Cochlear pathology in human temporal bones with otitis media

Evaluation of postural stability and vestibulo-ocular reflex in adults with chronic suppurative otitis media

PURPOSE

To evaluate the vestibulospinal reflex and vestibulo-ocular reflex (VOR) in patients with chronic suppurative otitis media (CSOM) using posturography and the video head impulse test (vHIT).

METHODS

Sixty-five patients with CSOM and 65 healthy participants as controls were included. Patients with CSOM were instructed to complete the dizziness handicap inventory (DHI). All participants underwent otoscopy, pure-tone audiometry, posturography sensory organization test (SOT), and vHIT.

RESULTS

Patients with CSOM exhibited a high prevalence of dizziness. The CSOM group had poor SOT vestibular scores compared to the control group. Patients with CSOM had worse sways in the antero-posterior and mediolateral planes. The CSOM group was divided into two subgroups according to the type of hearing loss. SOT vestibular scores were significantly poorer in the mixed hearing loss group than those in the conductive hearing loss group. We found a positive correlation between disease duration and poor SOT vestibular scores. Moreover, poor SOT vestibular scores correlated with high DHI scores. We found abnormalities in the vHIT results in the CSOM group in the form of low VOR gain and corrective saccades.

CONCLUSION

Our study provides clinical evidence of dizziness, poor postural control, and VOR abnormalities in patients with CSOM. The presence of sensory elements of hearing loss in patients with CSOM appears to be positively associated with vestibular dysfunction.

A Prospective Study of Audiological Manifestations in Patients of Allergic Rhinitis

Allergic rhinitis is a type-I hypersensitivity reaction of the nasal mucosa, primarily mediated by immunoglobulin E (IgE) with complex etiological factors.Allergic rhinitis may involve the inner ear. The scientific basis for this is poorly understood. However, the inner ear has been found to demonstrate both cellular and humoral immunity, and the seat of immuno-activity appears to reside in the endolymphatic sac and duct. To assess the audiological profile of patients with allergic rhinitis. 100 Study group patients and 50 control group subjects underwent detailed audiological assessment. Present study revealed high frequency sensorineural hearing loss with prolongation of Wave I and shortened wave I-III and Wave I-V interpeak latencies on ABR and abnormal DPOAE findings, compared with controls which indicate inner ear involvement (cochlear pathology). Individuals with allergic rhinitis are more prone to hearing abnormalities which can be detected even before any symptoms of hearing impairment are present. However, the exact pathophysiology of inner ear damage in patients of airway allergy is poorly understood and therefore, additional studies in this area are required with a larger sample population to assess the benefits of hearing assessment in patients of allergic rhinitis for early detection of hearing loss.

Audiological characteristics and exploratory treatment of a rare condition of acute-otitis-media-associated sudden sensorineural hearing loss

BACKGROUND

Acute otitis media (AOM) is a common disease that is more prevalent in children. Most studies concerning AOM-associated sudden sensorineural hearing loss are case reports and retrospective in nature, hence the etiology of AOM-associated sudden hearing loss has not been fully established.

AIM

To analyze audiological characteristics of AOM-associated sudden hearing loss and evaluate efficacy of combined tympanostomy tube placement (TTP) and intratympanic methylprednisolone.

METHODS

Eight adult patients who were diagnosed with AOM-associated sudden hearing loss and ineffectively treated by conventional medical therapy were enrolled in this study. Basic data were collected, and pure tone audiometry was performed to assess the audiological characteristics. Combination therapy with TTP and intratympanic methylprednisolone injection was given to the patients.

RESULTS

Mixed or sensorineural hearing loss was observed at high frequencies (2–4 kHz). All the cases in this study were cured after TTP and intratympanic methylprednisolone. After treatment, the average hearing threshold at affected frequencies was significantly lower than those in the pretreatment group (P < 0.05) and was similar to that in the healthy ears (P > 0.05).

CONCLUSION

AOM rarely induces sudden sensorineural hearing loss. Combination therapy with TTP and intratympanic methylprednisolone injection may be effective after failure of conventional medical treatment.

Extended high frequency hearing loss in tinnitus-positive chronic suppurative otitis media patient

OBJECTIVES

To determine the association between extended high frequency hearing loss and tinnitus in normal cochlear function based on a conventional audiometry chronic suppurative otitis media (CSOM) patient.

DESIGN AND METHODS

A cross-sectional study was conducted on 220 ears diagnosed as having CSOM with an equal number of tinnitus and without tinnitus groups. Only those with normal cochlear function based on conventional pure tone audiometry (250 Hz to 8 kHz) were included. They were further tested for hearing at extended high frequencies of up to 16 kHz. The severity of tinnitus was tested using a tinnitus questionnaire.

RESULTS

The prevalence of extended high frequency hearing loss in the normal cochlear function CSOM patients with tinnitus was 81.8% (95% CI 74.5%, 89.1%), whereas the prevalence in the tinnitus negative group was 30.0% (95% CI 21.3%, 38.7%). There was a significant association between extended high frequency hearing loss and tinnitus in CSOM patients (P < .001). The average thresholds were significantly higher in the tinnitus group at all extended high frequencies tested with an increasing trend of significance toward the higher frequencies. However, this study did not observe any association between the severity of tinnitus and extended high frequency hearing loss.

CONCLUSION

The development of tinnitus among normal cochlear function CSOM patients indicates that the damage has occurred at a higher frequency level. However, the severity of tinnitus does not predict the degree of higher frequency hearing loss. Therefore, the presence of tinnitus warrants more aggressive monitoring and treatment to prevent sensorineural hearing loss from developing into the speech frequencies.

LEVEL OF EVIDENCE

4.

Otitis Media in Childhood and Disease in Adulthood: A 40-Year Follow-Up Study

OBJECTIVES

The pathogenesis of chronic suppurative otitis media (CSOM) includes complex interactions between microbial, immunologic, and genetic factors. To our knowledge, no study has focused on the association between childhood otitis media, immune regulation, inflammatory conditions, and chronic disease in adulthood. The present study aims to assess whether CSOM in childhood predicts immune-related inflammatory disorders or cardiovascular disease in adulthood. Another aim is to assess the association with oto-vestibular diseases in adulthood.

DESIGN

Population cohort study in Norway comprised 51,626 participants (mean age 52 years) who underwent a hearing investigation at 7 to 13 years of age where 189 were diagnosed with CSOM (otorhinolaryngologist diagnose) and 51,437 had normal hearing thresholds (controls). Data on adult disease were obtained from the Norwegian Patient Registry (ICD-10 codes from the specialist health services). We estimated associations with logistic regression analyses.

RESULTS

The associations between CSOM in childhood and disease in adulthood were as follows: chronic sinusitis (odds ratio 3.13, 95% confidence interval 1.15 to 8.52); cardiovascular disease (1.38, 1.01 to 1.88); hearing loss (5.58, 3.78 to 8.22); tinnitus (2.62, 1.07 to 6.41). The adult hearing loss among cases with childhood CSOM was most frequently registered as sensorineural. There was no statistically significant increased risk of later asthma (1.84 [0.98 to 3.48]), inflammatory bowel disease, inflammatory joint disease, systemic tissue disease, or vestibulopathy. The estimates were adjusted for age, sex, socio-economic status, and smoking.

CONCLUSION

Our large cohort study, which is the first to focus on the link between otitis media in childhood and immune-related inflammatory disorders later in life, does not confer a clear association. CSOM in childhood was strongly related to adult tinnitus and hearing loss, which was most frequently registered as sensorineural.

Chronic Conductive Hearing Loss Is Associated With Speech Intelligibility Deficits in Patients With Normal Bone Conduction Thresholds

OBJECTIVES

The main objective of this study is to determine whether chronic sound deprivation leads to poorer speech discrimination in humans.

DESIGN

We reviewed the audiologic profile of 240 patients presenting normal and symmetrical bone conduction thresholds bilaterally, associated with either an acute or chronic unilateral conductive hearing loss of different etiologies.

RESULTS

Patients with chronic conductive impairment and a moderate, to moderately severe, hearing loss had lower speech recognition scores on the side of the pathology when compared with the healthy side. The degree of impairment was significantly correlated with the speech recognition performance, particularly in patients with a congenital malformation. Speech recognition scores were not significantly altered when the conductive impairment was acute or mild.

CONCLUSIONS

This retrospective study shows that chronic conductive hearing loss was associated with speech intelligibility deficits in patients with normal bone conduction thresholds. These results are as predicted by a recent animal study showing that prolonged, adult-onset conductive hearing loss causes cochlear synaptopathy.

Three-Dimensional Analysis of Round Window Membrane in the Chinchilla Model with Acute Otitis Media Induced with Streptococcus Pneumoniae 7F

Objective:

The purpose of this study was to investigate the morphological changes of round window membrane (RWM) in chinchillas with Streptococcus pneumoniae (S. pneumoniae) serotype 7F induced acute otitis media (AOM) by two dimensional (2D) and three dimensional (3D) measurements.

Methods:

Temporal bone specimens taken from 12 chinchillas were divided into two groups. The control group consisted of healthy animals that were injected with intrabullar saline. The subjects in the experimental group were induced with AOM by intrabullar injection of S. pneumoniae 7F. The 2D and 3D measurements of RWM were compared between the groups.

Results:

Dramatic changes were noted in the RWM of the experimental group compared to the control group. The thickness [mean ± standard deviation (SD)] of the RWM was significantly (p<0.05) increased in the experimental group compared to the control group by 2D measurements taken at three different points of RWM. Moreover, 3D measurements revealed that the volume (mean ± SD) of RWM was significantly (p=0.009) increased in the experimental group.

Conclusion:

The results of our study, which indicated significant change in RWM in both 2D and 3D measurements, may shed light on the relationship between AOM and inner ear diseases. Based on our results, we recommend evaluating 3D analyses of RWM, which provide useful data, to better understand the changes in the membrane.

Otopathogenic Staphylococcus aureus Invades Human Middle Ear Epithelial Cells Primarily through Cholesterol Dependent Pathway

Chronic suppurative otitis media (CSOM) is one of the most common infectious diseases of the middle ear especially affecting children, leading to delay in language development and communication. Although Staphylococcus aureus is the most common pathogen associated with CSOM, its interaction with middle ear epithelial cells is not well known. In the present study, we observed that otopathogenic S. aureus has the ability to invade human middle ear epithelial cells (HMEECs) in a dose and time dependent manner. Scanning electron microscopy demonstrated time dependent increase in the number of S. aureus on the surface of HMEECs. We observed that otopathogenic S. aureus primarily employs a cholesterol dependent pathway to colonize HMEECs. In agreement with these findings, confocal microscopy showed that S. aureus colocalized with lipid rafts in HMEECs. The results of the present study provide new insights into the pathogenesis of S. aureus induced CSOM. The availability of in vitro cell culture model will pave the way to develop novel effective treatment modalities for CSOM beyond antibiotic therapy.

[Evaluation of structural changes of bone in chronic purulent otitis media]

Fragments of bone tissue of the temporal bone, obtained during reconstructive-sanitizing operations in patients with chronic purulent otitis media, were studied by light and electron microscopy. An analysis was made of the degree of structural changes in bone tissue in chronic inflammation at the cellular and tissue levels after a histomorphological study in microwave decalcification. The method of diagnosis reliably allowed to differentiate the diseases characterized by the rarefaction of bone tissue, due to chronic inflammation, and also to determine the processes of transformation of bone tissue. The method of diagnosis reliably allows to differentiate diseases characterized by the rarefaction of bone tissue due to chronic inflammation, as well as to determine the processes of bone tissue transformation, however, the study is time-consuming, long-lasting and expensive.

Inner ear disturbances related to middle ear inflammation

The inner and middle ear are connected mainly through round and oval windows, and inflammation in the middle ear cavity can spread into the inner ear, which might induce a disturbance. In cases with intractable otitis media, attention should also be paid to symptoms related to the inner ear. In this paper, middle ear inflammation and related inner ear disturbances are reviewed with a focus on representative middle ear diseases (such as acute otitis media, chronic otitis media, otitis media with anti-neutrophil cytoplasmic antibody-associated vasculitis, eosinophilic otitis media, cholesteatoma with labyrinthine fistula, and reflux-related otitis media). Their clinical concerns are then discussed with reference to experimental studies. In these diseases, early diagnosis and adequate treatment are required to manage not only middle ear but also inner ear conditions.

Active Transport of Peptides Across the Intact Human Tympanic Membrane

We previously identified peptides that are actively transported across the intact tympanic membrane (TM) of rats with infected middle ears. To assess the possibility that this transport would also occur across the human TM, we first developed and validated an assay to evaluate transport in vitro using fragments of the TM. Using this assay, we demonstrated the ability of phage bearing a TM-transiting peptide to cross freshly dissected TM fragments from infected rats or from uninfected rats, guinea pigs and rabbits. We then evaluated transport across fragments of the human TM that were discarded during otologic surgery. Human trans-TM transport was similar to that seen in the animal species. Finally, we found that free peptide, unconnected to phage, was transported across the TM at a rate comparable to that seen for peptide-bearing phage. These studies provide evidence supporting the concept of peptide-mediated drug delivery across the intact TM and into the middle ears of patients.

Current evidence of peripheral vestibular symptoms secondary to otitis media

BACKGROUND

The association between otitis media and vestibular symptoms has been hypothesized in the past. Thus, in this study, we aimed to critically analyze (based in a systematic review of the literature) whether patients who have otitis media are at greater risk of developing vestibular impairment or not.

METHODS

We performed a systematic review of the literature and identified potentially relevant articles reporting vestibular symptoms and results of vestibular function tests in patients with otitis media through searches of the PubMED, Web of Science, Scopus, and Google Scholar databases. The quality of the final set of records was assessed using the "Newcaste-Ottawa Scale".

RESULTS

Of the 2334 records searched, 43 met our inclusion and exclusion criteria, and those included 2250 patients. The records comprised 20 longitudinal studies, 21 cross-sectional studies, and 2 case reports. Regarding the type of otitis media studied, 25 examined vestibular impairment in otitis media with effusion, 6 acute otitis media, and 12 chronic otitis media. Results of anamnesis, clinical exams, and several vestibular function tests are reported and critically discussed.

CONCLUSION

Most studies evaluating the association between otitis media and vestibular symptoms have potential methodological flaws. Clinical evidence suggests that patients with otitis media have increased chances for having vestibular symptoms, delayed acquisition of developmental milestones, and abnormalities in several vestibular function tests as compared with controls. Future studies with rigorous methodology aiming to assess the clinical significance (and prognostic factors) of the association between otitis media and vestibular impairment are warranted. Key message Several studies demonstrated long-term sequelae secondary to otitis media. However, the evidence supporting those assumptions are based in low-quality evidence. Thus, better structured studies are warranted to better understand the clinical relevance of such association.

A program to respond to otitis media in remote Australian Aboriginal communities: a qualitative investigation of parent perspectives

Background

Indigenous infants and children in Australia, especially in remote communities, experience early and chronic otitis media (OM) which is difficult to treat and has lifelong impacts in health and education. The LiTTLe Program (Learning to Talk, Talking to Learn) aimed to increase infants’ access to spoken language input, teach parents to manage health and hearing problems, and support children’s school readiness. This paper aimed to explore caregivers’ views about this inclusive, parent-implemented early childhood program for 0–3 years in an Aboriginal community health context.

Methods

Data from in-depth, semi-structured interviews with 9 caregivers of 12 children who had participated in the program from one remote Aboriginal community in the Northern Territory are presented. Data were analysed thematically. Caregivers provided overall views on the program. In addition, three key areas of focus in the program are also presented here: speech and language, hearing health, and school readiness.

Results

Caregivers were positive about the interactive speech and language strategies in the program, except for some strategies which some parents found alien or difficult: such as talking slowly, following along with the child’s topic, using parallel talk, or baby talk. Children’s hearing was considered by caregivers to be important for understanding people, enjoying music, and detecting environmental sounds including signs of danger. Caregivers provided perspectives on the utility of sign language and its benefits for communicating with infants and young children with hearing loss, and the difficulty of getting young community children to wear a conventional hearing aid. Caregivers were strongly of the opinion that the program had helped prepare children for school through familiarising their child with early literacy activities and resources, as well as school routines. But caregivers differed as to whether they thought the program should have been located at the school itself.

Conclusions

The caregivers generally reported positive views about the LiTTLe Program, and also drew attention to areas for improvement. The perspectives gathered may serve to guide other cross-sector collaborations across health and education to respond to OM among children at risk for OM-related disability in speech and language development.

Electronic supplementary material

The online version of this article (10.1186/s12887-018-1081-3) contains supplementary material, which is available to authorized users.

Optimisation of peptides that actively cross the tympanic membrane by random amino acid extension: a phage display study

Local treatment of middle ear (ME) disease currently requires surgical penetration of the tympanic membrane (TM). We previously discovered 12-mer peptides that are actively transported across the intact TM, a process that could be used for non-invasive drug delivery into the ME. To optimise transport and provide further understanding of the peptides transport mechanism, we extended two of the candidate peptides by six additional amino acids at random, and screened the resulting 18-mers libraries on TMs of rats with active bacterial otitis media (OM) for transport efficiency using phage display. Six identified peptides were individually tested in vivo for trans-TM transport to verify the tissue specificity. Three exhibited enhanced transport compared to their parent 12-mer scaffold, with the best showing an approximately nine-fold increase. Sequence analysis revealed anchor residues and structural features associated with enhanced transport. This included the prominent display of conserved sequence motifs at the extended free ends of the predicted peptide structures.

The Severity of Infection Determines the Localization of Damage and Extent of Sensorineural Hearing Loss in Experimental Pneumococcal Meningitis

Hearing loss is an important sequela of pneumococcal meningitis (PM), occurring in up to 30% of survivors. The role of the severity of infection on hearing function and pathomorphological consequences in the cochlea secondary to PM have not been investigated to date. Using a well-established model of PM, we systematically investigated the functional hearing outcome and the long-term fate of neurosensory cells in the cochlea, i.e., hair cells and spiral ganglion neurons (SGNs), with a focus on their tonotopic distribution. Intracisternal infection of infant rats with increasing inocula of Streptococcus pneumoniae resulted in a dose-dependent increase in CSF levels of interleukin-1β, interleukin-6, tumor necrosis factor α, interleukin-10, and interferon-γ in acute disease. The severity of long-term hearing loss at 3 weeks after infection, measured by auditory brainstem response recordings, correlated to the initial inoculum dose and to the levels of proinflammatory cytokines determined in the acute phase of PM. Quantitative cochlear histomorphology revealed a significant loss of SGNs and outer hair cells that strongly correlated to the level of infection, with the most severe damage occurring in the basal part of the cochlea. Inner hair cells (IHCs) were not significantly affected throughout the entire cochlea. However, surviving IHCs lost synaptic connectivity to remaining SGNs in all cochlear regions. These findings provide evidence that the inoculum concentration, i.e., severity of infection, is the major determinant of long-term morphological cell pathologies in the cochlea and functional hearing loss.

SIGNIFICANCE STATEMENT

Hearing loss is a neurofunctional deficit occurring in up to 30% of patients surviving pneumococcal meningitis (PM). Here, we analyze the correlation between the severity of infection and the inflammatory response in the CSF, the tonotopic distribution of neurosensory pathologies in the cochlea, and the long-term hearing function in a rat model of pneumococcal meningitis. Our study identifies the severity of infection as the key determinant of long-term hearing loss, underlining the importance of the prompt institution of antibiotic therapy in patients suffering from PM. Furthermore, our findings reveal in detail the spatial loss of cochlear neurosensory cells, providing new insights into the pathogenesis of meningitis-associated hearing loss that reveal new starting points for the development of otoprotective therapies.

Progression of changes in the sensorial elements of the cochlear and peripheral vestibular systems: The otitis media continuum

Our study aimed to evaluate pathologic changes in the cochlear (inner and outer hair cells and stria vascularis) and vestibular (vestibular hair cells, dark, and transitional cells) sensorial elements in temporal bones from donors who had otitis media. We studied 40 temporal bones from such donors, which were categorized in serous otitis media (SOM), serous-purulent otitis media (SPOM), mucoid/mucoid-purulent otitis media (MOM/MPOM), and chronic otitis media (COM); control group comprised 10 nondiseased temporal bones. We found significant loss of inner and outer cochlear hair cells in the basal turn of the SPOM, MOM/MPOM and COM groups; significant loss of vestibular hair cells was observed in the MOM/MPOM and COM groups. All otitis media groups had smaller mean area of the stria vascularis in the basal turn of the cochlea when compared to controls. In conclusion, our study demonstrated more severe pathologic changes in the later stages of the continuum of otitis media (MOM/MPOM and COM). Those changes seem to progress from the basal turn of the cochlea (stria vascularis, then inner and outer hair cells) to the middle turn of the cochlea and to the saccule and utricle in the MOM/MPOM and COM stages.

Acute otitis media associated bilateral sudden hearing loss: case report and literature review

Background:

Sudden sensorineural hearing loss is a rare otological condition with potential for dire outcomes including permanent hearing loss. Although the majority of cases are deemed idiopathic, bilateral sudden sensorineural hearing loss represents a rare subset typically related to systemic conditions, with higher morbidity and mortality. A controversial association with acute otitis media has been reported, with few bilateral cases published in the literature.

Case report:

A very rare case of bilateral sudden sensorineural hearing loss associated with acute otitis media is described, with a review of the literature.

Conclusion:

The limited evidence available suggests that acute otitis media with tinnitus and/or bacterial pathology may have an increased risk of sudden sensorineural hearing loss, which is consistent with the case described. Although there is no sufficiently powered published evidence to provide definitive treatment guidelines, the literature reviewed suggests that early myringotomy and antibiotics may greatly improve treatment outcomes.

Peptides actively transported across the tympanic membrane: Functional and structural properties

Otitis media (OM) is the most common infectious disease of children under six, causing more antibiotic prescriptions and surgical procedures than any other pediatric condition. By screening a bacteriophage (phage) library genetically engineered to express random peptides on their surfaces, we discovered unique peptides that actively transport phage particles across the intact tympanic membrane (TM) and into the middle ear (ME). Herein our goals were to characterize the physiochemical peptide features that may underlie trans-TM phage transport; assess morphological and functional effects of phage peptides on the ME and inner ear (IE); and determine whether peptide-bearing phage transmigrate from the ME into the IE. Incubation of five peptide-bearing phage on the TM for over 4hrs resulted in demonstrably superior transport of one peptide, in level and in exponential increase over time. This suggests a preferred peptide motif for TM active transport. Functional and structural comparisons revealed unique features of this peptide: These include a central lysine residue, isoelectric point of 0.0 at physiological pH and a hydrophobic C-terminus. When the optimal peptide was applied to the TM independent of phage, similar transport was observed, indicating that integration into phage is not required. When 10⁹ particles of the four different trans-TM phage were applied directly into the ME, no morphological effects were detected in the ME or IE when compared to saline or wild-type (WT) phage controls. Comparable, reversible hearing loss was observed for saline controls, WT phage and trans-TM peptide phage, suggesting a mild conductive hearing loss due to ME fluid. Perilymph titers after ME incubation established that few copies of trans-TM peptide phage crossed into the IE. The results suggest that, within the parameters tested, trans-TM peptides are safe and could be used as potential agents for noninvasive delivery of drugs, particles and gene therapy vectors to the ME.

Expression of macrophage migration inhibitory factor and CD74 in the inner ear and middle ear in lipopolysaccharide-induced otitis media

CONCLUSION

Significant expression of macrophage migration inhibitory factor and its receptor (CD74) was observed in both the middle ear and inner ear in experimental otitis media in mice. Modulation of macrophage migration inhibitory factor and its signaling pathway might be useful in the management of inner ear inflammation due to otitis media.

OBJECTIVES

Inner ear dysfunction secondary to otitis media has been reported. However, the specific mechanisms involved are not clearly understood. The aim of this study is to investigate the expression of macrophage migration inhibitory factor and CD74 in the middle ear and inner ear in lipopolysaccharide-induced otitis media.

METHOD

BALB/c mice received a transtympanic injection of either lipopolysaccharide or phosphate-buffered saline (PBS). The mice were sacrificed 24 h after injection, and temporal bones were processed for polymerase chain reaction (PCR) analysis, histologic examination, and immunohistochemistry.

RESULTS

PCR examination revealed that the lipopolysaccharide-injected mice showed a significant up-regulation of macrophage migration inhibitory factor in both the middle ear and inner ear as compared with the PBS-injected control mice. The immunohistochemical study showed positive reactions for macrophage migration inhibitory factor and CD74 in infiltrating inflammatory cells, middle ear mucosa, and inner ear in the lipopolysaccharide-injected mice.

Morphological changes in the round window membrane associated with Haemophilus influenzae-induced acute otitis media in the chinchilla

OBJECTIVE

The round window membrane (RWM) encloses the round window, the opening into the scala tympani (ST) from the middle ear. During the course of acute otitis media (AOM), structural changes of the RWM can occur that potentially affect sound transmission into and out of the cochlea. The relationship between such structural changes and conductive hearing loss during AOM has remained unclear. The focus of the current study was to compare the thickness distribution across the RWM surface between normal ears and those with AOM in the chinchilla. We assessed the occurrence of AOM-associated histological changes in this membrane compared to uninfected control animals after AOM of two relatively short durations.

MATERIAL AND METHODS

AOM was induced by transbullar injection of the nontypeable Haemophilus influenzae strain 86-028NP into two groups of adult chinchillas (n = 3 each). Bullae were obtained from the two infected groups, at 4 days or 8 days post challenge. Structures and thickness of these RWMs were compared between the two infected treatment groups and to RWMs from uninfected control animals (n = 3) at seven different RWM locations.

RESULTS

RWM thickness in infected chinchillas increased significantly at locations along the central line on the 4th day post bacterial challenge compared to values found for uninfected control animals. Lymphocyte infiltration and edema were the primary contributors to these thickness increases. No significant further increases in RWM thickness were observed when RWMs from chinchillas ears infected for 4 and 8 days were compared. Thickness and structural changes at the RWM lateral and medial areas were less visually obvious and not statistically significant among the three treatment groups. These latter RWM regions clearly were less affected during AOM than the central areas.

CONCLUSIONS

This histological study establishes that H. influenzae-induced AOM causes significant acute changes in chinchilla RWM structure that are characterized by region-specific increases in thickness. Our new morphological findings comparing normal and diseased chinchilla RWMs identify yet another biomechanical mechanism by which nontypeable H. influenzae may contribute to hearing loss in AOM.

Prevalence and Nature of Hearing Loss in 22q11.2 Deletion Syndrome

PURPOSE

The purpose of this study was to clarify the prevalence, type, severity, and age-dependency of hearing loss in 22q11.2 deletion syndrome.

METHOD

Extensive audiological measurements were conducted in 40 persons with proven 22q11.2 deletion (aged 6-36 years). Besides air and bone conduction thresholds in the frequency range between 0.125 and 8.000 kHz, high-frequency thresholds up to 16.000 kHz were determined and tympanometry, acoustic reflex (AR) measurement, and distortion product otoacoustic emission (DPOAE) testing were performed.

RESULTS

Hearing loss was identified in 59% of the tested ears and was mainly conductive in nature. In addition, a high-frequency sensorineural hearing loss with down-sloping curve was found in the majority of patients. Aberrant tympanometric results were recorded in 39% of the ears. In 85% of ears with a Type A or C tympanometric peak, ARs were absent. A DPOAE response in at least 6 frequencies was present in only 23% of the ears with a hearing threshold ≤30 dB HL. In patients above 14 years of age, there was a significantly lower percentage of measurable DPOAEs.

CONCLUSION

Hearing loss in 22q11.2 deletion syndrome is highly prevalent and both conductive and high-frequency sensorineural in nature. The age-dependent absence of DPOAEs in 22q11.2 deletion syndrome suggests cochlear damage underlying the high-frequency hearing loss.

Pathologic Changes of the Peripheral Vestibular System Secondary to Chronic Otitis Media

OBJECTIVE

To evaluate the histopathologic changes of dark, transitional, and hair cells of the vestibular system in human temporal bones from patients with chronic otitis media.

STUDY DESIGN

Comparative human temporal bone study.

SETTING

Otopathology laboratory.

SUBJECTS AND METHODS

To compare the density of vestibular dark, transitional, and hair cells in temporal bones with and without chronic otitis media, we used differential interference contrast microscopy.

RESULTS

In the chronic otitis media group (as compared with the age-matched control group), the density of type I and type II hair cells was significantly decreased in the lateral semicircular canal, saccule, and utricle (P < .05). The density of type I cells was also significantly decreased in the chronic otitis media group in the posterior semicircular canal (P = .005), but that of type II cells was not (P = .168). The mean number of dark cells was significantly decreased in the chronic otitis media group in the lateral semicircular canal (P = .014) and in the posterior semicircular canal (P = .002). We observed no statistically significant difference in the density of transitional cells between the 2 groups (P > .1).

CONCLUSION

The findings of our study suggest that the decrease in the number of vestibular sensory cells and dark cells could be the cause of the clinical symptoms of imbalance of some patients with chronic otitis media.

Effect of intratympanic steroid administration on sensorineural hearing loss associated with acute otitis media

OBJECTIVE

To evaluate a small cohort of patients who presented with symptoms and signs consistent with acute infective sensorineural hearing loss who were treated with intratympanic steroids.

METHOD

Seven patients received a 7-day course of oral antibiotics and oral prednisolone followed by 3 intratympanic injections of methylprednisolone and 1 week of topical dexamethasone drops.

RESULTS

Hearing improved in 57 per cent of patients (four out of seven). The mean improvement in this group was 24 dB (range, 10-52 dB). The magnitude of the sensorineural hearing loss at presentation was less in those who responded to intratympanic steroid therapy than in non-responders (mean pure tone average of 30 dB versus 65 dB pre-intratympanic steroids, and 14 dB versus 83 dB post-intratympanic steroids, respectively).

CONCLUSION

The results of our study suggest that intratympanic steroids provide a valuable contribution to the treatment of acute infective sensorineural hearing loss and may provide additional benefit by virtue of a concentrated local steroid effect in patients who do not respond to antibiotics.

Cochlear changes in serous labyrinthitis associated with silent otitis media: A human temporal bone study

PURPOSE

To determine histopathological findings in the cochlea of human temporal bones with serous labyrinthitis.

MATERIALS AND METHODS

We compared human temporal bones with serous labyrinthitis (20 cases) associated with silent otitis media and without serous labyrinthitis (20 cases) to study location of serous labyrinthitis, the degree of endolymphatic hydrops, number of spiral ganglion cells and hair cells, loss of fibrocytes in the spiral ligament, and areas of the spiral ligament and stria vascularis.

RESULTS

The serous labyrinthitis caused significant loss of outer hair cells in the lower basal (P=0.006), upper basal (P=0.005), and lower middle (P=0.011) cochlear turns, and significant increase in the degree of endolymphatic hydrops than the control group (P=0.036). No significant difference was found in the loss of inner hair cells, in the number of spiral ganglion cells and fibrocytes in the spiral ligament, and in areas of the stria vascularis and spiral ligament (P>0.05).

CONCLUSIONS

Serous labyrinthitis resulted in significant loss of outer hair cells and significant increase in the degree of endolymphatic hydrops.

Childhood Otitis Media: A Cohort Study With 30-Year Follow-Up of Hearing (The HUNT Study)

OBJECTIVES

To study the extent to which otitis media (OM) in childhood is associated with adult hearing thresholds. Furthermore, to study whether the effects of OM on adult hearing thresholds are moderated by age or noise exposure.

DESIGN

Population-based cohort study of 32,786 participants who had their hearing tested by pure-tone audiometry in primary school and again at ages ranging from 20 to 56 years. Three thousand sixty-six children were diagnosed with hearing loss; the remaining sample had normal childhood hearing.

RESULTS

Compared with participants with normal childhood hearing, those diagnosed with childhood hearing loss caused by otitis media with effusion (n = 1255), chronic suppurative otitis media (CSOM; n = 108), or hearing loss after recurrent acute otitis media (rAOM; n = 613) had significantly increased adult hearing thresholds in the whole frequency range (2 dB/17-20 dB/7-10 dB, respectively). The effects were adjusted for age, sex, and noise exposure. Children diagnosed with hearing loss after rAOM had somewhat improved hearing thresholds as adults. The effects of CSOM and hearing loss after rAOM on adult hearing thresholds were larger in participants tested in middle adulthood (ages 40 to 56 years) than in those tested in young adulthood (ages 20 to 40 years). Eardrum pathology added a marginally increased risk of adult hearing loss (1-3 dB) in children with otitis media with effusion or hearing loss after rAOM. The study could not reveal significant differences in the effect of self-reported noise exposure on adult hearing thresholds between the groups with OM and the group with normal childhood hearing.

CONCLUSIONS

This cohort study indicates that CSOM and rAOM in childhood are associated with adult hearing loss, underlining the importance of optimal treatment in these conditions. It appears that ears with a subsequent hearing loss after OM in childhood age at a faster rate than those without; however this should be confirmed by studies with several follow-up tests through adulthood.

Chronic Conductive Hearing Loss Leads to Cochlear Degeneration

Synapses between cochlear nerve terminals and hair cells are the most vulnerable elements in the inner ear in both noise-induced and age-related hearing loss, and this neuropathy is exacerbated in the absence of efferent feedback from the olivocochlear bundle. If age-related loss is dominated by a lifetime of exposure to environmental sounds, reduction of acoustic drive to the inner ear might improve cochlear preservation throughout life. To test this, we removed the tympanic membrane unilaterally in one group of young adult mice, removed the olivocochlear bundle in another group and compared their cochlear function and innervation to age-matched controls one year later. Results showed that tympanic membrane removal, and the associated threshold elevation, was counterproductive: cochlear efferent innervation was dramatically reduced, especially the lateral olivocochlear terminals to the inner hair cell area, and there was a corresponding reduction in the number of cochlear nerve synapses. This loss led to a decrease in the amplitude of the suprathreshold cochlear neural responses. Similar results were seen in two cases with conductive hearing loss due to chronic otitis media. Outer hair cell death was increased only in ears lacking medial olivocochlear innervation following olivocochlear bundle cuts. Results suggest the novel ideas that 1) the olivocochlear efferent pathway has a dramatic use-dependent plasticity even in the adult ear and 2) a component of the lingering auditory processing disorder seen in humans after persistent middle-ear infections is cochlear in origin.

Current concepts in the pathogenesis and treatment of chronic suppurative otitis media

Otitis media (OM) is an inflammation of the middle ear associated with infection. Despite appropriate therapy, acute OM (AOM) can progress to chronic suppurative OM (CSOM) associated with ear drum perforation and purulent discharge. The effusion prevents the middle ear ossicles from properly relaying sound vibrations from the ear drum to the oval window of the inner ear, causing conductive hearing loss. In addition, the inflammatory mediators generated during CSOM can penetrate into the inner ear through the round window. This can cause the loss of hair cells in the cochlea, leading to sensorineural hearing loss. Pseudomonas aeruginosa and Staphylococcus aureus are the most predominant pathogens that cause CSOM. Although the pathogenesis of AOM is well studied, very limited research is available in relation to CSOM. With the emergence of antibiotic resistance as well as the ototoxicity of antibiotics and the potential risks of surgery, there is an urgent need to develop effective therapeutic strategies against CSOM. This warrants understanding the role of host immunity in CSOM and how the bacteria evade these potent immune responses. Understanding the molecular mechanisms leading to CSOM will help in designing novel treatment modalities against the disease and hence preventing the hearing loss.

Pre- and post-operative clinical findings of tympanomastoid surgery in female divers (Haenyeo) of Jeju Island with chronic otitis media

CONCLUSIONS

A tympanomastoid surgery can control chronic otitis media (COM) and improve hearing effectively in Jeju women divers (Haenyeo) without any complications.

OBJECTIVE

To evaluate the long-term results of tympanomastoid surgery in Haenyeo patients with COM to determine any link between their diving behavior and COM.

METHODS

The medical records of 207 COM patients who underwent tympanomastoid surgery were reviewed for demographic characteristics, etiologic analyses, pre- and post-operative hearing levels, types of tympanomastoid surgery with ossiculoplasty, and post-operative complications. The patients were divided into a 'Haenyeo COM group' of 98 patients and a 'general COM group' of 109, and followed up for at least 3 years.

RESULTS

In the audiologic study, the Haenyeo COM group showed a relatively larger pre-operative air-bone gap than the general COM group. There were no statistically significant differences in middle ear swab culture results, the rates of re-perforation of the tympanic membrane or re-operation, or the risk of post-operative complications between the two groups. However, the possibility of COM accompanying cholesteatoma was higher and the canal wall down mastoidectomy was more frequently performed in the Haenyeo COM group (both p < 0.05).

Effect of otitis media with effusion on cochlear implant surgery: technical difficulties, post-operative complications and outcome

Objective:

This study evaluated the complications and outcomes of cochlear implantation in patients who had otitis media with effusion at the time of surgery.

Methods:

A retrospective chart review study was performed of 87 consecutive paediatric patients (age range 22 months to 10 years, mean 4.8 years) who underwent successful cochlear implantation, with follow-up periods of 5–6 years. All patients had unilateral implants, with eight on the left side. All devices were activated two weeks after implantation. The effect of the middle-ear condition on the procedure, post-operative complications and outcome were evaluated.

Results:

Unilateral ears of 17 otitis media with effusion patients were implanted with some surgical difficulties but no long-term post-operative complications.

Conclusion:

For children admitted for cochlear implantation who are subsequently found to have otitis media with effusion, surgeons should be aware of possible surgical difficulties. Greater intra-operative risks should be anticipated and more surgical time allowed for cochlear implantation in these patients.

Correlative mRNA and protein expression of middle and inner ear inflammatory cytokines during mouse acute otitis media

Although the inner ear has long been reported to be susceptible to middle ear disease, little is known of the inflammatory mechanisms that might cause permanent sensorineural hearing loss. Recent studies have shown inner ear tissues are capable of expressing inflammatory cytokines during otitis media. However, little quantitative information is available concerning cytokine gene expression in the inner ear and the protein products that result. Therefore, this study was conducted of mouse middle and inner ear during acute otitis media to measure the relationship between inflammatory cytokine genes and their protein products with quantitative RT-PCR and ELISA, respectively. Balb/c mice were inoculated transtympanically with heat-killed Haemophilus influenzae and middle and inner ear tissues collected for either quantitative RT-PCR microarrays or ELISA multiplex arrays. mRNA for several cytokine genes was significantly increased in both the middle and inner ear at 6 h. In the inner ear, these included MIP-2 (448 fold), IL-6 (126 fold), IL-1β (7.8 fold), IL-10 (10.7 fold), TNFα (1.8 fold), and IL-1α (1.5 fold). The 24 h samples showed a similar pattern of gene expression, although generally at lower levels. In parallel, the ELISA showed the related cytokines were present in the inner ear at concentrations higher by 2-122 fold higher at 18 h, declining slightly from there at 24 h. Immunohistochemistry with antibodies to a number of these cytokines demonstrated they occurred in greater amounts in the inner ear tissues. These findings demonstrate considerable inflammatory gene expression and gene products in the inner ear following acute otitis media. These higher cytokine levels suggest one potential mechanism for the permanent hearing loss seen in some cases of acute and chronic otitis media.

Risk factors for sensorineural hearing loss in pediatric chronic otitis media

OBJECTIVES

To assess the clinical significance of sensorineural hearing loss (SNHL) in a group of pediatric patients suffering from unilateral chronic otitis media (COM) with or without cholesteatoma, using the contralateral healthy ear as a control, and to define risk factors for the development of SNHL in such patients.

METHODS

The subjects of this retrospective study were 124 pediatric patients with unilateral COM admitted for surgery. Mean age at surgery was 13.3±3.2 years (range, 7-18) and mean duration of the disease was 88.4±45.0 months (range, 6-192 months). The preoperative pure-tone average value (PTA) for bone conduction (BC) was calculated in each ear (BC-PTA) as the average of BC thresholds at 500, 1000, 2000, and 4000Hz. Potential risk factors for SNHL that we evaluated were demographics, duration of disease, presence of cholesteatoma, and previous otologic history.

RESULTS

Mean BC-PTA values in the diseased ears prior to surgery differed significantly from those in the healthy ears (12.74±8.75dB and 9.36±6.33dB, respectively; P<0.01). The degree of SNHL in the diseased ear at 2000Hz was found to be significantly correlated with the presence of cholesteatoma and with age above 10 years.

CONCLUSIONS

One of the complications of COM, with or without cholesteatoma, in addition to the conductive hearing loss, is the development of clinically significant SNHL. It is therefore imperative to actively treat pediatric patients diagnosed with COM, with the aim of preventing the possible development of SNHL.

Relationship between CT findings and sensorineural hearing loss in chronic otitis media

OBJECTIVE

To investigate the relationships between the temporal bone CT findings and sensorineural hearing loss in ears with non-cholesteatomatous chronic otitis media (COM).

METHODS

Preoperative bone conduction (BC) hearing thresholds of 266 patients (304 ears) with COM were compared with those of 342 normal individuals (440 ears) by audiometry. The incidence of abnormal BC threshold at lower frequencies (250-1000 Hz) and at higher frequencies (2000-4000 Hz) were examined and the differences between control and COM groups were compared by using χ2 test. In the COM group, the cross-sectional area of the mastoid air cells based on the axial CT image (n=255) were correlated with the results of BC threshold.

RESULTS

The percentage in the COM group exceeds 15% in their 50s at lower frequencies while in their 40s at higher frequencies. The BC thresholds were significantly better in the group with normal mastoid area than in those with smaller mastoid area at each decadal age group. The BC impairment from COM becomes worse as the course of the disease progresses and deteriorated from 40s rapidly, especially at higher frequencies and in the group with smaller mastoid area.

CONCLUSION

These results recommend that early treatment, including surgery, should be considered as early as possible before BC impairment occurs, especially for COM cases with smaller mastoid area, which may indicate the existence of more severe otitis media since earlier childhood.

Inner ear tissue remodeling and ion homeostasis gene alteration in murine chronic otitis media

HYPOTHESIS

Studies were designed to ascertain the impact of chronic middle ear infection on the numerous ion and water channels, transporters, and tissue remodeling genes in the inner and middle ear.

BACKGROUND

Permanent sensorineural hearing loss is a significant problem resulting from chronic middle ear disease, although the inner ear processes involved are poorly defined. Maintaining a balanced ionic composition of endolymph in the inner ear is crucial for hearing; thus, it was hypothesized that this may be at risk with inflammation.

METHODS

Inner and middle ear RNA collected separately from 6-month-old C3H/HeJ mice with prolonged middle ear disease were subjected to qRT-PCR for 8 common inflammatory cytokine genes, 24 genes for channels controlling ion (sodium, potassium, and chloride) and water (aquaporin) transport, tight junction claudins, and gap junction connexins, and 32 tissue remodeling genes. Uninfected Balb/c mice were used as controls.

RESULTS

Significant increase in inner ear inflammatory and ion homeostasis (claudin, aquaporin, and gap junction) gene expression, and both upregulation and downregulation of tissue remodeling gene expression occurred. Alteration in middle ear ion homeostasis and tissue remodeling gene expression was noted in the setting of uniform upregulation of cytokine genes.

CONCLUSION

Chronic inflammatory middle ear disease can impact inner ear ion and water transport functions and induce tissue remodeling. Recognizing these inner ear mechanisms at risk may identify potential therapeutic targets to maintain hearing during prolonged otitis media.

Panel 4: Recent advances in otitis media in molecular biology, biochemistry, genetics, and animal models

BACKGROUND

Otitis media (OM) is the most common childhood bacterial infection and also the leading cause of conductive hearing loss in children. Currently, there is an urgent need for developing novel therapeutic agents for treating OM based on full understanding of molecular pathogenesis in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM.

OBJECTIVE

To provide a state-of-the-art review concerning recent advances in OM in the areas of molecular biology, biochemistry, genetics, and animal model studies and to discuss the future directions of OM studies in these areas.

DATA SOURCES AND REVIEW METHODS

A structured search of the current literature (since June 2007). The authors searched PubMed for published literature in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM.

RESULTS

Over the past 4 years, significant progress has been made in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM. These studies brought new insights into our understanding of the molecular and biochemical mechanisms underlying the molecular pathogenesis of OM and helped identify novel therapeutic targets for OM.

CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Our understanding of the molecular pathogenesis of OM has been significantly advanced, particularly in the areas of inflammation, innate immunity, mucus overproduction, mucosal hyperplasia, middle ear and inner ear interaction, genetics, genome sequencing, and animal model studies. Although these studies are still in their experimental stages, they help identify new potential therapeutic targets. Future preclinical and clinical studies will help to translate these exciting experimental research findings into clinical applications.

Pseudo-sudden deafness

OBJECTIVES

We describe the symptom complex and management of a clinical entity we refer to as "pseudo-sudden deafness," which is an episode of acute otitis media that leads to sensorineural hearing loss with reduced speech discrimination.

METHODS

We included 8 adult patients with audiometrically confirmed, asymmetric sensorineural hearing loss with decreased speech discrimination that presented after an episode of acute otitis media. Magnetic resonance imaging ruled out retrocochlear disease. Both physical examination and myringotomy helped confirm the diagnosis of serous otitis media (SOM). Myringotomy, tympanostomy tubes, oral antibiotics, and otic antibiotic-steroid drops were used to treat the SOM. Oral steroids were used to treat the sensorineural component.

RESULTS

Pretreatment and posttreatment audiograms showed an improvement in speech discrimination score, pure tone thresholds, or both after treatment for underlying SOM and sensorineural hearing loss in 6 of the 8 patients.

CONCLUSIONS

Patients who present with an acute onset of unilateral sensorineural hearing loss with decreased speech discrimination may be mistakenly thought to have idiopathic sudden sensorineural hearing loss when, in fact, they may have an SOM-induced phenomenon that is potentially reversible. The distinguishing feature is a preexisting otitis media, which must be treated first, before the administration of steroids.

Vitamin A supplementation in preschool children and risk of hearing loss as adolescents and young adults in rural Nepal: randomised trial cohort follow-up study

OBJECTIVE

To determine whether vitamin A supplementation administered in the preschool years can lower the risk of hearing loss in adolescence and adulthood.

DESIGN

Follow-up study of adolescents and young adults who, as preschool aged children in 1989, were enrolled into a cluster randomised, double blinded, placebo controlled trial of vitamin A supplementation.

SETTING

South central, rural Nepal.

PARTICIPANTS

2378 adolescents and young adults aged 14 to 23, representing 51% of those who finished the original trial and 71% of those living in the study area in 2006.

INTERVENTIONS

Every four months for 16 months preschool children were visited at home, given an oral 200,000 IU dose of vitamin A (half dose at age 1-11 months, quarter dose at <1 month) or placebo and the parents were queried about any childhood illnesses in the previous week, including purulent discharge from the ears.

MAIN OUTCOME MEASURES

Prevalence of mild or worse hearing loss (≥ 30 dB) in the most affected ear and tympanometric measures of middle ear function (peak height, ear canal volume, and gradient).

RESULTS

During the original trial, the prevalence of middle ear infection during the preschool years did not differ between the supplement groups. By adolescence and early adulthood, a non-significant 17% reduction in hearing loss occurred among those who had periodically received vitamin A compared with placebo as preschool aged children (odds ratio 0.83, 95% confidence interval 0.62 to 1.12). Among participants with any ear discharge in early childhood, vitamin A supplementation was associated with a reduced risk of hearing loss, by 42% (0.58, 0.37 to 0.92) compared with controls, after adjusting the confidence interval for the design effect of the original trial. Abnormal tympanometric peak height of the middle ear system was less likely among participants supplemented with vitamin A in childhood.

CONCLUSION

In undernourished settings, periodic, high dose vitamin A supplementation may reduce the risk of hearing loss associated with purulent ear infections in early childhood.

Hearing loss in adults surviving pneumococcal meningitis is associated with otitis and pneumococcal serotype

We assessed the incidence of hearing loss and its relationship with clinical characteristics and pneumococcal serotypes in adults surviving pneumococcal meningitis. We analysed hearing loss in 531 adults surviving pneumococcal meningitis included in two prospective nationwide cohort studies performed from April 1998 through to October 2002 and March 2006 through to January 2009. Hearing loss was evaluated on admission and discharge for all patients. Severe hearing loss was assessed by pure tone average on audiology and corrected for age, or by the combination of hearing loss on discharge and a score on the Glasgow Outcome Scale below 5, which could not be explained by other neurological sequelae. A total of 531 episodes of pneumococcal meningitis with non-lethal outcome were included. Predisposing conditions for pneumococcal meningitis were present in the majority of patients (64%), most commonly otitis (36%). Hearing loss was present at discharge in 116 patients (22%) and was classified as mild in 53% and severe in 47%. Hearing loss was related to otitis (odds ratio [OR], 2.58; 95% confidence interval [CI], 1.66-4.02; p < 0.001) and inversely related to serotype 23 F infection (OR, 0.36; 95% CI, 0.13-0.98; p = 0.025), but not with parameters of disease severity or indicators of cerebrospinal fluid inflammation severity. Meningitis due to pneumococcal serotype 3 was associated with the highest rate of hearing loss. Hearing loss frequently complicates pneumococcal meningitis. Risk factors for hearing loss were infection with pneumococcal serotype 23 F and otitis, but not disease severity. Otitis and resulting perilympathic inflammation contribute to meningitis-associated hearing loss.

Spiral ligament fibrocyte-derived MCP-1/CCL2 contributes to inner ear inflammation secondary to nontypeable H. influenzae-induced otitis media

Background

Otitis media (OM), one of the most common pediatric infectious diseases, causes inner ear inflammation resulting in vertigo and sensorineural hearing loss. Previously, we showed that spiral ligament fibrocytes (SLFs) recognize OM pathogens and up-regulate chemokines. Here, we aim to determine a key molecule derived from SLFs, contributing to OM-induced inner ear inflammation.

Methods

Live NTHI was injected into the murine middle ear through the tympanic membrane, and histological analysis was performed after harvesting the temporal bones. Migration assays were conducted using the conditioned medium of NTHI-exposed SLFs with and without inhibition of MCP-1/CCL2 and CCR2. qRT-PCR analysis was performed to demonstrate a compensatory up-regulation of alternative genes induced by the targeting of MCP-1/CCL2 or CCR2.

Results

Transtympanic inoculation of live NTHI developed serous and purulent labyrinthitis after clearance of OM. THP-1 cells actively migrated and invaded the extracellular matrix in response to the conditioned medium of NTHI-exposed SLFs. This migratory activity was markedly inhibited by the viral CC chemokine inhibitor and the deficiency of MCP-1/CCL2, indicating that MCP-1/CCL2 is a main attractant of THP-1 cells among the SLF-derived molecules. We further demonstrated that CCR2 deficiency inhibits migration of monocyte-like cells in response to NTHI-induced SLF-derived molecules. Immunolabeling showed an increase in MCP-1/CCL2 expression in the cochlear lateral wall of the NTHI-inoculated group. Contrary to the in vitro data, deficiency of MCP-1/CCL2 or CCR2 did not inhibit OM-induced inner ear inflammation in vivo. We demonstrated that targeting MCP-1/CCL2 enhances NTHI-induced up-regulation of MCP-2/CCL8 in SLFs and up-regulates the basal expression of CCR2 in the splenocytes. We also found that targeting CCR2 enhances NTHI-induced up-regulation of MCP-1/CCL2 in SLFs.

Conclusions

Taken together, we suggest that NTHI-induced SLF-derived MCP-1/CCL2 is a key molecule contributing to inner ear inflammation through CCR2-mediated recruitment of monocytes. However, deficiency of MCP-1/CCL2 or CCR2 alone was limited to inhibit OM-induced inner ear inflammation due to compensation of alternative genes.

Ion homeostasis in the ear: mechanisms, maladies, and management

PURPOSE OF REVIEW

To describe ion and water homeostatic mechanisms in the inner ear, how they are compromised in hearing disorders, and what treatments are employed to restore auditory function.

RECENT FINDINGS

The ion and water transport functions in the inner ear help maintain the proper endolymph K concentration required for hair cell function. Gene defects and idiopathic alterations in these transport functions cause hearing loss, but often the underlying cause is unknown. Current therapies largely involve glucocorticoid treatment, although the mechanisms of restoration are often undeterminable. Recent studies of these ion homeostatic functions in the ear are characterizing their cellular and molecular control. It is anticipated that future management of these hearing disorders will be more targeted to the cellular processes involved and improve the likelihood of hearing recovery.

SUMMARY

A better understanding of the ion homeostatic processes in the ear will permit more effective management of their associated hearing disorders. Sufficient insight into many homeostatic hearing disorders has now been attained to usher in a new era of better therapies and improved clinical outcomes.