The importance of bone density and anatomical structure in superior semicircular canal dehiscence

OBJECTIVE

This study investigates the importance of bone density, surface area, and diameter of anatomical structures of the superior semicircular canal (SSC), lateral semicircular canal (LSC), posterior semicircular canal (PSC), utricle, and saccule in patients diagnosed with superior semicircular canal dehiscence (SSCD).

MATERIALS AND METHODS

The bone density, surface area, and diameter of SSC, LSC, PSC, utricle, and saccule were measured and compared between the SSCD group and control group. Fifteen ears in the SSCD group and 60 ears in the control group were evaluated. Additionally, within the SSCD group, the dehiscent and healthy sides were evaluated independently.

RESULTS

SSC's bone density was significantly lower in the SSCD group compared to the control group (p = 0.008). No significant differences were found in surface area and diameter between the groups (p > 0.05). While most of the anatomical structures showed no significant difference in bone density between dehiscent and healthy ears (p > 0.05), SSC bone density was significantly lower in affected ears (p = 0.000) in SSCD group.

CONCLUSION

Based on the data obtained in this study, bone density and anatomical structure may be useful in patients diagnosed with SSCD.

Characteristic findings in the human fetus vestibule: A human temporal bone study

OBJECTIVE

The "collapse," a highly flexed, dented, or caved membrane between the endo- and peri-lymph of the saccule and utricle in adults, is considered as a morphological aspect of Ménière's syndrome. Likewise, when mesh-like tissues in the perilymphatic space are damaged or lost, the endothelium loses mechanical support and causes nerve irritation. However, these morphologies were not examined in fetuses.

METHODS

By using histological sections from 25 human fetuses (crown-rump length[CRL] 82-372 mm; approximately 12-40 weeks), morphologies of the perilymphatic-endolymphatic border membrane and the mesh-like tissue around the endothelium were examined.

RESULTS

The highly flexed or caved membrane between the endo- and peri-lymphatic spaces was usually seen in the growing saccule and utricle of fetuses, especially at junctions between the utricle and ampulla at midterm. Likewise, the perilymphatic space around the saccule, utricle and semicircular ducts often lost the mesh-like tissues. The residual mesh-like tissue supported the veins, especially in the semicircular canal.

CONCLUSION

Within a cartilaginous or bony room showing a limited growth in size but containing increased perilymph, the growing endothelium appeared to become wavy. Owing to a difference in growth rates between the utricle and semicircular duct, the dentation tended to be more frequently seen at junctions than at free margins of the utricle. The difference in site and gestational age suggested that the deformity was not "pathological" but occurred due to unbalanced growth of the border membrane. Nevertheless, the possibility that the deformed membrane in fetuses was an artifact caused by delayed fixation is not deniable.

Dynamic patterns of YAP1 expression and cellular localization in the developing and injured utricle

The Hippo signaling pathway is a key regulator of tissue development and regeneration. Activation of the Hippo pathway leads to nuclear translocation of the YAP1 transcriptional coactivator, resulting in changes in gene expression and cell cycle entry. Recent studies have demonstrated the nuclear translocation of YAP1 during the development of the sensory organs of the inner ear, but the possible role of YAP1 in sensory regeneration of the inner ear is unclear. The present study characterized the cellular localization of YAP1 in the utricles of mice and chicks, both under normal conditions and after HC injury. During neonatal development, YAP1 expression was observed in the cytoplasm of supporting cells, and was transiently expressed in the cytoplasm of some differentiating hair cells. We also observed temporary nuclear translocation of YAP1 in supporting cells of the mouse utricle after short periods in organotypic culture. However, little or no nuclear translocation of YAP1 was observed in the utricles of neonatal or mature mice after ototoxic injury. In contrast, substantial YAP1 nuclear translocation was observed in the chicken utricle after streptomycin treatment in vitro and in vivo. Together, these data suggest that differences in YAP1 signaling may partially account for the differing regenerative abilities of the avian vs. mammalian inner ear.

Simultaneous gentamicin-mediated damage and Atoh1 overexpression promotes hair cell regeneration in the neonatal mouse utricle

Loss of hair cells from vestibular epithelium results in balance dysfunction. The current therapeutic regimen for vestibular diseases is limited. Upon injury or Atoh1 overexpression, hair cell replacement occurs rapidly in the mammalian utricle, suggesting a promising approach to induce vestibular hair cell regeneration. In this study, we applied simultaneous gentamicin-mediated hair cell ablation and Atoh1 overexpression to induce neonatal utricular hair cell formation in vitro. We confirmed that type I hair cells were the primary targets of gentamicin. Furthermore, injury and Atoh1 overexpression promoted hair cell regeneration in a timely and efficient manner through robust viral transfection. Hair cells regenerated with type II characteristics in the striola and type I/II characteristics in non-sensory regions. Rare EdU⁺/myosin7a⁺ cells in sensory regions and robust EdU⁺/myosin7a⁺ signals in ectopic regions indicate that transdifferentiation of supporting cells in situ, and mitosis and differentiation of non-sensory epithelial cells in ectopic regions, are sources of regenerative hair cells. Distinct regeneration patterns in in situ and ectopic regions suggested robust plasticity of vestibular non-sensory epithelium, generating more developed hair cell subtypes and thus providing a promising stem cell-like source of hair cells. These findings suggest that simultaneously causing injury and overexpressing Atoh1 promotes hair cell regeneration efficacy and maturity, thus expanding the understanding of ectopic plasticity in neonatal vestibular organs.

Knockdown of Foxg1 in Sox9+ supporting cells increases the trans-differentiation of supporting cells into hair cells in the neonatal mouse utricle

Foxg1 plays important roles in regeneration of hair cell (HC) in the cochlea of neonatal mouse. Here, we used Sox9-CreER to knock down Foxg1 in supporting cells (SCs) in the utricle in order to investigate the role of Foxg1 in HC regeneration in the utricle. We found Sox9 an ideal marker of utricle SCs and bred Sox9^CreER/+Foxg1^loxp/loxp mice to conditionally knock down Foxg1 in utricular SCs. Conditional knockdown (cKD) of Foxg1 in SCs at postnatal day one (P01) led to increased number of HCs at P08. These regenerated HCs had normal characteristics, and could survive to at least P30. Lineage tracing showed that a significant portion of newly regenerated HCs originated from SCs in Foxg1 cKD mice compared to the mice subjected to the same treatment, which suggested SCs trans-differentiate into HCs in the Foxg1 cKD mouse utricle. After neomycin treatment in vitro, more HCs were observed in Foxg1 cKD mice utricle compared to the control group. Together, these results suggest that Foxg1 cKD in utricular SCs may promote HC regeneration by inducing trans-differentiation of SCs. This research therefore provides theoretical basis for the effects of Foxg1 in trans-differentiation of SCs and regeneration of HCs in the mouse utricle.

MRI utricle diameter asymmetry is significantly greater in dogs with idiopathic vestibular syndrome compared with unaffected dogs

Idiopathic vestibular syndrome (IVS) is the most common cause of acute unilateral peripheral vestibular dysfunction in older dogs. The purpose of this retrospective, cross-sectional study was to characterize morphological changes in the utricle of dogs affected by IVS, using MRI. To evaluate differences between affected and unaffected utricles, the ratio of the largest to the smallest utricle diameter was obtained, as measured on transverse T2-weighted images, and defined as the utricle asymmetricity ratio (UAR). Out of 137 patients diagnosed with IVS after excluding other vestibular diseases by MRI, 101 were eligible for inclusion. Additionally, 31 older dogs with no signs of vestibular disorders or other intracranial diseases were included as a control group. The disease group was divided into two subgroups in which the direction of head tilt and nystagmus symptoms versus the decreased utricle diameters were consistent or inconsistent. The medians of UARs of the IVS and control groups were 0.83 (range 0.37-1.00) and 0.98 (0.70-1.00), respectively. The medians of the UARs of the consistent and inconsistent IVS subgroups were 0.82 (0.37-0.99) and 0.90 (0.74-1.00), respectively. The UAR of the IVS group was significantly decreased than that of the control group and UAR of the consistent sub-group was significantly decreased than that of the inconsistent sub-group (P < .01). In conclusion, significant asymmetry of utricle diameter was identified in dogs with IVS versus unaffected dogs. We propose that canine IVS may possibly be correlated with structural atrophy of the vestibular system.

Transient Vertigo with Horizontal Nystagmus to Loud Noise and Pressure: Utricular Hydrops or Vestibular Atelectasis?

We present an unusual case of a patient with a positive Tullio phenomenon, brief Valsalva-induced transient horizontal nystagmus, reduced left caloric response, and bilateral vestibulo-ocular reflex loss. This study discusses the pathophysiology and differential diagnosis concerning the suspected pathology for the phenomenon of utricular hydrops or vestibular atelectasis and presents a literature review.

Saccular Impairment in Alzheimer's Disease Is Associated with Driving Difficulty

BACKGROUND/AIMS

Patients with Alzheimer's disease (AD) experience increased rates of vestibular loss. Recent studies suggest that saccular impairment in mild cognitive impairment (MCI) and AD patients is associated with impaired spatial cognitive function. However, the impact of saccular impairment on everyday behaviors that rely on spatial cognitive function is unknown.

METHODS

We recruited 60 patients (21 MCI and 39 AD) from an interdisciplinary Memory Clinic. Saccular function was measured, and a visuospatial questionnaire was administered to assess whether participants experienced impairments in terms of driving difficulty, losing objects, falls, and fear of falling.

RESULTS

In multiple logistic regression analyses, MCI and AD patients with bilateral saccular impairment had a significant, greater than 12-fold odds of driving difficulty (OR 12.1, 95% CI 1.2, 117.7) compared to MCI and AD patients with normal saccular function, and the association appears to be mediated by spatial cognition as measured by the Money Road Map Test.

CONCLUSION

This study suggests a novel link between saccular impairment and driving difficulty in MCI and AD patients and demonstrates that driving difficulty may be a real-world manifestation of impaired spatial cognition associated with saccular impairment.

Dose-dependent cochlear and vestibular toxicity of trans-tympanic cisplatin in the rat

In vivo studies are needed to study cisplatin ototoxicity and to evaluate candidate protective treatments. Rats and mice are the preferred species for toxicological and pharmacological pre-clinical research, but systemic administration of cisplatin causes high morbidity in these species. We hypothesized that trans-tympanic administration of cisplatin would provide a good model for studying its auditory and vestibular toxicity in the rat. Cisplatin was administered by the trans-tympanic route in one ear (50μl, 0.5-2mg/ml) of rats of both sexes and two different strains. Cochlear toxicity was corroborated by histological means. Vestibular toxicity was demonstrated by behavioral and histological analysis. Cisplatin concentrations were assessed in inner ear after trans-tympanic and i.v. administration. In all experiments, no lethality and only scant body weight loss were recorded. Cisplatin caused dose-dependent cochlear toxicity, as demonstrated by hair cell counts in the apical and middle turns of the cochlea, and vestibular toxicity, as demonstrated by behavioral analysis and hair cell counts in utricles. High concentrations of cisplatin were found in the inner ear after trans-tympanic administration. In comparison, i.v. administration resulted in lower inner ear concentrations. We conclude that trans-tympanic administration provides an easy, reproducible and safe model to study the cochlear and vestibular toxicity of cisplatin in the rat. This route of exposure may be useful to address particular questions on cisplatin induced ototoxicity and to test candidate protective treatments.

Relationship Between Hair Cell Loss and Hearing Loss in Fishes

Exposure to intense sound or ototoxic chemicals can damage the auditory hair cells of vertebrates, resulting in hearing loss. Although the relationship between such hair cell damage and auditory function is fairly established for terrestrial vertebrates, there are limited data available to understand this relationship in fishes. Although investigators have measured either the morphological damage of the inner ear or the functional deficits in the hearing of fishes, very few have directly measured both in an attempt to find a relationship between the two. Those studies that have examined both auditory hair cell damage in the inner ear and the resulting hearing loss in fishes are reviewed here. In general, there is a significant linear relationship between the number of hair cells lost and the severity of hearing threshold shifts, although this varies between species and different hair cell-damaging stimuli. After trauma to the fish ear, auditory hair cells are able to regenerate to control level densities. With this regeneration also comes a restoration of hearing. Thus there is also a significant relationship between hair cell recovery and hearing recovery in fishes.

[Air-conducted ocular vestibular-evoked myogenic potential in patients with sudden sensorineural hearing loss]

OBJECTIVE

To investigate the characteristics of air-conducted ocular vestibular-evoked myogenic potential(oVEMP) in patients with sudden sensorineural hearing loss (SSHL). So as to understanding the range and the degree of the vestibular system damage in patients with SSHL.

METHOD

Thirty-five cases of unilateral SSHL were enrolled as the observing group from December in 2013 to December in 2014. 500 Hz air-conducted tone burst was employed as stimulation. Fifity-five healthy young subjects were recruited as the control group. The results were compared between the affected ears, the contralateral ears and the normal controls.

RESULT

Thirty-five patients with SSHL, 31 of them in both ears lead to oVEMP Waveform, 4 sick ears did not elicit oVEMP waveform, extraction rate of 88%. 95 dBHL air-conducted get the latencies of P1 and N1, P1-N1 interval, peak-to-peak P1-N1 amplitude in healthy ear were (11.92 ± 0.85)ms; (17.07 ± 1.04)ms, (5.15 ± 0.69)ms, (5.44 ± 2.53) µv. 95 dBHL air-conducted get the latencies of P1 and N1, P1-N1 interval, peak-to-peak P1-N1 amplitude in sick ear were (12.16 ± 0.76) ms; (16.94 ± 2.57)ms, (5.16 ± 0.73)ms, (2.89 ± 1.66) v. The 55 cases (110 ears) were elicited P1-N1 complex typical, extraction rate was 100%. The threshold of oVEMP examination was (82.23 ± 2.92) dBHL, 95 dBHL air-conducted get the latencies of P1 and N1, P1-N1 interval, peak-to-peak P1-N1 amplitude in these healthy young people were (11.53 ± 0.80)ms, (16.61 ± 0.87) ms, (5.18 ± 1.04) ms, (5.96 ± 2.59) µv, there were no significant differences between the affected ears, the contralateral ears and the normal controls in the latencies P1 and N1, P1-N1 interval. The wave amplitude in SSHL were lower than the healthy ear and the healthy control group.

CONCLUSION

Through the detection of oVEMP in patients with SSHL,we observed that P1-N1 wave amplitude decreased, and it may be related to the damage of the utricle and vestibular nerve.

Systemic connective tissue abnormalities in patients with saccular intracranial aneurysms

OBJECTIVES

Our purpose was to identify the incidence and significance of markers of systemic connective tissue abnormalities (CTA) in patients with saccular intracranial aneurysms (SIA).

MATERIALS AND METHODS

This prospective case-control study included 199 consecutive patients with SIA (103 women and 96 men, mean age - 43.2 years) and 194 control patients - blood donors (108 - men, 86 - women, mean age - 38.4 years). Aneurysms were verified by conventional cerebral angiography. All patients were examined by the first author using a specially designed questionnaire and a standardized physical examination with special emphasis on systemic CTA.

RESULTS

Twelve markers of systemic CTA were significantly higher in patients with SIA than in controls: visible vessels on face and chest (59.8%), scoliosis (44.7%), varicose veins in legs (39.7%), flatfoot (34.6%), hyperextensibility of the skin (33.6%), spontaneous epistaxis (25.6%), easy bruising (20.6%), abdominal hernia (13.6%), periodontal disease (10.5%), chest deformations (7.5%), abdominal striae (3.5%), joint hypermobility (2.5%). A blinded validation study in a subset of 43 patients showed similar results. Among patients with SIA, 125 of 199 patients (62.8%) had at least three markers of systemic CTA compared with 23 (11.8%) of the controls (P < 0.0001, OR = 12.5, 95% CI 7.45-21.1). The mean number of markers of systemic CTA in patients with SIA was 3.07 and 1.17 in controls.

CONCLUSION

Patients with SIA have multiple markers of systemic connective tissue abnormalities. Systemic weakness of connective tissue represents a risk factor for development of SIA. Identification of these markers may help in detection of high-risk patients.

Headbobber: a combined morphogenetic and cochleosaccular mouse model to study 10qter deletions in human deafness

The recessive mouse mutant headbobber (hb) displays the characteristic behavioural traits associated with vestibular defects including headbobbing, circling and deafness. This mutation was caused by the insertion of a transgene into distal chromosome 7 affecting expression of native genes. We show that the inner ear of hb/hb mutants lacks semicircular canals and cristae, and the saccule and utricle are fused together in a single utriculosaccular sac. Moreover, we detect severe abnormalities of the cochlear sensory hair cells, the stria vascularis looks severely disorganised, Reissner's membrane is collapsed and no endocochlear potential is detected. Myo7a and Kcnj10 expression analysis show a lack of the melanocyte-like intermediate cells in hb/hb stria vascularis, which can explain the absence of endocochlear potential. We use Trp2 as a marker of melanoblasts migrating from the neural crest at E12.5 and show that they do not interdigitate into the developing strial epithelium, associated with abnormal persistence of the basal lamina in the hb/hb cochlea. We perform array CGH, deep sequencing as well as an extensive expression analysis of candidate genes in the headbobber region of hb/hb and littermate controls, and conclude that the headbobber phenotype is caused by: 1) effect of a 648 kb deletion on distal Chr7, resulting in the loss of three protein coding genes (Gpr26, Cpmx2 and Chst15) with expression in the inner ear but unknown function; and 2) indirect, long range effect of the deletion on the expression of neighboring genes on Chr7, associated with downregulation of Hmx3, Hmx2 and Nkx1.2 homeobox transcription factors. Interestingly, deletions of the orthologous region in humans, affecting the same genes, have been reported in nineteen patients with common features including sensorineural hearing loss and vestibular problems. Therefore, we propose that headbobber is a useful model to gain insight into the mechanisms underlying deafness in human 10qter deletion syndrome.

Association between hearing loss and saccular dysfunction in older individuals

OBJECTIVE

1) Describe the association between hearing loss and dysfunction of each of the 5 vestibular end-organs--the horizontal, superior, and posterior semicircular canals; saccule; and utricle--in older individuals. 2) Evaluate whether hearing loss and vestibular end-organ deficits share any risk factors.

STUDY DESIGN

Cross-sectional study.

SETTING

Academic medical center.

PATIENTS

Fifty-one individuals age 70 years or older.

INTERVENTIONS

Audiometry, head-thrust dynamic visual acuity (htDVA), sound-evoked cervical vestibular-evoked myogenic potential (cVEMP), and tap-evoked ocular VEMP (oVEMP).

MAIN OUTCOME MEASURES

Audiometric pure-tone averages (PTA), htDVA LogMAR scores as a measure of semicircular canal function in each canal plane, and cVEMP and oVEMP amplitudes as a measure of saccular and utricular function, respectively.

RESULTS

We observed a significant correlation between hearing loss at high frequencies and reduced cVEMP amplitudes (or reduced saccular function; r = -0.37, p < 0.0001) in subjects age 70 years or older. In contrast, hearing loss was not associated with oVEMP amplitudes (or utricular function), or htDVA LogMAR scores (or semicircular canal function) in any of the canal planes. Age and noise exposure were significantly associated with measures of both cochlear and saccular dysfunction.

CONCLUSION

The concomitant decline in the cochlear and saccular function associated with aging may reflect their common embryologic origin in the pars inferior of the labyrinth. Noise exposure seems to be related to both saccular and cochlear dysfunction. These findings suggest a potential benefit of screening individuals with presbycusis-particularly those with significant noise exposure history-for saccular dysfunction, which may contribute to fall risk in the elderly.

Comparison of phenotypes between different vangl2 mutants demonstrates dominant effects of the Looptail mutation during hair cell development

Experiments utilizing the Looptail mutant mouse, which harbors a missense mutation in the vangl2 gene, have been essential for studies of planar polarity and linking the function of the core planar cell polarity proteins to other developmental signals. Originally described as having dominant phenotypic traits, the molecular interactions underlying the Looptail mutant phenotype are unclear because Vangl2 protein levels are significantly reduced or absent from mutant tissues. Here we introduce a vangl2 knockout mouse and directly compare the severity of the knockout and Looptail mutant phenotypes by intercrossing the two lines and assaying the planar polarity of inner ear hair cells. Overall the vangl2 knockout phenotype is milder than the phenotype of compound mutants carrying both the Looptail and vangl2 knockout alleles. In compound mutants a greater number of hair cells are affected and changes in the orientation of individual hair cells are greater when quantified. We further demonstrate in a heterologous cell system that the protein encoded by the Looptail mutation (Vangl2^S464N) disrupts delivery of Vangl1 and Vangl2 proteins to the cell surface as a result of oligomer formation between Vangl1 and Vangl2^S464N, or Vangl2 and Vangl2^S464N, coupled to the intracellular retention of Vangl2^S464N. As a result, Vangl1 protein is missing from the apical cell surface of vestibular hair cells in Looptail mutants, but is retained at the apical cell surface of hair cells in vangl2 knockouts. Similarly the distribution of Prickle-like2, a putative Vangl2 interacting protein, is differentially affected in the two mutant lines. In summary, we provide evidence for a direct physical interaction between Vangl1 and Vangl2 through a combination of in vitro and in vivo approaches and propose that this interaction underlies the dominant phenotypic traits associated with the Looptail mutation.

Evaluation of vestibular evoked myogenic potentials during benign paroxysmal positional vertigo attacks; neuroepithelial degeneration?

OBJECTIVE

Recent studies show that benign paroxysmal positional vertigo (BPPV) may also affect the macula of the saccule. We investigated vestibular evoked myogenic potential (VEMP) results in patients with BPPV.

MATERIALS AND METHODS

The study group included 31 patients (31 ears) diagnosed with posterior canal BPPV and the control group included 23 healthy volunteers (46 ears) with no neurotologic symptoms. After VEMP recordings were performed, mean latency values for p13 of the study and control groups were compared.

RESULTS

VEMP responses were elicited in all controls (46 ears). In the study group, responses were normal in 19, delayed in 5, and absent in 7 ears. There was a significant difference between abnormal VEMP rates for patients versus controls (p < 0.001). Although VEMP responses were elicited in all non-affected ears of patients, there was a delayed response in 6 (19%) non-affected ears. This was statistically significant when compared with controls (p = 0.002). There was no correlation between abnormal VEMPs and the number of canalith reposition maneuvers required (p = 0.392).

CONCLUSION

Our findings suggest the prolongation of mean latency values for p13 of VEMP in patients with BPPV might signify neuronal degeneration in the macula of the saccule, and the absence of VEMP waves might represent the extent of damage. Also, high latency values for p13 in non-affected ears of patients might indicate bilateral neural degeneration in BPPV.

Epithelial cell stretching and luminal acidification lead to a retarded development of stria vascularis and deafness in mice lacking pendrin

Loss-of-function mutations of SLC26A4/pendrin are among the most prevalent causes of deafness. Deafness and vestibular dysfunction in the corresponding mouse model, Slc26a4^−/−, are associated with an enlargement and acidification of the membranous labyrinth. Here we relate the onset of expression of the HCO₃⁻ transporter pendrin to the luminal pH and to enlargement-associated epithelial cell stretching. We determined expression with immunocytochemistry, cell stretching by digital morphometry and pH with double-barreled ion-selective electrodes. Pendrin was first expressed in the endolymphatic sac at embryonic day (E) 11.5, in the cochlear hook-region at E13.5, in the utricle and saccule at E14.5, in ampullae at E16.5, and in the upper turn of the cochlea at E17.5. Epithelial cell stretching in Slc26a4^−/− mice began at E14.5. pH changes occurred first in the cochlea at E15.5 and in the endolymphatic sac at E17.5. At postnatal day 2, stria vascularis, outer sulcus and Reissner's membrane epithelial cells, and utricular and saccular transitional cells were stretched, whereas sensory cells in the cochlea, utricle and saccule did not differ between Slc26a4^+/− and Slc26a4^−/− mice. Structural development of stria vascularis, including vascularization, was retarded in Slc26a4^−/− mice. In conclusion, the data demonstrate that the enlargement and stretching of non-sensory epithelial cells precedes luminal acidification in the cochlea and the endolymphatic sac. Stretching and luminal acidification may alter cell-to-cell communication and lead to the observed retarded development of stria vascularis, which may be an important step on the path to deafness in Slc26a4^−/− mice, and possibly in humans, lacking functional pendrin expression.

Identification of genetic and chemical modulators of zebrafish mechanosensory hair cell death

Inner ear sensory hair cell death is observed in the majority of hearing and balance disorders, affecting the health of more than 600 million people worldwide. While normal aging is the single greatest contributor, exposure to environmental toxins and therapeutic drugs such as aminoglycoside antibiotics and antineoplastic agents are significant contributors. Genetic variation contributes markedly to differences in normal disease progression during aging and in susceptibility to ototoxic agents. Using the lateral line system of larval zebrafish, we developed an in vivo drug toxicity interaction screen to uncover genetic modulators of antibiotic-induced hair cell death and to identify compounds that confer protection. We have identified 5 mutations that modulate aminoglycoside susceptibility. Further characterization and identification of one protective mutant, sentinel (snl), revealed a novel conserved vertebrate gene. A similar screen identified a new class of drug-like small molecules, benzothiophene carboxamides, that prevent aminoglycoside-induced hair cell death in zebrafish and in mammals. Testing for interaction with the sentinel mutation suggests that the gene and compounds may operate in different pathways. The combination of chemical screening with traditional genetic approaches is a new strategy for identifying drugs and drug targets to attenuate hearing and balance disorders.

Loss of sensory hair cells in the inner ear is observed in the majority of hearing and balance disorders, affecting the health of more than 600 million people worldwide. Exposure to environmental toxins and certain pharmaceutical drugs such as aminoglycoside antibiotics and some cancer chemotherapy agents account for many of these hearing and balance problems. Variation in the genetic makeup between individuals plays a major role in establishing differences in susceptibility to environmental agents that damage the inner ear. Using zebrafish larvae, we developed a screen to uncover genes leading to differences in antibiotic-induced death of hair cells and to identify compounds that protect hair cells from damage. The combination of chemical screening with traditional genetic approaches offers a new strategy for identifying drugs and drug targets to attenuate hearing and balance disorders.

Shape change controls supporting cell proliferation in lesioned mammalian balance epithelium

Mature mammals are uniquely vulnerable to permanent auditory and vestibular deficits, because the cell proliferation that produces replacement hair cells in other vertebrates is limited in mammals. To investigate the cellular mechanisms responsible for that difference, we created excision lesions in the sensory epithelium of embryonic and 2-week-old mouse utricles. Lesions in embryonic utricles closed in <24 h via localized expansion of supporting cells, which then reentered the cell cycle. Pharmacological treatments combined with time-lapse microscopy demonstrated that the healing depended on Rho-mediated contraction of an actin ring at the leading edge of the lesion. In contrast, lesions in utricles from 2-week-old and older mice remained open even after 48 h. Supporting cells in those utricles remained compact and columnar and had significantly stouter cortical actin belts than those in embryonic sensory epithelia. This suggests that cytoskeletal changes may underlie the age-related loss of proliferation in mammalian ears by limiting the capacity for mature supporting cells to change shape. In mature utricles, exogenous stimulation with lysophosphatidic acid overcame this maturational block and induced closure of lesions, promoting supporting cell expansion and subsequent proliferation. After lysophosphatidic acid treatment, 85% of the mature supporting cells that had spread to a planar area >300 microm2 entered S-phase, whereas only 10% of those cells that had a planar area <100 microm2 entered S-phase. Together, these results indicate that cellular shape change can overcome the normal postnatal cessation of supporting cell proliferation that appears to limit regeneration in mammalian vestibular epithelia.

Otosclerosis associated with Ménière's disease: a histological study

A histological study of a pair of temporal bones was performed in a case of Menière's disease. A severe endolymphatic hydrops and extensive capsular otosclerosis bilaterally was found. Severe endolympathic hydrops results from otosclerotic endolympahtic duct occlusion. Our unique histopathological findings show that a causal association exists between these two entities.

Inferior vestibular neuritis: 3 cases with clinical features of acute vestibular neuritis, normal calorics but indications of saccular failure

Background

Vestibular neuritis (VN) is commonly diagnosed by demonstration of unilateral vestibular failure, as unilateral loss of caloric response. As this test reflects the function of the superior part of the vestibular nerve only, cases of pure inferior nerve neuritis will be lost.

Case presentations

We describe three patients with symptoms suggestive of VN, but normal calorics. All 3 had unilateral loss of vestibular evoked myogenic potential. A slight, asymptomatic position dependent nystagmus, with the pathological ear down, was observed.

Conclusion

We believe that these patients suffer from pure inferior nerve vestibular neuritis.

Vestibular Evoked Myogenic Potentials in Acute Acoustic Trauma

OBJECTIVES

Anatomical proximity of the saccule to the stapedial footplate points to the possibility of acoustic trauma associated with saccular dysfunction. Therefore, it was the authors' premise that abnormal vestibular evoked myogenic potential (VEMP) after acute acoustic trauma may be caused by saccular damage from very high intensity noise; consequently, irreversible hearing loss ensued. The aim of this study was to investigate the VEMP responses in those with acute acoustic trauma.

STUDY DESIGN

A prospective study.

SETTING

University hospital.

PATIENTS

Twenty patients (29 ears) without previous ear disorders diagnosed as acute acoustic trauma were enrolled in this study.

MAIN OUTCOME MEASURES

Before treatment, each patient underwent pure tone audiometry and caloric and VEMP tests. Correlations between the hearing outcome and mean hearing level, sources of noise, caloric responses, or VEMP results were investigated.

RESULTS

After 3 months of medication, complete recovery was achieved in 4 ears and hearing improvement in 4 ears, whereas hearing in 21 ears (72%) remained unchanged. Eighteen ears presenting normal VEMPs revealed hearing improvement in eight ears (44%) and unchanged hearing in ten ears (56%). However, hearing loss remained unchanged in all 11 ears (100%) with absent or delayed VEMPs, exhibiting a significant relationship between VEMP results and hearing outcome. Thus, VEMP test can predict the hearing outcome after acute acoustic trauma with a sensitivity of 44% and a specificity of 100%.

CONCLUSION

The greater the noise intensity, the severer damage on the cochlea and saccule is shown. Absent or delayed VEMPs in ears after acute acoustic trauma may indicate poor prognosis with respect to hearing improvement, whereas normal VEMP is not a powerful indicator for expectation of hearing improvement.

Saccular damage in patients with high-frequency sensorineural hearing loss

Subjects with high frequency sensorineural hearing loss (HF-SNHL) without retrocochlear pathology are those group which certainly encountered inner ear damaging factors. This study was designed to evaluate the effects of cochlear damaging factors on the sacculocollic pathway. Fifty patients (76 ears) with varying degrees of HF-SNHL but without clinical manifestations of vestibular pathology tested for vestibular evoked myogenic potentials (VEMP). The results were compared with those of 18-healthy referents (32 ears) examined in the same way. Subjects with HF-SNHL greater than 40 dB HL showed significantly more saccular deterioration, estimated as negative VEMP responses than did the referents. This suggests subclinical disturbances of the vestibular system especially of the saccule in these patients. The underlying mechanism may be simultaneous damage to both the cochlea and saccule by the same factors.

Disruption and restoration of cell-cell junctions in mouse vestibular epithelia following aminoglycoside treatment

The intracellular junction complexes, which consist of tight junctions (TJ), adherens junctions (AJ), and desmosomes, mediate cell-cell adhesion in epithelial cells. E-cadherin, which is a major component of AJ, plays a role not only in the maintenance of cell-cell junctions, but also in repressing cell proliferation. In this study, we examined changes of E-cadherin expression in mouse vestibular epithelia following local application of neomycin using immunohistochemistry and western blotting, and morphology of cell-cell junctions by transmission electron microscopy (TEM). Immunohistochemistry and western blotting revealed down-expression of E-cadherin and its consecutive recovery. TEM demonstrated temporal disruption of cell-cell junctions. Morphology of cell-cell junctions was more rapidly restored than recovery of E-cadherin expression. Transient disruption of cell-cell junctions and down-expression of E-cadherin is a rational response for the deletion of dying hair cells, and may be associated with a limited capacity for cell proliferations in mammalian vestibular epithelia following their rapid restoration.

2,3-Dihydroxybenzoic acid attenuates kanamycin-induced volume reduction in mouse utricular type I hair cells

The aminoglycoside kanamycin is a commonly used antibiotic, but unfortunately it is oto- and nephrotoxic in large doses. The negative effects are thought to be due to the formation of free radicals which is why strong antioxidants and iron chelators like 2,3-dihydroxybenzoic acid (DHB) are of great interest. This study estimates cellular quantitative changes in the utricular macula of mice following systemic treatment with kanamycin alone or in combination with DHB. The animals were injected with either saline, kanamycin or kanamycin + DHB for 15 days and perfusion fixed three weeks after last injection. Total volume of the utricle, as well as total number of hair and supporting cells, were estimated on light microscopic sections. Total volume and mean volume of hair cell types I and II and supporting cells were estimated on digital transmission electron micrographs. Total volume of the utricular macula, hair cell type I and supporting cells decreased significantly in animals injected with kanamycin but not in animals co-treated with DHB. Hair and supporting cell numbers remained unchanged in all three groups. In conclusion, the kanamycin-induced volume reduction of type I hair cells was attenuated by DHB.

Gentamicin induced nitric oxide-related oxidative damages on vestibular afferents in the guinea pig

Gentamicin is a well-known ototoxic aminoglycoside. However, the mechanism underlying this ototoxicity remains unclear. One of the mechanisms which may be responsible for this ototoxicity is excitotoxic damage to hair cells. The overstimulation of the N-methyl-d-aspartate (NMDA) receptors increases the production of nitric oxide (NO), which induces oxidative stress on hair cells. In order to determine the mechanism underlying this excitotoxicity, we treated guinea pigs with gentamicin by placing gentamicin (0.5 mg) pellets into a round window niche. After the sacrifice of the animals, which occurred at 3, 7 and 14 days after the treatment, the numbers of hair cells in the animals were counted with a scanning electron microscope. We then performed immunostaining using neuronal nitric oxide synthase (nNOS), inducible NOS (iNOS) and nitrotyrosine antibodies. The number of hair cells in the animals was found to decrease significantly after 7 days. nNOS and iNOS expression levels were observed to have increased 3 days after treatment. Nitrotyrosine was expressed primarily at the calyceal afferents of the type I hair cells 3 days after treatment. Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining revealed positive hair cells 3 days after treatment. Our results suggest that inner ear treatment with gentamicin may upregulate nNOS and iNOS to induce oxidative stress in the calyceal afferents of type I hair cells, via nitric oxide overproduction.

Self-treatment for benign paroxysmal positional vertigo of the posterior semicircular canal

The authors compared the efficacy of the Epley procedure with and without self-treatment in 80 patients with benign paroxysmal positional vertigo of the posterior semicircular canal. The self-treatment group (88%) had better results than the Epley-alone group (69%) based on both symptoms and nystagmus (p = 0.048). Complications occurred in 2.6% of the Epley-alone group and in 7.5% of the self-treatment group (p = 0.62).

Observation of the morphology and calcium content of vestibular otoconia in rats after simulated weightlessness

Reduction in bone formation may have been the main reason for the lower calcium content of the otoconia after simulated weightlessness in rats. The head-ward distribution of blood volume may explain the morphological changes observed in the middle and inner ears. To observe morphological changes in the vestibular organs and measure the calcium content of otoconia in rats after simulated weightlessness. We used a tail suspension model of simulated weightlessness and then investigated changes in the vestibular organs using scanning electron microscopy and X-ray microanalysis. In comparison to untreated rats, the vestibular otoconia of the rats subjected to simulated weightlessness were small, irregularly shaped or fissured, and were arranged loosely and out of order. In addition, the calcium content of the otoconia was markedly decreased.

Streptidine, a metabolic derivative produced after administration of streptomycin in vivo, is vestibulotoxic in rats

Streptomycin is the treatment of choice in developing countries for patients suffering from tuberculosis or other infectious diseases. However, it produces incapacitating vestibular symptoms whose onset is delayed and gradual. This observation led to the notion that a streptomycin metabolic derivative and not the antibiotic itself is the damaging agent for the inner ear. To study further the existence of this ototoxic metabolite, chronic treatment with streptomycin or its putative derivative streptidine was carried out in young male Long Evans rats. The presence of streptomycin or streptidine in the blood of animals of either experimental group was assessed by high performance liquid chromatography and analysis of swimming behavior was used to evaluate vestibular damage. Features of the sensory epithelium and quantification of hair cells were attained in sections of the utricular organ of all groups by light microscopy. After 25, 35 and 45 days of treatment with streptomycin, a metabolite with the same chromatographic properties as the streptidine standard run in parallel was identified in the blood of rats. Concentrations of the metabolite were 2.26 microg/ml on the 25th day and around 8.0 microg/ml in both the 35th and the 45th day of treatment, while streptomycin was below its detection level at either period. In streptidine-treated rats, the concentration of this compound was 1.0, 1.84 and 4.94 microg/ml on the 25th, 35th and 45th treatment days, respectively. Treatment with either streptomycin or streptidine resulted in similar abnormal swimming patterns and histological alterations of the utricular epithelium. Loss of hair cells was roughly equivalent even though streptidine was administered in a dose 90% lower than streptomycin. The gradual appearance of streptidine as a metabolic derivative of the antibiotic in the blood of rats or the administration of this compound alone, causing similar functional and structural vestibular deterioration seen in streptomycin-treated animals, supports the notion that streptidine is a potential contributor to ototoxicity after prolonged antibiotic administration.

Repeated vs single physical maneuver in benign paroxysmal positional vertigo

OBJECTIVES

To evaluate the effectiveness and possible side effects of a single session of repeated particle repositioning maneuver (PRM) to treat posterior canal benign paroxysmal positional vertigo (BPPV) and the usefulness of post-treatment restrictions.

MATERIALS AND METHODS

A total of 125 consecutive patients with idiopathic BPPV participated in the study. Fifty patients received a single session of repeated PRM only (group I). Results were compared with those of 50 patients with BPPV who received a single PRM (group IIb), and 25 patients who received a single PRM followed by the use of a neck collar and keeping the head upright for 48 h (group IIa).

RESULTS

Forty-six patients (92%) of group I, 40 patients (80%) of group IIb, and 21 patients (84%) of group IIa were completely free of signs and symptoms when re-examined 1 week after treatment. Transient nausea and disequilibrium following treatment were reported equally in all subgroups and well tolerated. Nearly all patients of group IIa considered the post-treatment restrictions very inconvenient.

CONCLUSIONS

A single session of repeated physical procedure seems to be clinically superior to one single maneuver and well tolerated. Additional post-treatment measurements are inconvenient and should be abandoned.

Overexpression of Bcl-2 prevents neomycin-induced hair cell death and caspase-9 activation in the adult mouse utricle in vitro

Mechanosensory hair cells of the inner ear are especially sensitive to death induced by exposure to aminoglycoside antibiotics. This aminoglycoside-induced hair cell death involves activation of an intrinsic program of cellular suicide. Aminoglycoside-induced hair cell death can be prevented by broad-spectrum inhibition of caspases, a family of proteases that mediate apoptotic and programmed cell death in a wide variety of systems. More specifically, aminoglycoside-induced hair cell death requires activation of caspase-9. Caspase-9 activation requires release of mitochondrial cytochrome c into the cytoplasm, indicating that aminoglycoside-induced hair cell death is mediated by the mitochondrial (or "intrinsic") cell death pathway. The Bcl-2 family of pro-apoptotic and anti-apoptotic proteins are important upstream regulators of the mitochondrial apoptotic pathway. Bcl-2 is an anti-apoptotic protein that localizes to the mitochondria and promotes cell survival by preventing cytochrome c release. Here we have utilized transgenic mice that overexpress Bcl-2 to examine the role of Bcl-2 in neomycin-induced hair cell death. Overexpression of Bcl-2 significantly increased hair cell survival following neomycin exposure in organotypic cultures of the adult mouse utricle. Furthermore, Bcl-2 overexpression prevented neomycin-induced activation of caspase-9 in hair cells. These results suggest that the expression level of Bcl-2 has important effects on the pathway(s) important for the regulation of aminoglycoside-induced hair cell death.

Cochleosaccular dysplasia: a morphometric and histopathologic study in a series of temporal bones

OBJECTIVE

The objective of this study was to perform a morphometric analysis of a series of temporal bones with cochleosaccular dysplasia to clarify the extent of inner ear changes in this disease.

STUDY DESIGN

This human temporal bone histopathologic study of a series of deaf-mute cases involves morphometric analysis, including stria vascularis and spiral ligament area measurements and spiral ganglion and hair cells counts.

SUBJECTS

Thirteen temporal bones were selected from 35 with deaf mutism based on the histopathologic findings described by Scheibe. Twenty normal age-matched control subjects were used for comparisons.

RESULTS

All temporal bones had the main histopathologic findings described by Scheibe, as well as severe affected stria vascularis. Seven temporal bones had cystic areas in the stria and three had concretions. Cross-sectional strial areas in temporal bones with cochleosaccular dysplasia were smaller than normal in all cochlear turns; however, no difference was found in spiral ligament cross-sectional areas. Reissner's membrane was hydropic in three temporal bones and the organ of Corti was absent in at least one cochlear turn in five. Concretions were present in the macula of seven temporal bones. Twelve temporal bones showed some level of spiral ganglion cell loss. No hair cells were observed in any temporal bone. A familial history of deafness was found in three cases.

CONCLUSION

Pathologic findings were variable and limited to the saccule and scala media. The variation, perhaps, reflects the different etiologies involved in the origin of cochleosaccular dysplasia.

On the origin of susceptibility to kinetotic swimming behaviour in fish: a parabolic aircraft flight study

Humans taking part in parabolic aircraft flights (PAFs) may suffer from motion sickness (SMS, a kinetosis; it comprises a dynamic and a static component). It has been argued that the so-called static variety of SMS during PAFs might be based on asymmetric statoliths (i.e., differently weighed statoliths on the right and the left side of the head), with asymmetric inputs to the brain being disclosed in microgravity. Since it has been repeatedly shown earlier that some fish of a given batch reveal a kinetotic behaviour during PAFs (especially so-called spinning movements and looping responses), we investigated whether fish swimming kinetotically in microgravity have a pronounced inner ear otolith asymmetry. Therefore, the swimming behaviour of larval cichlid fish was video-recorded during PAFs and subsequently, size and asymmetry (size difference between the left and the right side) of inner ear otoliths were determined. The asymmetry of utricular otoliths of kinetotic samples was found to be significantly higher than that of normally behaving experimental specimens. Regarding the asymmetry of saccular otoliths of the two groups, statistically different results were not obtained. The findings strongly support the earlier theoretical concept, according to which otolith asymmetry causes (static) SMS.

[Temporal bone histopathology exhibiting cochleosaccular degeneration in a patient with profound deafness]

We herein report the histopathological findings of the temporal bone taken from a patient with unilateral profound deafness since early childhood. The patient was a 72-year-old male who died of lung cancer and extensive metastases including the tongue. The patient had a history of profound hearing loss in his left ear since childhood. The histopathological finding of the left temporal bone revealed a severe atrophy of the organ of Corti, a detached and rolled-up tectorial membrane, a moderate loss of the stria vascularis, and a severe loss of spiral ganglion cells. In addition, the macula of the saccule was severely degenerated. The marked degeneration in the inner ear indicated a cochleosaccular disorder, which is a typical temporal bone finding in cases of viral labyrinthitis and hereditary hearing impairment. The present patient was suspected to have suffered cochleosaccular degeneration as a result of an inner ear viral infection during childhood because the number of spiral ganglion cells was significantly reduced because of secondary neural degeneration.

Expression of calretinin by fetal otocyst cells after transplantation into damaged rat utricle explants

Severe damage by acoustic overstimulation or ototoxins induces inner ear hair cell loss, resulting in permanent hearing loss and balance disorders because hair cell regeneration scarcely occurs in the inner ear sensory organs of mammals. In this study, to evaluate the possibilities of cell transplantation therapy for damaged inner ear sensory organs, dissociated cell cultures of fetal otocyst cells (FOCs) were established from embryonic day 12.5 (E12.5) rat inner ears, and transplanted into gentamicin-treated explants of vestibular sensory epithelia. Two weeks after transplantation, immunohistochemical analysis demonstrated that some of the grafted FOCs survived within the vestibular sensory epithelia and expressed epitopes of calretinin. one of the hair cell marker proteins. These findings indicate that FOCs have the potential to migrate into damaged vestibular epithelia and differentiate into hair cell immunophenotypes. Cell transplantation therapy may be available for functional regeneration in inner ear diseases.

Histology of the utricle in kinetotically swimming fish: a parabolic aircraft flight study

OBJECTIVES

Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness, which is a form of kinetosis. As it has been repeatedly shown that some fish in a given batch also reveal kinetotic behaviour (especially so-called spinning movements and looping responses) during PAFs, and as a result of the homology of the vestibular apparatus of all vertebrates, fish can be used as model systems to investigate the origin of susceptibility to motion sickness. Therefore. we were prompted to examine the utricular maculae, which are responsible for the internalization of gravity in teleosteans of fish swimming kinetotically in microgravity (microg) in comparison with those of animals from the same batch who swam normally.

MATERIAL AND METHODS

Larval cichlid fish (Oreochromis mossambicus) were subjected to PAFs. Post-flight, animals which had behaved normally or kinetotically during the microg phases were examined histologically The sizes of the inner ear utricular maculae as well as the numbers of sensory and supporting cells were determined.

RESULTS

The total numbers of both sensory and supporting cells of the utricular maculae did not differ between kinetotic and normally swimming fish. Cell density (number of sensory and supporting cells/100 microm2) was, however, reduced in kinetotic animals (p < 0.0001), which seemed to be due to the presence of malformed epithelial cells of increased size in the kinetotic specimens.

CONCLUSION

These results indicate that susceptibility to kinetosis may originate from genetically predisposed malformed sensory epithelia.

Size and cell number of the utricle in kinetotically swimming fish: a parabolic aircraft flight study

Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness (SMS, a kinetosis). Since it has been repeatedly shown earlier that some fish of a given batch also reveal a kinetotic behavior during PAFs (especially so-called spinning movements and looping responses) and due to the homology of the vestibular apparatus among all vertebrates, fish can be used as model systems to investigate the origin of susceptibility to motion sickness. Therefore, we examined the utricular maculae (they are responsible for the internalization of gravity in teleosteans) of fish swimming kinetotically at microgravity in comparison with animals from the same batch who swam normally. On the histological level, it was found that the total number of both sensory and supporting cells of the utricular maculae did not differ between kinetotic animals as compared to normally swimming fish. Cell density (sensory and supporting cells/100 micrometers2), however, was reduced in kinetotic animals (p<0.0001), which seemed to be due to malformed epithelial cells (increase in cell size) of the kinetotic specimens. Susceptibility to kinetoses may therefore originate in malformed sensory epithelia.

Gentamicin tympanoclysis: effects on the labyrinthine sensory cells

OBJECTIVES

The objective of the study was to determine whether a selective vestibular hair cell toxicity with sparing of the cochlear hair cells could be achieved by infusing different concentrations of gentamicin into the middle ears of adult cats.

STUDY DESIGN

Prospective experimental animal study treating only the left ear of each cat, the right ear serving as individual control.

METHODS

Gentamicin solution at concentrations of either 30 or 3 mg/mL was infused daily into the left middle ear of adult cats until overt ataxia occurred. After 1 month or 6 months, each cat was killed and its temporal bones prepared for optical microscopy.

RESULTS

Animals treated with 30 mg/mL gentamicin until ataxic required a median of five daily doses. These animals had clear-cut cochlear basal turn hair cell losses accompanying toxic lesions in the utricle and cristae. In contrast, animals treated with 3 mg/mL gentamicin until ataxic required an average of 19 daily doses. These animals had lesions restricted to the utricle and cristae with sparing of the cochlea hair cells. Animals that failed to develop ataxia manifested neither lesions of the cochlear nor vestibular hair cells.

CONCLUSION

Gentamicin tympanoclysis in the cat animal model, using a dilute solution and continued once daily until clinical ataxia occurs, is capable of producing selective vestibular hair cell toxicity while sparing cochlea hair cells.

Weightlessness affects cytoskeleton of rat utricular hair cells during maturation in vitro

The aim of this study was to investigate whether an altered gravitational environment affected the phenotype of vestibular hair cells during maturation. We developed, using an automated incubator, a 3D culture of utricles from newborn rats. These cultures were subjected to weightlessness for 1 or 3 days, and then compared with control cultures developed in natural and induced 1G gravity. Immunocytochemistry for alpha-tubulin and calretinin revealed disorganisation of the microtubules and a loss of hair cell shape in cells subjected to weightlessness during maturation. We conclude that the lack of gravitational strain affected cytoskeletal dynamics, resulting in loss of the specific morphological phenotype of the cells.

Ante mortem ruptures of the endolymphatic membranes in children: real finding or artifact?

We undertook this study to determine whether or not ante mortem ruptures of the endolymphatic membranes occurred naturally in the infantile labyrinth, what were the most frequent locations and to assess the statistical correlation of an earlier finding of bulging of Reissner's membrane in pediatric temporal bones. We examined 128 temporal bones from 80 children between the ages of newborn to 12 years with an average age of 15.4 months. All temporal bones were prepared by the celloidin technique and studied by light microscopy. The endolymphatic membranes of the cochlear duct, saccule, utricle and semicircular ducts were examined for ruptures. A rupture of the saccule and utricle was considered to be an ante mortem event if its edges were rolled and bound with fine adhesions and could be identified in adjacent sections. Ante mortem ruptures were seen in 11.1% of the specimens and occurred in 2.4% in Reissner's membrane, in 6.3% in the saccular membrane and in 2.4% in the utricular membrane. In these specimens, the histopathological changes included atrophy of the stria vascularis and collapse of the organ of Corti, which provided further evidence of an ante mortem event. Infants with extralabyrinthine congenital anomalies or children who were treated with chemotherapy were more likely to develop ruptures of the endolymphatic membranes if they also received aminoglycosides.

Revision surgery after saccotomy for Meniere's disease: does it make sense?

Saccotomy is an established surgical treatment for Meniere's disease that involves exposing and opening the endolymphatic sac and draining the endolymph. However, in patients experiencing recurrent vertigo after saccotomy, it is questionable whether revision saccotomy should be recommended as opposed to more invasive procedures, such as neurectomy of the vestibular nerve. To determine the utility of revision saccotomy, we conducted a retrospective study of 29 patients undergoing this procedure for recurrent vertigo. Patient charts were reviewed for the re-occurrence of any vertiginous symptoms and outcomes with regard to hearing results and post-operative complications. An attempt was made to correlate vertigo status post-revision with surgical findings at the time of revision. After an average follow-up of 20 months, 18 patients (62%) were free of vertigo, and four patients (14%) had a significant decrease in the frequency and intensity of vertiginous attacks. Two patients (7%) relapsed after a vertigo-free period of 18 months, and five patients (17%) experienced no clinical improvement after revision surgery. In patients with a successful sac revision, a common finding at the time of revision was new bone formation in the endolymphatic sac area (n=11), which may have caused blocking of the endolymphatic drainage. Our results demonstrate that revision saccotomy should be considered for recurrent Meniere disease before other, more invasive, surgical options.

Cochleosaccular pathology after perinatal and postnatal asphyxia: histopathologic findings

OBJECTIVE

This study describes the histopathologic findings of a patient with severe bilateral sensorineural hearing loss after perinatal and postnatal hypoxia and asphyxia.

STUDY DESIGN

Histopathologic examination on the temporal bones.

SETTING

The study was performed at the Elizabeth McCullough Knowles Otopathology Laboratory, Division of Otopathology, Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.

RESULTS

Histopathologic examination on the left temporal bone revealed severe atrophy of the organ of Corti throughout the entire cochlea, decrease in the number of the spiral ganglion cells especially in the basal turn, and mild atrophy of saccular macula. In the right temporal bone, similar abnormalities were observed in the inner ear, but the changes were milder than those in the left temporal bone. No other distinct pathologic finding was observed in either ear.

CONCLUSION

These findings suggest that the presence of severe hypoxic ischemia causes cochleosaccular atrophy. To our knowledge, this is the first histopathologic case report describing the long-term effect of perinatal and postnatal hypoxia and asphyxia that produced cochleosaccular abnormalities in the human inner ear.

Treatment outcomes of benign paroxysmal positional vertigo

OBJECTIVE

The purpose of this study was to examine the efficacy of the particle repositioning manoeuvre (PRM) in the treatment of benign paroxysmal positional vertigo (BPPV).

DESIGN

A randomized prospective study of patients with BPPV.

METHODS

Seventy-one patients were randomized to one of three groups at their first clinic visit. These groups included the PRM, a sham PRM, and a control group. Patients were followed up in clinic at 2 weeks and 3 months. The mean long-term follow-up was 12 months. A telephone questionnaire was also conducted.

RESULTS

At 2-week follow-up, 81.8% of patients in the PRM group had a resolution of symptoms and a negative Dix-Hallpike test compared with 15.3% in the sham PRM group and 60% in the control group. This difference was statistically significant between the treatment (PRM) and sham PRM groups and between the sham and control groups. It nearly reached significance between the treatment and control groups (p = .06). The sham treatment group had by far the worst outcome at the 2-week interval. There was no statistically significant difference between the groups after 2 weeks.

CONCLUSION

The PRM is side specific. It may help induce remission of the vertiginous symptoms of BPPV in the short term. This cannot be attributable to a placebo effect. The PRM does not seem to affect the natural history of the disorder in the long term. The sham treatment causes a delay in spontaneous recovery, possibly by preventing the particles from falling into the utricle. This study has not compared the frequency or severity of symptoms.

Cytoskeletal protein mRNA expression in the chick utricle after treatment in vitro with aminoglycoside antibiotics: effects of insulin, iron chelators and cyclic nucleotides

In birds, spontaneous recovery of the hair cells of the inner ear can occur after damage induced by aminoglycoside antibiotics. The factors that influence this recovery and the process of hair cell regeneration itself have until recently been investigated largely by morphological and histological methods. The aim of this work was to use a molecular biological approach to the analysis of hair cell regeneration by measuring the changes that occur in expression of mRNA for hair cell-specific cytoskeletal proteins fimbrin and class III beta-tubulin, along with that for beta-actin, in the utricle of chicks after hair cell damage both in vitro and in vivo. Utricles were removed from 1-day-old chicks and incubated with the aminoglycoside antibiotics gentamicin or neomycin (both 1 mM), or chicks were injected intraperitoneally with 100 mg/kg gentamicin or neomycin for 4 consecutive days. At the end of the treatment periods, total RNA was extracted from single utricles, reverse transcribed to cDNA and the cDNA amplified by PCR with primers for beta-actin, fimbrin and class III beta-tubulin. Co-amplification allowed quantitative comparison of mRNA between fimbrin, or class III beta-tubulin and beta-actin from the same utricle. Both aminoglycosides, either after 48 h in vitro or immediately after treatment in vivo, caused a significant decrease in the expression of fimbrin mRNA and class III beta-tubulin mRNA, relative to beta-actin mRNA, which itself increased. Light and electron microscopy confirmed that this corresponded to loss of, and damage to, hair cells. The relative expression of fimbrin and class III beta-tubulin mRNAs was partly restored almost to control levels 4 days after cessation of treatment in vivo and fully normalised by 4 weeks, by which time hair cells appeared normal. However, their relative expression remained depressed 4 days after removal of antibiotic in vitro. The iron chelator desferrioxamine (100 microM) in vitro prevented the aminoglycoside-induced reduction in relative expression of mRNA for both fimbrin and class III beta-tubulin. Neither insulin (5 microM) nor a combination of dibutyryl cyclic AMP (5 mM) and the phosphodiesterase inhibitor IBMX (0.5 mM) prevented the decrease in relative expression of the mRNAs for the hair cell-specific proteins, but both treatments allowed their partial recovery in vitro during the 4-day-period after removal of aminoglycoside. It is concluded that the cells of the sensory epithelium of the chick utricle subjected to aminoglycoside-induced damage undergo a process in which mRNA expression is switched away from the production of functional proteins and towards proteins necessary for structural re-organisation. The restoration of mRNA expression to a normal pattern is promoted by the growth factor insulin and by cyclic AMP.

The canalith repositioning procedure for the treatment of benign paroxysmal positional vertigo: a randomized controlled trial

OBJECTIVE

To compare the canalith repositioning procedure (CRP) with a sham maneuver for the treatment of benign paroxysmal positional vertigo.

PATIENTS AND METHODS

We recruited 50 patients with a history of positional vertigo and unilateral positional nystagmus on physical examination (Dix-Hallpike maneuver). Patients were randomized to either the CRP (n = 24) or a sham maneuver (n = 26). Measured outcomes included resolution of vertigo and positional nystagmus at follow-up examination.

RESULTS

The mean duration of follow-up was 10 days for both groups. Resolution of symptoms was reported by 12 (50%) of the 24 patients in the CRP group and by 5 (19%) of the 26 patients in the sham group (P = .02). The results of the Dix-Hallpike maneuver were negative for positional nystagmus in 16 (67%) of 24 patients in the CRP group and in 10 (38%) of 26 patients in the sham group (P = .046).

CONCLUSION

The CRP is effective treatment of benign paroxysmal positional vertigo, and this procedure can be performed by general internists on outpatients with this disorder.

Neurogenin 1 null mutant ears develop fewer, morphologically normal hair cells in smaller sensory epithelia devoid of innervation

The proneuronal gene neurogenin 1 (ngn1) is essential for development of the inner-ear sensory neurons that are completely absent in ngn1 null mutants. Neither afferent, efferent, nor autonomic nerve fibers were detected in the ears of ngn1 null mutants. We suggest that efferent and autonomic fibers are lost secondarily to the absence of afferents. In this article we show that ngn1 null mutants develop smaller sensory epithelia with morphologically normal hair cells. In particular, the saccule is reduced dramatically and forms only a small recess with few hair cells along a duct connecting the utricle with the cochlea. Hair cells of newborn ngn1 null mutants show no structural abnormalities, suggesting that embryonic development of hair cells is independent of innervation. However, the less regular pattern of dispersal within sensory epithelia may be caused by some effects of afferents or to the stunted growth of the sensory epithelia. Tracing of facial and stato-acoustic nerves in control and ngn1 null mutants showed that only the distal, epibranchial, placode-derived sensory neurons of the geniculate ganglion exist in mutants. Tracing further showed that these geniculate ganglion neurons project exclusively to the solitary tract. In addition to the normal complement of facial branchial and visceral motoneurons, ngnl null mutants have some trigeminal motoneurons and contralateral inner-ear efferents projecting, at least temporarily, through the facial nerve. These data suggest that some neurons in the brainstem (e.g., inner-ear efferents, trigeminal motoneurons) require afferents to grow along and redirect to ectopic cranial nerve roots in the absence of their corresponding sensory roots.

Stereocilia defects in the sensory hair cells of the inner ear in mice deficient in integrin alpha8beta1

The mammalian inner ear contains organs for the detection of sound and acceleration, the cochlea and the vestibule, respectively. Mechanosensory hair cells within the neuroepithelia of these organs transduce mechanical force generated by sound waves or head movements into neuronal signals. Defects in hair cells lead to deafness and balance defects. Hair cells have stereocilia that are indispensable for mechanosensation, but the molecular mechanisms regulating stereocilia formation are poorly understood. We show here that integrin alpha8beta1, its ligand fibronectin and the integrin-regulated focal adhesion kinase (FAK) co-localize to the apical hair-cell surface where stereocilia are forming. In mice homozygous for a targeted mutation of Itga8 (encoding the alphabeta8 subunit), this co-localization is perturbed and hair cells in the utricle, a vestibular subcompartment, lack stereocilia or contain malformed stereocilia. Most integrin alpha-8beta1-deficient mice die soon after birth due to kidney defects. Many of the survivors have difficulty balancing, consistent with the structural defects of the inner ear. Our data suggest that integrin alpha8beta1, and potentially other integrins, regulates hair-cell differentiation and stereocilia maturation. Mutations affecting matrix molecules cause inherited forms of inner ear disease and integrins may mediate some effects of matrix molecules in the ear; thus, mutations in integrin genes may lead to inner-ear diseases as well.

Neither endocochlear potential nor tegmentum vasculosum are affected in hearing impaired belgian waterslager canaries

We previously showed that the Belgian Waterslager canary strain is affected by a hereditary hearing loss that is associated with a reduced number of hair cells and hair cell pathologies in the basilar papilla. Since hair cell pathologies were also present in the sacculus, Weisleder et al. (1994) suggested that these birds are afflicted by Scheibe's like dysplasia, a cochleo-saccular defect. In mammals, cochleo-saccular defects are characterized primarily by the lack of an endocochlear potential and abnormalities in the Stria vascularis which only secondarily lead to hair cell loss (Steel and Bock, 1983; Steel, 1994; 1995). Here we report the endocochlear potential of six ears from three non-Belgian Waterslager canaries and three ears of two Belgian Waterslager canaries to decide if Waterslager canaries are affected by a cochleo-saccular or by a neuroepithelial defect. The mean endocochlear potential was 17.6+/-2. 5 mV in the non-Waterslager canaries and 20.3+/-0.6 mV in Waterslager canaries. In addition, and consistent with the presence of a normal endocochlear potential, light microscopy of the tegmentum vasculosum provided no evidence for pathology. These data show that Belgian Waterslager canaries are affected by a neuroepithelial rather than a cochleo-saccular inner ear defect.