Smooth pursuit eye movements when tracking sine waveform target movements of 30° amplitude and 1/3 Hz frequency (eye tracking test : ETT) were quantitatively assessed in 18 patients with aphasia.Almost all old aphasic patients, mainly those with cerebro-vascular disorders, showed abnormal values.A few young aphasic patients, mainly those with brain trauma, also had abnormal values. The degree of the eye movement disorder seems to be independent of the degree of aphasia.
In order to clarify the influence of vestibular stimulation (pressure applied to the external auditory canal and monopolar galvanic stimulation) and vestibular disorders on the formation of stepping rhythm, we investigated the timing of the swing phase of stepping rhythm (1.2Hz) in 15 normal subjects and seven patients with Meniere's disease. 1) There was no difference between the duration of the swing phase from the right foot to the left foot and from the left foot to the right foot. 2) Pressure applied to the ears unilaterally or bi-laterally caused on earlier swing phase in normal subjects. 3) In the normal subjects with galvanic stimulation, there was a significant difference between the start of the swing phase from the right foot to the left foot and that from the left foot to the right foot. 4) The timing of the swing phases in patients with Meniere's disease was similar to that in normal subjects with pressure applied to the external auditory canal.
Eye movements induced by the I.V. injection of ketamine hydrochloride (Group 1; n=8) and diazepam (Group 2; n=7) were axamined electro-nystagmographically in 15 healthy adults. Complete gaze nystagmus and horizontal rebound nystagmus were observed in all 8 subjects of Group 1, and rebound nystagmus in all 4 directions in 2, but none had positional nystagmus. Primary position downbeat nystagmus was observed in 5 subjects of Group 2, and horizontal gaze nystagmus in all 7, but none had rebound nystagmus, vertical gaze nystagmus or positional nystagmus.
Questionaires were sent to 8442 students of elementary school, junior high school and senior high school in Totsukawa Village, Amagasaki city and Yao city. The responders were divided into three groups : frequent motion sickness, occasional and never any motion sickness. The answers to the questionaires were classified as background factors or direct factors. 1. Among primary and junior high school students, the group with frequent motion sickness had significantly background and direct factors more than the groups with little or no motion sickness. 2. The frequent motion sickness group of primary and junior high school students had many more background factors and direct factors than did the senior high school students. 3. The factors causing motion sickness were, in general, background factors in primary and junior high school students and direct factors in senior high school students.
Eye monements were recorded by a scleral search coilmagnetic field system. We studied how the coil fitted the eyes, and how the amplitude changed when the coils moved in the magnetic field. 1. The amplitudes of eye movements of 30° which were recorded by a scleral coil-magnetic field system were equal to the amplitudes of 30° of the coil movement at the same position as the eyes in the magnetic field. Therefore, there seemed to be no slipping of the coils on the eyes. However, when the coils became old, or frequently used, sometimes the fitting of the coils on the eyes was very loose. 2. The more the coil moved forwards or backwards, the smaller were the amplitudes of the horizontal and vertical coil movements. The more the coil moved upwards or downwards, the smaller were the amplitudes of the horizontal coil movements, however the vertical coil movements became larger. The more the coil moved to the right, or to the left, from center of the magnetic field, the larger were the amplitudes of the horizontal coil movements, however the vertical coil monements became smaller. 3. The same amplitudes of coil movements as of eye movements recorded by coils at the center of the magnetic field occurred when the coils moved from the center of the magnetic field; 10cm to the right or to the left, 5cm upwards, 10cm downwards and 25cm backwards.
This study was performed to determine the influence of repeated rotatostimulation on the vestibulo-ocular reflex. Three figure skaters and three ballet dancers with careers of more than 10 years were examined by two rotation tests with Contraves' computerized rotary chair on the same day. The two tests were Trapezoid Rotation (TR) test (±2, 4, 6, 8, 10°/sec2, 10″) and Sinusoidal Harmonic Acceleration (SHA) test (0.01, 0.02, 0.04, 0.08, 0.16 Hz). 1) The TR test showed that skaters and ballet dancers had equivalent values of VOR-Gains as the average of healthy untrained subjects. 2) VOR-Gains measured by the SHA test were lower than the average of healthy untrained subjects.The difference was most clearly noticed with rotations of 0.16Hz. 3) No subjects showed vestibular asymmetry, except for one subject who showed directional preponderance to the left. 4) Nystagmus duration measured by the TR test was within the normal range.
In the present study, the values of parameters, such as peak velocity and amplitude of the fast phase of optokinetic nystagmus (OKN), were measured quantitatively in 5 normal subjects by a microcomputer, and the effects of several methodological factors on nystagmus parameters were investigated. 1) The relationship between peak velocities and amplitude of the fast phase of OKN could be obtained from a bestfit exponential equation, i. e., velocity=K (1-exp [-amplitude/L]), where K is the asymptotic maximum velocity and L is a curvature parameter. 2) Analog filters with highcutoff frequencies affected the computation of peak velocities of the fast phase of OKN. The results showed that the analog filter should be about 10Hz or higher. 3) Sampling frequencies influenced the velocity of the fast phase of OKN, and it was shown that the analog data should be digitized at a rate of 200 samples/sec or more. 4) It was recognized that the value of the velocity at each amplitude obtained from a best-fit exponenntial equation could be used as an index for the evaluation of the fast phase of OKN.
Vestibular findings were studied in 27 patients with acoustic neurinoma. Four of them had experienced vertigo and/or dizziness at the onset of the disease, and 14 other patients had these complaints during the course. Vestibular symptoms were more prominent with middle-sized tumors which extended to the posterior cranial fossa than with those in the internal auditory canal. Although most acoustic neurinomas originate from the vestibular nerve, the incidence of vestibular symptoms is rather infrequent. This is probably due to a compensating mechanism of the central nervous system while the tumor grows slowly. Therefore, the growth rate of the tumor is considered to be most important for the concomitance of vestibular symptoms. The origin of the tumor was identified in 13 cases; in 3 it was from the inferior vestibular nerve and in 10 from the superior vestibular nerve. No significant difference in caloric test results could be seen between the tumors of different origins. The incidence of vestibular symptoms was more frequent when the tumor originated from the superior vestibular nerve than from the inferior vestibular nerve. The recover time required from the dysequilibrium after extirpation of the tumor depended on the degree of preoperative vestibular function.
It is well known that pressure changes applied to the external auditory canal produce eye movements in some cases of Ménière, s disease (Hennebert's sign or pseudofistula sign). Theire influence on posture was studied by measuring the change in lateral body sway when a quantitatively regulated pressure load was applied to the external ear canal (PLT). A total of 82 subjects were sutudied by this method. Of these 47 suffered from Ménière's disease and 15 from sud-den profound sensorineural hearing loss; 20 normal subjects were served as controls. Our test results showed that 26 (55%) of the 47 patients with Ménière's disease showed a difference in PLT thres-hold between the right and left ears and only 3 (20%) of the 15 patients suffering from sudden profound hearing loss and 1 (5%) of the normal subjects exibited such a differece. In the patients with Ménière's disease, a statistically significant correlation was found between the PLT and low tone hearing level and also between the PLT and the flluctuation of hearing in the low tone range. The presence of a positive PLT provides usefull information not only about the site of the lesion but also about the stage of Ménière's disease.
We have recently treated two patients with neurovascular cross compression (NVCC) of the eighth cranial nerve in the cerebellopontine angle, one with progressive sensorineural hearing loss and one with Ménière's disease. In these patients with NVCC who had a very high pure tone threshold fluctuating with a low frequency disorder, the AICA and its branches were found to be entrapped between the seventh and eighth cranial nerves. Ultimately, NVCC of the eighth cranial nerve seems to be composed of one group of NVCC with a circulatoroy disorder of the AICA entrapped between the seventh and eighth nerves, and another group of NVCC with irritative nerve dysfunction of the eighth cranial nerve compressed by AICA, as we reported previously.
Principles of eye recording in electronystagmography (ENG) have been established phenomenologically on the basis of the experimental results of Mowrer, Ruch and Miller (1936). However, unexpected recordings, for example, so-called pseudo-eye-movements, may be experienced in clinical use. These have been described from the phenomenological view point in the author's previous reports. In this study, a theoretical equation to predict eye positions and eye movements on the basis of a dipole theory is presented. Comparison between the predicted eye movements and the record of eye movements in ENG revealed fairly a good agreement. It is assumed that the equation has values to predict eye movements in ENG and to support the principles of electronystagmography as explained by the dipole theory.
It is said that lateral-to-medial retraction of the cerebellar hemisphere is hazardous because it may cause avulsion injury of the cochlear nerve and internal auditory artery. Caudal-to-rostral retraction of the cerebellar hemisphere is, therefore, recommended in operations on the CP angle such as microvascular decompression procedures. The results of our present study, however, show that caudal-to-rostral retraction can easily cause vestibular nerve damage, although rostral-to-caudal retraction may mainly damage the cochlear nerve as does lateral-to-medial retraction. These differences of eighth nerve injuries according to the direction of cerebellar retraction can be explained by the fact that the vestibule and vestibular nerve are located posterior to the cochlea and cochlear nerve. Most cases of dysequilibrium after manipulations in the CP angle area may be due to vestibular nerve damage-avulsion of the vestibular nerve and its accompanying vessels from the vestibular apparatus.