Peripheral vestibular system of the otolithic device balloon and ellipsoidal bursa perceive linear acceleration. Current otolithic functional examinations include horizontal, vertical and torsional eye movements as well as psychophysiological conditions. Linear acceleration is generated by means of swings, sled-like devices, centrifuges, tilt chairs, etc. The equipment used for clinical examination must be robust, safe, practical and reproducible. It is also sensitive to otolithic hypofunction, especially on one side. Currently, only two tests meet these requirements: subjective vertical vision and vestibular evoked myogenic potentials. The other two more important tests are: deviated vertical axis rotation and centrifugal rotation test. [Subjective vertical (horizontal) vision: Examination of elliptical saccade function] 1. Physiological basis: A normal person can tune the luminous optic bar to vertical or horizontal in a totally dark room with an error of 2o or less. A study of patients with loss of vestibular dominance on one side revealed that: preoperatively, subjects adjusted the optic bar within the normal range. Postoperatively, all were deviated more than 15o to the affected side. They viewed the vertical optic bar as deviating to the healthy side. The direction of the optic bar was recovering at 6 weeks postoperatively, and there was a 4o deviation after 6 months. Thus, some degree of ipsilateral deviation of subjective vertical vision may persist long after vestibular innervation on one side. The cause of this misperception may be an apparent imbalance in afferent input from the otolith to the vestibular nucleus. Opponents of this mechanism argue that despite the loss of vestibular innervation on one side, the patient does not perceive the body as skewed and appears normal in the dark. In other words, the patient is not offsetting the body obliquity with visual obliquity, even though he or she is turning the optic bar to the affected side. Another possible cause of subjective vertical vision is torsional obliquity of the eye position. The ocular tilt response is a postural linkage response that includes cephalic deviation, convergent eye torsion, and downward strabismus, all of which are congruent. Following damage to one side of the peripheral vestibule, the patient may develop a transient tonic ocular tilt response to the affected side, including convergent ocular torsion. Tonic torsional ophthalmoplegia to the affected side with vertical line deviation to the affected side is present after a loss of innervation of one side of the vestibule. After a week of vestibular innervation on one side, there is a 15o torsional deviation to the affected side. The amplitude of torsion is closely related to the balance of the subjective vertical vision. Ocular torsion is closely related to subjective vertical vision. After one month, the equilibrium of ocular torsion and subjective vertical vision is half of that at one week. 4-5o ocular torsion and equilibrium of subjective vertical vision may be a permanent feature. Experimental studies confirm that ocular torsion eye position and balance of subjective vertical vision are closely related, and that ocular torsion produces perception that matches vision. The mechanism of ocular torsion in one side of the vestibular loss of innervation may be similar to that of spontaneous nystagmus. The resting potential of neurons in the vestibular nucleus on the injured side decreases due to the loss of primary afferents from the ipsilateral elliptical sac. It is generally believed that the elliptical capsule controls the tonic ocular torsion and compensates for the reverse rotation of the eye. 2. Vestibular lesions and subjective vertical vision: Clinical studies have shown that acute spontaneous one-sided peripheral vestibular lesions such as vestibular neuritis also fail to tune the optic bar to vertical or horizontal, always being biased to the affected side. Acute focal brainstem lesions also present with subjective vertical visual deviation. Lower brainstem lesions, including the vestibular nucleus, are deviated to the affected side; whereas cerebellar lesions involving the superior brainstem of the interstitial nucleus (Cajal nucleus) and affecting the cerebellar nodes, tune the optic bar to the healthy side. Most patients have a tonic deviation of the torsional eye position in the same direction as the subjective vertical vision. The amplitude of subjective vertical vision is not as closely associated with ocular torsion as in peripheral lesions, and may vary widely between eyes. If the lateral medullary infarct usually involves the vestibular nucleus, the outward ciliary torsion of the eye on the side of the lesion is greater than the inward ciliary torsion of the contralateral eye.3. Clinical significance: Accurate standardized measurements of subjective vertical vision can provide valuable diagnostic information. Deviation to the affected side suggests lesions of the affected vestibular end organ, vestibular nerve, or low brainstem; whereas deviation to the contralateral side is seen in lesions of the superior brainstem or caudal cerebellum. The greater the degree of deviation, the more extensive the lesion, and many patients will have some degree of residual deviation. Because the production of deviation is dependent on the tonic resting activity of neurons in the vestibular nucleus, subjective vertical visual examination is not indicated for bilateral symmetrical otolithic impairment. [Vestibular evoked myogenic potentials: examination of balloon function] 1. Physiological basis: monaural 0.1ms short acoustic stimulation (> 95dB nHL) elicits a short latency (8ms) tonic contraction of large amplitude in the ipsilateral sternocleidomastoid muscle, which is an inhibitory potential. Selective vestibular nerve resection eliminated the onset of positive and negative potentials peaking at 13ms (p13) and 23ms (p23), while severe sensorineural deafness was present. Patients can still have p13-p23 potentials even if they cannot hear short sounds. The posterior component has different characteristics from the p13-p23 potential and may not depend on vestibular afferents. Therefore, the p13-p23 potential is referred to as the vestibular evoked myogenic potential (VEMP). VEMP is 500-1000 times larger than ABR. The amplitude of VEMP is linearly correlated with short sound intensity and linearly correlated with sternocleidomastoid muscle activity. Conductive deafness can cause VEMP to disappear, a condition that can be elicited by tapping on the frontal bone conduction. Improper contraction of the sternocleidomastoid muscle decreases the amplitude of VEMP, and uncontrolled intensity of sternocleidomastoid activity yields erroneous results. the main evidence that VEMP originates from the balloon is that (1) the balloon is the most sound-sensitive part of the vestibular organ, probably because it is located just below the pedicle of the stirrup and is most susceptible to sound waves coming from the tympanic membrane, and (2) it is not only vestibular neurons sensitive to short sounds that respond to tilt. VEMP can be obtained indirectly by measuring the vestibular neck reflex, which is transmitted through the lateral vestibulospinal tract of the medial vestibular nucleus. the latency and absolute limitation of VEMP to one side suggests that it is mediated by a dual synaptic pathway and most likely the medial vestibulospinal tract. 2. Methods: VEMP Since VEMP is linearly related to short sound intensity, correct short sound measurements are required and corrected background EMG activity of the sternocleidomastoid muscle is recorded. absence of VEMPs or less than 50 mV may be due to conduction deafness and abnormal sternocleidomastoid contractile function. vEMP does not cause dizziness and 128 short sounds over 3 min are sufficient. completed. Superimposition of three averages usually gives a good result. The patient is examined in the prone position with head elevation to activate the sternocleidomastoid muscle. Unconscious patients, patients with neck pain, and other uncooperative patients cannot be examined. Binaural function can be derived by comparing VEMP. Smaller differences in latency may be due to changes in electrode placement or muscle anatomical variation. Three superimposed clinical screenings (128 times × 3, 100 dB) are sufficient. The effect of muscle activity differences can be excluded by comparison with corrected background EMG. A more accurate (and more time consuming) approach would be to vary the level of tonic activity and repeat the observation. 2.5:1 can be used as an indicator of low vestibular function on one side.3. Clinical applications: (1) Tullio’s phenomenon Tullio first described that sound can induce nystagmus and that strong human sound can also elicit nystagmus. When a patient presents with Tullio’s phenomenon, it is primarily a vibratory hallucination rather than vertigo. Vibratory hallucinations are caused by vertical torsional nystagmus, which should originate from the superior hemianopia. These patients may have different ear conditions. Some patients may suffer from stirrup pedicle overactivity or may have a cleft in the superior semicircular canal. The characteristic change in VEMP in these patients is an abnormally large VEMP and an abnormally low threshold. The threshold in normal subjects is generally 90-95 dB. in Tullio’s phenomenon. >20 dB. The amplitude of VEMP is >500 mV at 100-105 dB nHL. If 70-dB nHL can be elicited, suggesting the presence of Tullio’s phenomenon. (2) Vestibular neuritis-neurovaginitis and BPPV BPPV occurs within 3 months in 1/3 of patients after vestibular neuritis. it is noteworthy that VEMPs are normal in BPPV after vestibular neuritis. That is, normal VEMPs may be necessary for the appearance of BPPV after vestibular neuronitis. It may be that only the superior vestibular nerve, which innervates the superior vagus, is involved in these patients. In contrast, the inferior vestibular nerve innervates the posterior semicircular canal and balloon, and the presence of BPPV and VEMP in the posterior semicircular canal suggests that the inferior vestibular nerve is not involved. The presence of VOR in the posterior semicircular canal in some patients with vestibular neuritis supports this interpretation. (3) Auditory neuromas Most patients with auditory neuromas have hearing loss on one side, but only some patients present with vestibular ataxia. Because most auditory neuromas originate from the inferior vestibular nerve, VEMP may be absent or of low amplitude. Therefore, the importance of VEMP examination for auditory neuroma is that VEMP can still detect abnormalities even if ABR cannot be elicited and cold and heat tests function normally. Off vertical axix rotation】1. Basic principle: Off vertical axix rotation (OVAR) stimulates the otolithic organ by constantly changing the orientation between the subject and gravity. Constant velocity OVAR induces a sustained nystagmus with a slow-phase component velocity opposite to the direction of rotation. The slow-phase component velocity of this sustained nystagmus includes a periodic component-modulation component and a non-zero component-offset component. These two response components are the tools for OVAR evaluation of the otolith-ocular reflex. These two components are separately visible when the otolith-ocular reflex decays to zero. Sinusoidal OVAR is a method for evaluating the canal-ocular interaction. Animal experiments show that the modulation component relies on stimulation of the otolithic organ; the offset component relies on integration of the otolithic stimulus and the semicircular canal stimulus. This suggests that the offset component is partly due to the activity of the CNS velocity storage component when the OVAR is tilted 90o, the so-called parallel to the ground (EHA) rotation. the EHA rotation is cumbersome and it is more difficult for the patient to leave the instrument; therefore, the clinical application of this instrument is limited. In recent years, OVARs with a tilt angle of 30o or less have been applied. the method is easy to operate, and this device can also be used to rotate with the ground in a perpendicular axis. The ease with which the subject can leave the instrument is important because the OVAR is prone to vomiting and in some cases requires the patient to leave the instrument quickly. Constant velocity and sinusoidal stimulation are now used for the examination. Two examination modes are available: T- R mode and R-T mode, where the former tilts the subject (T) → rotates perpendicular to the ground (R) → canal-ocular reflex decay is complete → tilts the spool; the latter applies to constant velocity rotation (R) → canal-ocular reflex decay is complete, and then the otolith-ocular reflex is analyzed separately. 2. Standard values: Constant velocity OVAR produces a reliable modulation component and offset component, requiring a 30 o tilt angle and constant velocity of 60 o/sec. Low amplitude stimuli are not sufficient to elicit a recognizable otolith-eye response, at least in EOG. Application of more sensitive eye-movement recording methods such as magnetic search coils, available with low-intensity stimuli. the results obtained for R-T and T-R are consistent. Nausea was rarely observed, although the former was more likely to cause disorientation and produce rare hallucinations. Sinusoidal OVAR is less common than constant velocity OVAR nausea. The sinusoidal OVAR response contains a sinusoidal component at the frequency of the stimulus, and its high-frequency component is thought to be otolithogenic. Sinusoidal OVAR has a lower gain and smaller phase difference than sinusoidal rotation around the vertical axis and is thought to be an interaction between hemianopsia and otolithic stimulation.3. Clinical data: OVAR was applied to study two types of patients: (1) with surgically confirmed peripheral damage to one side of the vestibule, and (2) with cerebellar damage. The semicircular canal-ocular reflex components decayed in powers accompanied by a non-zero baseline, a modulated component was superimposed on these response components, and the offset component had a large amplitude when rotated toward the affected ear. The application of OVAR confirms the asymmetry of the offset component, which may reflect an asymmetry in the peripheral otolith function itself or an asymmetry in velocity storage caused by peripheral vestibular peripheral abnormalities on one side. Obviously, the modulation component is normal, suggesting that this response to one side of the vagus is sufficient. The inclusion of OVAR as a routine clinical evaluation of vestibular function based on these results alone is not sufficient, because the asymmetry of loss of peripheral vestibular function on one side is weak in OVAR. the clinical utility of OVAR remains to be further determined. The use of OVAR to study cerebellar abnormalities includes (1) a group of patients with periodic alternating nystagmus (PAN), which is localized in the cerebellar nodules or pendula, or in the brainstem vestibular inter-nuclear fibers, and (2) the evaluation of patients with olive brainstem cerebellar atrophy, whose modulation component is several times larger than normal, as shown by PAN studies. Several times larger than normal. This increase in the vestibulo-ocular reflex response is similar to the increase in the otolith-ocular reflex in patients with vestibulocerebellar lesions. It is clear that the cerebellar nodules or the suspensory plexus are important for the modulation of the otolith-eye reflex and the canal-eye reflex. OVAR in the second group of patients showed a slow sweep in oculomotor examination and nystagmus evoked by canal stimulation; also, a fast component was lacking in OVAR. In normal subjects, the fluctuation in intermediate eye position was small, whereas at this time it was large, making the eye position sometimes fixed to the left and sometimes to the right. The effect of post-rotation head position deflection on post-rotation nystagmus is correlated with the OVAR. This stimulus can be stimulated with an axis perpendicular to the ground (EVA). At the end of the rotation, the subject was allowed to tilt the head position or to stop the rotation by OVAR while the axis remained tilted. In either case, the subject is simultaneously stimulated by decelerated rotation-induced hallux valgus stimulation and otolith stimulation due to the angle between the tilt and the gravitational line. The time constant was shortened in normal subjects during post-rotation head deflection. Both animal and human studies have shown that damage to one side of the peripheral vestibule does not eliminate the short time constants during post-rotational head deflection. The PAN also loses the effect of post-rotational cephalic deflection. These studies suggest that OVAR is not a perfect method for evaluating the otolith-ocular reflex and further studies are needed. Centrifugal rotation test】1. Basic principle: The subject rotates at a certain distance from the Z-axis, and this rotation is composed of angular acceleration and two linear accelerations, namely tangential acceleration and centripetal acceleration. Tangential acceleration is a function of the rate of change of angular acceleration, while centripetal acceleration is a function of the instantaneous rotational velocity. Therefore, constant speed rotation has no angular acceleration and no tangential acceleration, only centripetal acceleration, a situation similar to rotating the head at a fixed angle. However, at non-constant angular velocities, such as sinusoidal rotation, both angular and tangential accelerations are present in addition to centripetal acceleration. The monkey caused an increase in VOR gain when rotating centrifugally at a centrifugal distance of 23 cm. The animal was placed in an orientation such that the tangential acceleration pointed to the X-axis of the animal. Particularly in the dark, the gain increased from 0.67 to 1.0 at a frequency of 1.0 Hz; there was no increase in gain when the animal’s tangential force was directed toward the Y-axis or in any direction at 0.5 Hz. The researchers also observed a decrease in gain during centrifugal rotation after the loss of innervation of one side of the otolith apparatus, with complete recovery within 8 weeks; no increase in gain was seen during centrifugal rotation after bilateral otolith removal. These studies suggest that the tangential acceleration perceived by the otoliths underlies the change in VOR gain during centrifugal rotation.2. Standard values: Standard values for normal human subjects have been studied in several studies, but with conflicting results.Benson and Th. Vieville found that 0.3 Hz and 1.0 Hz frequency stimuli, central rotation and eccentric oscillation did not show any abnormalities, but only one subject Gresty et al. observed an increased gain in centrifugal rotation compared to central rotation in normal human subjects with tangential forces pointing to the x-axis. As with the animal results, this gain was most pronounced at about 1 Hz. He also observed an increase in VOR gain when extending the neck and leaning forward so that the head was 30 cm away from the rotation axis. In particular, at 0.5 Hz and 1.2 Hz, the peak angular velocity was 60o/s, which corresponds to 0.1g peak tangential acceleration and 0.24g peak linear acceleration. The gain increase was significantly greater as the subjects imagined approaching the target. The latter is consistent with the notion that eye movements that compensate for linear head displacement are important when viewing a near target. As a function of head position in the center or centrifugally, the phase of the response was not altered. gresty et al. list several possible explanations for the increase in gain during centrifugal rotation: (1) non-visual enhancement of VOR autonomy (although the gain increase exceeds the level at which such effects are predictable), (2) the effect of neck position, and (3) otolithic stimulation. koizuka et al. used 90 cm off-axis centrifugal rotation with the head located in the tangential direction of the x-axis On centrifugal and eccentric rotation the head and neck positions were similar. They found that centrifugal rotation at a frequency of 0.64 Hz increased VOR gain in normal subjects and attributed this to ellipsoidal saccade stimulation.3. Clinical data: Study of patient centrifugal rotation showed that this test, although promising in its application, may not be a particularly practical clinical examination of the otolith-ocular reflex. Barratt et al. observed a significant asymmetry in VOR due to surgically confirmed peripheral vestibular lesions on one side compared to central rotation. However, the direction of positional nystagmus does not necessarily coincide with the direction of the effect of centrifugal rotation on nystagmus, and no abnormalities were seen during centrifugal rotation in patients with BPPV and other suspected otolithic abnormalities.Koizuka et al. studied Ménière’s disease and vestibular Ménière’s disease and found no increase in gain during centrifugal rotation in both patients during the exacerbation month. Therefore, it can be assumed that elliptical sac function is the same in both patients. These centrifugal rotation studies show that although the otolith-ocular reflex can be examined in this way, otolith function can only be evaluated by contrast canal-otolith response and simple semicircular canal stimulation. Further, the effect of proximity gaze cannot be underestimated. Centrifugal experiments are valuable for further research, but clinical use to evaluate the otolith-ocular reflex is imperfect.