Three-component analysis of caloric nystagmus in humans

Vestibular and oculomotor influences on visual dependency

Participants made verticality judgments using the rod-and-disk test, a test of visual dependence, and then repeated after caloric irrigation. If the combination of rotating disk and caloric increased the slow-phase velocity of the torsional nystagmus the tilt in subjective verticality increased, whereas reductions in eye velocity were associated with reduced tilt. Thus visual dependency measures are not only modulated by perceptual style but can also reflect local vestibulo-ocular function, specifically torsional eye movements.

The degree to which a person relies on visual stimuli for spatial orientation is termed visual dependency (VD). VD is considered a perceptual trait or cognitive style influenced by psychological factors and mediated by central reweighting of the sensory inputs involved in spatial orientation. VD is often measured with the rod-and-disk test, in which participants align a central rod to the subjective visual vertical (SVV) in the presence of a background that is either stationary or rotating around the line of sight—dynamic SVV. Although this task has been employed to assess VD in health and vestibular disease, what effect torsional nystagmic eye movements may have on individual performance is unknown. Using caloric ear irrigation, 3D video-oculography, and the rod-and-disk test, we show that caloric torsional nystagmus modulates measures of VD and demonstrate that increases in tilt after irrigation are positively correlated with changes in ocular torsional eye movements. When the direction of the slow phase of the torsional eye movement induced by the caloric is congruent with that induced by the rotating visual stimulus, there is a significant increase in tilt. When these two torsional components are in opposition, there is a decrease. These findings show that measures of VD can be influenced by oculomotor responses induced by caloric stimulation. The findings are of significance for clinical studies, as they indicate that VD, which often increases in vestibular disorders, is modulated not only by changes in cognitive style but also by eye movements, in particular nystagmus.

The second and third phases of caloric nystagmus

CONCLUSION

The second and third phases of caloric nystagmus occur at a high rate. We can explain this phenomenon based on the hydrostatic pressure theory involved in perilymph.

OBJECTIVES

To clarify the incidence of the second and third phases of caloric nystagmus, and to measure their intensity.

METHODS

The subjects were 12 healthy humans. The right ear was stimulated using iced water. The first phase of caloric nystagmus was recorded in a supine position. Immediately after the cessation of the first phase, each subject was repositioned to a prone position, and the second phase was recorded. Immediately after the halt of the second phase, each subject was repositioned to a supine position, and the third phase was recorded. Nystagmus was analyzed using three-dimensional video-oculography.

RESULTS

The mean value of maximum slow-phase velocity (MSV) of the first phase was 27.2°/s. All subjects revealed the second phase, and the direction was toward the right. The mean value of MSV was 7.2°/s. Nine subjects (75%) showed the third phase, and the direction was toward the left. The mean value of MSV was 2.7°/s.

A biomechanical model of the inner ear: numerical simulation of the caloric test

Whether two vertical semicircular canals can receive thermal stimuli remains controversial. This study examined the caloric response in the three semicircular canals to the clinical hot caloric test using the finite element method. The results of the developed model showed the horizontal canal (HC) cupula maximally deflected to the utricle side by approximately 3 μm during the hot supine test. The anterior canal cupula began to receive the caloric stimuli about 20 s after the HC cupula, and it maximally deflected to the canal side by 0.55 μm. The posterior canal cupula did not receive caloric stimuli until approximately 40 s after the HC cupula, and it maximally deflected to the canal side by 0.34 μm. Although the endolymph flow and the cupular deformation change with respect to the head position during the test, the supine test ensures the maximal caloric response in the HC, but no substantial improvement for the responses of the two vertical canals was observed. In conclusion, while the usual supine test is the optimum test for evaluating the functions of the inner ear, more irrigation time is needed in order to effectively clinically examine the vertical canals.

Does the superior semicircular canal receive caloric stimulation?

BACKGROUND

Caloric nystagmus contains not only a horizontal component but also vertical and torsional components. Several researchers considered that their origins are the posterior and superior semicircular canals. If the right superior canal receives caloric stimulation in the left-ear-down 40° position, an endolymphatic flow occurs in the direction of gravity in the long arm and induces ampullofugal cupular deflection. As a result, the direction of the vertical component of nystagmus should be downward (toward the lower eyelid), and the direction of the torsional component should be rightward.

PURPOSE

The purpose of this study is to confirm the hypothesis that the superior semicircular canal receives caloric stimulation.

METHODS

The subjects were 10 healthy humans. The right ear was stimulated using iced water. Each subject was kept in a left-ear-down 40° position for 60 seconds and then repositioned to a supine position. Nystagmus was analyzed by 3-dimensional video-oculography.

RESULTS

In the left-ear-down 40° position, the direction of quick phase of the horizontal component was leftward in all subjects. Eight subjects exhibited a vertical component, and the direction was upward (toward the upper eyelid). Six subjects showed a torsional component, and the direction was leftward (the superior pole of the eyeball moved toward the left ear of the subject in a quick phase). These findings contradict the hypothesis.

CONCLUSION

Caloric stimulation does not reach the superior canal; therefore, caloric testing cannot be used to evaluate the function of superior canal.

Is horizontal semicircular canal ocular reflex influenced by otolith organs input?

CONCLUSION

Otolith organs input influences the axis of horizontal semicircular canal ocular reflex; therefore, the plane of compensatory eye movements induced by the horizontal canal stimulation is not always parallel to the canal.

OBJECTIVE

To clarify whether horizontal canal ocular reflex is influenced by otolith organs input.

METHODS

The subjects were seven healthy humans. The right ear was stimulated using ice-water. Each subject was kept in a left-ear-down position for 20 s and then repositioned to a prone position, a right-ear-down position and a supine position with 20 s intervals. Nystagmus was analysed using three-dimensional video-oculography.

RESULTS

Eye movements in the supine position and the prone position were not in a symmetric fashion. Nystagmus in the left-ear-down position and the right-ear-down position were not symmetric either. These phenomena indicate that the axis of the eyeball rotation was affected by the shift of the direction of gravity exerted on the head.

Persistent direction-changing geotropic positional nystagmus

The aims of the study were to clarify whether persistent direction-changing geotropic positional nystagmus contains vertical and torsional components, and to quantify the asymmetry. We analyzed nystagmus in four positions (healthy-ear-down, affected-ear-down, supine, nose-down) using three-dimensional video-oculography. Subjects were 18 patients with persistent direction-changing geotropic positional nystagmus, 16 females and 2 males, with a mean age of 55 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed three-dimensional video-oculography and measured maximum slow-phase velocity (MSV) of three components. Positional nystagmus was not purely horizontal. Eight (44%) patients revealed a vertical component (upward) and 15 (83%) patients had a torsional component in the healthy-ear-down position. Seven (39%) patients revealed a vertical component (downward) and 10 (56%) patients showed a torsional component in the nose-down position. The mean value of MSV of the horizontal component in the supine position was 9.3°/s and that in the nose-down position was 15.7°/s. The latter was significantly greater than the former (p < 0.05). Eye movements in the supine position and the nose-down position were not mirror images. These results suggest that vertical and torsional components occur from the horizontal semicircular canal, and that horizontal canal ocular reflex is influenced by input from the otolithic organs.

Can caloric testing evaluate the function of vertical semicircular canals?

CONCLUSION

Neither posterior nor superior semicircular canal receives a caloric effect; therefore, caloric testing cannot evaluate the function of vertical semicircular canals.

OBJECTIVE

To clarify whether caloric stimulation reaches the posterior and superior semicircular canals.

METHODS

The subjects were 10 healthy humans. The right ear was stimulated using ice-water. Each subject was kept in a supine position for 40 s and then repositioned to a sitting position until horizontal nystagmus stopped; afterwards, a nose-down position was adopted. Nystagmus was analyzed by three-dimensional video-oculography.

RESULTS

In the supine position, four subjects revealed a vertical component and five subjects showed a torsional component. In the sitting position, neither a vertical nor a torsional component occurred when the horizontal component stopped. Three subjects revealed a vertical component and four subjects showed a torsional component in the nose-down position.

Cupulolithiasis of the horizontal semicircular canal

To clarify whether positional nystagmus of horizontal cupulolithiasis contains vertical and torsional components, and to quantify the asymmetry, we analyzed nystagmus in four positions (healthy-ear-down, affected-ear-down, supine, nose-down), using 3-dimensional video-oculography. Subjects were 20 patients with direction-changing apogeotropic positional nystagmus, 11 females and 9 males, with a mean age of 58.1 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed 3-dimensional video-oculography and measured maximum slow-phase velocity (MSV) of three components. Positional nystagmus was not purely horizontal. Eleven (55%) patients revealed a vertical component, and 14 (70%) patients had a torsional component in the healthy-ear-down position. The mean value of MSV of the horizontal component in the healthy-ear-down position was 18°/s and that in the affected-ear-down position was 7.8°/s. For the horizontal component, MSV in the healthy-ear-down position was significantly greater than that in the affected-ear-down position (p < 0.01). These results suggest that vertical and torsional components occur from the horizontal semicircular canal, and the response to ampullopetal bending is more than two times as strong as that to ampullofugal bending.

Positional nystagmus of horizontal canalolithiasis

CONCLUSION

Vertical and torsional components occur from the horizontal semicircular canal, and the response to ampullopetal flow is greater than that to ampullofugal flow in every component.

OBJECTIVES

To clarify whether positional nystagmus of horizontal canalolithiasis contains vertical and torsional components, and to quantify the asymmetry of nystagmus.

METHODS

Twenty patients with transient direction-changing geotropic positional nystagmus were examined, and we performed three-dimensional video-oculography and measured the maximum slow-phase velocity (MSV) of three components.

RESULTS

Positional nystagmus was not purely horizontal. Fifteen (75%) patients revealed a vertical component and 19 (95%) patients had a torsional component. The mean value of MSV of the horizontal component in the affected-ear-down position was 51.5°/s and that in the healthy-ear-down position was 19.1°/s. The mean value of MSV of the vertical component in the affected-ear-down position was 8.7°/s and that in the healthy-ear-down position was 3.0°/s. The mean value of MSV of the torsional component in the affected-ear-down position was 12.8°/s and that in the healthy-ear-down position was 6.5°/s. For every component, MSV in the affected-ear-down position was significantly greater than that in the healthy-ear-down position (p < 0.01).

A new coordinates system for cranial organs using magnetic resonance imaging

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 degrees; posterior semicircular canal plane and sagittal plane, 50.9 +/- 4.7 degrees; and horizontal semicircular canal plane and sagittal plane, 90.4 +/- 7.0 degrees. The angle between the anterior and posterior semicircular canal planes was 95.1 +/- 4.2 degrees; anterior and horizontal semicircular canal planes, 92.3 +/- 7.5 degrees; and posterior and horizontal semicircular canal planes, 93.5 +/- 4.9 degrees.

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 degrees from the sagittal plane to place the posterior canal to earth-vertical. Thereafter we rotated the head 45 degrees 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.

Nystagmus as a sign of labyrinthine disorders--three-dimensional analysis of nystagmus

In order to diagnose the pathological condition of vertiginous patients, a detailed observation of nystagmus in addition to examination of body equilibrium and other neurotological tests are essential. How to precisely record the eye movements is one of the goals of the researchers and clinicians who are interested in the analysis of eye movements for a long time. For considering that, one has to think about the optimal method for recording eye movements. In this review, the author introduced a new method, that is, an analysis of vestibular induced eye movements in three-dimensions and discussed the advantages and limitations of this method.

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).

Spatial orientation of caloric nystagmus in semicircular canal-plugged monkeys

We studied caloric nystagmus before and after plugging all six semicircular canals to determine whether velocity storage contributed to the spatial orientation of caloric nystagmus. Monkeys were stimulated unilaterally with cold ( approximately 20 degrees C) water while upright, supine, prone, right-side down, and left-side down. The decline in the slow phase velocity vector was determined over the last 37% of the nystagmus, at a time when the response was largely due to activation of velocity storage. Before plugging, yaw components varied with the convective flow of endolymph in the lateral canals in all head orientations. Plugging blocked endolymph flow, eliminating convection currents. Despite this, caloric nystagmus was readily elicited, but the horizontal component was always toward the stimulated (ipsilateral) side, regardless of head position relative to gravity. When upright, the slow phase velocity vector was close to the yaw and spatial vertical axes. Roll components became stronger in supine and prone positions, and vertical components were enhanced in side down positions. In each case, this brought the velocity vectors toward alignment with the spatial vertical. Consistent with principles governing the orientation of velocity storage, when the yaw component of the velocity vector was positive, the cross-coupled pitch or roll components brought the vector upward in space. Conversely, when yaw eye velocity vector was downward in the head coordinate frame, i.e., negative, pitch and roll were downward in space. The data could not be modeled simply by a reduction in activity in the ipsilateral vestibular nerve, which would direct the velocity vector along the roll direction. Since there is no cross coupling from roll to yaw, velocity storage alone could not rotate the vector to fit the data. We postulated, therefore, that cooling had caused contraction of the endolymph in the plugged canals. This contraction would deflect the cupula toward the plug, simulating ampullofugal flow of endolymph. Inhibition and excitation induced by such cupula deflection fit the data well in the upright position but not in lateral or prone/supine conditions. Data fits in these positions required the addition of a spatially orientated, velocity storage component. We conclude, therefore, that three factors produce cold caloric nystagmus after canal plugging: inhibition of activity in ampullary nerves, contraction of endolymph in the stimulated canals, and orientation of eye velocity to gravity through velocity storage. Although the response to convection currents dominates the normal response to caloric stimulation, velocity storage probably also contributes to the orientation of eye velocity.

Three-dimensional analysis of post-caloric nystagmus caused by postural change

In order to record caloric nystagmus (CN) using three-dimensional videonystagmography (3D VNG) 14 subjects were placed in the supine position with the head tilted up 30 degrees relative to the earth's horizontal plane. After the primary-phase CN had terminated, the subjects were repositioned from a supine to a sitting position, with the head anteflexed 30 degrees for recording the post-caloric nystagmus (PCN). In addition, 8 of the original subjects were placed in the supine position but with the head turned 40 degrees to the left so that the irrigated (right) ear was oriented upwards. After the primary-phase CN had terminated, the subjects were rotated by 180 degrees so that the irrigated ear was oriented downwards to record PCN. The results indicated that both methods successfully provoked horizontal and vertical CN. For torsional CN, the irrigated ear up/down method produced a higher provocation rate (75%) than the supine/sitting method (50%), but the difference was not significant. Comparing the provocation rate of the PCN for the horizontal component revealed that the two methods do not differ significantly. However, when comparing the provocation rates of PCN for the vertical component, the irrigated ear up/down method showed a higher rate (82%) than the supine/sitting method (18%). Thus using 3D VNG coupled with postural change during caloric testing, the horizontal or vertical components of PCN can be successfully provoked.

Image analysis of quick phase eye movements in nystagmus with high-speed video system

There are several methods of measuring horizontal, vertical and torsional nystagmus for the diagnosis of vertigo. Using Frentzel glasses, electronystagmography (ENG) and video-oculography (VOG) are common methods for observing nystagmus. In this study, a high-speed video camera is used to analyse high-speed eye movements, including three components of nystagmus, in order to monitor precisely the amplitude and velocity of the quick phase of nystagmus. To confirm the accuracy of the analysis, images of optokinetic nystagmus (OKN) evoked by a stimulating device were analysed. We obtained a high linearity with regard to the relation between the horizontal nystagmus amplitude detected with the high-speed video system and ENG (R2= 0.99). On comparison of the maximum velocities detected with 30Hz and with 250 Hz at each amplitude, the velocities calculated at 30Hz were smaller than those calculated at 250 Hz. At an amplitude of 5 degrees , the 30 Hz velocity decreased by 50%, while a decrease of 35% was observed at 15 degrees. The vertical nystagmus data obtained using high-speed VOG was different in appearance to that obtained using ENG. The torsional component of nystagmus was also measured, and was recorded in the form of a large number of sampling points.

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.

Contribution of the vertical semicircular canals to the caloric nystagmus

Modulation of the caloric nystagmus in response to repositioning the plane of one vertical semicircular canal from gravitational horizontal to vertical during continuous caloric stimulation was used to measure the vertical canal's contribution to the nystagmus. The rationale was to examine the thermovective response from one vertical canal at a time, after a temperature gradient had been established across its two limbs. The nystagmus was measured and analysed in three dimensions using orthogonal head-referenced coordinates. The magnitude of each semicircular canal's contribution to the overall caloric response, the canal vector, was determined in non-orthogonal, contravariant semicircular canal plane coordinates. By using the canal plane reorientation technique and contravariant canal plane coordinates, we were able to measure the proportional thermovective response magnitude generated by each vertical canal during caloric stimulation. We found that the anterior canal contributed about one-third and the posterior canal about one-tenth as much as the lateral canal did to the overall caloric response magnitude when it was reoriented from horizontal to vertical. Comparison of the eye rotation axis before and after each vertical canal plane reorientation, with the geometry of the stimulated semicircular canals, also showed directional modulation of the caloric nystagmus by the vertical canal response. When one vertical canal plane was horizontal during caloric stimulation, the eye rotation axis aligned with the resultant of the other vertical canal and the lateral canal response axes. After vertical canal plane reorientation, the eye rotation axis realigned towards the resultant of the maximally stimulated vertical canal and the lateral canal, by 55.2+/-33.9 degrees (mean+/-SD) after anterior canal plane reorientation and by 32.3+/-21.2 degrees after posterior canal reorientation.

3D analysis of nystagmus in peripheral vertigo

Three-dimensional analysis of nystagmus was carried out in patients with peripheral vestibular diseases using a computerized image recognition technique developed by us. In the present study, we analyzed data from patients with Meniere's disease and vestibular neuritis with the central premise of localizing the pathology in the peripheral vestibular organs. In Meniere's disease, the recordings of all subjects showed two components of eye movements, namely the horizontal and torsional components. On the other hand, most of the patients with vestibular neuritis exhibited all three components of spontaneous nystagmus. The horizontal and vertical components of nystagmus in patients with vestibular neuritis were directed towards the contralateral side of the lesion and upwards. Based on these results and with reference to animal experiments that have related the eye movements with each labyrinthine end organ, it can be speculated that in Meniere's disease the pathological changes may involve all semicircular canals, whereas the main site of lesion in vestibular neuritis could be localized to the superior vestibular nerve.

Contributions of single semicircular canals to caloric nystagmus as revealed by canal plugging in rhesus monkeys

We demonstrated specific responses from the anterior and the posterior semicircular canal to irrigation of the outer ear canal with cold water in the Rhesus monkey. This required i) three-dimensional analysis of the evoked eye movements in the planes of the semicircular canals (canal plane vectors, CPV); ii) assessing these CPV responses in eight different head positions relative to gravity; iii) comparing the responses in 6 normal animals (12 ears) with responses after selective plugging of pairs of semicircular canals (all, both lateral, and right anterior + left posterior). The results showed: i) Irrigation of the outer ear canal with cold water induces thermoconvection also in the posterior and anterior semicircular canals. This can be inferred from the sinusoidal modulation of eye movement components with changes in position of the corresponding semicircular canal plane relative to gravity; ii) Specific vertical canal responses occur exclusively in the direction of the corresponding semicircular canal, though they are superimposed with response components of other origin, one probably related to endolymph shift in the lateral semicircular canal; iii) before possible clinical application, these different response components of vertical canals will need to be determined in humans.

Three-dimensional analysis of nystagmus induced by neck vibration

The role of dorsal neck proprioceptive inputs to vestibular compensation was investigated in 11 patients with unilateral vestibular dysfunction. Subjects had neither spontaneous nystagmus nor disequilibrium, indicating that they were well compensated. Vibratory stimulation to the dorsal neck produced marked nystagmus. All subjects showed horizontal component directed towards the contralateral side of the lesion. Vertical and torsional components of the nystagmus were exhibited by 10 and 7 subjects, respectively. These results indicate that the neck vibration caused a discompensation in vestibularly well compensated subjects after unilateral dysfunction. In addition, the influence of neck afferent on the vestibulo-ocular reflex pathways, not only of the horizontal, but also the vertical systems, is discussed.

Afternystagmus, its specific features

There are important issues and new observations concerning 'afternystagmus'. Recent findings were mostly supplied by 3-dimensional records of eye movements. 'After-nystagmus' appears to be secondary to the reactions to the visual and vestibular inputs. The beginning of afternystagmus, however, is not always clear, and the distinction from the primary reaction is not clear either. The axis of eyeball rotation during afternystagmus is not necessarily the same as that of the primary reaction, but frequently changes gradually with time. The change in the plane of eyeball rotation during afternystagmus appears to follow a certain rule, which appears to be under specific influences from the otolith organs. Afternystagmus and its related phenomena seem to be explained by a hypothetical 'velocity storage'.

Three-component analysis of benign paroxysmal positional nystagmus

Three-component analysis of Benign Paroxysmal Positional Nystagmus (BPPN), focusing on the horizontal, vertical, and torsional, using a computerized eye movement analysis system, was carried out in 10 patients. Using a pendular rotation stimulus, we also measured three components of eye movement elicited from the vertical semicircular canals in normal subjects. We compared two components (vertical and torsional) of BPPN with that of eye movements elicited from the vertical semicircular canals. In BPPN, the torsional component of eye movements was larger than that of the vertical component. Conversely, the vertical component from the vertical semicircular canals was larger than that of the torsional component. From these results, by analysing the vestibulo-ocular reflex of the vertical semicircular canals, it is difficult to support the idea that the pathology of the BPPV is localized in the posterior semi-circular canal alone.

Nystagmus in benign paroxysmal positional vertigo: a three-component analysis

Three-component analysis of nystagmus was carried out in 10 patients with benign paroxysmal positional vertigo (BPPV), focusing on the horizontal, vertical and torsional components, with the aid of a computerized eye movement analysis system. Using a pendular rotation stimulus we also measured three eye components of eye movement evoked from the vertical semicircular canals in 3 normal subject; two components (vertical and torsional) of nystagmus in patients with BPPV were compared with that of eye movements derived from the vertical semicircular canals. The time course of slow phase velocity of three components in BPPV patients was similar. In BPPV, the torsional component of eye movements was larger than that of the vertical component without obvious horizontal eye deviation. On the other hand, the vertical component from vertical semicircular canals was larger than that of the torsional component. From the view point of the vestibulo-ocular reflex, it is difficult to support the idea that the pathology of BPPV is localized only to the posterior semicircular canal.