Assessments of Subjective Visual Gravity and Spontaneous Nystagmus in Patients With Vestibular Neuritis.

OBJECTIVE: This study aimed to assess the correlation between the spontaneous nystagmus (SN) and the subjective visual vertical/horizontal (SVV/SVH) among patients with vestibular neuritis (VN) at the different head positions. STUDY DESIGN: Case-control study. SETTING: Affiliated Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine. METHODS: This study evaluated the SVV/SVH in both healthy subjects and patients with VN. These evaluations were performed in 5 different head positions: upright, 45° tilt to the left, 90° tilt to the left, 45° tilt to the right, and 90° tilt to the right. Additionally, the intensity of SN, as measured by slow-phase velocity, was recorded. RESULTS: In patients with VN, a significant correlation was observed between SN and SVV/SVH in an upright position. The intensity of SN was higher when the head was tilted 90° toward the affected side compared to other positions. The SVV/SVH displayed an ipsiversive shift, when the head was tilted toward both the lesion and unaffected sides, exhibiting a contraversive direction. Furthermore, the changes in position-induced SN were consistent with the displacements of SVV and SVH caused by head tilt. CONCLUSION: The presence of SN in patients with VN was observed to vary across different head position. These variations could potentially be attributed to the diverse activation patterns of the mechanical properties of otolith organs that are induced by head tilts.

Dynamic changes of otolith organ function before and after repositioning in patients with benign paroxysmal positional vertigo detected by virtual reality auxiliary technology: A cohort study.

Objectives: To dynamically investigate otolith function in patients with benign paroxysmal positional vertigo (BPPV) before, after, and 1 month after repositioning, and explore the possible compensation mechanisms. Methods: Thirty-six patients confirmed with BPPV (canal lithiasis) treated in our hospital between August 2020 and March 2021, as well as 36 health controls matched for age and gender (normal control group, NC group) were enrolled. For NC group, the virtual reality (VR) auxiliary static subjective visual vertical (SVV), subjective visual horizontal (SVH), and SVV of dynamic unilateral centrifugation (DUC), were measured at inclusion. For the BPPV group, visual analog scale (VAS) was used to assess the vertigo degree, while static SVV, SVH, and DUC were performed before, after, and 1 month after repositioning. First, we compare the deviations of SVV0/SVH0° when the subject's head is in the positive position, and SVV of DUC between BPPV and NC groups before repositioning, after which we compared the deviations in SVV45, SVV90, SVH45, SVH90°, and SVV of DUC between the affected and unaffected sides before repositioning. Finally, paired t-test was used to compare the VAS score, deviations in static SVV0, SVV45, SVV90, SVH0, SVH45, and SVH90°, and deviations in SVV of DUC before, after, and 1 month after repositioning. (Here, 0, 45, and 90° refer to the angle which the center axis of head deviates from the gravity line.). Results: SVV0 SVH0°, and SVV of DUC at 120 and 180°/s 0 significantly differed between BPPV and NC group before repositioning. The deviations in SVV45, SVV90, SVH45, SVH90°, and SVV of DUC at 120°/s-2 and 180°/s-4.5 did not significantly differ between bilateral sides in BPPV patients before repositioning. The deviation in SVH90° was significantly lower after repositioning than before. The deviation in SVH45° was significantly higher 1 month after repositioning than before. The deviation angle of SVV of DUC at 180°/s-0 was significantly lower after repositioning than before. The vertigo VAS score of patient with BPPV continued to decrease after repositioning. Conclusion: Before repositioning, the otolithic organ function of BPPV patients was obviously impaired, with no significant difference between the healthy and affected ear. After repositioning, there was a transient recovery of otolithic organ dysfunction followed by a sustained decline to similar levels to before repositioning.

Vestibular evoked myogenic potential may predict the hearing recovery in patients with unilateral idiopathic sudden sensorineural hearing loss.

Objective: This study investigates the association between vestibular function and prognosis in patients with unilateral idiopathic sudden sensorineural hearing loss (UISSNHL). Design: A retrospective analysis of 64 patients with UISSNHL was performed. Pure tone audiometry and vestibular function tests for otoliths and semicircular canals were performed to assess the influence of vestibular functional status on the outcome of patients with UISSNHL. Results: Patients with abnormal cervical vestibular evoked myogenic potential (cVEMP) or ocular vestibular evoked myogenic potential (oVEMP) responded less favorably to treatment. In the ineffective group, cVEMP was normal in four patients (6.3%) and oVEMPs in three (4.7%). Meanwhile, cVEMP was abnormal in 32 patients (50.0%) and oVEMP in 33 (51.6%). Better hearing recovery occurred in those with normal cVEMP (33.76 ± 15.07 dB HL improvement) or oVEMP (32.55 ± 19.56 dB HL improvement), but this was not the case in those with normal caloric tests. Patients with abnormalities in both cVEMP and oVEMP were less responsive to treatment and had worse hearing recovery than those with normal results in only one of the two tests. Conclusion: Abnormal oVEMP and/or cVEMP results indicate poor auditory outcomes in patients with UISSNHL. Patients with impaired otolith organ function are likely to have a larger and more severe pathological change in their inner ear.

High frequency hearing loss may act as a screening index evaluating otolith function in vertigo patients with normal semi-circular canal function.

Objective: To investigate whether otolith dysfunction is related to hearing impairment in vertigo patients with normal semicircular canal function, and to clarify the types of hearing impairment that may be related to otolith organ damage. Methods: The demographic data, pure tone threshold audiometry (PTA) results (air-conduction), data of bithermal and video-head impulse test (vHIT), and vestibular evoked myogenic potential (VEMP) results (reaction threshold, P1-N1 amplitude) of patients with vertigo in outpatient clinic from April 2017 to January 2020 were collected. The clinical records of 51 vertigo patients with normal semicircular canal function were included in this study. Low-frequency, speech-frequency, high-frequency, full-frequency PTA were defined as the average of PTA in different frequency bands, respectively (low: 0.125, 0.25, 0.5 kHz; speech: 0.5, 1, 2 kHz, high: 4, 8 kHz, full 0.125-8 kHz). The correlations between hearing impairment in different frequency bands and otolith function impairment were analyzed. Results: The mean thresholds of 51 patients (102 ears) in low-PTA, speech-PTA, high-PTA, full-PTA were 20.95 ± 6.01, 21.92 ± 6.90, 40.12 ± 17.47, 26.97 ± 8.53 dB nHL, respectively. Among 102 ears, 87 ears (85.3%) could elicit c-VEMP waveforms and 65 ears (63.7%) had o-VEMP waveforms. The mean threshold and P1-N1 amplitude of c-VEMP were 83.10 ± 6.96 dB nHL and 176.79 ± 103.10 uV, while those of o-VEMP were 87.92 ± 5.99 dB nHL and 21.45 ± 32.22 uV. The mean threshold in high-PTA was significantly linearly correlated with c-VEMP threshold (P = 0.01) and P1-N1 amplitude (P = 0.028). There were not significant linear correlations between the mean threshold in each frequency band of PTA and o-VEMP threshold (low-PTA: P = 0.266, speech-PTA: P = 0.33, high-PTA: P = 0.311) or P1-N1 amplitude (low-PTA: P = 0.414, speech-PTA: P = 0.069, high-PTA: P = 0.08). Conclusions: There is a positive linear correlation between saccule dysfunction and high-frequency hearing impairment in vertigo patients with normal semi-circular canal function. High frequency hearing loss can be expected in patients who have saccular damage. It suggests that high frequency hearing loss in PTA may act as a screening index that otolith organ function should be comprehensively evaluated.

Clinical characteristics of vestibular evoked myogenic potentials in children with recurrent vertigo of childhood.

OBJECTIVE: To explore the possible pathogenesis of recurrent vertigo of childhood (RVC) and the clinical diagnosis value of vestibular-evoked myogenic potentials (VEMPs). METHODS: The clinical data of 19 children (5.95 ± 0.38 years) diagnosed with RVC and 17 normal children (5.35 ± 0.31 years) enrolled in the control (NC) group from April 2017 to February 2021 was collected and analyzed. All subjects were tested for both cervical VEMP (cVEMP) and ocular VEMP (oVEMP). The elicit rate, thresholds, N1 latency, P1 latency, interval, amplitude, and amplitude asymmetry ratio (AAR) of VEMPs were compared and analyzed between the two groups. RESULTS: (1) The elicit rates of cVEMP and oVEMP have no significant difference between the two groups (P > 0.05). (2) The thresholds of cVEMP and oVEMP in the RVC group were higher than that in the NC group (P < 0.05). (3) The N1 latency of cVEMP in the RVC group was longer than that in the NC group (P < 0.05). The P1 latency of cVEMP and latencies of oVEMP have no significant difference between the two groups (P > 0.05). (4) The interval of cVEMP in the RVC group was longer than that in the NC group (P < 0.05), while the interval of oVEMP has no significant difference between the two groups (P > 0.05). (5) The amplitude of cVEMP in the RVC group was higher than that in the NC group (P < 0.05), while the amplitude of oVEMP was similar in the two groups (P > 0.05). (6) The AAR values of oVEMP and cVEMP were similar in the two groups (P > 0.05). CONCLUSIONS: The elicit rates of VEMPs in children with RVC did not differ from that of normal children, but the thresholds were all increased, suggesting reduced sensitivity of the otolith organ and vestibular nerve conduction pathways. The P1 latency of cVEMP was normal in children with RVC, but N1 latency and interval of cVEMP were increased, we finally reached a conclusion that there might be potential impairment in the inferior vestibular nerve and the subsequent nerve conduction pathway in RVC.

A Reversal in Hair Cell Orientation Organizes Both the Auditory and Vestibular Organs.

Sensory hair cells detect mechanical stimuli with their hair bundle, an asymmetrical brush of actin-based membrane protrusions, or stereocilia. At the single cell level, stereocilia are organized in rows of graded heights that confer the hair bundle with intrinsic directional sensitivity. At the organ level, each hair cell is precisely oriented so that its intrinsic directional sensitivity matches the direction of mechanical stimuli reaching the sensory epithelium. Coordinated orientation among neighboring hair cells usually ensures the delivery of a coherent local group response. Accordingly, hair cell orientation is locally uniform in the auditory and vestibular cristae epithelia in birds and mammals. However, an exception to this rule is found in the vestibular macular organs, and in fish lateral line neuromasts, where two hair cell populations show opposing orientations. This mirror-image hair cell organization confers bidirectional sensitivity at the organ level. Here I review our current understanding of the molecular machinery that produces mirror-image organization through a regional reversal of hair cell orientation. Interestingly, recent evidence suggests that auditory hair cells adopt their normal uniform orientation through a global reversal mechanism similar to the one at work regionally in macular and neuromast organs. Macular and auditory organs thus appear to be patterned more similarly than previously appreciated during inner ear development.

Ocular counter-rolling in scuba divers with motion sickness.

OBJECTIVE: Motion sickness (MS) is a familiar condition to scuba divers. The purpose of this study was to compare otolith organ function of scuba divers who have MS to those without MS. METHOD: Video-oculography (VOG) goggles were used to measure video ocular counter-roll (vOCR) in 50 healthy scuba divers with no vestibular pathology. Divers with MS (n = 30) had Graybiel motion sickness (GMS) scores of ≥1 point, and divers without MS (n = 20) had GMS scores of 0. Divers with MS also completed the Motion Sickness Susceptibility Questionnaire short form (MSSQs). For all divers, otolith-ocular function of both ears was tested separately via vOCR testing, which was performed during 30° head tilt. An R-L side asymmetry ratio for vOCR values (%OCRA) was compared to divers' static OCR. RESULTS: MSSQs and %OCRA scores differed significantly (p<0.01and p<0.001, respectively) between divers with MS and divers without MS. Their %OCRA scores and severity of MS were significantly correlated. Female divers were more susceptible to MS. ROC analysis for %OCRA revealed that the AUC for divers with MS and divers without MS was 0.8967 (95% CI, 0.8114 to 0.9819), the specificity was 1.000, and the sensitivity was 0.700, with a cutoff value of 45.946. CONCLUSION: Physiological differences between R-L otolith organ function could affect the severity and susceptibility to MS. Female hormones may also increase susceptibility to MS. Thus, MS may be a physiological phenomenon induced by functional ear differences in the absence of pathology. As MS is caused by multiple factors, otolaryngologists need to consider various causative factors beyond those related to otolith organ function in scuba divers with MS.

Stabilization of Gaze during Early Xenopus Development by Swimming-Related Utricular Signals.

Locomotor maturation requires concurrent gaze stabilization improvement for maintaining visual acuity [1, 2]. The capacity to stabilize gaze, in particular in small aquatic vertebrates where coordinated locomotor activity appears very early, is determined by assembly and functional maturation of inner ear structures and associated sensory-motor circuitries [3-7]. Whereas utriculo-ocular reflexes become functional immediately after hatching [8, 9], semicircular canal-dependent vestibulo-ocular reflexes (VORs) appear later [10]. Thus, small semicircular canals are unable to detect swimming-related head oscillations, despite the fact that corresponding acceleration components are well-suited to trigger an angular VOR [11]. This leaves the utricle as the sole vestibular origin for swimming-related compensatory eye movements [12, 13]. We report a remarkable ontogenetic plasticity of swimming-related head kinematics and vestibular end organ recruitment in Xenopus tadpoles with beneficial consequences for gaze-stabilization. Swimming of older larvae generates sinusoidal head undulations with small, similar curvature angles on the left and right side that optimally activate horizontal semicircular canals. Young larvae swimming causes left-right head undulations with narrow curvatures and strong, bilaterally dissimilar centripetal acceleration components well suited to activate utricular hair cells and to substitute the absent semicircular canal function at this stage. The capacity of utricular signals to supplant semicircular canal function was confirmed by recordings of eye movements and extraocular motoneurons during off-center rotations in control and semicircular canal-deficient tadpoles. Strong alternating curvature angles and thus linear acceleration profiles during swimming in young larvae therefore represents a technically elegant solution to compensate for the incapacity of small semicircular canals to detect angular acceleration components.

Correlation between High-Resolution Computed Tomography Scan Findings and Histological Findings in Human Vestibular End Organs and Surgical Implications.

BACKGROUND: Histological study of vestibular end organs has been challenging due to the difficulty in preserving their structures for histological analysis and due to their complex geometry. Recently, radiology advances have allowed to deepen the study of the membranous labyrinth. SUMMARY: A review and analysis of surgical implications related to the anatomy of the vestibular end organ is performed. Radiological advances are key in the advancement of the knowledge of the anatomy and pathology of the vestibule. Thus, application of such knowledge in the development or improvement of surgical procedures may facilitate the development of novel techniques. Key Messages: During the last few decades, the knowledge of the anatomy of the auditory system through histology and radiology had improved. Technological advances in this field may lead to a better diagnosis and therapeutic approach of most common and important diseases affecting the inner ear.

Semicircular Canal Influences on the Developmental Tuning of the Translational Vestibulo-Ocular Reflex.

Vestibulo-ocular reflexes (VORs) rely on neuronal computations that transform vestibular sensory signals into spatio-temporally appropriate extraocular motor commands. The motoneuronal discharge for contractions of the superior oblique eye muscle during linear translation derives from a utricular epithelial sector that is spatially aligned with the pulling direction of this muscle. In Xenopus laevis, the alignment is gradually achieved during larval development and requires motion-related semicircular canal afferent activity. Here, we studied the origin of semicircular canal and utricular signals responsible for the establishment and maturation of the extraocular motor response vector. Experiments were conducted on semi-intact preparations of Xenopus tadpoles before and after unilateral transection of the VIIIth nerve and in preparations of animals in which semicircular canal formation was prevented on one side by the injection of hyaluronidase into the otic capsule prior to the establishment of the tubular structures. Unilateral VIIIth nerve sections revealed that the excitation underlying the contraction of the superior oblique eye muscle during horizontal linear acceleration and clockwise/counter-clockwise roll motion derives exclusively from the utricle and the posterior semicircular canal on the ipsilateral side. In contrast, the developmental constriction of the otolith response vector depends on signals from the posterior semicircular canal on the contralateral side. These latter signals suppress directionally incorrect components that derive from the utricular sector perpendicular to the superior oblique eye muscle. This directional tuning complies with a stabilization of spatially correct utricular inputs that are aligned with the extraocular motor target muscle. In addition, misaligned signals are concurrently suppressed by semicircular canal-related commissural pathways from the contralateral side and through local interneuronal inhibitory circuits within the ipsilateral vestibular nuclei.

Special Anatomic Considerations in Otosclerosis Surgery.

The anatomy of the vestibular organs together with considerations of the middle and inner ear anatomy relevant to stapes surgery is discussed. An archival collection of macerated and freshly frozen human temporal bones underwent micro-computed tomography (CT) with subsequent volume-rendering. Three-dimensional (3D) reconstructions and the topographic anatomy of the oval window were considered. Micro-CT and 3D rendering revealed the relationship between the otolith organs and the oval window. Anatomic variations were extensive and included the distance between the footplate and the reconstructed macula margins. A "no-go" zone is suggested for the surgeon to avoid injury during stapes surgery.

Effects of Head Position on Perception of Gravity in Vestibular Neuritis and Lateral Medullary Infarction.

OBJECTIVE: Internal representation of gravity can be quantified by measuring the subjective visual vertical (SVV). Modulation of verticality perception during head tilts may be perturbed in vestibular disorders causing SVV tilts in the upright head position. This study aimed to determine the influence of head tilts on the estimation of SVV in acute vestibular disorders. METHODS: We measured the SVV in 37 patients with acute vestibular symptoms due to unilateral vestibular neuritis (VN) (n = 28) and lateral medullary infarction (LMI) (n = 9). Measurements of the SVV were performed under head upright, head tilt 30° and 60° in each direction. Seventeen normal subjects served as the control. RESULTS: In controls, head tilt of 30° produced a contraversive shift of the SVV (the E-effect), and head tilt of 60° generated an ipsiversive shift (the A-effect). Patients with VN showed only the A-effect irrespective of the direction and amplitude of head tilt. Patients with LMI could estimate earth verticality accurately during head tilts. Patients with VN during the recovery phase showed the patterns of SVV modulation similar to those observed in the controls either with head upright or tilted. CONCLUSION: Given the absence of the E-effect in acute VN, the peripheral otolithic inputs appear to be essential in the perception of earth vertical during small static head tilts.

Adaptation of the vertical vestibulo-ocular reflex in cats during low-frequency vertical rotation.

OBJECTIVE: We examined plastic changes in the vestibulo-ocular reflex (VOR) during low-frequency vertical head rotation, a condition under which otolith inputs from the vestibular system are essential for VOR generation. METHODS: For adaptive conditioning of the vertical VOR, 0.02Hz sinusoidal pitch rotation for one hour about the earth's horizontal axis was synchronized with out-of-phase vertical visual stimulation from a random dot pattern. RESULTS: A vertical VOR was well evoked when the upright animal rotated around the earth-horizontal axis (EHA) at low frequency due to the changing gravity stimulus and dynamic stimulation of the otoliths. After adaptive conditioning, the amplitude of the vertical VOR increased by an average of 32.1%. CONCLUSION: Our observations showing plasticity in the otolithic contribution to the VOR may provide a new strategy for visual-vestibular mismatch training in patients with otolithic disorders. This low-frequency vertical head rotation protocol also provides a model for investigating the mechanisms underlying the adaptation of VORs mediated by otolith activation.

Is Alteration of Tuning Property in Cervical Vestibular-Evoked Myogenic Potential Specific for Ménière's Disease?

OBJECTIVE: The aim of this study is to show sensitivity and specificity of cervical vestibular-evoked myogenic potential (cVEMP) tuning property test to Ménière's disease (MD) in comparison with healthy controls (HC) and patients with other vestibular diseases. SUBJECTS: Totally 92 subjects (50 women and 42 men, 20-77 years of age) were enrolled in this study. Subjects were composed of 38 definite unilateral MD patients, 11 unilateral benign paroxysmal positional vertigo patients, 14 vestibular migraine patients, 19 unilateral vestibular neuritis patients, and 10 HC. METHODS: The subjects underwent cVEMP testing to 500 and 1,000 Hz short tone bursts (125 dBSPL). The corrected amplitudes of the first biphasic responses (p13-n23) (cVEMP) were measured. Then, a tuning property index (the 500-1,000 Hz cVEMP slope) was calculated. RESULTS: The area of under the ROC curve (AUC) was 0.75 in comparison with other vestibular disease patients, while AUC was 0.77 in comparison with other vestibular disease patients plus HC. The best cutoff point of the 500-1,000 Hz cVEMP slope was -19.9. Sensitivity of the tuning property test to MD was 0.74, while specificity was 0.76 to other vestibular disease patients. CONCLUSION: The tuning property test of cVEMP is useful as a screening test of MD.

Do patients with Ménière's disease have attacks of syncope?

The aim of the present study was to evaluate the prevalence and associated factors for syncope among patients with Ménière's disease (MD). An attack of syncope was defined as a sudden and transient loss of consciousness, which subsides spontaneously and without a localizing neurological deficit. The study used an across-sectional survey design. Information from a database consisting of 961 individuals was collected from the Finnish Ménière Association. The data contained case histories, general health-related quality of life (HRQoL), and impact measurements of the complaints. In the current study sample, syncope occurred in 12.3% of the patients with MD. It was more prevalent among elderly persons and among those with a longer duration of MD. Syncope was significantly associated with disturbances of otolith function reflected as Tumarkin attacks, gait and balance problems, environmental change of pressure, and physical strain. It was also associated with visual blurring; in fact, patients with otolith dysfunction in MD often experience visual field changes. It was also associated with headache, but not with migraine. Syncope was experienced as frightening and HRQoL was significantly worsened. The patient had higher anxiety scores, and suffered more from fatigue. The results demonstrate that neurally mediated syncope occurs in patients with an advanced form of MD who suffer from Tumarkin attacks due to failure in otolith function. The mechanism seems to be triggered through the vestibular sympathetic reflex when the otolith system fails due to disrupted utricular otolithic membrane mediate erroneous positional information from the otolith organ to the vasomotor centres in the brain stem and medulla.

Effect of Noisy Galvanic Vestibular Stimulation on Ocular Vestibular-Evoked Myogenic Potentials to Bone-Conducted Vibration.

OBJECTIVE: Galvanic vestibular stimulation (GVS) delivered as zero-mean current noise (noisy GVS) has been shown to improve static and dynamic postural stability probably by enhancing vestibular information. The purpose of this study was to examine the effect of an imperceptible level noisy GVS on ocular vestibular-evoked myogenic potentials (oVEMPs) in response to bone-conducted vibration (BCV). MATERIALS AND METHODS: oVEMPs to BCV were measured during the application of white noise GVS with an amplitude ranging from 0 to 300 µA [in root mean square (RMS)] in 20 healthy subjects. Artifacts in the oVEMPs caused by GVS were reduced by inverting the waveforms of noisy GVS in the later half of the stimulus from the one in the early half. We examined the amplitudes of N1 and N1-P1 and their latencies. RESULTS: Noisy GVS significantly increased the N1 and N1-P1 amplitudes (p < 0.05) whereas it had no significant effects on N1 or P1 latencies (p > 0.05). Noisy GVS had facilitatory effects in 79% of ears. The amplitude of the optimal stimulus was 127 ± 14 µA, and it increased the N1 and N1-P1 amplitude by 75.9 ± 15% and 47.7 ± 9.1%, respectively, as compared with 0 µA session (p < 0.05). CONCLUSION: Noisy GVS can increase the amplitude of oVEMPs to BCV in healthy subjects probably via stochastic resonance. The results of the present study suggest that noisy GVS may improve static and dynamic postural stability by enhancing the function of the vestibular afferents.

Ontogenetic Development of Vestibulo-Ocular Reflexes in Amphibians.

Vestibulo-ocular reflexes (VOR) ensure gaze stability during locomotion and passively induced head/body movements. In precocial vertebrates such as amphibians, vestibular reflexes are required very early at the onset of locomotor activity. While the formation of inner ears and the assembly of sensory-motor pathways is largely completed soon after hatching, angular and translational/tilt VOR display differential functional onsets and mature with different time courses. Otolith-derived eye movements appear immediately after hatching, whereas the appearance and progressive amelioration of semicircular canal-evoked eye movements is delayed and dependent on the acquisition of sufficiently large semicircular canal diameters. Moreover, semicircular canal functionality is also required to tune the initially omnidirectional otolith-derived VOR. The tuning is due to a reinforcement of those vestibulo-ocular connections that are co-activated by semicircular canal and otolith inputs during natural head/body motion. This suggests that molecular mechanisms initially guide the basic ontogenetic wiring, whereas semicircular canal-dependent activity is required to establish the spatio-temporal specificity of the reflex. While a robust VOR is activated during passive head/body movements, locomotor efference copies provide the major source for compensatory eye movements during tail- and limb-based swimming of larval and adult frogs. The integration of active/passive motion-related signals for gaze stabilization occurs in central vestibular neurons that are arranged as segmentally iterated functional groups along rhombomere 1-8. However, at variance with the topographic maps of most other sensory systems, the sensory-motor transformation of motion-related signals occurs in segmentally specific neuronal groups defined by the extraocular motor output targets.

Vestibular animal models: contributions to understanding physiology and disease.

Our knowledge of the vestibular sensory system, its functional significance for gaze and posture stabilization, and its capability to ensure accurate spatial orientation perception and spatial navigation has greatly benefitted from experimental approaches using a variety of vertebrate species. This review summarizes the attempts to establish the roles of semicircular canal and otolith endorgans in these functions followed by an overview of the most relevant fields of vestibular research including major findings that have advanced our understanding of how this system exerts its influence on reflexive and cognitive challenges encountered during daily life. In particular, we highlight the contributions of different animal models and the advantage of using a comparative research approach. Cross-species comparisons have established that the morpho-physiological properties underlying vestibular signal processing are evolutionarily inherent, thereby disclosing general principles. Based on the documented success of this approach, we suggest that future research employing a balanced spectrum of standard animal models such as fish/frog, mouse and primate will optimize our progress in understanding vestibular processing in health and disease. Moreover, we propose that this should be further supplemented by research employing more "exotic" species that offer unique experimental access and/or have specific vestibular adaptations due to unusual locomotor capabilities or lifestyles. Taken together this strategy will expedite our understanding of the basic principles underlying vestibular computations to reveal relevant translational aspects. Accordingly, studies employing animal models are indispensible and even mandatory for the development of new treatments, medication and technical aids (implants) for patients with vestibular pathologies.

Clinical application of vestibular evoked myogenic potential (VEMP).

The author reviewed clinical aspects of vestibular evoked myogenic potentials (VEMPs). Now two types of VEMPs are available. The first one is cervical VEMP, which is recorded in the sternocleidomastoid muscle and predominantly reflects sacculo-collic reflex. The other is ocular VEMP, which is usually recorded below the lower eye lid and predominantly reflects utriculo-ocular reflex. VEMPs play important roles not only for assessment of common vestibular diseases but also for establishment of new clinical entities. Clinical application in Meniere's disease, vestibular neuritis, benign paroxysmal positional vertigo, vestibular migraine, idiopathic otolithic vertigo, and central vertigo/dizziness was reviewed.

Is otolithic vertigo accompanied by hearing loss caused by sacculocochlear endolymphatic hydrops?

CONCLUSION: Otolithic vertigo is sometimes accompanied by hearing loss. Otolithic vertigo accompanied by hearing loss seems to be caused by sacculocochlear endolymphatic hydrops. OBJECTIVES: To clarify the lesion site and pathophysiology of otolithic vertigo (OV) accompanied by hearing loss. METHODS: The clinical records of four patients (two men and two women) that had been diagnosed with OV accompanied by hearing loss according to pre-determined diagnostic criteria were reviewed. RESULTS: The patients' main symptoms involved a sensation of movement in the pitch plane. All of the patients had low frequency-dominant hearing loss and either exhibited decreased cervical vestibular evoked myogenic potentials (cVEMP) or did not produce cVEMP. Two patients produced normal ocular VEMP (oVEMP). Caloric tests obtained normal results in all patients.