Yasuhiko Takei

Study on Experimental Motion Sickness in Children

To clarify the characteristics of motion sickness in children we investigated autonomic nervous symptoms and instability evoked by walking while wearing horizontally reversing goggles in 90 children aged 4 to 15 years. Kindergarten children had hardly any autonomic nervous symptoms except headache; however, they often fell, could not stand up or move, and exhibited a to-and-fro deviation gait. Although the frequency and severity of sickness gradually increased during growth, the severity of gait disorder became milder as age increased. On the basis of these findings it seems likely that functions which perceive disorder of spatial orientation and action are immature in young children, and once spatial orientation is impaired, instability becomes very severe, since inadequate control is not stopped by an alarm function against disorientation.

Planer orientation of the bilateral semicircular canals in dizzy patients

OBJECTIVE Recent development of 3-dimensional analysis of eye movement enabled to detect the eye rotation axis, which is used to determine the responsible semicircular canal(s) in dizzy patients. Therefore, the knowledge of anatomical orientation of bilateral semicircular canals is essential, as all 6 canals influence the eye movements. SUBJECTS AND METHODS Employing the new head coordinate system suitable for MR imaging, we calculated the angles of semicircular canal planes of both ears in 11 dizzy patients who had normal caloric response in both ears. RESULTS The angles between adjacent canal pairs were nearly perpendicular in both ears. The angle between the posterior canal planes and head sagittal plane was 51° and significantly larger the angle between the anterior canal planes and head sagittal plane, which was 35°. The angle between the horizontal canal plane and head sagittal plane was almost orthogonal. Pairs of contralateral synergistic canal planes were not parallel, forming 10° between right and left horizontal canal planes, 17° between right anterior and left posterior canal planes and 19° between the right posterior and left anterior canal planes. CONCLUSION Our measurement of the angles of adjacent canal pairs and the angle between each semicircular canal and head sagittal plane coincided with those of previous reports obtained from CT images and skull specimens. However, the angles between contralateral synergistic canal planes were more parallel than those of previous reports.

Spatial Gaze Stability under Active High-Frequency Head Oscillation After Acoustic Neuroma Surgery

Spatial gaze stability under active high-frequency head oscillations was investigated in 31 patients after acoustic neuroma surgery. Whereas gaze stability upon rotation to the intact side was excellent during the entire time course after surgery, rotation to the affected side produced marked gaze disturbance at frequencies higher than 1.0 Hz, and did not recover even several years after surgery. The maximal oscillation frequency decreased in the patient group. Oscillopsia, being found in 20% of the patients, showed little correlation with gain value or maximal oscillation frequency. Long-lasting disturbances of active head oscillation, gaze stability and perception after unilateral labyrinthine loss may indicate persistent asymmetry of spatial orientation during high-frequency head movements.