Sachiko Aoki

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.

A head-tilt caloric test for evaluating the vertical semicircular canal function.

Conclusions: The caloric test with head-tilt can be used as a tool for assessing vertical canal function as an office procedure. Objective: Evaluation of vertical canal function. Patients and methods: We provoked caloric response by cold water in the vertiginous patients in supine position. During the culmination of the response we rotated the head 45° from the sagittal plane to place the posterior canal to earth-vertical. Thereafter we rotated the head 45° to the opposite direction to place the anterior canal to earth-vertical. The eye movements were recorded by two-dimensional electronystagmography. The data collected from the examination of 100 ears with normal caloric response in horizontal component were analyzed. Results: The down-beating vertical component intensified when the posterior canal was placed to earth-vertical. The up-beating vertical component intensified when the anterior canal was placed to earth-vertical. These findings suggested that the vertical canals were functioning.

Clinical significance of vertical component of caloric response including its second phase in vertiginous patients

Conclusions. Up-beating vertical component recorded in the caloric first phase was attributed mainly to the inhibitory endolymph flow in the anterior canal. Down-beating vertical component recorded in the caloric second phase provoked by a positional change could be explained by a reversed endolymph flow in vertical canal(s). Objective. To investigate the origin of a vertical component in caloric response. Materials and methods. We analyzed electronystagmography (ENG) of caloric responses, which had measurable horizontal component in the caloric first phase in both ears in 200 ears of 100 vertiginous patients. A caloric first phase was provoked by cold water in the supine position with the lateral semicircular canal earth-vertical. A caloric second phase was provoked by re-orienting the lateral canal from the earth-vertical to earth-horizontal after the cessation of the first phase (provoked second phase). The nystagmus of the whole procedure was recorded by two-dimensional ENG. Results. We recorded the vertical component in 103/200 ears in the caloric first phase, which was directed mostly upward (92/103 ears). We also recorded the vertical component in 91/200 ears in the provoked second phase, which was directed almost exclusively downward (90/91 ears).

A new coordinates system for cranial organs using magnetic resonance imaging.

Abstract Conclusion: We developed a new coordinates system for magnetic resonance imaging (MRI) that utilizes the labyrinth and eyeballs as references to measure the spatial arrangement of cranial organs, and we verified its usefulness by observing small structures in the labyrinth in 39 ears from 33 patients. Our new coordinates system could be used for stereotactic analysis of cranial organs in MRI. Objectives: To research semicircular canal anatomy in healthy organisms, we propose a method that employs references visible on MRI for stereotactic measurement of cranial structures, and we evaluated the usefulness of our method. Methods: Using the new coordinates system and vector analysis, we calculated angles among the semicircular canals and sagittal head plane from MRI volume data containing temporal bone and orbit. Results: The angle between the anterior semicircular canal plane and sagittal plane was 35.3 ± 4.1°; posterior semicircular canal plane and sagittal plane, 50.9 ± 4.7°; and horizontal semicircular canal plane and sagittal plane, 90.4 ± 7.0°. The angle between the anterior and posterior semicircular canal planes was 95.1 ± 4.2°; anterior and horizontal semicircular canal planes, 92.3 ± 7.5°; and posterior and horizontal semicircular canal planes, 93.5 ± 4.9°.