Three-dimensional analysis of eye movements during off vertical axis rotation in patients with unilateral labyrinthine loss.

3D analysis of eye movements during off vertical axis rotation (OVAR) was carried out in seven subjects with unilateral labyrinthine loss (ULL). The modulation component (MOC) of these patients was not different from that of normal subjects. However, the horizontal MOC was significantly smaller when the rotation was directed towards the diseased side as opposed to the healthy side. With rotation to the diseased side, most subjects exhibited a horizontal bias component (BIC) to the opposite side as compared with the diseased side in normal subjects. The vertical and torsional BICs were also influenced to some extent by lack of input from the unilateral labyrinth. These results indicate that a unilateral otolith organ plays a major role in the production of the horizontal BIC contralateral to the direction of rotation, which is strongly related to the velocity storage mechanism in the central nervous system. In addition, the unilateral otolith organ exerts some influence on the generation of the horizontal MOC and also the BIC of vertical and torsional eye movements.

Is the pathology of horizontal canal benign paroxysmal positional vertigo really localized in the horizontal semicircular canal?

In order to clarify the pathological localization of horizontal canal benign paroxysmal positional vertigo (HC-BPPV), we performed 3D analysis of positional nystagmus in 11 patients with HC-BPPV. In addition, these results were compared with 3D analysis data of pressure nystagmus in patients with HC fistula. 3D analysis of nystagmus was carried out using a video image analysis system. In seven patients with HC-BPPV, the velocity vectors were well aligned with the axes of the HC and in four patients they were not. In addition, the 3D velocity vectors of the slow phase of pressure nystagmus in all 11 subjects with HC fistula were closely aligned with the axes of the HC. The pathology of HC-BPPV in most patients with apogeotropic positional nystagmus has been considered to be localized in the HC. However, our results strongly suggest that the pathology of HC-BPPV with geotropic nystagmus is localized in the utricle. This is the first report concerning the pathological localization of HC-BPPV based on physiological evidence.

Three dimensional eye movement analysis during off vertical axis rotation in human subjects.

Three dimensional analysis of eye movements during OVAR was performed in 37 healthy human subjects using the computerized image recognition technique developed by us. The modulation component of eye movement was observed in all three components (horizontal, vertical and torsional), whereas the bias component was only clearly seen in the horizontal eye movement. The phase lag of the torsional component was quite consistent with a small variation between each subject with respect to the head position. The phase of vertical eye movement was, however, less consistent compared to that of the horizontal and torsional eye movements. From these results, in human subjects, there should be some differences in the dynamic function of the otolith system compared to that observed in monkeys.

Three-dimensional analysis of pressure nystagmus in labyrinthine fistulae.

In this study we analysed pressure nystagmus three-dimensionally in subjects with labyrinthine fistulae. The fistulae were localized in the lateral canal in five patients, in the posterior canal in one patient and in both lateral and anterior canals in two patients. The eye velocities during the fistula test in patients with lateral canal fistula and in a patient with posterior canal fistula were closely aligned with the anatomical axes. On the other hand, pressure nystagmus in cases with fistulae of both the lateral and anterior canals were not aligned with the anatomical axes of the combination of both canals.

[Three-dimensional analysis of eye movements induced by off-vertical axis rotation].

Off-vertical axis rotation (OVAR) is a method to stimulate the otolith organ. In order to elucidate the function of the otolith organ, we analyzed three-dimensional eye movements by video-oculographic technique during OVAR in 30 normal subjects. The eye movements induced by OVAR stimulation have two components: a constant horizontal deviation in the direction opposite to the rotation known as the bias component, and sinusoidal amplitude changes of eye movements known as the modulation component. Modulation components were detected in the horizontal, vertical, and torsional eye movements, but the bias components were only detected in the horizontal eye movements. The modulation components may compensate for changes in head orientation with respect to gravity. Since the bias component is caused by the velocity storage mechanism, the lack of bias components in vertical and torsional eye movements may suggest its specific relation to only horizontal eye movements. Our results also demonstrated that torsional and horizontal eye movements may originate from the utricle, whereas vertical eye movement may originate from the saccule. However, a lag phase between torsional and horizontal eye movements suggests that the most effective direction for stimulation of these two eye movements may be different.

[Analysis of tympanoplasty at Chiba-Hokuso Hospital, Nippon Medical School].

We evaluated tympanoplasty statistically at Chiba-Hokuso Hospital, a branch hospital of Nippon Medical School. Especially, we discussed the improvement of auditory thresholds after operation, the type of tympanoplasty in valved, the availability of patch tests and complications.