Two types of head-shaking tests in vestibular examination

In clinical vestibular examination, there are two types of head-shaking tests, in each of which the patient's head is shaken in a similar way. One is the head-shaking test for the detection of latent spontaneous vestibular nystagmus. In this test, the patient's eyes are observed for nystagmus immediately after a passive rapid head-shaking around a vertical axis, using Frenzel's glasses in a dark room. The nystagmus is induced frequently in patients with peripheral and central vestibular disturbances. In peripheral vestibular disturbances, the induced nystagmus can be classified into deficiency-type nystagmus, recovery-type nystagmus and biphasic nystagmus which is usually a mixture of the two. A second head-shaking test is the head-shaking test for the evaluation of jumbling. In this test binocular visual acuity is measured while the patient shakes his head two or three times per second, ten to twenty degrees horizontally or vertically, and compared with that when his head is still. A diagnosis of jumbling is made when the visual acuity during head-shaking is less than half the visual acuity when the head is motionless.