Robinson D A, Zee D S, Hain T C, Holmes A, Rosenberg L F
Ann Neurol. 1984 Dec;16(6):714-22. doi: 10.1002/ana.410160614.
Alexander's law refers to the phenomenon in which the spontaneous nystagmus of a patient with a vestibular lesion is more intense when the patient looks in the quick-phase than in the slow-phase direction. Alexander's law was investigated in normal subjects as well as patients with vestibular lesions. During sinusoidal rotations of normal subjects, there was no trace of this phenomenon when subjects looked 25 degrees left and right in the dark. The phenomenon of Alexander's law is therefore created centrally and is not due to any mechanical properties of the orbit. During rotation at constant velocity in the dark, normal subjects did weakly demonstrate Alexander's law because of a mild gaze-evoked nystagmus present in normal subjects in the dark. Gaze-evoked nystagmus from a cerebellar lesion involved a pronounced demonstration of Alexander's law during rotatory nystagmus. In patients with a vestibular lesion and a mild spontaneous nystagmus in the dark that obeyed Alexander's law, the nystagmus reversed upon far gaze in the slow-phase direction. We propose that in patients with a vestibular lesion, the phenomenon of Alexander's law is created by the sum of vestibular nystagmus and an abnormally large gaze-evoked nystagmus that is consequent to the vestibular lesion. This conclusion has a number of neurological implications concerning the ways in which the nervous system attempts to compensate for vestibular lesions.
亚历山大定律指的是前庭病变患者的自发性眼球震颤在患者看向快相方向时比看向慢相方向时更强烈的现象。正常受试者以及前庭病变患者都对亚历山大定律进行了研究。在正常受试者进行正弦旋转时，当受试者在黑暗中向左和向右各看25度时，没有这种现象的迹象。因此，亚历山大定律现象是在中枢产生的，并非由于眼眶的任何机械特性。在黑暗中以恒定速度旋转时，正常受试者确实微弱地表现出亚历山大定律，这是因为正常受试者在黑暗中存在轻度的凝视诱发眼球震颤。小脑病变引起的凝视诱发眼球震颤在旋转性眼球震颤期间明显表现出亚历山大定律。在前庭病变且在黑暗中存在遵循亚历山大定律的轻度自发性眼球震颤的患者中，眼球震颤在慢相方向的远凝视时会反转。我们提出，在前庭病变患者中，亚历山大定律现象是由前庭眼球震颤与前庭病变导致的异常大的凝视诱发眼球震颤之和产生的。这一结论对于神经系统试图补偿前庭病变的方式具有许多神经学意义。
