Weber Konrad P, Landau Klara, Palla Antonella, Haslwanter Thomas, Straumann Dominik
Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
Invest Ophthalmol Vis Sci. 2004 Feb;45(2):455-65. doi: 10.1167/iovs.02-1223.
To explain the positive Bielschowsky head-tilt (BHT) sign in unilateral trochlear nerve palsy (uTNP) by the kinematics of three-dimensional eye rotations.
Twelve patients with uTNP monocularly fixed on targets on a Hess screen were oscillated (+/- 35 degrees, 0.3 Hz) about the roll axis on a motorized turntable (dynamic BHT). Three-dimensional eye movements were recorded with dual search coils. Normal data were collected from 11 healthy subjects.
The rotation axis of the viewing paretic or unaffected eye was nearly parallel to the line of sight. The rotation axis of the covered fellow eye, however, was tilted inward relative to the other axis. This convergence of axes increased with gaze toward the unaffected side. Over entire cycles of head roll, the rotation axis of either eye remained relatively stable in both the viewing and covered conditions.
In patients with uTNP, circular gaze trajectories of the covered paretic or unaffected eye during dynamic BHT are a direct consequence of the nasal deviation of the rotation axis from the line of sight. This, in turn, is a geometrical result of decreased force by the superior oblique muscle (SO) of the covered paretic eye or, according to Hering's law, increased force parallel to the paretic SO in the covered unaffected eye. The horizontal incomitance of rotation axes along horizontal eye positions can be explained by the same mechanism.
通过三维眼球旋转运动学来解释单侧滑车神经麻痹（uTNP）中的阳性比尔绍夫斯基头倾斜（BHT）征。
12例uTNP患者单眼注视赫斯屏上的目标，在电动转台上绕滚动轴摆动（±35度，0.3赫兹）（动态BHT）。用双搜索线圈记录三维眼球运动。从11名健康受试者收集正常数据。
注视侧麻痹或未受影响眼的旋转轴几乎与视线平行。然而，被遮盖的对侧眼的旋转轴相对于另一轴向内倾斜。随着注视向未受影响侧移动，轴的这种汇聚增加。在整个头部滚动周期中，无论是注视还是遮盖状态下，任何一只眼的旋转轴都保持相对稳定。
在uTNP患者中，动态BHT期间被遮盖的麻痹或未受影响眼的圆形注视轨迹是旋转轴偏离视线向鼻侧偏移的直接结果。反过来，这是被遮盖的麻痹眼上斜肌（SO）力量减弱的几何结果，或者根据赫林定律，是被遮盖的未受影响眼平行于麻痹SO的力量增加的几何结果。沿水平眼位旋转轴的水平非共转性可用相同机制解释。
