Vection is similar to self-motion perception, which may be induced by the stabilizing sensory systems: visual, vestibular, and somatosensory. Vection is a common visual illusion from which inferences concerning visual-vestibular interaction may be drawn. There are three kinds of vection: circular vection, roll vection, and linear vection. Circular vection may be caused by the mismatch of the vision-horizontal semicircular canals, roll vection by that of the vision-vertical semicircular canals-otoliths, and linear vection by that of the vision-otoliths. It has been argued that the vestibular nuclei serve as a switch for the perceptual interpretation of seen motion.
There are two bases for the effective use of anti-vertigo drugs. One is being clinically well informed of anti-vertigo drugs and the other is grasping the clinical situations in which anti-vertigo drugs should be used. Regarding the former, we must fully understand the effectiveness, safety, suitability and cost of anti-vertigo drugs. That is to say, we must hold evidence of high quality for anti-vertigo drugs. Regarding the latter, we should make practical use of the concept of Personal-drug (P-drug). In the Cochrane Library (Issue 3, 2003. Oxford), 85 randomized control studies (RCT) of anti-vertigo drugs were found. However, evidence that could be applied immediately to patients under treatment was insufficient. Especially lacking were the following: (1) RCT for specific vertigo diseases or RCT for specific pathophysiologies of vertigo; (2) outcomes described by patients themselves; and (3) RCTs that were performed with the intention to treat analysis. In the selection of P-drugs, two treatment goals for anti-vertigo drugs have been designed. One is treatment for the relaxation of symptoms (nausea and vomiting) during the acute phase of vertigo. The other is the prevention of the recurrence of vertigo in the chronic stage of the disease. P-drugs selected by the author were introduced and evidence for each P-drug was also investigated. Because there are no perfect anti-verti-go drugs at present, safety should be the first consideration in the selection of P-drugs. In the application of P-drugs, the root cause leading to the patient's vertigo must be strongly considered.
The purpose of the present study was to verify our hypothesis that perception of the outer world determines sensations, eye movements and bodily movements. We did so by assessing the effects of Coriolis stimulation under a μG condition during parabolic flight. Using a suspended rotary chair, we subjected five young men to Coriolis forces under μG and 1-G conditions. Wearing a linear accelerometer on their chest, and goggles with a CCDcamera, which recorded eye movements, each subject was rotated clockwise at speeds of 50, 100, 150 deg/s under 1 G and at 100 deg/s under μG. Under the 1-G condition, the subject's body was displaced in response to inertial inputs provoked by Coriolis stimulation, i.e., momentarily accelerated leftwards while bending during clockwise rotations. Torsional nystagmus, moving sensation, and motion sickness were produced under 1 G. Under the μG condition, subjects shifted slightly to the right, but nystagmus was as pronounced as that under 1 G. Moving sensation and motion sickness were far less pronounced under μG than under 1 G. The results can be explained by our hypothesis. When gravity provides the Z-axis of the three-dimensional outer world, inertial inputs from the labyrinths displace the coordi-nates in the head, producing body sways, nystagmus and moving sensations. Because the Z-axis of the outer world is not ordained under μG, inertial inputs do not influence spatial orientation. Thus, neither body movements nor moving sensations are produced. However, because gaze is controlled by both head and eye movements, eye movements in the head are evoked directly by head movements, whether or not orientation in space is based on gravity. Space motion sickness is likely provoked by a failure in posture control depending on the outer world under 1 G.
In order to assess an association between orthostatic dysregulation (OD) and stress, we investigated the life-change-unite (LCU) score of dizzy patients with OD (n=258) and dizzy patients without OD (n=252) using the social readjustment rating scale (Holmes & Rahe, 1967), and also depression scores of the patients with a selfrated questionnaire for depression (SRQ-D). Nonparametric statistics used to analyze the data showed that at the .01 level of confidence, dizzy patients with OD had a significantly higher stress score than the dizzy patients without OD. Forty-eight percent of the patients with OD showed a significantly higher rate score on the SRQ-D, over 16 points, indicating that they were depressed, compared with that of the patients without OD. Particularly in the group of the dizzy male patients with OD between 40 and 64 years of age, rank order correlations between patients' LCU total and depression scores proved significant by Kendall's. We suggest that stress may be related to dizziness with OD and that a psychological approach may be useful for treatment of dizziness with OD.
We examined the age-related changes in autonomic nerve function affecteding the regulation of blood flow. We used the Schellong test and a questionnaire for orthostatic dysregulation. Two handred seventy-two elderly subjects over 70 years old were examined in this study and 192 healthy volunteers under 70 years old were examined as controls. We classified the former subjects into two groups, one group with dizziness and vertiginous sensation (vertigo group, N=222), and the other with no symptoms (non-vertigo group, N=50). Then, we statistically analyzed the above three groups. More changes in decrease of systolic blood pressure, pulse pressure and/or increase of pulse rate were observed with age increasing, excluding the young subjects in their 20s. In the increase of systolic blood pressure in particular, the vertigo group showed clear changes, and a higher positive rate on the Schellong test and questionnaire. It was suggested that the increase of orthostatic dysregulation with aging might be one factor for the increase of senior vertiginous patients.
Health examination using stabilometry was studied to check the health condition from the standpoint of body equilibrium. Using a stabilometer, sway of the center of gravity in upright standing was recorded with eyes open and closed for 60 seconds. The parameters measured were the area, locus length, right-left and forward-backward deviation of the center of sway, power spectrum, position and velocity vectors and standard deviation, skewness and kurtosis of amplitude histogram. Each measurement value was compared with standard values in healthy subjects and evaluated as stable (normal) or unstable (abnormal). The stabilometry was carried out in 1179 subjects of the ages 19-87. 1. The relationship of the parameters measured to the detection rate of the abnormal indicated that stabilometry evaluating area and right-left deviation was suitable for health checkup. 2. The number of subjects evaluated as abnormal in the stabilometry among care staff was significantly more than that among office staff. 3. The number of subjects with hypertension, high arteriosclerosis index and low glucose tolerance in the abnormal group in the stabilometry was significantly more than that in the normal group. Stabilometry evaluating area and right-left deviation was useful for checking on health condition and detecting dangerous factors of cerebral vascular disorders.
Falls and falling accidents occurring in hospitals have become a problem in recent years, and some of those events have been documented to have occurred after patients ingested sleep-inducers (hypnotics). One of the pharmacological actions of hypnotics is muscle-relaxing activity, and it has been clarified in animal studies that this activity causes falls and falling accidents. However, this association has not yet been proven in humans. In this study, conducted in eight healthy adult volunteers, we compared the manifestation of balance disorders after ingestion of four test drugs, consisting of two ultra-short-acting hypnotics (zolpidem and triazolam), a long-acting hypnotic (qazepam) and a placebo (i.e., the control). Zolpidem and qazepam, which are said to express weak muscle-relaxing activity, both caused balance disorders. Also, strong correlations were found between the manifestation of balance disorders after drug ingestion and the plasma concentrations of zolpidem, triazolam and some of the metabolites of qazepam. In addition, in the case of zolpidem, which caused the most severe balance disor-ders, gaze deviation nystagmus was detected. For this reason, it was surmised that balance disorders occurring after ingestion of hypnotics involve some inhibition of the central nervous system, including the cerebellum and brain stem, rather than the mus-cle-relaxing activity of the drugs. Differences were observed among the tested hypnotics in relation to the time of occurrence of balance disorders postmedication and also to the severity of the symp-toms. Accordingly, for the prevention of falling accidents, it is considered necessary that the physician be fully cognizant of the patient's age, medical history and physical condition, as well as not only the characteristics of the hypnotics but also the time-course changes in their concentration in the blood. Then, adequate caution must be applied with regard to the time period in which the patient is in a half-awake state.
Three child cases of conversion disorder presented with psychogenic vertigo and gait disturbance, one of which also had functional hearing loss and loss of visual acuity, were reported. It is speculated that abnormal findings, such as the tendency to fall and the disturbance of gait or standing up, without other abnormal findings in vestibular laboratory tests are very important for suspecting conversion disorder, and the discrepancy between symptoms and findings in audiometric or vestibular tests is the essential clue for reaching a diagnosis of conversion disorder. We should not be in a hurry to treat patients with conversion disorder, and should not hesitate to consult psychiatrists if necessary, because many patients have problems in school or at home, and some cases repeat their symptoms and take long periods to recover.
Vestibular evoked myogenic potential (VEMP) is a biphasic response which is recorded over the ipsilateral sternocleidomastoid muscle following intense sound stimulation. VEMP has potential as a new functional test of the saccular and inferior vestibular nerve tracts. In this report, VEMP, caloric response, and auditory brain stem response (ABR) were analyzed in 21 patients (10 male and 11 female; mean age, 57.2 years) with acoustic neuroma to evaluate the clinical usefulness of the VEMP test. In the VEMP examination, intense clicks (100 dBnHL) were delivered at a stimulation rate of 5 Hz. Two hundred responses were averaged. Sixteen of the 21 patients (76.2%) showed abnormal VEMPs on the affected side. Twelve of these 16 patients (75.0%) had abnormal caloric responses on the affected side. Two of the 4 patients with normal caloric responses showed abnormal VEMPs. Of the 8 patients who were excluded from the evaluation of ABRs because of profound sensorineural hearing loss, 7 showed abnormal VEMPs. Four of the 13 patients with abnormal ABRs showed normal VEMPs. These results suggest that the measurement of VEMP in addition to caloric response and ABR might provide greater precision in the screening of acoustic neuroma.
Intratympanic gentamicin injection has been used as a treatment of intractable Meniere's disease (MD). Although this therapy is supposed to be applied to unilateral MD, it should be noted that unilateral MD progresses to bilateral MD at a rate of 10-40%. Involvement of the contralateral ear after gentamicin injection could cause the serious problem of bilateral inner ear disfunction. To predict the future involvement of the contralateral ear, we reported a prospective study of patients that were diagnosed with unilateral MD at the first examination. Among 71 patients with unilateral MD, 9 (12.6%) showed fluctuating hearing loss in the contralateral ear. The average interval of the contralateral involvement after the unilateral involvement was 8.7 years. Although the prediction of the contralateral involvement was difficult from the results of the pure tone audiometry, caloric test and vestibular evoked myogenic potential, these bilateral cases tended to be seen more in females and in patients of older ages at the onset of the disease. The results of this study revealed that there is a possibility of contralateral involvement for more than 10 years, and the incidence of bilateral involvement is high in female patients who were over 60 at the onset of the disease.