Brantberg Krister, Westin Magnus, Löfqvist Lennart, Verrecchia Luca, Tribukait Arne
Department of Audiology, Karolinska Hospital, 171 76 Stockholm, Sweden.
Clin Neurophysiol. 2009 May;120(5):974-9. doi: 10.1016/j.clinph.2009.03.008. Epub 2009 Apr 18.
To explore the mechanisms for skull tap induced vestibular evoked myogenic potentials (VEMP).
The muscular responses were recorded over both sternocleidomastoid (SCM) muscles using skin electrodes. A skull tapper which provided a constant stimulus intensity was used to test cervical vestibular evoked myogenic potentials (VEMP) in response to lateral skull taps in healthy subjects (n=10) and in patients with severe unilateral loss of vestibular function (n=10).
Skull taps applied approximately 2 cm above the outer ear canal caused highly reproducible VEMP. There were differences in VEMP in both normals and patients depending on side of tapping. In normals, there was a positive-negative ("normal") VEMP on the side contra-lateral to the skull tapping, but no significant VEMP ipsi-laterally. In patients, skull taps above the lesioned ear caused a contra-lateral positive-negative VEMP (as it did in the normals), in addition there was an ipsi-lateral negative-positive ("inverted") VEMP. When skull taps were presented above the healthy ear there was only a small contra-lateral positive-negative VEMP but, similar to the normals, no VEMP ipsi-laterally.
The present data, in conjunction with earlier findings, support a theory that skull-tap VEMP responses are mediated by two different mechanisms. It is suggested that skull tapping causes both a purely ipsi-lateral stimulus side independent SCM response and a bilateral and of opposite polarity SCM response that is stimulus side dependent. Possibly, the skull tap induced VEMP responses are the sum of a stimulation of two species of vestibular receptors, one excited by vibration (which is rather stimulus site independent) and one excited by translation (which is more stimulus site dependent).
Skull-tap VEMP probably have two different mechanisms. Separation of the two components might reveal the status of different labyrinthine functions.
探讨颅骨轻敲诱发前庭诱发肌源性电位（VEMP）的机制。
使用皮肤电极在双侧胸锁乳突肌（SCM）上记录肌肉反应。使用提供恒定刺激强度的颅骨敲击器，测试健康受试者（n = 10）和重度单侧前庭功能丧失患者（n = 10）对颅骨外侧轻敲的颈前庭诱发肌源性电位（VEMP）。
在外耳道上方约2 cm处进行颅骨轻敲可引起高度可重复的VEMP。正常人和患者的VEMP根据轻敲侧不同而有所差异。在正常人中，颅骨轻敲对侧出现正负（“正常”）VEMP，同侧无明显VEMP。在患者中，病耳上方的颅骨轻敲引起对侧正负VEMP（与正常人相同），此外同侧还有负正（"倒置"）VEMP。当在健耳上方进行颅骨轻敲时，仅出现较小的对侧正负VEMP，但与正常人相似，同侧无VEMP。
目前的数据与早期研究结果相结合，支持颅骨轻敲VEMP反应由两种不同机制介导的理论。提示颅骨轻敲既引起纯粹的同侧刺激侧独立的SCM反应，也引起双侧且极性相反的刺激侧依赖的SCM反应。颅骨轻敲诱发的VEMP反应可能是两种前庭感受器刺激的总和，一种由振动兴奋（刺激部位依赖性较小），另一种由平移兴奋（刺激部位依赖性较大）。
颅骨轻敲VEMP可能有两种不同机制。分离这两个成分可能揭示不同迷路功能的状态。
