Direction-changing positional nystagmus towards the uppermost ear was noted in 8 of 14 normal subjects and in 7 of 16 patients with Meniere's disease given glycerol (1.5 g/kg). The slow phase velocities of the nystagmus reached a muximum about 3 hours after the oral administration of glycerol. Positional nystagmus was suspected of originating from changes in the specific gravity of the endolymph caused by the infiltration of glycerol into the endolymphatic space, which may indicate that glycerol can pass through the bloodlabyrinth barrier. It may be useful in the investigation of this barrier in patients with Meniere's disease to observe positional nystagmus in response to the glycerol test.
We compared the body sway of patients with spinocerebellar degeneration with that of healthy adults. The distances of sway in the X-direction, the Y-direction, the XY-direction and the area of sway in the patients were greater than in the healthy adults with both eyes open and closed. Healthy adults swayed right and left, while patients with spino-cerebellar degeneration swayed forward and backward in non-sequential 8 vector analysis especially with eyes closed. Non-sequential 8 vector analysis seems to be a good method of comparing the extent and direction of body sway.
We developed a new recording system of eye movements with a CCD image-sensor in a video-camera. Eye movements are recorded as movements of the pupil which are pictured with a CCD image-sensor. The eye movements, which we can watch on green display, are recorded simultaneously on recording papers. The recordings are stored on floppy disks and analyzed by a computer off-line. We can record not only horizontal but also vertical eye movements with our recording system. The noise level of this system is below 1% while the recording area is ±15° in the horizontal plane and is ±10° in the vertical plane. There are high linearities in eye positions and no drifts of base lines in recording. The clinical uses of this system are as follows: 1 Precise recordings of abnormal eye movements. 2 Quantitative analysis of horizontal and vertical smooth pursuits. 3 Quantitative analysis of eye drift on fixation.
In 1983, the board of the Japan Society for Equilibrium Research presented a standard of stabilometry, but some problems remain. In order to determine the test conditions, we performed the following examination with a standard stabilometer. 1 . For visual target testing, the distance from the subject to the target and the illumination of the peripheral visual field were studied. 2. For the standing posture, body sway in the military standing posture was compared with that in natural standing. 3. For foot position, body sway while standing with both feet together was compared with that feet in the fan-shaped position and with feet apart but parallel. 4. For recording time, body sway while standing for 30 seconds was compared with that while standing for 60 seconds. 5. To elimilinate transitional sway after standing erect with eyes closed, the time when the recording should start was studied. The parameters for stabilometry are as follows ; unit locus lengh, forward-backward and right-left diameters, area, rejection ellipse, center of sway, standard deviation, skewness and kurtosis of amplitude probability density distribution, velocity, vector of velocity, power spectrum. 1. When the visual target was placed one meter from the subject and the peripheral field of vision was lighted, the mean and standard deviation of all parameters in stabilometry were the smallest. 2. Standard deviations of the unit locus length, area and velocity during military posture standing were lower than during natural standing. However, maintenance of military standing for 60 seconds was difficult. Therefore, stabilometry with natural standing was considered more suitable for clinical examinations. 3. Body sway while standing with feet 10 cm apart was less than when standing with the feet close together or in the fan-shaped position. However, standing with the feet close together was suitable for detecting slight equilibrium disturbances. 4. Body sway observation for 60 seconds clarified the pattern of the body sway more definitely than did observation for 30 seconds. 5.Irregular sway was recorded after the subject stood erect with eyes closed for 10 seconds. To eliminate transitional sway, the recording should be started when the body movements of the standing subject are stabilized.
Normal stabilogram were examined in 38 subjects, 38 males and 7 females, aged 30 to 62 years, standing erect in Romberg's posture with eyes open and with eyes closed. From analog data of body sways in both lateral (RL) and anterior-posterior (AP) directions, digital data of 51.2 sec duration with a sampling time 50 msec were obtained in each case. Each serial partial statokinesigram of 5 or 10 msec duration was displayed on rectangular coordinates, the origin of which was fixed at the mean value of each location of the center of gravity during 51.2 sec with the use of a microcomputer (NEC PC 9801). The slow deviation with a period of about 50 sec or with 0.02 Hz, of body sway in the RL or AP direction was not infrequently observed when the eyes were open. However, it was eliminated or negligible when the eyes closed. When such a slow deviation of body sway appeared, larger values of standard deviation and maximal range of body sway occurred in spite of the short length of the trace of the center of gravity. The incidence of slow deviation of body sway decreased in the RL direction and increased in the AP direction with the age of the test subjects. The origin of such a slow deviation is considered to be a redundancy of human standing ability, because it appeared only in stable and safe standing in normal subjects with eyes open.
Pseudo-eye-movement weves, or PEWs, which represent false eye movements on electronystagmograms in the horizontal eye lead during vertical rotation of the eye or in the vertical eye lead during horizontal eye rotation, cause some difficulties in clinical practice. This electronystagmographic study is aimed to find a way to cope with PEWs and to clarify their nature. Twelve electrodes were attached to 12 points of the face, and one electrode was placed on a mastoid process. The electric potential at each point was measured monopolarly or bipolarly by a topography system (NEC San-ei, Japan) during both horizontal and vertical alternating gaze. 1) Eye movements were successfully recorded from all 12 points. The maximum amplitude was seen in a pair of horizontal eye leads during horizontal eye movements and in a pair of vertical eye leads during vertical eye movements. 2) Horizontal and vertical PEWs disappeared or were reduced in amplitude when the electrodes at the inner canthus, nasal and lower margin of the orbit were shifted slightly lower than their conventional points. 3) A PEW is assumed to appear when the potential difference between a pair of conventional horizontal or vertical electrodes is not zero, during vertical and horizontal eye movements, respectively.
With a micro-computer-gravicorder SG-1, the Length/Time (LNG/T), Root Mean Square (RMS) and Standard Deviation Area (SD-Area) of body sway were analyzed automatically in 14 kinds of visual and somatosensory condition. The test was done in 22 normal subjects (NS) and 55 patients with vertebrobasilar insuffiency who were classified into 6 groups by the results of caloric testing. Eighteen kinds of calculation and statistical analyses were done with a computer to compose NS and each patient group. All the groups showed different chara-cteristic body sways under different external condi-tions. 1) In the NS group, body sway in the dark>body sway while looking at OKN>body sway while watching LED≅body sway in the light. 2) In group A, the SD-Area of body sway while watching LED was larger than in the dark on the S-G board. 3) In group B, the RMS and the SD-Area in the dark was smaller than while looking at OKN, while watching LED or in the light on the S-G board. The RMS while watching LED was larger than in the dark or while looking at OKN on the flat board. 4) In group D, the LNG/T while watching LED was larger than while looking at OKN on both boards. 5) In group E, there were no characteristic findings. With those tests, we could demonstrate the effects of visualvestibular-somatosensory interactions on body sway.
In this study of the static coordination of the ocular and the cervical muscles the rotatory angle the head makes with the trunk and the angle of ocular version in the orbit were measured in the right and left directions in 20 healthy persons (40 measurements) who maintained a fixed lateral gaze in a natural, unrestricted condition or with the head turned through a certain angle. 1. There was no difference in measured values between the right and the left directions. There was a close positive correlation of measurements between the two angles (r>0.9). 2. The fixed lateral gaze was the sum of the ocular version and head rotation in the same direction. As the angle of gaze increased, there appeared three linear relations of differing inclination where the ocular muscle played the leading role when the subject gazed in the lateral direction at an angle of less than 20 degrees, while the cervical muscles took the place of the ocular muscles when the angle of gaze was greater than 70 degrees. These muscles were in coordination when the angle of gaze was between these ranges. 3. The maintenance of a rotated head position was achieved by the ocular version in the same direction. As the angle of head rotation increased, there appeared three linear relations of differing inclination where the cervical muscle assumed the leading role when the angle of head rotation was smaller than 10 degrees and the ocular muscle took its place when the angle of head rotation was greater than 60 degrees. These muscles were in coordination when the angle of head rotation was between these ranges. 4. Despite the difference in the muscular task (or purpose of movement) there was a shift in the inclination of the three linear relations of ocular and cervical muscle coordination at the critical angles of ocular version, that is, 8 and 22 degrees. These critical angles of ocular version appear to have specific physiological implications in regard to equilibrium. These observation suggest that there is a direct reflex system as a mechanism of static coordination, as distinguished from the known dynamic coordination, and that it is regulated by the ocular muscles.