Strupp M, Arbusow V, Dieterich M, Sautier W, Brandt T
Department of Neurology, University of Munich, Klinikum Grosshadern, Germany.
Brain. 1998 Apr;121 ( Pt 4):677-85. doi: 10.1093/brain/121.4.677.
Afferent cervical somatosensory input may substitute for absent vestibular information as part of central vestibular compensation after unilateral peripheral vestibular deficit. In order to determine the particular contribution of neck muscle spindles to the perception of body orientation and to the oculomotor system, we measured (i) the subjective visual straight ahead (SVA) by psychophysical tests and (ii) the changes in eye position by video-nystagmography during unilateral stimulation of the posterior neck muscles by vibration (100 Hz). Twenty-five patients with subacute unilateral vestibular lesion (vestibular neuritis) and 25 controls participated in the study. Vibration elicited a horizontal displacement of SVA towards the side of stimulation in all subjects. Mean displacement (+/- SD) was 3.28 +/- 2.96 degrees for right-side and 3.45 +/- 2.93 degrees for left-side stimulation in controls. Muscle stimulation on the patients' lesion side induced a significantly higher displacement (11.51 +/- 6.63 degrees) than contralateral stimulation (3.04 +/- 2.95 degrees, P < 0.01, paired Student's t test). The mean difference during stimulation between the two sides in the patients was 8.02 +/- 5.52 degrees; in the controls, however, it was only 0.74 +/- 0.47 degree (P < 0.001, Student's t test). This asymmetry increased gradually in patients over a period of weeks, reaching a maximum at days 60-80 and declining thereafter. Videonystagmography revealed that ipsilateral stimulation in patients induced large horizontal eye deviations of up to 25 degrees towards the side of the lesion (9.1 +/- 7.6 degrees, n = 18). Contralateral stimulation induced only small shifts, which were within the range of controls. The correlation coefficient between displacement of the SVA and change in eye position was high (r = 0.94, P < 0.0001), indicating that the shift of SVA is the perceptual correlate of the directional change of gaze in space. This interpretation was supported by two control experiments in which the subject was required to (i) indicate the subjective straight ahead by finger-pointing with the eyes closed and (ii) adjust SVA when looking through horizontally reversing prisms. Vibration of neck muscles caused almost no displacement of the SVA when it was indicated by pointing with the eyes closed, but reversed the direction of the displacement if the subject wore reversing prisms. In summary, our data showed: (i) an increase in muscle spindle input following unilateral vestibular lesion; (ii) this increase is asymmetrical, restricted to the affected side, and gradually builds up over weeks; and (iii) the perceived effects during vibration are secondary to changes in eye position rather than changes in cortical representation of body orientation. This is the first study to demonstrate a unilateral increase in somatosensory weight, which substitutes for missing vestibular input.
在单侧外周前庭功能缺失后，作为中枢前庭代偿的一部分，传入性颈躯体感觉输入可能替代缺失的前庭信息。为了确定颈部肌梭对身体定向感知和动眼系统的具体作用，我们通过心理物理学测试测量了主观视觉正前方（SVA），并在通过振动（100Hz）单侧刺激后颈部肌肉时，通过视频眼震图测量了眼位变化。25例亚急性单侧前庭病变（前庭神经炎）患者和25名对照者参与了本研究。振动在所有受试者中均引起SVA向刺激侧的水平位移。对照组右侧刺激的平均位移（±标准差）为3.28±2.96度，左侧刺激为3.45±2.93度。在患者病变侧进行肌肉刺激所诱发的位移（11.51±6.63度）显著高于对侧刺激（3.04±2.95度，P<0.01，配对学生t检验）。患者两侧刺激期间的平均差异为8.02±5.52度；然而，在对照组中，差异仅为0.74±0.47度（P<0.001，学生t检验）。这种不对称性在患者数周内逐渐增加，在第60 - 80天达到最大值，此后下降。视频眼震图显示，患者同侧刺激可诱发高达25度的向病变侧的大水平眼偏斜（9.1±7.6度，n = 18）。对侧刺激仅诱发小的偏移，在对照组范围内。SVA位移与眼位变化之间的相关系数很高（r = 0.94，P<0.0001），表明SVA的偏移是空间中注视方向变化的感知相关因素。两项对照实验支持了这一解释，在这两项实验中，要求受试者（i）闭眼用手指指示主观正前方，以及（ii）通过水平反转棱镜观察时调整SVA。当闭眼指示时，颈部肌肉振动几乎未引起SVA位移，但当受试者佩戴反转棱镜时，位移方向相反。总之，我们的数据表明：（i）单侧前庭病变后肌梭输入增加；（ii）这种增加是不对称的，仅限于患侧，并在数周内逐渐增强；（iii）振动期间的感知效应继发于眼位变化而非身体定向的皮层表征变化。这是第一项证明躯体感觉权重单侧增加以替代缺失的前庭输入的研究。
