In vivo 3D imaging of the human tympanic membrane using a wide-field diagonal-scanning optical coherence tomography probe.

A wide-field optical coherence tomography (OCT) probe was developed that adapts a diagonal-scanning scheme for three-dimensional (3D) in vivo imaging of the human tympanic membrane. The probe consists of a relay lens to enhance the lateral scanning range up to 7 mm. Motion artifacts that occur with the use of handheld probes were found to be decreased owing to the diagonal-scanning pattern, which crosses the center of the sample to facilitate entire 3D scans. 3D images could be constructed from a small number of two-dimensional OCT images acquired using the diagonal-scanning technique. To demonstrate the usefulness and performance of the developed system with the handheld probe, in vivo tympanic membranes of humans and animals were imaged in real time.

Methionine sulfoxide reductase B3 deficiency causes hearing loss due to stereocilia degeneration and apoptotic cell death in cochlear hair cells.

Methionine sulfoxide reductase B3 (MsrB3) is a protein repair enzyme that specifically reduces methionine-R-sulfoxide to methionine. A recent genetic study showed that the MSRB3 gene is associated with autosomal recessive hearing loss in human deafness DFNB74. However, the precise role of MSRB3 in the auditory system and the pathogenesis of hearing loss have not yet been determined. This work is the first to generate MsrB3 knockout mice to elucidate the possible pathological mechanisms of hearing loss observed in DFNB74 patients. We found that homozygous MsrB3(-/-) mice were profoundly deaf and had largely unaffected vestibular function, whereas heterozygous MsrB3(+/-) mice exhibited normal hearing similar to that of wild-type mice. The MsrB3 protein is expressed in the sensory epithelia of the cochlear and vestibular tissues, beginning at E15.5 and E13.5, respectively. Interestingly, MsrB3 is densely localized at the base of stereocilia on the apical surface of auditory hair cells. MsrB3 deficiency led to progressive degeneration of stereociliary bundles starting at P8, followed by a loss of hair cells, resulting in profound deafness in MsrB3(-/-) mice. The hair cell loss appeared to be mediated by apoptotic cell death, which was measured using TUNEL and caspase 3 immunocytochemistry. Taken together, our data suggest that MsrB3 plays an essential role in maintaining the integrity of hair cells, possibly explaining the pathogenesis of DFNB74 deafness in humans caused by MSRB3 deficiency.

Dexamethasone Is One of the Factors Minimizing the Inner Ear Damage from Electrode Insertion in Cochlear Implantation.

The aim of this study was to investigate the efficacy of preoperative and intraoperative steroid administration for inner ear protection in cochlear implantation (CI). Nineteen subjects who underwent CI were included in the study, and 10 subjects were enrolled as controls (steroid-administered group, n = 19; control group, n = 10). Dexamethasone (dexamethasone sodium phosphate, 5 mg/ml) was systemically administered preoperatively (1 ml) and topically applied during CI (0.5 ml). The extent of hearing preservation (HP) after CI and the change in the bithermal caloric response were evaluated. Hearing level was calculated using mean thresholds [(250 Hz + 500 Hz + 1,000 Hz + 2,000 Hz)/4]. Preoperative hearing thresholds were similar in the steroid-administered and control groups (100.92 ± 12.60 vs. 103.29 ± 14.39 dB, p = 0.650). The mean thresholds significantly increased in both groups after surgery (108.46 ± 14.08 dB, p = 0.006, for the steroid-administered group; 117.50 ± 6.34 dB, p = 0.027, for the control group), and the difference between the groups was also significant (p = 0.027). The postoperative shift in the hearing thresholds at frequencies of 500 and 1,000 Hz was significant in the steroid-administered group and that at the frequencies of 500, 1,000 and 2,000 Hz was significant in the control group. However, the extent of the shift in hearing threshold levels at each frequency was not significantly different between the groups. Preservation of hearing thresholds was compared between the groups, and there were significantly more subjects with complete and partial HP in the steroid-administered group than in the control group (p = 0.008). The preoperative caloric response was maintained after CI in the steroid-administered group. This study suggests that the perioperative use of a steroid could minimize the inner ear damage after CI.

Optical coherence tomography for the diagnosis and evaluation of human otitis media.

We report the application of optical coherence tomography (OCT) to the diagnosis and evaluation of otitis media (OM). Whereas conventional diagnostic modalities for OM, including standard and pneumatic otoscopy, are limited to visualizing the surface of the tympanic membrane (TM), OCT effectively reveals the depth-resolved microstructure below the TM with very high spatial resolution, with the potential advantage of its use for diagnosing different types of OM. We examined the use of 840-nm spectral domain-OCT (SD-OCT) clinically, using normal ears and ears with the adhesive and effusion types of OM. Specific features were identified in two-dimensional OCT images of abnormal TMs, compared to images of healthy TMs. Analysis of the A-scan (axial depth scan) identified unique patterns of constituents within the effusions. The OCT images could not only be used to construct a database for the diagnosis and classification of OM but OCT might also represent an upgrade over current otoscopy techniques.

Functional mapping of the auditory tract in rodent tinnitus model using manganese-enhanced magnetic resonance imaging.

Animal models of salicylate-induced tinnitus have demonstrated that salicylate modulates neuronal activity in several brain structures leading to neuronal hyperactivity in auditory and non-auditory brain areas. In addition, these animal tinnitus models indicate that tinnitus can be a perceptual consequence of altered spontaneous neural activity along the auditory pathway. Peripheral and/or central effects of salicylate can account for neuronal activity changes in salicylate-induced tinnitus. Because of this ambiguity, an in vivo imaging study would be able to address the peripheral and/or central involvement of salicylate-induced tinnitus. Therefore, in the present study, we developed a novel manganese-enhanced magnetic resonance imaging (MEMRI) method to map the in vivo functional auditory tract in a salicylate-induced tinnitus animal model by administrating manganese through the round window. We found that acute salicylate-induced tinnitus resulted in higher manganese uptake in the cochlea and in the central auditory structures. Furthermore, serial MRI scans demonstrated that the manganese signal increased in an anterograde fashion from the cochlea to the cochlear nucleus. Therefore, our in vivo MEMRI data suggest that acute salicylate-induced tinnitus is associated with higher spontaneous neural activity both in peripheral and central auditory pathways.

Different functional consequences of two missense mutations in the GJB2 gene associated with non-syndromic hearing loss.

Mutations in the GJB2 gene, which encodes the gap junction (GJ) protein connexin26 (Cx26), are the most common cause of inherited non-syndromic hearing loss (NSHL). We identified two missense mutations, p.D46E (c.138T>G) and p.T86R (c.257C>G), of GJB2 in Korean HL families. The novel p.D46E mutation exhibited autosomal dominant inheritance, while the p.T86R mutation, which is exclusively found in Asians, segregated with an autosomal recessive pattern. Thus, we sought to elucidate the pathogenic nature of such different inherited patterns of HL. We studied protein localization and gap junction functions in cells transfected with wild-type or mutant Cx26 tagged with fluorescent proteins, which allowed visual confirmation of homozygous or heterozygous mutant GJs. The Cx26-D46E mutant was targeted to the plasma membrane, but this mutant protein failed to transfer Ca(2+) or propidium iodide intercellularly, suggesting disruption of both ionic and biochemical coupling. Heterozygous GJs also showed dysfunctional intercellular couplings and hemichannel opening, confirming the dominant-negative nature of the p.D46E mutation. The Cx26-T86R mutant protein did not form GJs, since the mutated protein was confined in the cytoplasm and not transported to the cell membrane. When Cx26-T86R was co-expressed with Cx26-WT, ionic and biochemical coupling was normal, consistent with the recessive nature of the mutation. These studies revealed distinct pathogenic mechanisms of two GJB2 mutations identified in Korean families.

Molecular analysis of mitochondrial gene mutations in Korean patients with nonsyndromic hearing loss.

Mutations in mitochondrial DNA (mtDNA) are a major cause of hearing loss. In this study, we performed a systematic mutational screening of the 12S rRNA, tRNA Ser(UCN), tRNA Lys and tRNA Leu(UUR) genes in 227 unrelated patients with nonsyndromic hearing impairment for the first time in a Korean population. We found two individuals with an A1555G mutation, which is a frequency (0.9%) lower than that of other East Asians. Furthermore, two novel variants (C895T and 961-CC insertion) in the 12S rRNA gene were identified in the affected individuals, but were absent in 217 controls, indicating that they may play a role in the pathogenesis of hearing loss. Notably, 961delT and T1005C mutations were identified at similar frequencies in both patients and control subjects. Our data suggest that these variants seem to be polymorphisms rather than causes of disease. On the other hand, we did not find any of the known deafness-associated mutations in these tRNA genes. These data suggest that the 12S rRNA gene may be a hot spot for mitochondrial mutations causing hearing loss in the Korean population.

Effect of bimodal hearing in Korean children with profound hearing loss.

CONCLUSION: Bimodal hearing with combined acoustic stimulation and electric stimulation could enhance speech performance in deaf patients by residual hearing even though the amount of residual hearing is not enough to be used for communication by amplification. OBJECTIVES: The cochlear implant (CI) is a well-known therapeutic option for patients with profound hearing loss. However, deaf patients with a CI still have trouble in localization of sounds and understanding speech in a noisy environment. The aim of this study was to evaluate the benefits of bimodal hearing with a CI in one ear and a hearing aid in the contralateral ear in Korean children with profound hearing loss. SUBJECTS AND METHODS: Fourteen deaf children with residual hearing participated in this study. There were eight male and six female patients, with an age range of 4.6-13.8 years at the time of testing. The test was conducted between 3 months and 4.2 years after cochlear implantation. Speech performance was examined in a noisy environment using Korean word lists. A speech sound and the noise were presented to the child from the front loudspeaker. RESULTS: The results showed that speech performance in a noisy environment was significantly better with bimodal hearing than with a CI alone.

Association of a genetic polymorphism of IL1RN with risk of acute pancreatitis in a Korean ethnic group.

BACKGROUND/AIMS: Several epidemiological studies have validated the association of interleukin gene polymorphisms with acute pancreatitis (AP) in different populations. However, there have been few studies in Asian ethnic groups. We aimed to investigate the relationships between inflammatory cytokine polymorphisms and AP as pilot research in a Korean ethnic group. METHODS: Patients who had been diagnosed with AP were prospectively enrolled. DNA was extracted from whole blood, and DNA sequencing was subsequently performed. Single-nucleotide polymorphisms (SNPs) of the interleukin 1ß (IL1B), interleukin 1 receptor antagonist (IL1RN), and tumor necrosis factor α (TNFA) genes of patients with AP were compared to those of normal controls. RESULTS: Between January 2011 and January 2013, a total of 65 subjects were enrolled (40 patients with AP vs. 25 healthy controls). One intronic SNP (IL1RN -1129T>C, rs4251961) was significantly associated with the risk of AP (odds ratio, 0.304; 95% confidence interval, 0.095 to 0.967; p = 0.043). However, in our study, AP was not found to be associated with polymorphisms in the promoter regions of inflammatory cytokine genes, including IL1B (-118C>T, c47+242C>T, +3954C/T, and -598T>C) and TNFA (-1211T>C, -1043C>A, -1037C>T, -488G>A, and -418G>A). CONCLUSION: IL1RN -1129T>C (rs4251961) genotypes might be associated with a significant increase of AP risk in a Korean ethnic group.

Diagnostic role of cone beam computed tomography for the position of straight array.

OBJECTIVE: To assess the usefulness of cone beam computed tomography (CBCT) for characterizing electrode insertion and evaluate the influence of electrode insertion status on post-cochlear implantation (CI) outcomes. DESIGN: Twenty-six ears with post-CI CBCT scans were included. The devices were MED-EL Flex28 (n = 21) and Nucleus slim straight (n = 5). The parameters including cochlear duct length (CDL), insertion depth angle (IDA), insertion length of electrode (IL), and cochlear coverage (CC) were analyzed and compared with aided pure-tone threshold (PTA) with implant in free field, and open-set sentence score. RESULTS: The mean CDL was 36.8 ± 1.4 mm. Electrode array was dislocated into scala tympani in two ears. The mean IL and IDA were 26.5 ± 1.9 mm and 541.4 ± 70.2°. The mean linear CC (IL/CDL, 0.73 ± 0.06) was larger than the mean angular CC (IDA/900, 0.60 ± 0.08). The CBCT parameters showed correlation one another. While the aided pure-tone threshold was correlated with IL and IDA, there were no significant correlations in the open-set sentence score. For the postlingually deaf patients with single electrode (Flex 28), the sentence score had no significant correlation and the aided PTA was positively correlated with IL (R = 0.517, p = .028). CONCLUSIONS: This study validated the CBCT evaluating the electrode array position. The CBCT could be helpful for the preoperative selection of the optimal array and prediction of the CC.

Optical assessment of the in vivo tympanic membrane status using a handheld optical coherence tomography-based otoscope.

OBJECTIVE: Conventional otoscopes and oto-endoscopes, which are used to examine the tympanic membrane (TM), do not provide tomographic information. Optical coherence tomography (OCT) non-invasively reveals the depth-resolved internal microstructure of the TM with very high spatial resolution. We designed this study to examine the TMs with middle ear diseases using a handheld otoscope employing 860 nm spectral domain (SD)-OCT, combined with video camera and to demonstrate the clinical applicability of this system. DESIGN: A total of 120 patients with otologic symptoms were enrolled. TM images were obtained using the handheld OCT-based otoscope (860 nm central wave length, 15 µm axial resolution, 15 µm lateral resolution, and 7 mm scanning range using relay lens). Both OCT and oto-endoscope images were compared according to the clinical characteristics such as perforation, retraction, and postoperative healing process. RESULTS: The objective grade about the thickness of perforation margins and the accurate information about the extent of TM retraction that was not distinguishable by oto-endoscopic exam could be identified using this system. The postoperative healing process of TMs could be also followed using the OCT device. CONCLUSION: These analyses from the surgeon-oriented perspective suggest another useful application of the handheld OCT device.

Manganese-enhanced auditory tract-tracing MRI with cochlear injection.

Recent studies have demonstrated the use of manganese ion (Mn2+)) as an in vivo neuronal tract tracer. In contrast to histological approaches, manganese tracing can be performed repeatedly on the same living animal. In this study, we describe the neuroaxonal tracing of the auditory pathway in the living guinea pig, relying on the fact that Mn2+ ion enters excitable cells through voltage-gated calcium channels and is an excellent MRI paramagnetic tract-tracing agent. Small focal injections of Mn2+ ion into the cochlea produced significant contrast enhancement along the known neuronal circuitry. This in vivo approach, allowing repeated measures, is expected to open new vistas to study auditory physiology and to provide new insights on in vivo axonal transport and neuronal activity in the central auditory system.

Novel therapy for hearing loss: delivery of insulin-like growth factor 1 to the cochlea using gelatin hydrogel.

HYPOTHESIS: Local application of recombinant human insulin-like growth factor 1 (rhIGF-1) via a biodegradable hydrogel after onset of noise-induced hearing loss (NIHL) can attenuate functional and histologic damage. BACKGROUND: The biodegradable gelatin hydrogel makes a complex with drugs by static electric charges and releases drugs by degradation of gelatin polymers. We previously demonstrated the efficacy of local rhIGF-1 application via hydrogels before noise exposure for prevention of NIHL. METHODS: First, we used an enzyme-linked immunosorbent assay to measure human IGF-1 concentrations in the cochlear fluid after placing a hydrogel containing rhIGF-1 onto the round window membrane of guinea pigs. Second, the functionality and the histology of guinea pig cochleae treated with local rhIGF-1 application at different concentrations after noise exposure were examined. Control animals were treated with a hydrogel immersed in physiologic saline alone. RESULTS: The results revealed sustained delivery of rhIGF-1 into the cochlear fluid via the hydrogel. The measurement of auditory brainstem responses demonstrated that local rhIGF-1 treatment significantly reduced the threshold elevation from noise. Histologic analysis exhibited increased survival of outer hair cells by local rhIGF-1 application through the hydrogel. CONCLUSION: These findings indicate that local rhIGF-1 treatment via gelatin hydrogels is effective for treatment of NIHL.

Evaluation of white matter structures in patients with tinnitus using diffusion tensor imaging.

Recent functional imaging studies have demonstrated that the sensation of tinnitus is associated with activity in cortical regions functionally linked to subserve the generation, perception and processing of the tinnitus stimulus. Previous functional imaging studies have focused primarily on the cortical centers. However, none of these examined the functional nature of associated white matter interconnecting these cortical centers. In this study, we investigate the integrity of white matter tracts interconnecting the auditory system to the parietal and frontal corticies in tinnitus patients using diffusion tensor imaging. Our preliminary results suggest the possible involvement of associated white matter structures in addition to processing cortical centers in tinnitus patients compared with healthy subjects.

Novel EYA1 mutation in a Korean branchio-oto-renal syndrome family.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder that is characterized by branchial cysts or fistulae, external ear malformations and/or preauricular pits, hearing loss and renal anomalies. Recent advances in molecular genetics have shown a human homologue of the Drosophila 'eyes absent' gene (EYA1) on chromosome band 8q13.3 to be the most common cause of BOR syndrome. Several mutations have been identified in the EYA1 gene in patients with BOR syndrome worldwide. Here, we report a second Korean family with BOR syndrome with a novel nonsense EYA1 mutation.

Decalcification using ethylenediaminetetraacetic acid for clear microstructure imaging of cochlea through optical coherence tomography.

The aim of this study was to analyze the effectiveness of decalcification using ethylenediaminetetraacetic acid (EDTA) as an optical clearing method to enhance the depth visibility of internal soft tissues of cochlea. Ex vivo mouse and guinea pig cochlea samples were soaked in EDTA solutions for decalcification, and swept source optical coherence tomography (OCT) was used as imaging modality to monitor the decalcified samples consecutively. The monitored noninvasive cross-sectional images showed that the mouse and guinea pig cochlea samples had to be decalcified for subsequent 7 and 14 days, respectively, to obtain the optimal optical clearing results. Using this method, difficulties in imaging of internal cochlea microstructures of mice could be evaded. The obtained results verified that the depth visibility of the decalcified ex vivo samples was enhanced.

Prediction of Cochlear Implant Outcomes in Patients With Prelingual Deafness.

OBJECTIVES: To evaluate the factors that limit post-cochlear implantation (CI) speech perception in prelingually deaf children. METHODS: Patients with CI were divided into two groups according to Category of Auditory Performance (CAP) scores 3 years post-CI: the poor performance group (poor performance group, CAP scores≤4, n=41) and the good performance group (good performance group, CAP scores≥5, n=85). The distribution and contribution of the potential limiting factors related to post-CI speech perception was compared. RESULTS: Perinatal problems, inner ear anomalies, narrow bony cochlear nerve canal (BCNC), and intraoperative problems was significantly higher in the poor performance group than the good performance group (P=0.010, P=0.003, P=0.001, and P=0.045, respectively). The mean number of limiting factors was significantly higher in the poor performance group (1.98±1.04) than the good performance group (1.25±1.11, P=0.001). The odds ratios for perinatal problems and narrow bony cochlear nerve canal in the poor performance group in comparison with the good performance group were 4.878 (95% confidence interval, 0.067 to 0.625; P=0.005) and 4.785 (95% confidence interval, 0.045 to 0.972; P=0.046). CONCLUSION: This study highlights the comprehensive prediction of speech perception after CI and provides otologic surgeons with useful information for individualized preoperative counseling of CI candidates.

Conductive hearing loss with an intact tympanic membrane due to non-inflammatory causes.

OBJECTIVE: We analyzed audiologic and surgical findings in patients with conductive hearing loss (CHL) with an intact tympanic membrane (TM) that was of a non-inflammatory origin. METHODS: We reviewed data from patients who underwent exploratory tympanotomy for CHL with intact TM from January 1995 to November 2012. Patients with diseases of non-inflammatory origin were enrolled (69 patients; 79 ears). Patients were categorized into two groups: non-trauma (50 ears) and trauma (29 ears). Demographic data, intraoperative findings, and audiologic results were obtained and analyzed. RESULTS: Overall, the second decade was the most common age of diagnosis in both the non-trauma and trauma groups. Operative findings showed that ossicular dislocation was more prevalent than ossicular fixation; all trauma group subjects had ossicular dislocation. Short columellization or partial ossicular replacement was the most frequently adopted surgical procedures in both groups. Overall, audiologically, air-conduction thresholds (ACs) and air-bone gaps were significantly improved over the short- and long-term period in both groups. However, the non-trauma group had significantly higher preoperative ACs than the trauma group, especially at low frequencies. CONCLUSION: This study provides clinicians with useful information regarding the clinical characteristics of CHL with intact TM of non-inflammatory origin.

Clinical Aspects and Surgical Outcomes of Congenital Cholesteatoma in 93 Children: Increasing Trends of Congenital Cholesteatoma from 1997 through 2012.

BACKGROUND AND OBJECTIVES: The recent increase in the reported incidence of congenital cholesteatoma (CC) may be secondary to the widespread use of otoendoscopy as well as an increased awareness of these lesions among primary care physicians. However, little research about CC has been conducted in a large group of patients. This study aimed to analyze the clinical characteristics of CC including the annual number of patients, symptoms, age at diagnosis, stage and type of disease, surgical techniques, recurrence, and postoperative complications. SUBJECTS AND METHODS: Retrospective chart review was performed for patients who met the inclusion criteria between January 1997 and June 2012. RESULTS: Ninety-three patients underwent surgery for CC. The age at operation ranged from 12 months to 17 years (mean age, 6.1 years). The number of patients was less than 4 per year until 2005, but increased to more than 10 per year since 2008. CC was most commonly reported as an incidental finding (58.1%). The operative procedures included the transcanal myringotomy approach (46.2%), canal wall up mastoidectomy (37.6%), tympanoplasty (8.6%), and canal wall down mastoidectomy (7.5%). The recurrence rate was 20.4% and the complication rate was 12.9%. No patients with stage I CC had complications. CONCLUSIONS: This study showed that the incidence of CC has recently increased notably. Most patients with stage I and II CC were completely cured by transtympanic surgery, and complication and recurrence rates increased according to the extent of disease. Early detection of CC is important to facilitate minimally invasive surgery and to reduce complication and recurrence rates.