A Study of Vestibular Disorders Using a Tilt Apparatus-Nystagmus in Benign Paroxysmal Positional Vertigo Induced by Tilting

Over the past 5 years we observed ocular reflexes produced by tilting stimulation with a subject sitting in an orthocephalic posture on a chair apparatus with a continuous tilt. The vector acceleration separate from the gravity force gives a stimulus to the two otolithic organs, while the tilt apparatus moves slowly at a speed of 0.5 degrees or 1 degree per second. At that point vector acceleration upon each maculas changes continuously. We made use of a tilt chair apparatus which was electrically driven as far as 25 degrees at a speed of 1 degree per second. Eye movement was observed using a nystagmograph and through an infrared TV-camera in front of the eyes. Even in healthy persons nystagmoid eye movement (weak nystagmus) is observed, though only slightly, and patients with vertigo clearly develop nystagmus. Thus this eye movement can be used as an index for the study. Two hundred and four patients who complained of vertigo or dizziness were examined by means of our new method. Classification of the nystagmus response is as follows: Type I is of fixed direction, Type II is of changed direction and Type III is a combination of the two. Most healthy persons show no clear nystagmus. Patients with Meniere's disease, sudden deafness and vestibular neuronitis show direction-fixed nystagmus (Type I). In patients with otolithic disorders such as positional vertigo of benign paroxysmal type, when their head and limbs were tilted to the right the nystagmus beat to the left. Similary, when the head was tilted to the left the nystagmus was directed to the opposite side (Type II). Healthy persons were studied by dividing them into three groups by age, namely 20-35 years old (A group), 36-55 years old (B), and over 56 years old (C). Each group consisted of 20 persons or more. One of the 20 in the A group showed nystagmoid eye movements at a minor amplitude and a small beat number. The incidence of eye movements was minimal but it tended to increase by age, which is considered to be due to geriatric degeneration of static organs including the otolithic organ. Motion sickness in healthy persons was also studied with tilting stimulation. The intensity of nystagmus in persons with motion sickness tended to increase as symptoms became severer. A survey was made referring to motion sickness in relation to vestibular disorders. There were many patients with a history of motion sickness. The incidence was statistically high in benign paroxysmal positional vertigo compared with Meniere's disease and sudden deafness. In the future, in addition to basic study to endorse these findings, study should be made of whether this tilting stimulation is really related to the otolithic organ only, and whether there is any influence on the semicircular canals and the proprioceptive receptor system as well as on the control of the central nervous systems.