Stereocilia have “rootlets,” that penetrate the cytoplasm; these rootlets comprise bundles of actin filaments, the function of which was unknown because of the lack of a molecular description. Mutations in TRIOBP were identified from human deafness pedigrees. Immunohistochemical studies revealed that TRIOBP is the first molecule that specifically localized in the rootlets. Biochemical studies have revealed that TRIOBP bundles comprise actin filaments. Triobp-deficient mice lack stereocilia rootlets, indicating that TRIOBP is indispensable for rootlet generation. Stereocilia without rootlets show progressive degeneration, causing deafness. There are multiple TRIOBP isoforms; TRIOBP-1, TRIOBP-4, and TRIOBP-5. A comparison of Triobp-4/5 deficient mice and Triobp-5 specific deficient mice revealed a functional difference between TRIOBP isoforms.

Successful implantation of bone-anchored hearing aids (Baha) depends upon effective osseointegration at the bone-implant interface. We investigated implant stability of Baha implants among Japanese patients. The study included four patients (four ears) who underwent Baha BI300 implantation. The implants were loaded after 3 weeks. The control group included five patients (five ears) who used the Baha implant for more than one year. The implant stability quotient (ISQ) was measured at 0, 1, 3 weeks, and 3 months after implant surgery. The ISQ value at the time of surgery was 59.3 ± 1.4, which was equal to that observed in the control group. ISQ values increased 3 weeks postoperatively. Based on the findings of the current study, we conclude that loading the Baha implants 3 weeks postoperatively is safe among Japanese patients. Our results also suggest that vibrant stimulation by loading may promote osseointegration of baha implants.

Surgical insertion of electrodes of cochlear implants has been reported to induce various changes within the cochlea. These changes include insertional trauma to the cochlea; a tissue response consisting of inflammation, fibrosis, and neo-osteogenesis; and an immunological reaction to the foreign body.

First, we investigated the factors influencing the word recognition scores and calculated the volumes of fibrous tissue and new bone in the scala tympani and scala media/vestibuli in 17 cases using three-dimensional reconstruction software (Amira^®). We found that the postoperative consonant–nucleus vowel–consonant (CNC) word score was positively correlated with spiral ganglion cell count and negatively correlated with the percentage volume of new bone within the scala tympani, scala media/vestibuli, and cochlea, but not with the percentage volume of fibrous tissue. The percentage volume of new bone in the scala media/vestibuli was positively correlated with the degree of intracochlear insertional trauma.

Next, the preservation of hair cells, supporting cells, and innervating dendritic processes following cochlear implantation was evaluated using immunostaining. Two sections including the modiolus or basal turn from each temporal bone were stained for hair cells, supporting cells (the inner and outer pillar cells and Deiters’ cells), and dendritic processes using anti-myosin-VIIa, anti-tubulin, and anti-neurofilament, respectively, in both implanted and unimplanted ears. The immunoreactivity of the inner and outer hair cells was significantly reduced both along and apical to the electrode in the implanted ear and in the basal turn of the unimplanted ear. The immunoreactivity of dendritic processes in the osseous spiral lamina was significantly negatively affected along the electrode. The immunoreactivity of the supporting cells was significantly reduced in the implanted and unimplanted ears similarly. Preservation of the inner and outer pillar cells and Deiters’ cells, which are possible candidates for hair cell regeneration, was similar in the implanted and unimplanted cochlea, and therefore, it may be possible to regenerate hair cells in implanted as well as unimplanted cochleae in the future.

Cochlear hair cells (HCs) and auditory neurons (ANs) are often the primary site of cochlear damage induced by acoustic overstimulation, which often leads to secondary neural degeneration in ANs after HC loss and suppresses hippocampal neurogenesis, resulting in cognitive decline. However, it is unclear whether the loss of HCs or decreasing auditory inputs alone causes secondary degeneration in ANs and hippocampal neurogenesis. Selective HC ablation and noise exposure have shown different patterns of pathology in the auditory pathway, in which decreasing auditory inputs from selective HC loss or conductive hearing loss led to secondary neural degeneration in ANs and hippocampal neurogenesis. Furthermore, auditory deprivation could lead to increased microglial invasion and stress responses, which might be a risk factor for hippocampal neurogenesis impairment. Therefore, auditory activities are required to maintain the fundamental functions of ANs and hippocampus.

The approach to the jugular foramen is exceptionally challenging. Various surgical approaches to the jugular foramen have been reported. The approaches to the jugular foramen from the lateral and posterior side generally involve the following three key approaches: (1) retrosigmoid (the lateral suboccipital approach), (2) infralabyrinthine mastoidectomy, and (3) cervical exposure. The previously reported approaches combined various elements of these three approaches. To open the jugular foramen, two operative steps are involved; infralabyrinthine mastoidectomy and resection of the jugular process of the occipital bone. These two steps may be combined with one or more of the key approaches. While infralabyrinthine mastoidectomy exposes the superior and lateral surface of the jugular bulb., resection of the jugular process exposes its posterior and inferior surfaces. These two steps are crucial in gaining adequate jugular bulb exposure and access to the tumor inside the jugular foramen. From the viewpoint of microsurgical anatomy, we classified the lateral and posterior approaches into Type 1 (retrosigmoid), Type 2 (infralabyrinthine mastoidectomy), and Type 3 (cervical exposure) for intradural, foraminal, and extracranial tumors, respectively. Combined procedures, which include one or more of the three basic approaches combined with infralabyrinthine mastoidectomy and/or resection of the jugular process, were categorized separately into Type 4 to 6 based on the combination with the three basic approaches. This classification may reduce confusion surrounding the approaches to these tumors.

A thorough understanding of the microsurgical anatomy and approaches to the jugular foramen is crucial for the safe, accurate, and gentle exposure of the jugular foramen. This report shows the microsurgical anatomy of the jugular foramen and related structures and a basic surgical approach to the jugular foramen in a step-by-step manner with cadaveric dissection.

A typical disease in the otologic lateral skull base requiring surgery is vestibular schwannoma (acoustic neuroma). The transpetrosal (trans-temporal) approach to auditory nerve tumors requires surgical techniques outside the scope of middle ear surgery. It requires a better understanding of the various anatomies of the temporal bone, thus improving the level of middle ear surgery itself. The most frequently used representative transpetrosal approach is the translabyrinthine approach. We aimed to master the translabyrinthine approach first. Other transpetrosal approaches include the retrolabyrinthine approach to preserve hearing function, the transotic approach to facilitate the anterior approach to the internal auditory canal, and the expanded transcanal transpromontorial approach, an endoscopic approach through the external auditory canal. This article explains the outlines of each approach and presents specific cases based on our experience in our department.

Meniere’s disease is characterized by dizziness and is caused by inner ear disorder. Its characteristic histopathological finding is endolymphatic hydrops. Meniere’s disease is characterized by a triad of repeated vertigo attack, fluctuating hearing loss, and tinnitus. In this session, we comment on the mechanisms of spontaneous nystagmus using mainly the results from animal experiments.

From clinical practice experience and experimental studies, the formation of endolymphatic hydrops relates to the dysfunction of the endolymphatic sac and a high plasma level of the antidiuretic hormone. Thus, the mechanism that dizziness occurs when endolymphatic hydrops is formed remains unclear. The results of the animal experiment showed that an increase in perilymph potassium ion concentration is associated with the formation of endolymphatic hydrops. A high concentration of perilymph potassium causes spontaneous nystagmus to change from the stimulus to the paralytic state. The single nerve units of the vestibular nerve disappear after the rise in the firing rate. Hence, considering these results, an increase in perilymphatic potassium ion concentration is regarded as the cause of dizziness.

The more common the use of magnetic resonance imaging becomes for the differential diagnosis of symptoms such as sudden hearing loss or vertigo, the more vestibular schwannoma cases we encounter in the form of incidentally observed small tumors. A small tumor is not an entity that immediately affects the vital prognosis or induces serious neurological symptoms such as facial palsy. However, no standard management has been delineated for small vestibular schwannoma so far. Our management goals prioritize (I) prognosis while emphasizing on (II) hearing preservation, and (III) decreasing the chance of facial dysfunction throughout life. Our experiences indicate that early surgical intervention using the middle cranial fossa approach is a beneficial option, especially for hearing preservation when the candidacy with neurotological test results are evaluated. Here we introduce our approach based on treatment outcomes at Nagoya City University Hospital.

Autoinflammatory diseases are characterized by hyperactivation of the innate immune system without high titers of autoantibodies or antigen-specific T cells. Cryopyrin-associated periodic syndrome (CAPS) is a spectrum of inherited autoinflammatory syndromes caused by a gain-of-function mutation of the NLRP3 gene. CAPS includes familial cold autoinflammatory syndrome, Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disease (NOMID). Among these, MWS and NOMID are associated with a high incidence of sensorineural hearing loss. Recently, we identified a missense mutation, p.Arg918Gln in NLRP3 in a family segregating sensorineural hearing loss without any other target-organ manifestations of CAPS. The family members carrying the mutation had bilateral sensorineural hearing loss with onset in the late 2^nd to 4^th decade of life. The hearing loss initially primarily affected high frequencies and slowly progressed. We also identified another unrelated family segregating p.Arg918Gln mutation. In the family, hearing loss was accompanied by autoinflammatory signs and symptoms. Postcontrast magnetic resonance imaging with fluid-attenuation inversion recovery showed pathologic enhancement of the cochlea in the affected members. The hearing loss was reversed or improved by IL-1β blockade therapy. These observations suggest that mutations of NLRP3 may cause hearing loss due to local autoinflammation within the inner ear.

In this study, we examined the relationship between cognitive function and hearing impairment or balance disability in a community-dwelling population. The subjects were volunteers who participated in the Iwaki Health Promotion Project. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) assessment tool. The subjects underwent hearing tests by pure tone audiometry and balance tests by static posturography. We found significant correlations between high MMSE scores and hearing thresholds at 1, 2, and 4 kHz, Furthermore, the MMSE score was significantly associated with path length with eyes open or closed in male subjects, indicating that in males, the longer the path length with eyes open and closed, the lower the MMSE score. In this study, we investigated the association between balance ability and early cognitive decline before dementia in a general population. We found that static posturography might be a useful balance test to assess early cognitive decline in males.

We investigated the association between hearing loss and cognitive impairment in the National Institute for Longevity Sciences, Longitudinal Study for Aging. We used the data from the 2nd to 7th study waves, which covered the years 2000–2012. On average, the prevalence of hearing loss was 44.8%, and the prevalence of hearing aid usage was 1.25% in the mild hearing loss group, 22.4% in the moderate hearing loss group, and 77.4% in the severe to profound hearing loss group. We recruited 1193 participants with hearing loss (3260 cumulative observations) for the generalized estimating equation analysis. The dependent variable was cognitive impairment; the independent variables were the pure-tone average threshold levels at 4 frequencies (500, 1000, 2000, and 4000 Hz) by the better hearing ear (PTABHE) and hearing aid usage; and the covariates were age, sex, depressed mood, smoking status, alcohol intake, education, obesity, physical activity, household income, and history of hypertension, dyslipidemia, diabetes, ischemic heart disease, stroke, ear disease, and occupational noise exposure. PTABHE was significantly associated with cognitive impairment in both the mild and moderate hearing loss groups. In the moderate hearing loss group, the odds ratio of cognitive impairment was significantly lower among regular users of hearing aids than among non-users.

With the increase in the geriatric population and the prevalence of diabetes, the incidence of malignant external otitis (MEO) is on the rise. If not diagnosed and treated adequately and appropriately, MEO can process up to the bone marrow involving the soft tissues at the skull base and result in progressive paralysis of the lower cranial nerves. In this study, we retrospectively reviewed the pathogenic bacteria involved and the efficacy of the antibiotics used in five cases of MEO with skull base osteomyelitis by reviewing their medical records. All five cases had an early MEO diagnosis and prompt antibiotic therapy; hence they all recovered before showing paralysis of the lower cranial nerves. It is necessary to investigate more such cases and select intravenous antibiotics with a proven record of success and efficacy against diverse and resistant pathogenic bacteria to diagnose and treat MEO adequately and appropriately.

Malignant external otitis is a refractory disease with a high mortality and recurrence rate due to its complications, the absence of standard therapy, and difficulty in assessing the therapeutic effects. Gallium scintigraphy was conventionally used to diagnose malignant external otitis and is now used to assess the therapeutic effects. Contrast-enhanced magnetic resonance imaging (MRI) is not indicated in patients with malignant external otitis because they frequently have renal impairment. Assessing the therapeutic effects with MRI is often difficult due to contrast enhancement; however, gallium scintigraphy can be performed in patients with renal impairment and its uptake quickly declines when the inflammation improves. We report three cases who achieved disease control on long-term antibacterial treatment, two of which were assessed using gallium scintigraphy to evaluate the therapeutic effects.

Staged surgery is often selected for congenital cholesteatoma because of frequent residual recurrence. However, because it often occurs in children, it is desirable to select staged surgery according to the residual recurrence risk.

We examined the residual recurrence risk and validity of selecting staged surgery in 27 ears of 27 patients who underwent congenital cholesteatoma surgery in our hospital between January 2008 and April 2018.

Residual recurrence occurred in 26% of the 27 ears. The rate of residual recurrence was significantly higher in patients with advanced cholesteatoma and ossicular defects. Staged surgeries were more frequently performed in patients with stage Ic cholesteatoma and ossicular defects, as well as in those with stage II or higher cholesteatoma. Among these patients, the residual rate was found to be high.

The extent of cholesteatoma progression and ossicular defects may be an indicator for staged surgery. We must select staged surgery for patients with stage Ic cholesteatoma and ossicular defects and for those with stage II or higher cholesteatoma.

Conductive hearing loss with an intact tympanic membrane is diagnostically challenging. The differential diagnosis includes ossicular malformation, otosclerosis, congenital cholesteatoma, and traumatic ossicular chain transection. Depending on the patient’s background, usually surgery is the first-choice treatment to improve hearing loss. However, patients with few subjective symptoms such as hearing loss since childhood may not wish to receive treatment or may discontinue follow-up. We report two cases of conductive hearing loss with an intact tympanic membrane in adults diagnosed with congenital cholesteatoma by surgery. Both patients had a history of hearing loss since childhood; however, they presented for clinical consultation on an outpatient basis only during adulthood. Preoperative diagnostic confirmation of middle ear lesions was difficult; therefore, the patient was explained the possibility of ossicular reconstruction, cholesteatoma, and stapes surgery before we obtained written informed consent. Intraoperative findings revealed congenital cholesteatoma. Conductive hearing loss is associated with several etiopathogenetic contributors and occurs in a wide range of age groups. Diagnosis of this condition is often challenging based exclusively on hearing or imaging evaluation; therefore, surgeons should obtain preoperative informed consent only after a thorough explanation regarding the possible pathological conditions, surgical indications, timing, surgical procedure and its effectiveness, as well as the associated risks. Usually, adult cholesteatoma is an acquired condition, and even in patients who present with a congenital cholesteatoma, the disease is often advanced at the time of diagnosis. Clinicians should consider a congenital cholesteatoma in the differential diagnosis in patients who undergo careful evaluation of hearing and imaging tests, and computed tomography of the middle ear reveals a slight soft tissue shadow around the ossicles.

The purpose of this study was to examine the selection criteria for planned tympanoplasty in pars tensa cholesteatoma and also to evaluate the postoperative outcome after S_2p tympanoplasty using a survival analysis.

Out of 163 patients with pars tensa cholesteatoma treated with canal wall reconstructed tympanoplasty from January 1, 1991 to December 31, 2017, we included 29 patients with planned tympanoplasty. The follow-up period of patients was more than 1 year and the median period was 9 years 2 months after S_2p surgery.

1. Staged surgery was selected for the following reasons:

(1) When one-stage surgery which was to be carried on ventilation and drainage, between the Eustachian tube and the reconstructed middle ear cavity was judged difficult to preserve the function. (2) When the residual cholesteatoma was suspected to be in areas with poor visual field, such as the tympanic sinus. (3) For the purpose of avoiding inner ear damage, cholesteatomas in dangerous sites were left on purpose during the S₁ surgery; for example, cholesteatomas with infectious granulation at the labyrinthine fistula. During the S_2p surgery, safe removal of cholesteatomas was attempted in a prepared infection-free environment. (4) To ensure ossicular chain repair, especially in the type of Oft.

As a result, in the 29 ears of stage surgery, majority were complicated with severe conditions, such as infection, adhesive otitis, and labyrinthine fistula.

2. The postoperative outcome was evaluated using the following method:

First, a disease-free case was one with postoperative air-bone gap maintained within 20 dB without a S_2r surgery. Therefore, the cumulative frequency of disease-free cases was visualized by the Kaplan-Meyer survival curve.

We found no significant difference between the staged surgery group and the one-stage surgery group.

Based on these results, we found a useful way of selecting staged surgery in cases with pars tensa cholesteatoma with severe pathological conditions.

We assessed pre- and post-operative tympanograms and postoperative tympanic membrane findings in 43 patients who underwent tympanoplasty for cholesteatoma. While we found no significant relationship between the preoperative tympanograms (classified as types A or C) and the presence or absence of postoperative tympanic membrane retraction in 31 cases with habitual sniffing, we found a significant relationship between postoperative tympanic membrane retraction and the tympanograms obtained 3–6 months after surgery. The pre- and 3–6 months post-operative tympanograms were both significantly related to postoperative tympanic membrane retraction in 12 cases without habitual sniffing. Our findings suggest that tympanic membrane retraction may be caused by the pressure in the tympanic cavity after surgery. The probability of severe tympanic membrane retraction is higher in patients with a C2-type 3–6 months postoperative tympanogram. In cases of habitual sniffing, similar to cases without habitual sniffing, a type A tympanogram obtained 3–6 months after surgery is associated with low likelihood of tympanic membrane retraction. In the future, doctors must address how they can guide patients on ceasing habitual sniffing before and after the operation, and be able to accurately judge the cessation of this habit before the operation.

The introduction of transcanal endoscopic ear surgery (TEES) has made it necessary to prescreen patients to determine whether TEES or microscopic ear surgery (MES) would be the most appropriate intervention. One associated area that must be carefully examined in the presurgical screening is the sinus tympani (ST). The ST exhibits considerable variation in morphology, particularly in regard to its depth. In general, TEES is indicated for shallow ST, while MES is indicated for deep ST, but objective guidelines are still being developed. In this study, we evaluated ST morphology for 130 normal ears of 65 Japanese patients based on temporal bone computed tomography (CT) examination. We also investigated factors which could influence the ST morphology. ST depth has been classified by Marchioni into four types (A, B1, B2 and C), going from shallow to deep based, on axial CT imaging. Our results revealed a wide range of variation with Type A: 31 ears (23.8%); Type B1: 79 ears (60.8%); Type B2: 18 ears (13.8%); and Type C: 2 ears (1.5%). We further found that the ST type was not significantly correlated with patient age or the development of mastoid cells. In conclusion, the depth of ST should be assessed in the presurgical CT screening. This information will allow the surgeon to make an informed decision on the optimal procedure when performing surgery involving the ST.

Cochlear implantation is indicated in patients with deafness and concomitant eosinophilic otitis media. However, the long-term safety of the procedure remains unclear because inflammation of the middle ear mucosa shows recurrent worsening and remission in cases of eosinophilic otitis media. Moreover, it is often complicated with bacterial infection. Since 2014, we have performed cochlear implantation via the M3a mastoidectomy (subtotal petrosectomy) approach in three patients with deafness, who underwent surgery for eosinophilic otitis media; postoperatively, all patients showed good hearing ability, without any complications. This surgical method involves complete removal of the mucous membrane of the middle ear and the mastoid cells with elimination of the sites showing eosinophilic infiltration. The Eustachian tube and external auditory canal were occluded, and entry of the causal stimulus, with eosinophilic inflammation was blocked to prevent postoperative eosinophilic inflammation. This surgical approach improved patients’ hearing ability and also obviated the need for treatment of postoperative eosinophilic otitis media. Our results remain inconclusive owing to the small sample size of this study. However, this surgical procedure may be a safe and effective approach in patients with deafness and concomitant eosinophilic otitis media.

Objective: During mapping with cochlear implant users, we often have to partially turn off active electrode channels in the cochlea for various reasons. The objective of this study was to evaluate the effects of deactivation of selected channels on the Japanese speech recognition ability of Nucleus^®24 Cochlear Implant users.

Design: The subjects were 12 Japanese adults with Cochlear Implants who were able to use all 22 channels in the cochlea. From the round window, twenty-two channels in the cochlea were divided into Proximal, Middle, and Distal. Two types of experimental maps were created: one in which 3, 5, and 7 continuous channels were deactivated in each division, representing –3, –5, and –7 maps, and another in which 3, 5, and 7 channels were deactivated by skipping adjacent channels at equal intervals (: Skip). The speech recognition abilities between these two experimental maps and the optimized maps were compared using 22 channels.

Results: There was significant deterioration in the Japanese speech recognition abilities of the patients with –5 and –7 maps in the Proximal, Middle, and Distal divisions. The results for the Distal division pointed to more significant deteriorations than those in other regions. The results with Skip-7, however, showed no significant decrease in noise.

Discussions: Dactivation of continuous channels at five or more regions caused decreases in Japanese listening abilities. The deactivations in the Distal division could lead to a considerable decrease in the understanding of speech. This finding suggests that it was not the full-insertions or migrations of the electrode arrays that caused significantly poor performances.