We performed two experiments to investigate the relationship between motion sickness and active or passive posture control. Experiment 1: Coriolis stimulation evokes not only motion sickness but also nystagmus and body sway. Eight subjects were asked to execute head tilt with eyes open or eyes covered while standing on a force-platform attached to a turntable. Eye movements were recorded using an infrared CCD camera. The center of pressure was recorded simultaneously. While gaze and posture became passive conditions and motion sickness was evoked with eyes covered, the subjects could maintain active control of posture and motion sickness was not evoked with eyes open. Experiment 2: Head tilt angle while riding in a car recorded on videotapes was quantitatively evaluated by computer analysis. While head movements of passengers became unstable and motion sickness was evoked, the head of the driver always tilted in the same direction as the curve and motion sickness was not evoked. Motion sickness appeared when the head returned from the tilted position to the original position. These results suggest that spatial orientation (the perception of the spatial relationship between self and the outer world) determines whether posture control will be active or passive, and whether motion sickness will be evoked.

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To confirm that stance is adaptive to high-speed Coriolis stimulation, we stimulated 20 healthy volunteers on 9 consecutive days, with or without vision. They stood on a rotating platform and at 1-min intervals tilted the head forward and returned it upright. We determined the initial maximum rotation speed for each individual and performed 20-min stimulation at that speed on day 1. Beginning on day 2, rotation speed was increased by 20°/s up to a maximum of 200°/s. Mean maximum speeds on the first and ninth days were 84°/s and 193°/s, respectively, in the vision group and 57°/s and 186°/s, respectively, in the non-vision group. Maximum speeds in the vision group were significantly greater than those in the non-vision group, but vision did not influence the increase to maximum speed during the 9-days training period. After the training period, both groups showed similar response to side-to-side head tiliting as they showed to forward tilting. However, on day 11, the groups did not respond similarly to a reversal in the rotation direction. Maximum rotation speed on day 11 was close to that of day 1. The results from the present study suggest that stance stability was attained by temporary adaptation of spatial orientation to the rotating environment. Vector analysis indicates that once a rotating space, instead of a stationary space, is represented as a spatial framework, inertial inputs at head tilting are canceled by fusion with the velocity vector of the new reference frame.

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We investigated the distribution of the maximum slow phase velocity of nystagmus (max.spv) induced by cold air caloric stimuli of both 5°C and 10°C at an insufflation flow rate of 5l/min for 60sec. Test subjects who had no spontaneous nystagmus with eyes open in darkness and showed max.spv of caloric nystagmus above 20°/sec (stimulation temperature 5°C) or above 10°/sec (stimulation temperature 10°C) were selected, and classified into three groups: the younger (21-39 years), middle aged (40-64 years) and older groups (above 65 years).
In stimulation at 5°C, the distribution histogram of the value of max.spv in all 355 subjects was skewed and differed from the Gaussian distribution. Each max.spv value was much more concentrated above the mean value than at the level below it. Both the younger and middle aged groups showed similar distribution histograms, but the older group showed a flat histogram with no peaks.
In stimulation at 10°C the distribution histogram of the value of the max.spv in all 403 subjects was not skewed as in Gaussian distribution, and the peak value of max.spv was close to the mean value covering a wide range. The younger and middle aged groups showed the same values in all subjects, but the older group showed a distribution histogram with a peak of max.spv below the mean value.
The stimulation at 5°C in the cold air caloric test seems to approach maximum stimulation, judging from its distribution histogram. When we obtain normal range results in the cold air caloric test, we have to remain aware of the stimulation temperature and subjects'ages.

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Magnetic resonance imaging showed impingement of a dolichoectatic vertebral artery on the medulla in 8 patients with auditory and/or vestibular symptoms. Unilateral auditory and/or vestibular symptoms on the same side as the impinged parts were recognized in 5 patients, who manifested no pyramidal or other central nervous signs. These unilateral lesions were speculated to be due to neurovascular compression of the 8th cranial nerve. Two patients revealed downbeat nystagmus without any other cen-tral nervous signs, which might have arisen from an ischemic brain stem lesion. One other patient with brain atrophy and cerebellar sign also showed downbeat nystagmus which might have been due to cerebellar atrophy.
Impingement of the vertebral artery on the medulla may not induce unilateral auditory and/or vestibular symptoms, but may represent a risk factor of circulatory disturbance in the brain stem.

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Vertigo attacks are caused by a combination of stress and mental illness, such as anxiety or depression. Occasionally, misdiagnosis of the disease may also lead patients to mental illness. In this study, we attempted to prevent vertigo attacks by psychoanalysis through group psychotherapy for 24 patients who had complained of at least one year of dizziness with occasional vertigo attacks and without clear abnormality of equilibrium tests.
Fourteen patients (58%) in the study were successfully treated in that the numbers of vertigo attacks had decreased >50% after a year of group psychotherapy. We found that patients in this study group were more supportive and stimulated by each other, and learned how to verbalize themselves by adopting the techniques into their daily lives. This strategy seemed to be more effective for females than the males.
Through group psychotherapy, the patients learned mental illness might be involved in vertigo attacks, and approximately 60% of the patients were able to prevent long term dizziness or vertigo attacks.

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Vestibular function gradually deteriorates with aging, however, its behavioral consequences are not easily recognized due to a substitution process by other sensory modalities such as visual or proprioceptive inputs. Not only age but also gender can make a significant difference in these functions. To reveal such hidden substitution processes by visual signals, the measurement of the static as well as the dynamic subjective visual vertical was performed in 65 healthy subjects of different age. The static subjective visual vertical was found to be stable among all subjects, whereas the shift of the dynamic subjective visual vertical during rotation of the background scene gradually increased with age. There was a significant difference between males and females in this trend. Females usually showed greater deviation with increased age. This finding indicates that the hormonal differences between genders make a difference in generation and recognition of roll vection.

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Orthostatic dysregulation (OD) has been identified as a kind of autonomic failure, however few studies have evaluated the autonomic dysfunction in patient with OD. Also the treatment of patients with OD has not been also necessarily standardized. We therefore investigated the cardiovascular autonomic function of 12 dizziness patients with OD using heart rate variability analysis (HRV) during the shellong test, and compared the findings with those of sex and aged-match healthy subjects. In addition, we discussed the clinical efficiency of cardiovascular α-adrenoreceptor stimulators or β-adrenoreceptor blockers for dizziness patients with OD.
There was no significant difference in LF (low frequency power), HF (high frequency power) or LF/HF of HRV analysis between patients with OD and healthy subjects. However, the intersubject variation of the LF/HF value in patients with OD in supine and upright positions was apparently larger than that of the healthy adults, and some patients with OD showed extremely high values of LF/HF when upright.
The cardiovascular α-adrenoreceptor stimulators improved dizziness symptoms in 4 of 8 patients that showed the lower values (<4.2) of LF/HF when upright. β-adreno-receptor blockers diminished dizziness symptoms in 3 of 5 patients that showed higher values (>4.2) of LF/HF value when upright. These results suggested that some dizziness patients with OD have an imbalance of sensitivity between α-adrenoreceptor and β-adrenoreceptor functions in the cardiovascular system. However, the cardiovascular autonomic function of OD patients requires further investigation.

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For patients with dizziness, the caloric test is useful to diagnose the dysfunction of the lateral semicircular canal in the inner ear. However, in some patients, stimulation induces autonomic symptoms, such as nausea and vomiting, during and after the test. The susceptibility of patients to autonomic symptoms in response to caloric stimulation was evaluated in this study in order to pinpoint these patients before the caloric test.
A bithermal caloric test was performed in 227 patients with dizziness. We used an air calorization, in which hot (50°C) or cold (24°C) air was injected into the external auditory canal for 60 sec (total 61).
Sixty-six of 227 (29.1%) subjects complained of nausea. Eight (3.5%) patients suffered from vomiting. In 11 (4.8%), the caloric test was interrupted because of severe nausea and vomiting. The autonomic symptoms were found to be more severe and more frequent in younger and female patients, patients with orthostatic hypotension, patients susceptible to motion sickness and patients with a higher maximum slow phase velocity of caloric nystagmus.

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A 24-year-old female presented with one-and-a-half syndrome accompanied by vertigo and hearing loss in her left ear. She had no caloric response to 0°C ice water and her pure tone average revealed 72.5 dB. She was diagnosed with left one-and-a-half syndrome due to leftward gaze palsy, adduction OS (left eye), a horizontal right-beating nystagmus OD (right eye) on her rightward gaze, normal convergence. These symptoms were also accompanied by vertical gaze palsy, mild left peripheral facial nerve palsy, left face and body hypesthesia, bulbar palsy and cerebellar symptoms. Abnormal eye movement, bilateral vestibular disfunction and left hearing loss improved with methylprednisolone pulse therapy. All her neurological symptoms except mild facial nerve palsy had disappeared one year after onset of the disease. The site of the lesion responsible for one-and-a-half syndrome was the left medial longitudinal fasciculus (MLF), paramedian pontine reticular formation (PPRF) and abducens nucleus. The lesion responsible for vertical gaze palsy seemed to occupy a wide area of the pons.

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Between 1993 and 1995, 178 patients complaining of fullness of the ear visited our clinic. Of these, 24 were found to have low-tone sensorineural hearing loss. Glycerol test revealed positive/ pseudopositive results in 20 of these 24 cases. Of these, 15 cases were followed up more than 3 years. Average hearing level at low-tone (125 Hz, 250 Hz and 500 Hz) in the 24 hearing-impaired patients were 34.0 dB. Clinical symptoms and low-tone sensorineural hearing loss of all patients were improved by isosorbide or betamethasone. The subjects who had temporary hearing impairment at 4, 000 Hz or 8, 000 Hz had significantly higher risk of recurrence. One findings suggested that low-tone deafness with a chief complaint of ear fullness is caused by endolymphatic hydrops. Prognosis may be dependent on the extent rather than the degree of the impairment in the inner ear. Prompt treatment and follow-up is important for patients who complain ear fullness, because some of them may progress to Meniere disease in the future.

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In this study we measured human Endolymphatic Sac Potential (EPS) in 8 patients with acoustic neuroma during the translabyrinthine removal of the tumor. EPS was measured with a glass electrode filled with 154 mM NaCL and with an outside tip diameter ranging from 2 to 3μm. The mean value of ESP in patients with acoustic neuroma was +13.3±1.9 mV. To our knowledge, our study was the first successful measurement of human ESP.

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We report a patient with Lermoyez's syndrome who was followed up for 9 years and whose hearing activity was well maintained. The main pathological factor in this case was considered to be endolymphatic hydrops, judging from such findings as positive glycerol test, repeated vertigo attacks like Meniere disease and well-maintained hearing activity under Isosorbide therapy. Since Dilazep dihydrochloride was also effective in preserving good hearing function, disturbance of vascular circulation might have played a role in the pathology of this case.

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