Aug;80(8):900-3. doi: 10.1136/jnnp.2009.174128. Epub 2009 Mar 30.
Most patients with acute vestibular syndrome have vestibular neuritis or labyrinthitis. Some harbour strokes that can only be differentiated on the basis of subtle eye movement findings, including nystagmus. Peripheral nystagmus should be enhanced by removal of visual fixation. Current bedside methods for removing fixation require expensive equipment or technical skill not routinely available. We sought to test a new method for blocking fixation.
Proof-of-concept study for a new bedside oculomotor diagnostic test using an established physiological measurement of eye movements (electro-oculography (EOG)) as the reference standard. We sampled unselected patients undergoing caloric testing (surrogate model for neuritis) in an academic vestibular clinic. During the brief (30-60 s) decay phase of caloric-induced peripheral vestibular nystagmus, we shone a penlight in the left eye while intermittently occluding the right. We assessed nystagmus intensity (slow-phase velocity) clinically in all subjects and quantified change in two exemplar cases.
Caloric responses frequently decayed before the test was complete, and artefacts rendered many EOGs uninterpretable during the short decay period. A clinically evident increase in nystagmus was seen 18 times in 10 patients and corroborated by EOG in 15. In quantified cases, slow-phase velocity increased as expected (mean change +42%) with fixation blocked.
The penlight-cover test could offer a low-cost, simple means of disrupting visual fixation in clinical settings where differentiating peripheral from central vestibular disorders is crucial, such as the emergency department. Prospective studies are needed to determine the test's utility for excluding dangerous central causes among patients with suspected peripheral lesions.
大多数急性前庭综合征患者患有前庭神经炎或迷路炎。有些患者存在中风情况，只能根据细微的眼球运动表现（包括眼球震颤）来鉴别。去除视觉固定可增强周围性眼球震颤。目前床边去除固定的方法需要昂贵设备或非常规可用的技术技能。我们试图测试一种新的固定阻断方法。
一项概念验证研究，采用既定的眼动生理测量方法（眼电图（EOG））作为参考标准，对一种新的床边动眼神经诊断测试进行研究。我们在一家学术性前庭诊所对未经过挑选的正在接受冷热试验（神经炎替代模型）的患者进行抽样。在冷热诱发的周围性前庭眼球震颤的短暂（30 - 60秒）衰减阶段，我们用手电筒照射左眼，同时间歇性遮挡右眼。我们对所有受试者的眼球震颤强度（慢相速度）进行临床评估，并对两个典型病例的变化进行量化。
冷热反应在测试完成前经常衰减，并且在短暂的衰减期内，伪迹使许多眼电图无法解读。10名患者中有18次出现临床上明显的眼球震颤增加，其中15次经眼电图证实。在量化病例中，随着固定被阻断，慢相速度如预期那样增加（平均变化 +42%）。
在区分周围性与中枢性前庭疾病至关重要的临床环境（如急诊科）中，手电筒 - 遮挡测试可以提供一种低成本、简单的破坏视觉固定的方法。需要进行前瞻性研究来确定该测试在排除疑似周围性病变患者中危险的中枢性病因方面的效用。
