The postural control system is considered to be comprised of vestibular, visual and proprioceptive endo-organs. When a person stands on a moving platform, changes of the center of gravity are measured and analyzed as displacements of vertical force on the platform constructed on the strain gauge principle. The vestibular endo-organ perceives the change of head movement and responds to velocity and acceleration of head movement. Also the visual system detects a moving target and responds to velocity. The proprioceptive system responds to changes of displacement of the center of gravity and the distention of the muscle spindles of the calf muscles. Postural control was studied in 48 healthy volunteers and 18 very old subjects with posturography and 20, 40, 60, 80, 100 Hz vibration to the calf muscles, which send misleading signals to the central nervous system. The purpose of this investigation was to determine the kind of postural testing to be used in healthy volunteers and very old persons. The postural control system was analzsed with cumulative recordings of position, velocity and acceleration. Postural control was amazingly stable in healthy subjects. However, variance of velocity and acceleration were greater in very old persons with and without vibration. Postural instability in the elderly was interpreted as a deterioration of many sensory organs : visual, vestibular and proprioceptive endo-organs.
Vestibular endo-organs are well known to be a major part of the control system at times of sudden perturbation, and reciprocal sensory systems are well constituted to keep postural control. It is impossible to explore further which one of these parameters is primarily responsible for postural control and to what degree because of good correlation between velocity and acceleration values. At least in the vestibular system, the acceleration parameter has a major function in posture control.

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The purpose of this study is to clarify the role of visual information in the regulation of the upright standing posture.
The subject was requested to stand on a stabilometer with the feet close together. The sway of the body's center of gravity was recorded for 60 seconds with an X-Y recorder and stored in the disk of a microcomputer. The examination was performed with eyes open and closed, and with the wearing of horizontal and vertical vision reversing prisms.
The stored data were processed by a program designed for stabilometry.
The body sway was evaluated by the following items : left-right diameter (X), forward-backward diameter (Y), Y/X ratio, area, displacement and velocity of the left-right (LR) and forward-backward (FB) sways, and power spectrum.
The subjects were 14 normal persons and 5 patients with labyrinthine disturbances.
1. Normal subjects
1) The body sway when wearing horizontal vision reversing prisms (HRP) or vertical vision reversing prisms (VRP) was larger than when the eyes were open without prisms. Furthermore, the body sway when wearing HRP tended to be larger than when the eyes were closed.
2) The power spectrum of the LR sway when wearing HRP was high at 0.2-0.4 Hz.
3) In maintaining the upright standing posture, confused visual information induced by wearing HRP provoked a marked body sway.
2. Patients with labyrinthine disturbances
1) The body sways of the patients when wearing HRP or VRP, in contrast to normal subjects, were smaller than when the eyes were closed.
2) The FB sways of the patients with eyes closed were markedly larger than those of normal subjects.The increased FB sway was decreased when wearing HRP or VRP.
3) The power spectra of the LR and FB sways of patients with eyes closed showed an increase of power at frequency range from 0.6 to 1 Hz above that when eyes were open. The increase of the power was lowered by the wearing of HRP or VRP.
4) The finding that body sways are better stabilized when wearing HRP and VRP than when the eyes are closed indicates the usefulness of reversed visual information and of the action of proprioceptive reflexes.

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A rare case of monocular nystagmus is reported. A 41-year-old man complained of blurred vision on right lateral gaze for two years. When examined in our department, he showed monocular rotatory nystagmus of the right eye mainly on right lateral gaze and also on downward gaze. Neurological examinations were unremarkable. CT scan revealed a small mass lesion in the right sphenoid sinus, but the relationship betweeen the mass lesion and the abnormal eye movement was not clear. No other abnormalities were found. Though the pathogenesis remained obscure in this case, similar cases have been reported in the literature.

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A study was carried out on caloric response and pure tone audiometry in 308 patients with internal ear disorders. 1. Patients with unilateral sensorineural hearing loss or bilateral asymmetrical sensorineural hearing loss had unilateral canal paresis more frequently than did patients with normal hearing or bilateral symmetrical hearing loss (p<0.01). 2. Those patients who had unilateral sensorineural hearing loss and unilateral canal paresis tended to experience only one episode of vertigo in comparison with those who had normal hearing and normal caloric responses, or bilateral symmetrical hearing loss and normal caloric responses (p<0.05).

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Case 1 : right acoustic neurinoma and cerebellar tentorial meningioma. Chief complaints were dizziness, right tinnitus, right deafness and headache. Neurotological examination revealed bilateral hearing disturbance, more prominent on the right side, decreased caloric reaction on the right and defect of waves on the right side after I on an ABR. These results suggested a right acoustic neurinoma. But spontaneus downbeat nystagmus could not be explained by a unilateral cerehellopontine angle tumor, so the presence of an other lesion was suspected.
Bilateral acoustic neurinoma and multiple meningiomas were found in Case 2.
Our diagnosis was neurofibromatosis 2 (NF-2). The only complaint was left tinnitus. Neurotological examination revealed left hearing disturbance, decreased caloric reaction on the left, spontaneous nystagmus directed to the right, defect of waves on the left side after I and prolongation of waves I-V IPL on the right side on an ABR. The ETT and OKIN tests were normal. The x-ray findings revealed dilatation of the left internal auditory canal. Neurological examination revealed a decreased gag reflex on the left, and mild right lower extremity motor weakness. Examinations were initiated because of a suspicion of left acoustic neurinoma. Many of the test results, however, could not be explained by a left acoustic reurinoma alone, suggesting multiple lesions even before CT and MRI were performed.
In general clinical medicine, the possibility of multiple lesions, as seen in the present cases, should be kept in mind during the process of neurotological and neurological examination, even in cases in which a unilateral acoustic neurinoma is suspected. Diagnostic imaging procedures, such as CT and MRI, should also be repeated until all clinical findings are explained.

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We selected 43 patients who had signs and symptoms of delayed hydrops and analyzed their clinical features statistically. The diagnosis had been made during the past 10 years. The most common type of hearing loss was juvenile unilateral hearing loss of unknown etiology. The interval between the onset of hearing loss and the start of vertigo was as long as 10 years or more. In patients whose symptoms were due to mumps or sudden deafness, the. latent period was generally within 20 years.

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For 48 months since 1986, a male patient in his early 60 s has been treated for Wallenberg's syndrome, we report our otoneurological and roentgenological findings.
Rotatory nystagmus is often found in medullary disturbances. In this case pure rotatory nystagmus to the affected left side was observed in the early stage, which then gradually moved up and down diagonally to different positions. In Wallenberg's syndrome, it is indeed difficult to predict the exact type of nystagmus because of variable symptoms in different types of disturbances.
Electronic nystagmography (ENG) improved at 8 months and angiography confirmed by-pass circulation to the affected side at 24 months. It seemed that the by-pass had been completed at 8 months, at the time of the improvement in ENG.
Urokinase administration proved helpful in this case, but it must be applied with great care because of the danger of bleeding cerebral disease.
ENG examinations and otoneurological finding were decisive in establishing an early diagnosis.

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Many kinds of aging processes are known in the central nervous system in human beings. In the eye movement system, it has been recognized that the eye speed of saccade becomes slow and the smoothness of the smooth pursuit eye movement system becomes irregular with aging. We analyzed this aging process in 44 normal volunteers by recording vertical optokinetic nystagmus (OKN).
1. In the vertical OKN, the number of beats of nystagmus and the slow phase velocity of nystagmus tended to be constant through the 7 th decade.
2. The temporal profile of the mean slow phase velocity of vertical OKN was strongly influenced by aging.

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A 68-year-old woman had a gait disturbance, diystonia, neck retroflexion, and disturbed vertical ocular movements which led us to the clinical diagnosis of progressive supranuclear palsy.
Neurootologically, upward and downward gaze were disturbed, and dolls eye phenomenon was positive. In addition, convergence was disturbed. In vertical eye movements, both smooth pursuit and saccade were disturbed, but in horizontal eye movements, only smooth pursuit was disturbed.
Optokinetic nystagmus featured poor responces both vertically and horizontally. A visual suppression test revealed marked firing bilaterally. The findings of various examinations suggested that the pathological focus in this case was in the supranuclear area of the midbrain.

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The properties of vestibulo-thalamic (VT) neurons projecting to the spinal cord were investigated in anesthetized cats. Forty VT neurons were recorded extracellularly ; 68% (27/40) of them responded monosynaptically from the posterior part of the contralateral thalamus, including VPL (nucleus ventralis posterolateralis), VPM (nucleus ventralis posteromedialis), VL (nucleus ventralis lateralis), SG (nucleus suprageniculatus) and PO (nucleus posteriores). A microstimulation technique showed that their axons arborized in narrow areas in the thalamus. About three quarters (17/22) of the VT neurons were also activated antidromically from the ventral funiculus in the C₁ segment of the spinal cord. Axonal branchings were investigated with the microstimulation technique and found in the contralateral C₁gray matter. The VT neurons both with and without descending axons were localized mainly in the descending vestibular nucleus.

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The purpose of this study is to clarify the role of visual information in walking.
The subject was requested to walk to a visual target placed 8 m away. The upward-downward, right-left, and forward-backward movements of the head and the activities of the soleus muscles were recorded by a pen osillograph with the aid of a five-channel telemeter. The subject was examined while walking with eyes open and closed, and while wearing horizontal vision reversing prisms (HRP).
Nine normal adult subjects were tested.
1 When walking with eyes open or closed, the gait was stable.
2 When wearing HRP, the gait was unstable. Eight of the 9 subjects lost the goal and stopped walking. This suggests that left-right reversed vesion caused a marked gait disturbance.
3 When walking repeatedly wearing HRP, 2 of the 6 examined had to stop because of disorientation and marked nausea. This suggests that confused visual information while walking caused vertigo and autonomic symptoms.
4 When walking repeatedly HRP, 4 of the 6 subjects reached the goal without interruption. Their steps were greatly shortened, suggesting that information from exteroceptors and proprioceptors was useful in stabilization of the gait while wearing HRP.

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Twelve patients with direction-changing horizontal positional nystagmus in the lateral position (7 geotropic and 5 apogeotropic) were examined. Their positional nystagmus showed some characteristic features : prolonged duration, mild vertigo and no fatiguability on repeated testing. The findings suggested a peripheral origin, and neurotological examinations and clinical courses showed no evidence of a central origin. Provocation of positional nystagmus occurred only with head positions and only slightly with head rotation. Positional nystagmus was also observed with every head position in the sagittal plane, which had a common pathogenesis with positional nystagmus in lateral positions. Positional nystagmus disappeared in the sitting position and in the head hanging position ; the direction of horizontal nystagmus was reversed in the sitting position. The slow phase velocity of the positional nystagmus varied like a sine curve with different head positions. These results suggest that positional nystagmus might be caused not by lateral canal dysfunction (especially due to specific gravity alteration) but by utricle dysfunction.

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