Asymmetry and tuning shift of the cervical vestibular evoked myogenic potential indicate saccular dysfunction in idiopathic normal pressure hydrocephalus.

OBJECTIVE: The purpose of this study was to investigate the effects of excessive cerebrospinal fluid (CSF) retention on the peripheral vestibular function and the inner ear fluid in patients with idiopathic normal pressure hydrocephalus (iNPH). METHODS: In 25 patients with iNPH (14 females, age 65-88 years), cervical vestibular evoked myogenic potential (cVEMP) was measured before the spinal tap test. The asymmetry ratios (ARs) and tuning properties in 500 Hz and 1,000 Hz short-tone burst stimuli of cVEMP were evaluated. Furthermore, cVEMP was measured in an age-matched control group of 12 non-iNPH patients. RESULTS: Seven (28%) iNPH patients exhibited a cVEMP asymmetry (AR > 33%). cVEMP tuning was significantly shifted to a higher frequency in the iNPH group than in the age-matched control group. CONCLUSIONS: One-fourth of patients with iNPH had obvious saccular dysfunction. A high rate of a shift in cVEMP tuning in the iNPH group indicated that excessive CSF accumulation propagated to the endolymph and perilymph. SIGNIFICANCE: Saccular dysfunction might be one of the possible causes of imbalance in iNPH, and the shift in cVEMP tuning may be a determining factor in the diagnosis and treatment strategy.

Characteristic manifestation of ocular and cervical vestibular evoked myogenic potentials findings in severe obstructive sleep apnea patients.

BACKGROUND: Studies of saccular and utricular function in patients with obstructive sleep apnea (OSA) are rare. We noticed that some OSA patients also had positive results in vestibular function tests, and this inspired our interest in exploring the vestibular function patterns of OSA patients. OBJECTIVES: To investigate otolithic organ function in severe OSA patients who lack vestibular symptoms and systemic disease. MATERIAL AND METHODS: 32 patients (64 ears) with severe OSA and 22 healthy controls (44 ears) were enrolled. The ocular and cervical vestibular-evoked myogenic potentials (oVEMP and cVEMP) and the caloric test were recorded and analyzed. RESULTS: The response rates of oVEMP (73.4%) and cVEMP (82.8%) in patients with severe OSA were significantly lower than those in controls. In oVEMP, elevated thresholds (p = .002), decreased n1-p1 amplitudes (p < .001), prolonged n1 latencies (p < .001) were observed. In cVEMP, the elevation of thresholds (p < .001), decrease in p1-n1 amplitudes (p < .001), and n1-p2 amplitudes (p < .001), prolongation of p1 latencies (p = .003) were observed. No significant difference in the caloric test was found between the two groups. CONCLUSIONS AND SIGNIFICANCE: Disappearance or impairment of VEMPs could be observed in patients with severe OSA, and reflects different degrees of impairment in the utricle and saccule.

Saccular function evolution related to cochlear implantation in hearing impaired children.

Vestibular sensorial input is essential for psychomotor development of the very small children. In consequence, possible vestibular impairment induced by cochlear implantation in deaf children could affect the balance and walking learning process. Some of cochlear implanted children can present congenital vestibular deficit. The anatomical and embryological relation between auditory and vestibular system explains why congenital neurosensorial hearing loss may associate vestibular impairment. The cochlear implant surgery presents a vestibular lesion risk. Bilateral vestibulopathy, as it appears in early childhood, has a poor prognosis for the psychomotor and cognitive development. Even probably rare, bilateral vestibulopathy induced by simultaneous bilateral cochlear implantation can delay the acquisition of motor skills. This pathology can be avoided by an appropriate surgical indication related to the vestibular preoperative status. This study reports the vestibular saccular functional modifications after the cochlear implantation in children. The cervical vestibular evoked myogenic potentials (cVEMPs) were performed in children before and after the cochlear implantation. Since previous studies report different vestibular impairment related to the portelectrode insertion approach, another objective of our study was to assess the saccular postoperative status depending of the insertion by cochleostomy (CO) or through the round window (RW). We performed cVEMPs for 80 patients (135 cochlear implanted ears) before and after cochlear implantation. We have detected preoperative saccular areflexia in 33 (24.4%) ears. In the group of 102 (75.6%) ears with preoperative normal saccular function, 72 (70.6%) ears preserved the cVEMP response after the surgery, while in 30 (29.4%) ears the cVEMP response was lost. Reporting our findings to the portelectrode insertion method, we found normal saccular function in 73.3% of the cochlear implanted ears by RW surgical approach and in 68.42% ears by CO approach. These results suggest that the RW portelectrode insertion is the recommended strategy in order to avoid the saccular vestibular impairment.

The acoustically evoked short latency negative response (ASNR) in a unilaterally deaf cat with histologically-confirmed cochleosaccular degeneration.

BACKGROUND: A negative potential is occasionally recorded in humans and animals with profound deafness during brainstem auditory evoked potential (BAER) tests if loud intensities are used. This acoustically evoked short latency negative response (ASNR) is hypothesized to be of saccular origin. The sensitivity to sound of vestibular end organs is also used to produce vestibular evoked myogenic potentials (VEMP), a test that evaluates vestibular function. The same saccular origin is accepted also for VEMP. CASE PRESENTATION: A neutered male white domestic short hair cat presented with profound deafness and an ASNR in the left ear during BAER test performed when he was 8 months old. BAER tracings were substantially unchanged at the age of 12 years, immediately before euthanasia that was requested by the owner for the presence of an unrelated neoplastic disorder. The cat underwent a complete post-mortem necropsy including histopathology of the middle and inner ears. Histopathologic results confirmed the presence of a cochleosaccular degeneration of the left ear while the cochlea and sacculus of the right ear and the utriculus and semicircular canals of both ears were histologically normal. CONCLUSIONS: This case report describes the auditory and histopathologic findings of a cat that showed an ASNR during BAER test despite the presence of cochleosaccular deafness. These results confirm that a saccular origin for the ASNR in this case, and in general in cats and dogs with congenital deafness associated with white pigmentation, is improbable. The hypothesis that the sacculus is the vestibular end organ responsible for the generation of the ASNR and VEMP in humans comes mainly from animal studies. The findings in this report may change the clinical interpretation of the results of BAER and VEMP not only in companion animals, but in humans as well.

Assessment of Vestibular Function in Adults with Prelingual Hearing Loss Using c/oVEMP Tests.

OBJECTIVES: The aim of the present study was to compare the vestibular system integrity of individuals with normal hearing with that of prelingual hearing impaired individuals. It is well known that ocular vestibular evoked myogenic potentials (oVEMPs) reflect utricular function, whereas cervical vestibular evoked myogenic potentials (cVEMPs) reflect saccular function. Therefore, oVEMP and cVEMP tests were applied to evaluate the vestibular system integrity of hearing impaired individuals participating in the research. MATERIALS AND METHODS: The study group consisted of sensorineural prelingual hearing-loss volunteers aged from 18 to 60 years, whereas the control group consisted of age- and gender-matched healthy volunteers. cVEMP and oVEMP tests were performed to evaluate the integrity of the vestibular system, and the results were compared with those of the control group. RESULTS: The study included 20 (76.9%) women and 6 (23.1%) men in the study group; on the other hand, the control group consisted of 19 (73.1%) women and 7 (26.9%) men. There was a difference between the study group and the control group when oVEMP and cVEMP responses were compared, and the response percentage was higher in the control group. The response rates of oVEMP and cVEMP in patients with prelingual hearing loss were 44.2% and 59.6%, respectively. There was also a statistically significant difference between the groups for oVEMP amplitude and cVEMP P1 latency (p≤0.05). CONCLUSION: These findings suggest that prelingual hearing loss is related to both utricular and saccular dysfunctions. However, oVEMPs were more often abnormal in prelingual deaf patients than cVEMPs, suggesting that utricular dysfunction may be more common than saccular dysfunction.

How sacculo-collic function assessed by cervical vestibular evoked myogenic Potentials correlates with the quality of postural control in hearing impaired children?

OBJECTIVE: Functional integrity of vestibular end organs is essential for gaze stabilization, dynamic visual acuity, postural control and spatial orientation. Some authors hypothesized on the importance of saccules for postural control and motor development in children, including achievements such as standing up and walking. The purpose of this article was to observe how saccular dysfunction assessed by cervical Vestibular Evoked Myogenic Potentials (cVEMPs) correlates with the quality of postural control in non-syndromic deaf children. METHOD: Seventy-six non-syndromic hearing-impaired children were retrospectively included. Sacculo-collic pathway was assessed with cVEMPs elicited in bone conduction. The response was quoted "normal" if a reproducible wave P13-N23 of at least 50µV in amplitude was present, if not, it was quoted "absent". The sample was divided in 3 groups depending on the presence of the sacculo-collic responses: normal bilateral group (Group 1), normal unilateral (Group 2) and absent bilaterally group (Group 3). Motor assessment was achieved with Movement Assessment Battery for Children, second edition (MABC-2). Postural control (PC) was assessed using the dynamic Balance Quest platform. The scores obtained with MABC-2, and the postural parameters recorded on the Balance Quest platform (sway of Centre of Pressure and spectral power index) were analyzed and compared throughout the groups. RESULTS: Group 1 (normal bilateral) showed the best scores regarding motor abilities and postural stability within available normative data. Group 3 (absent bilateral) had the lowest motor and postural control skills. A good correlation between the scores obtained by MABC-2 motor test and dynamic posturography (Balance Quest) was observed. CONCLUSIONS: The presence of at least one sacculo-collic response would predict satisfactory static and dynamic motor and postural control skills in non-syndromic hearing-impaired children. MABC-2 and Dynamic Posturography Balance Quest appears reliable and comparable tools for PC assessment in hearing impaired children. In the light of these results, it appears that in young children candidates for uni- or bilateral CI whose walking is not yet acquired, should receive a vestibular assessment before surgery to avoid the risk of bilateral sacculo-collic function impairment.

Intense noise exposure alters peripheral vestibular structures and physiology.

The otolith organs play a critical role in detecting linear acceleration and gravity to control posture and balance. Some afferents that innervate these structures can be activated by sound and are at risk for noise overstimulation. A previous report demonstrated that noise exposure can abolish vestibular short-latency evoked potential (VsEP) responses and damage calyceal terminals. However, the stimuli that were used to elicit responses were weaker than those established in previous studies and may have been insufficient to elicit VsEP responses in noise-exposed animals. The goal of this study was to determine the effect of an established noise exposure paradigm on VsEP responses using large head-jerk stimuli to determine if noise induces a stimulus threshold shift and/or if large head-jerks are capable of evoking VsEP responses in noise-exposed rats. An additional goal is to relate these measurements to the number of calyceal terminals and hair cells present in noise-exposed vs. non-noise-exposed tissue. Exposure to intense continuous noise significantly reduced VsEP responses to large stimuli and abolished VsEP responses to small stimuli. This finding confirms that while measurable VsEP responses can be elicited from noise-lesioned rat sacculi, larger head-jerk stimuli are required, suggesting a shift in the minimum stimulus necessary to evoke the VsEP. Additionally, a reduction in labeled calyx-only afferent terminals was observed without a concomitant reduction in the overall number of calyces or hair cells. This finding supports a critical role of calretinin-expressing calyceal-only afferents in the generation of a VsEP response.NEW & NOTEWORTHY This study identifies a change in the minimum stimulus necessary to evoke vestibular short-latency evoked potential (VsEP) responses after noise-induced damage to the vestibular periphery and reduced numbers of calretinin-labeled calyx-only afferent terminals in the striolar region of the sacculus. These data suggest that a single intense noise exposure may impact synaptic function in calyx-only terminals in the striolar region of the sacculus. Reduced calretinin immunolabeling may provide insight into the mechanism underlying noise-induced changes in VsEP responses.

Relationship between video head impulse test, ocular and cervical vestibular evoked myogenic potentials, and compartmental magnetic resonance imaging classification in menière's disease.

OBJECTIVES/HYPOTHESIS: Currently, it is possible to assess in vivo the morphology of each compartment of the endolymphatic spaces 4 hours after an intravenous administration of gadolinium on magnetic resonance imaging (MRI). The aim of this study was to assess the correlation between otolithic and ampullar functions (cervical vestibular evoked myogenic potential [cVEMP], ocular vestibular evoked myogenic potential [oVEMP], video head impulse test [VHIT]) and delayed inner ear MRI based on a compartmental, anatomically based classification that included the cochlea, the saccule, the utricle, and the ampullas. STUDY DESIGN: Retrospective case-control study. METHODS: In this retrospective study, we performed three-dimensional fluid-attenuated inversion recovery sequences with delayed acquisition in 26 healthy subjects and 31 definite Menière's disease (MD) patients. Each subject was then graded on MRI on the basis on cochlear, saccular, utricular, and ampullar hydrops in MD patients. All patients underwent pure-tone audiometry, VHIT, cVEMP, and oVEMP testing. RESULTS: Cochlear, saccular, utricular, and ampullar hydrops were found on MRI in 88%, 91%, 50%, and 8.5% respectively. We found no significant correlation between the presence of saccular hydrops versus cVEMP, utricular hydrops versus oVEMP, and ampullar hydrops versus VHIT. However, the severity of endolymphatic hydrops on MRI was correlated to the degree of hearing loss. CONCLUSIONS: We proposed a compartmental, anatomically based classification for endolymphatic hydrops on MRI, which included the whole vestibular compartment. Using this classification, we observed increasing morphological changes as the disease evolved, affecting first the saccule, then the utricle, and finally the ampullas. The severity of vestibular endolymphatic hydrops is only correlated to hearing loss severity. LEVEL OF EVIDENCE: 3 Laryngoscope, 130:E444-E452, 2020.

Clinical significance of cervical and ocular vestibular evoked myogenic potentials in benign paroxysmal positional vertigo: a meta-analysis.

PURPOSE: As the pathological cause of benign paroxysmal positional vertigo (BPPV), the dislocation or degeneration of otoconia in the utricle and saccule is suggested. Vestibular evoked myogenic potential (VEMP) could reflect otolithic dysfunction due to these etiologies of BPPV. The aim of this study was to validate the clinical significance of cervical (c) and ocular (o) VEMP in BPPV by a meta-analysis of previous articles. METHODS: Articles related to BPPV with data on cVEMP and oVEMP were collected. The following keywords were used to search PubMed and Scopus for English language articles: benign paroxysmal positional vertigo or BPPV and vestibular evoked myogenic potential or VEMP. RESULTS: The p13 latency in cVEMP and n1 latency in oVEMP were slightly but significantly prolonged in BPPV patients compared to control patients. AR in oVEMP of BPPV patients also showed higher value than that of control patients. However, the n23 latency and AR in cVEMP and p1 latency in oVEMP showed no significant difference between BPPV and control patients. Furthermore, latencies in VEMPs also showed no significant difference between an affected and a non-affected ear in BPPV patients. CONCLUSIONS: Our results indicated that otolith dysfunction of BPPVs was detected by latencies in VEMPs, and AR in oVEMP more sensitively reflects the difference between affected and non-affected ears in BPPV patients. The otolith dysfunction of BPPV might be induced by the systemic condition. However, the differences of latencies between BPPV patients and control patients were too small to use VEMPs as a prognostic predictor.

Are Meniere's disease patients with otolith organ impairment more likely to have balance dysfunction?

Background: Patients with Meniere's disease (MD) may present with peripheral vestibular end organ dysfunction and balance dysfunction. Objective: This study aimed to compare the results of vestibular evoked myogenic potential (VEMP) tests with those of the sensory organization test (SOT) in patients with MD to determine whether they are correlated. Material and methods: In total, 132 patients with unilateral MD were evaluated using an audiometric test, the SOT, a caloric test and VEMP tests. Results: Cervical VEMP and ocular VEMP tests were conducted in 132 patients with MD, and the response rates of the affected side were lower than those of the unaffected side. The composite score, C5ES, and C6ES of the SOT were significantly decreased in patients with no VEMP responses compared to those with VEMP responses. Conclusions and significance: MD patients with no VEMP responses are more likely to develop balance impairment than those with VEMP responses. MD patients with otolith organ impairment may therefore have balance disorders, and should exercise caution to prevent falls and subsequent injuries.

Estudio del daño otolítico en pacientes con vértigo posicional paroxístico benigno mediante potenciales vestibulares miogénicos evocados / Otolithic damage study in patients with benign paroxysmal positional vertigo with vestibular evoked myogenic potentials

Introducción: La fisiopatología del vértigo posicional paroxístico benigno (VPPB) se explica por la migración de otoconias de la mácula del utrículo a los canales semicirculares; no obstante, el papel del sáculo en esta entidad continúa en estudio. Nuestro objetivo es estudiar el daño otolítico en estos pacientes con potenciales vestibulares miogénicos evocados (VEMP) y relacionarlo con los resultados de la posturografía dinámica computarizada (PDC). Material y métodos: Presentamos 79 pacientes diagnosticados de VPPB de manera consecutiva entre marzo y junio de 2017 a quienes se les realizó un estudio con VEMP oculares y cervicales y PDC. Seleccionamos los 67 pacientes con VPPB del canal semicircular posterior y los comparamos con un grupo control de 60 pacientes. Resultados: Los pacientes con VPPB presentaron VEMP cervicales alterados en el 49,25% de los casos, frente al 16,67% en el grupo control. La alteración en VEMP oculares fue del 61,19% en el grupo de VPPB, frente al 6,67% en el grupo control. La prevalencia de VEMP oculares anormales en pacientes con VPPB recurrentes fue estadísticamente significativa. No se halló correlación significativa con los resultados alterados de la PDC. Conclusiones: La disfunción sacular y utricular en los pacientes con VPPB medida mediante VEMP es mayor que en la población sana. Esta alteración puede estar relacionada con la inestabilidad residual que a veces experimentan estos pacientes

Introduction: Benign paroxysmal positional vertigo (BPPV) pathophysiology is based on otoconia migration from the utricle and saccule to the semicircular canals, however, the role of the saccule is still under study. Our aim is to study the otolith damage in these patients with vestibular evoked myogenic potentials (VEMPS) and correlate the results with those of computerised dynamic posturography (CDP). Material and methods: We present 79 patients diagnosed with BPPV between March and June 2017. VEMPS and CDP studies were performed. We selected 67 patients with posterior semi-circular canal BPPV and we compared them with 60 healthy subjects. Results: BPPV group had abnormal cervical VEMPS in 49.25% of patients compared to 16.67% in the control group. Ocular VEMPS were altered in 61.19% of the patients and 6.67% of the healthy subjects. Abnormal ocular VEMPS in patients with recurrent BPPV was statistically significant. There was no significant correlation with CDP results. Conclusions: Utricular and saccular dysfunction in BPPV patients proved by VEMPS is higher than in healthy individuals. This result may be related to symptoms of instability experienced by these patients occasionally

Effects of cochlear implants on otolith function as evaluated by vestibulo-ocular reflex and vestibular evoked myogenic potentials.

OBJECTIVE: The aim of this study was to investigate whether the insertion of an implant into the cochlea is accompanied by a deterioration in otolith function. Cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP) and linear vestibulo-ocular reflex (lVOR) during eccentric rotation were assessed before and after cochlear implantation (CI) to evaluate otolith function. METHODS: Twelve patients with bilateral severe sensorineural hearing loss who had undergone CI surgery in our hospital between May 2016 and November 2017 were included in this study. cVEMP and oVEMP were assessed using the asymmetry ratio (AR), calculated with the following formula: [(peak-to-peak amplitude calculated as the sum of the p13 and n23 amplitudes in the non-operated side) - (that in the operated side)]/[(that in the non-operated side) + (that in the operated side)]. The ratio of VOR gain during eccentric rotation against VOR gain during center rotation was used to assess lVOR. For eccentric rotation, patients were rotated while displaced from the axis of rotation. At the same time, linear acceleration stimulated the utricle and induced lVOR. All patients underwent cVEMP and oVEMP tests and center and eccentric rotation tests before and about 30days after CI surgery. RESULTS: Three patients with absent cVEMP responses before surgery were excluded, leaving pre-surgery cVEMP results for 9/12 patients. In five of these patients, the AR of cVEMP increased after CI, indicating that saccular function, as evaluated by cVEMP, did not deteriorate significantly postoperatively. One patient with an absent oVEMP response before CI was excluded, leaving pre-surgery oVEMP results for 11/12 patients. In 10 of these patients, the AR of oVEMP increased after CI surgery, indicating that utricular function, as evaluated by oVEMP, deteriorated significantly postoperatively. However, because the ratio of VOR gain during eccentric rotation against VOR gain during center rotation did not become worse after CI, utricular function, as evaluated by lVOR, did not deteriorate significantly postoperatively. Symptoms of vertigo became worse after CI in two of the 12 patients. CONCLUSION: CI does not cause a deterioration in saccular function, as evaluated by cVEMP. Although CI does cause a deterioration in utricular function in oVEMP tests, this is not consistent in lVOR tests. These results indicate that CI causes a slight deterioration in utricular function that is insufficient to cause vertigo or deterioration of lVOR.

Deletion of Brg1 causes stereocilia bundle fusion and cuticular plate loss in vestibular hair cells.

Brg1 is an ATPase subunit of the SWI/SNF chromatin-remodeling complex, and it is indispensable for the development and homeostasis of various organs. Conditional deletion of Brg1 in cochlea hair cells (HCs) leads to multiple structural defects and profound deafness. However, the premature death of Brg1-deficient cochlea HCs hindered further study of the role of Brg1. In contrast to cochlea HCs, Brg1-deficient vestibular HCs survived for a long time. Therefore, HC apical structure and vestibular function were examined in inner HC-specific conditional Brg1 knockout mice. Vestibular HCs exhibited fused and elongated stereocilia bundles after deletion of Brg1, and the cuticular plate was absent in most HCs with fused stereocilia bundles. HC loss was observed in conditional Brg1 knockout mice at the age of 12 months. Morphological defects and HC loss were primarily restricted in the striolar region of the utricle and saccule and in the central region of ampulla. The behavioral tests revealed that Brg1 deletion in HCs caused vestibular dysfunction in older adult mice. These results suggest that Brg1 may play specific roles in the maintenance of the HC stereocilia bundle and the cuticular plate.

Vestibular function in panic disorder patients: a vestibular-evoked myogenic potentials and video head impulse test study.

PURPOSE: To evaluate the function of the utriculus and sacculus and their central connections by ocular and cervical vestibular-evoked myogenic potentials (oVEMPs and cVEMPs), and the function of high-frequency VOR of the semicircular canals by video head impulse test (vHIT) in patients with panic disorder (PD). METHODS: Forty-eight patients with PD (21 with agoraphobia) and 20 sex- and age-matched healthy controls took part in the investigation. The vestibulo-ocular reflex (VOR) gains and latencies and peak-to-peak amplitudes of sound-induced VEMPs were measured and compared with those of healthy controls. RESULTS: Any statistical differences in the parameters of cVEMP and oVEMP responses between both PD patients groups and between patients and healthy controls were not observed. Also, significant differences between VOR in patients and healthy controls were not found. The VOR gain, bilaterally in the three semicircular canals was within normal limits (0.8-1.2) for 67%, and higher for 33% of the patients with PD. Overt and covert saccades were not observed. The relationship between higher VOR gains and the increase of postural instability when a sensory conflict exists (standing on foam pad with eyes closed) for patients with PD was established. CONCLUSION: The VEMPs and vHIT tests demonstrated that there is no evidence of hypofunction of the semicircular canals in the high-frequency spectrum of VOR functioning. Nor are there any indications of impairment of the otolith system in patients with PD, regardless of their subjective vestibular sensations. The findings of the current study confirm the proposed link between anxiety, panic symptoms and postural instability in PD patients.

Utricular function in vestibular neuritis: a pilot study of concordance/discordance between ocular vestibular evoked myogenic potentials and ocular cycloposition.

Vestibular neuritis (VN) can affect utricular afferents. Utricular function can be assessed by ocular vestibular evoked myogenic potentials (oVEMPs) whose abnormalities include weak or absent responses, and ocular cycloposition whose abnormalities include ocular torsion (OT). When studied independently in vestibular neuritis, oVEMPs are abnormal in 61-82% of cases, and OT is present in 72-80% of cases. The similar range of abnormalities suggests the hypothesis that these tests should be concordantly abnormal. We tested this hypothesis by identifying consecutive adult cases of VN in whom both oVEMPs and OT were performed. OT and oVEMP overlapped (both were abnormal) in only 47% of cases. In 40% of cases oVEMPs alone were abnormal, and in 13% of cases, OT alone was present. These results suggest that oVEMPs and OT assess different aspects of utricular function believed to arise from discrete zones of the utricular macula; the former are thought to reflect the activity of extra-striolar afferents (which detect constant acceleration), and the latter reflects the activity of striolar afferents (which detect change in acceleration).

The Biomechanics of Lesion Formation in Endolymphatic Hydrops: Single and Double Hit Mechanisms.

BACKGROUND: The vestibular membranes of the cochlea and saccule are subject to two simultaneous constraints as they deform in endolymphatic hydrops. Boundary tethers impose a bulge-type constraint during pressure-induced transverse membrane displacement, while inherent elasticity imposes a stretch-type constraint during stress-induced longitudinal membrane distention. OBJECTIVE: The aim of this study is to reconcile the effect of these dual constraints on membrane deformation. It is hypothesized that it is the interaction of these constraints that determines whether a stable membrane configuration can be achieved or progression to endolymphatic hydrops will occur. METHODS: Reissner's membrane was modeled as a flat elastic ribbon that was bound along its lateral edges and subject to trans-mural pressure. The bulge and stretch constraints on membrane deformation were formulated mathematically. A graphic solution of the constraint functions was used to examine the nature of the interaction and determine how pressure and elasticity influence the hydropic process. RESULTS: The graphic analysis shows how bulge and stretch phenomena interact to achieve an equilibrium point that satisfies both physical requirements. Nominal values of pressure and elasticity are projected to result in a stable membrane equilibrium in the precritical zone with the modest isolated increases in either parameter alone compatible with stability. However, a sufficiently large increase in either pressure or elasticity alone can constitute a single hit mechanism to exceed the critical point and destabilize the membrane. Moreover, simultaneous modest increases in both pressure and elasticity, neither of which would be sufficient in its own right, can be additive and constitute a double hit mechanism to destabilize the membranes as well. Finally, extreme values of pressure and elasticity that fail to intersect imply that no solution is feasible and that the affected membranes will fail immediately. CONCLUSIONS: Sufficiently large increases in either endolymphatic pressure or membrane elasticity alone can destabilize the membranes and constitute single hit mechanisms for inducing hydrops. Combined moderate increases in both trans-mural pressure and membrane elasticity can also destabilize the membranes and constitute a double hit mechanism for hydrops induction.

Age-related deterioration of saccule-related neural function is associated with decreased estimated glomerular filtration rate and increased free thyroxine.

OBJECTIVE: This study attempted to identify systemic factors for age-related decline in neural function originating from the saccule using cervical vestibular-evoked myogenic potentials (cVEMP) parameters. METHODS: We recruited 129 symptomatic vertiginous patients who did not have known disorder affecting the cVEMP pathway (mean age = 52.4 ±â€¯13.9). The indicators of saccule-related neural function were the sum of normalized cVEMP amplitude (SNA) and the average of p13 latency on both sides (average latency, AL). Any associations between cVEMP and systemic factors were evaluated using a linear regression. RESULT: SNA decreased with ageing (p < 0.001) in univariable regression. The estimated glomerular filtration rate (eGFR) was positively associated with SNA (p = 0.002). Hematocrit, C-reactive protein, vitamin D, and free thyroxine (T4) showed a trend of association with SNA (p < 0.2). SNA was associated with ageing, increased free T4, and decreased eGFR in multivariable analysis. In the subgroup analysis, SNA was significantly associated with free T4 in younger patients (mean age = 41.5 ±â€¯9.91) but not in the older ones (mean age = 63.5 ±â€¯6.54). AL did not show any significant associations with systemic factors. CONCLUSION: Decreased eGFR and increased free T4 as well as aging may be risk factors for decline of saccule-related neural function. SIGNIFICANCE: Neural function originating from the saccule may be affected by systemic factors.

Vestibular and oculomotor function in children with CP: Descriptive study.

OBJECTIVE: We aimed to describe vestibular/oculomotor function of 7-12-year-old children with CP, Gross Motor Function Classification System (GMFCS) levels (I-III), in comparison to an age-matched control group to understand the effect of the vestibular system on activities and participation of children with CP. METHODS: Vestibular, oculomotor and balance function were tested in children with CP. Central and peripheral vestibular function was examined using an enclosed rotary chair and infrared video goggles (100 Hz) that measured eye movements. Oculomotor tests included smooth pursuit and optokinetic nystagmus (OKN). Vestibulo-Ocular Reflex (VOR) tests, done in complete darkness, included step rotation (STEP), sinusoidal harmonic acceleration (SHA) test, VOR cancellation and enhancement, and subjective visual vertical and horizontal (SVV/SVH). The integrity of the saccule was tested with the Cervical Vestibular Evoked Myogenic Potential. If able, the participants' balance abilities were examined using the Sensory Organization Test (SOT) to determine ability to maintain standing balance during six conditions that challenged the visual, somatosensory and vestibular systems. Independent t-tests and Mann-Whitney U tests were used to compare results between groups. RESULTS: Forty-one children with CP (mean age = 9.44 years, SD = 1.66; 23F/18M; Gross Motor Function Classification System levels: I (n = 19), II (n = 7), III (n = 15) and thirty-three typically developing (TD) children (mean age = 10.16 years, SD = 1.6; 13F/20M) were recruited from the Birmingham, AL community. There was no significant difference between children with CP and TD children in saccular function (i.e. C-VEMP test), and peripheral vestibular end organ (i.e. SHA test and STEP test), VOR enhancement, or OKN gain. Velocity gain for horizontal smooth pursuit was significantly worse in children with CP (p = 0.009), compared to TD children. Poor mediation of central vestibular function were that evident with significantly higher VOR cancellation gain in children with CP (p < 0.0001), compared to TD children and significantly higher SVV variance (p = 0.002), SVH mean (p = 0.001), and SVH variance (p < 0.0001) in children with CP compared to TD children. Compromised balance abilities in children with CP was evident with significantly lower composite scores (p < 0.0001), vestibular ratio (p < 0.0001), and visual ratio (p = 0.021). The somatosensory ratio (p = 0.798) of children with CP was similar to children with TD. CONCLUSIONS: Although peripheral vestibular function was intact, children with CP had difficulty coupling eye and head movement (VOR cancellation), using the vestibular system for postural control (SOT), demonstrated poor perception of upright (SVV/SVH), and had difficulty following a slow moving target (smooth pursuit eye movement). These results implicate a central vestibular and oculomotor function impairment the severity of which corresponded with severity of the level of CP.

How does cochlear implantation affect five vestibular end-organ functions and dizziness?

OBJECTIVE: To evaluate all five vestibular end-organ functions (lateral, anterior, posterior semicircular canal, utricule, and saccule) and to investigate the relationship between Dizziness Handicap Inventory (DHI) and vestibular functions prior to CI (cochlear implantation) and at postoperative day 3 and month 3. METHODS: A total of 42 patients (age 16-70years) with normal vestibular functions preoperatively and undergoing unilateral CI were included in this prospective descriptive study. Video head impulse test (vHIT) for three semicircular canal (SSC) functions, ocular vestibular-evoked myogenic potential (oVEMP) for utricule function, cervical vestibular-evoked myogenic potential (cVEMP) for saccule function and DHI for subjective vertigo symptoms were performed prior to CI and at postoperative day 3 and month 3. RESULTS: There was a significant impairment of vestibular function in 12 patients (28.5%) on the implantation side and significant DHI increase was observed in 13 of 42 (30.9%) patients at postoperative day 3 after CI (p<0.05). We found SSC dysfunction in 7 patients (16,6%) who underwent observation with vHIT, saccule dysfunction in 8 patients (19%) with cVEMP and utricule dysfunction in 5 patients (11.9%) with oVEMP on the operated side 3days after surgery (p<0.05). Posterior SSC functions (5 patients) were more affected than lateral SSC functions (3 patients). At postoperative month 3, six patients (14.2%) still had deteriorating results in the objective tests and significant DHI increase was continued in 4 (9.5%) patients (p<0.05). The deterioration in vHIT continued in only 1 (2.3%) patient (p>0.05). The deterioration in cVEMP continued in 5 (11.9%) patients (p<0.05). The deterioration in oVEMP continued in 2 (4.7%) patients (p>0.05). There was a significant correlation between DHI and objective vestibular tests both in the early and late postoperative period (r=0.795; p<0.05). CONCLUSION: Our study showed that both canal and otolith functions can be damaged after CI especially in the early postoperative period. Surprisingly, posterior SSC functions were more affected than lateral SSC. Therefore, a gold standard vestibular test battery that can evaluate each of three SSC canals and two otoliths functions is essential. Since a single vestibular test for this purpose is not available, we recommend the use of the three available vestibular tests together. This test battery, which is capable of evaluating five vestibular end-organ functions in preoperative and postoperative vestibular evaluations, can provide more accurate results not only for CI but also for most otologic surgeries.

Otolithic damage study in patients with benign paroxysmal positional vertigo with vestibular evoked myogenic potentials. / Estudio del daño otolítico en pacientes con vértigo posicional paroxístico benigno mediante potenciales vestibulares miogénicos evocados.

INTRODUCTION: Benign paroxysmal positional vertigo (BPPV) pathophysiology is based on otoconia migration from the utricle and saccule to the semicircular canals, however, the role of the saccule is still under study. Our aim is to study the otolith damage in these patients with vestibular evoked myogenic potentials (VEMPS) and correlate the results with those of computerised dynamic posturography (CDP). MATERIAL AND METHODS: We present 79 patients diagnosed with BPPV between March and June 2017. VEMPS and CDP studies were performed. We selected 67 patients with posterior semi-circular canal BPPV and we compared them with 60 healthy subjects. RESULTS: BPPV group had abnormal cervical VEMPS in 49.25% of patients compared to 16.67% in the control group. Ocular VEMPS were altered in 61.19% of the patients and 6.67% of the healthy subjects. Abnormal ocular VEMPS in patients with recurrent BPPV was statistically significant. There was no significant correlation with CDP results. CONCLUSIONS: Utricular and saccular dysfunction in BPPV patients proved by VEMPS is higher than in healthy individuals. This result may be related to symptoms of instability experienced by these patients occasionally.