Benign paroxysmal positional vertigo (BPPV) is classified into canalolithiasis and cupulolithiasis. Each of these shows characteristic nystagmus findings in the positional/positioning nystagmus test; however, the direction, strength, and duration of the nystagmus can change depending on the behavior of the otolith in the semicircular canal. The behavior of otolith on the macula, in the semicircular canals, and on the cupula was shown in the model experiments of BPPV using bullfrogs. By understanding the structure of the inner ear and the properties of otolith and cupula and considering the behavior of the otolith in the semicircular canals or utricle during the positional/positioning nystagmus test, the nystagmus findings could be even more helpful in daily clinical practice.

Previous studies have reported that humans use two types of otolith-ocular reflexes that control the gaze, to ensure stable perception of the environment during movement. One type of otolith-ocular reflex induces horizontal eye movement during lateral translational motion and the other type induces torsional eye movement during lateral tilting movement. In the interaural direction, linear acceleration is loaded during lateral translational motion, and gravity acceleration is loaded during lateral tilting movement. The otolith is a sensory organ that responds to linear accelerations. According to Einstein’s equivalence principle, the two types of accelerations cannot be discriminated. However, humans are typically able to discriminate these two acceleration types perceptually, and act in space accordingly. The present review showed that lateral-eyed mice exhibit only one type of otolith-ocular reflex, i.e., torsional eye movement.

The primitive otolith-ocular reflex, i.e., torsional eye movement has degenerated and become vestigial in humans and monkeys, and has evaluated to the other type of otolith-ocular reflex, i.e., horizontal eye movement.

Perivascular macrophages (PVMs) are a unique cell population of tissue-resident macrophages characterized by their close association with blood vessels and specific expression makers in certain tissues. PVMs are found in the inner ear, brain, skin, liver, and retina. Intrastrial macrophages are classified into PVMs and control vascular permeability as a member of the blood strial barrier. PVMs in the stria vascularis also have a phagocytic function against foreign substances, pathogens, and deposits or waste material and degenerated cells in the tissues. The morphology of PVMs is similar to that of microglia in the central nervous system and might be activated by excessive melanin granules in the stria vascularis. Macrophage activation is remarkable in the ears of the Slc26a4 KO mouse.

Description about the middle ear compartment, which is composed of the ossicles, mucosal folds and ligaments, and the ventilation route in the middle ear dates back to Prussak’s report in 1867. In the past, the description has been mainly from the viewpoint of surgical anatomy using a microscope; however, with the recent realization of transcanal endoscopic ear surgery (TEES) realized by the high resolution of optical instruments, the mucosal folds of the middle ear cavity and the compartments of the middle ear have been redefined from the viewpoint of endoscopic otologic surgery. In particular, surgical significance of the mucosal folds in the attic, have been rediscovered and redefined from the perspective of endoscopic otologic surgery.

The mucosal folds are membranous structures that connect the contents of the middle ear to the bony wall of the middle ear or to each other, dividing the middle ear into small compartments. The mucosal folds contain blood vessels and nerves, and play a role similar to that of the mesentery. In microsurgery, mucosal folds are often considered to be remnants of inflammation or the result of adhesions, but are constitutively present in the middle ear cavity, although their position and size vary in each patient. It is important to correctly recognize the anatomy of the middle ear compartment, sectioned by the mucosal folds, in order to understand the pathogenesis of the middle ear disease. TEES has the great advantage of minimizing the need for dissecting the bony wall of the external auditory canal or the mastoid air cells to sufficiently obtain the operative field, and has an advantage in recognizing the compartments of the middle ear. Preoperatively, a thorough evaluation of the extent of the lesion should be performed in the context of the anatomical compartments formed by mucosal folds and microstructures, and the surgical approach should be determined from the viewpoint of securing the ventilation route to the attic as well as removing the lesions.

Pendred syndrome is an autosomal recessive disorder characterized by goiter, sensorineural hearing loss, dizziness/vertigo, and mutations of the SLC26A4 gene. Hearing loss is generally profound and prelingual, although occasionally it has a late-onset and is progressive. Pendrin, a protein synthesized by SLC26A4, is expressed in the cochlea, vestibule, and endolymphatic sac of the mouse inner ear. The absence of normal pendrin expression leads to the enlargement of the cochlear duct and the acidification of endolymph fluid, resulting in stria vascularis dysfunction. In addition, equilibrium dysfunction is observed in the absence of pendrin expression, which might be associated with the abnormal development of otolith organs and otoconia. This review summarizes recent studies in mouse models that have been developed to delineate the role of pendrin in the normal cochlear and vestibular development. Additionally, this review addresses the pathogenesis of Mondini anomaly often observed in the patients with Pendred syndrome.

Pendred syndrome is a hereditary syndrome with fluctuating progressive hearing loss, vertigo, and goiter. It was named after Dr. Vaughan Pendred as he reported several cases of hearing loss and goiter in the Lancet in 1896. There has been a history of approximately 120 years of research on the disease, and especially in the last 20 years, remarkable advances have been made in this research. However, despite the fact that it is the most common type of syndromic hearing loss, there is still no specific treatment for the disease, and its pathophysiology is not fully unveiled.

In 2013, our department initiated research on this disease using human iPS cells and identified sirolimus as a candidate drug for treatment. In this article, we will outline the new findings that human iPS cell research has brought to this disease research and report on the developmental processes of iPS cells-based drug discovery research after drug identification.

In Darwin’s evolution theory, vertebrates have developed their brains for adaptation in their environments. The structure of different vertebrate brains is specific to each species. Although the histology of their central nervous system correlating with the behaviors in vertebrates has been investigated, limited reports discuss the comparison between each brain function and behavior in vertebrates.

In this study, we observed the histology of the telencephalon (cerebrum), cerebellum, and midbrain of Fish, Amphibians, Reptiles, Birds, and Mammals and investigated the common morphology in evolution. Fish or Amphibians are found to have larger volumes and more complex cytoarchitectural structures in the midbrain and cerebellum, suggesting that the midbrain is a higher center of the brain with a highly developed optic tectum. Conversely, Reptiles, Birds, or Mammals are found to have larger volumes in the telencephalon and layered structures with neuropils on the surface of the telencephalon. In the cerebellum of all species, we observed three-layered structures and Purkinje cells, suggesting that the cerebellum is an essential brain structure in all vertebrates to maintain their posture and locomotion for survival.

The Hegelian theory of recapitulation states that “Ontogeny recapitulates phylogeny”; this could give us a clue to think about the origin of human brains in our study as well.

There are four foraminal structures at the bottom of the internal auditory canal, namely, the tractus spiralis foraminosus (TSF), macula cribrosa superior (MCS)/media (MCM), and facial canal. The cochlear, superior vestibular, inferior vestibular, and facial nerves pass through TSF, MCS, MCM, and facial canal, respectively. TSF, MCS, and MCM show bony cribriform structures. The role and developmental process of these bony cribriform structures has remained unclear, so far.

The present study aimed to assess 1) the sizes of small holes composing these bony cribriform structures (TSF, MCS, and MCM), 2) the developmental process of ossification of bony cribriform structures during the fetal period and the number of weeks for its completion, and 3) the morphological features and role of bony cribriform structures based on the observation of a case of cerebellar hemorrhage.

1) The size of small holes of TSF, MCS, and MCM was measured from the continuous pathological specimen sections of the human temporal bone. The results show that the size of small holes of MCS located above the transverse crest is significantly larger than that of TSF and MCM located below the transverse crest. 2) The observations of human fetal specimens showed that the cochlear nerve formation and its distribution into the cochlea precedes the formation of the bony cribriform structure, and the formation of the bony cribriform structure begins around week 17 and is considered to be complete by 21 weeks. 3) In a case of cerebellar hemorrhage, blood had flown into the cochlea at the side of the inner auditory canal of the Scala tympani, but was localized. The bony cribriform structure was composed of the small holes densely packed with the periosteum and the nerves and perineurium that pass through the cribriform structure. The results suggest that one of the roles of the cribriform structure might be to act as a size barrier to protect the inner ear.

Fitting procedures must be matched to the user’s own needs. However, cochlear implant (CI) users who live in rural regions experience several limitations in receiving adequate care. Thus, to improve follow-up attendance, we have been constructing a tele-auditory network system from 2018 in Hokkaido (the largest state in Japan), which can be used as a suitable model to enable CI center access in the rural regions. Additionally, the COVID-19 pandemic created an urgent need for remote access to healthcare services to reduce the risk of community spread and protect patients. Most participants were satisfied with the telefitting sessions. Telefitting can also provide significant savings in cost and time for both patients and their families or guardians. It is an effective means for CI service delivery, particularly to nonambulatory CI users, those residing in remote areas, or during natural disasters, including the spread of pathogens such as SARS-CoV-2. Although the Nucleus Fitting Software could not operate each electrode serially and create precise programming and could only save one program, the Custom Sound Pro released in 2020 overcame these weaknesses. Based on our experience, we believe that telefitting technology is a potentially viable alternative to local fitting.

This report summarizes the findings obtained in 59 cases of adhesive otitis media that were treated using tympanoplasty. All patients received post-surgical follow-up evaluations for more than one year, of which 20 patients were followed up for more than 5 years postoperatively and were thus considered to be long-term follow-up cases. Hearing performance was successfully restored in 36 of the 47 cases (76.6%) with partial adhesions and 6 of the 12 cases (50%) with total adhesions.

Postoperative evaluations of CT scans for growth of mastoid air cells revealed 31 cases with poor mastoid cell development, although the postoperative outcomes were successful in 21 of these 31 cases (67.7%). Of these, 14 patients were followed up for more than 5 years, and 10 of these 14 cases showed successful long-term outcomes (71.4%). Thus, poor mastoid pneumatization showed no relationship with long-term outcomes.

Adhesive otitis media is associated with various pathological conditions such as reoccurring inflammation and complications of cholesteatoma. Thus, it is necessary to consider prevention of re-adhesion in these patients. We report that the hearing performance outcomes in these cases were similar to those of other tympanoplasty procedures.

In this study, we retrospectively investigated the effect of stapes surgery in cases of chronic otitis media with tympanosclerotic stapes fixation in two patients who underwent tympanoplasty at our hospital. No improvement in hearing was observed after tympanoplasty. One case was successful with the guidelines based on the result of this study. Opinions regarding the surgical treatment of tympanosclerosis with stapes fixation vary across studies. Reportedly, stapes mobilization, which removes sclerotic lesions around the stapes can improve hearing. In contrast, despite the risk of inner ear injury, stapes surgery is reported to result in excellent postoperative hearing improvement. However, one patient developed tympanic membrane retraction and dizziness after stapes surgery. Staged surgery is recommended in patients with a perforation or retraction of the tympanic membrane. A hearing aid is prescribed in patients without recovery of the tympanic cavity and tympanic membrane after staged surgery.

We retrospectively studied the clinical features and treatment course in 32 patients with congenital cholesteatoma who received tympanoplasty at our hospital over the past 10 years. Prior to 2018, the primary surgical method was microscopic ear surgery (MES) through a retroauricular skin incision, and endoscopy was also used for cases involving tympanic sinus extension. From 2018, transcanal endoscopic ear surgery (TEES) has been performed for tympanic cavity-limited cases, and MES was performed for cases involving an advanced mastoid cavity. Thus, 25 patients underwent MES, and seven patients underwent TEES. The treatment success rates of MES and TEES in the tympanic cavity were 78% (14/18 ears) and 71% (5/7 ears), respectively, and the treatment success rate of MES in cases with mastoid antrum progression was 57% (4/7 ears). Staged surgery was performed in 81% (26/32 ears) of the cases, of which 38% (10/26 ears) showed residual cholesteatoma in the second surgery. Thus, the treatment results for the surgical methods did not differ significantly, and TEES for congenital cholesteatoma was a useful method considering its ability to facilitate detection of residual cholesteatoma and the lower invasiveness.

In this study, we compared the performance and invasiveness of transcanal endoscopic ear surgery (TEES) and microscopic ear surgery (MES) for tympanic membrane reconstruction (tympanoplasty and myringoplasty). Surgeries for chronic otitis media were performed in 66 ears at our hospital from July 2018 to October 2019, and 60 ears were followed up for more than six months. These cases were categorized into the TEES and MES groups on the basis of the procedure used for reconstruction, and the MES group was further divided into transcanal MES and posterior ear incision MES.

The closure rate of tympanic membrane perforation was 95%, and the rate of successful hearing improvement was 95%. No significant differences were observed in the closure rate or hearing results among cases involving TEES, transcanal MES, and posterior ear incision MES in this study. In terms of invasiveness, the operative time did not differ significantly among cases involving TEES and transcanal MES.

In recent years, the number of tympanoplasty performed via transcanal endoscopic ear surgery (TEES) has been increasing instead of microscopic ear surgery (MES). TEES does not require a post-auricular incision but requires minimal bone removal and is minimally invasive. It is currently performed after hospitalization under general anesthesia at most facilities. All cases of tympanoplasty are performed as a day surgery under local anesthesia at my clinic. I examined postoperative hearing and complications in 39 cases of tympanoplasty performed via MES and 60 cases via TEES. All patients underwent surgery at my clinic and could be followed up for more than 1 year. Tests performed according to the 2010 Japan Otological Society revealed that the overall improvements in postoperative hearing was 71.8% via MES and 88.3% via TEES. No postoperative complications were observed, but re-perforation was observed in two cases of each treatment. Although there are restrictions on indications, one-day TEES under local anesthesia may be a useful method for clinics without beds.

Ossicular disruption is caused by trauma from head injury or congenital malformation. Transcanal endoscopic ear surgery (TEES) may be a feasible method of operation in the treatment of ossicular disruption because they have infection and the operative field is limited in the middle ear. In this study, we investigated the hearing results from tympanoplasty of ossicular disruption in our institution retrospectively. This study included 22 ears of 20 patients who had ossicular disruption and underwent TEES between April 2011 and April 2020. Of the 22 ears, 13 had congenital malformation, seven had traumatic ossicular disruption, and two had postoperative ossicular disruption. The mean preoperative hearing threshold was 56.1 ± 17.9 dB, and it significantly improved to 30.2 ± 22.6 dB postoperatively. According to the Guideline for Reporting Hearing Result in Middle Ear and Mastoid Surgery (2010) by Japan Otological Society, 20 of 22 ears (90.9%) were “successful cases”. There was no difference in hearing improvement between traumatic ossicular disruption and congenital ossicular disruption. No major complications, including facial palsy, vertigo, or elevation of bone-conduction thresholds more than 10 dB, were noted. Tympanoplasty by TEES was effective in the treatment of ossicular disruption.

The function of the eustachian tube in eustachian tube diseases can change within a short time. Therefore, it is challenging to correctly evaluate eustachian tube function during consultation hours. Cone beam computed tomography (CT), which has become popular in recent years, is useful for diagnosis, but its value has not been determined. Therefore, in this study, we examined the usefulness of cone beam CT in diagnosing patulous eustachian tube or eustachian tube insufficiency.

Logistic regression analysis was performed using three explanatory variables—(1) eustachian tube closure zone length and (2) pharyngeal orifice of eustachian tube volume, which were measured by cone beam CT, and (3) eustachian tube opening time, which was measured by sonotubometry; it revealed that the percentage of correct classifications was not high (76.6%). Subsequently, the cutoff value was obtained from the receiver operating characteristics curve of each explanatory variable and scored with 1 or 0 points. Consequently, the proportion of patulous eustachian tube or eustachian tube insufficiency for the total score of 3, 2, 1, and 0 was 94.1%, 45.8%, 24.8%, and 18.2%, respectively. Cone beam CT was considered to have a certain diagnostic usefulness.

Eosinophilic otitis media is a type of intractable otitis media that mostly occurs in patients with bronchial asthma and is complicated by bronchial asthma. It is characterized by the accumulation of eosinophils in the middle ear effusion and the middle ear mucosa. However, a therapeutic approach for treatment-resistant severe cases remains to be established. Anti-interleukin-5 (IL-5) therapy has been recently reported to be effective for the treatment of refractory bronchial asthma as well as for the comorbidities of eosinophilic otitis media and eosinophilic rhinosinusitis. Here, we observed three cases of eosinophilic otitis media treated with anti-IL-5 therapy. In patients with marked granulation tissue formation in the middle ear, although re-growth after granulation was controlled, otorrhea and prolongation of granulation were observed, and no significant improvement in local symptoms was achieved. The findings suggest that the local effect of this drug on the pathological condition in the middle ear is reduced as the local severity increases because of the difficulty in suppressing eosinophil inflammation, in comparison with the cases involving lesions of the lower respiratory tract and paranasal sinuses.

Solitary fibrous tumor (SFT), a rare neoplasm derived from mesenchymal cells is known to frequently originate in the thymus and peritoneum. This lesion is rarely encountered by otolaryngologists, although a few reports have described SFTs of the nasal sinuses, oral cavity, and neck. Some studies have reported SFTs of the ear canal; however, our literature search did not yield any report of this lesion originating from the middle ear. We report a case of a middle ear tumor that was diagnosed as a SFT after surgery performed for diagnostic purposes. A 52-year-old woman presented with right-sided hearing loss. Evaluation of the ear and imaging revealed a middle ear tumor. We performed mastoidectomy, tumor resection, and tympanoplasty under general anesthesia. Histopathological examination of the resected specimen confirmed a SFT without any malignant features. The patient underwent re-operation for recurrence, 1 year postoperatively. No recurrence or metastases are observed over 3 years since the re-operation.

Giant cell tumor of bone (GCTB) is a benign tumor that frequently affects the epiphysis of long bones and rarely involves the temporal bone. Radical surgical resection is the treatment of choice and is usually curative. Radiation therapy (RT) is an effective option, particularly for patients with unresectable, incompletely resected, or recurrent lesions, although the role of RT is controversial because of the radioresistant characteristics of GCTB and the risk of malignant transformation. GCTB shows a high local recurrence rate, and metastasis is known to occur, particularly to the lungs; therefore, long-term follow-up is essential. We report the case of a 45-year-old man with a GCTB of the temporal bone, accompanied by conductive hearing loss. The patient observed right ear fullness and right temporal swelling. Otoscopy revealed tumor-induced right external auditory canal obstruction. Pure tone audiometry findings showed right conductive hearing loss (53.3 dB). Computed tomography revealed an osteoclastic mass in the right temporal bone, with extension to the intracranial lesion superiorly and mandibular fossa inferiorly. Gadolinium-enhanced magnetic resonance imaging revealed an enhanced tumor in the right temporal bone with a hypointense signal on T1-weighted imaging, marginal hypointense and internal hyperintense signals on T2-weighted imaging, and a hypointense signal on diffusion-weighted imaging. Biopsy specimen evaluation showed a GCTB of the temporal bone. The patient underwent preoperative transcatheter embolization of the middle meningeal, superficial temporal, and anterior deep temporal arteries and radical resection of the GCTB. Histopathological examination of the resected specimen confirmed diagnosis of GCTB. Postoperative radiation therapy (50 Gy) was performed. Postoperative otoscopic evaluation showed normal findings, and hearing improved to 25 dB on pure tone audiometry. No clinical or radiological evidence of tumor recurrence was detected over 1-year follow-up.

We used an active middle ear implant (VSB) for patients showing single-sided conductive hearing loss due to congenital aural atresia. Patients who received the VSB showed improvements in the hearing threshold, the score for the speech perception test in noise, and direction localization ability at 6 months post-operatively. Here, we demonstrate the effectiveness of VSB in patients with conductive or mixed hearing loss.

The Slim Modiolar electrode (CI532/632), a pre-curved electrode for cochlear implants released by Cochlear^®, can effectively stimulate the nerves in its proximity and reduce the risk of cochlear injury and the likelihood of electrode translocation from the scala tympani to scala vestibuli in comparison with the Slim Straight electrode (CI522/622). In this study, 31 ears underwent implantation of the CI532/632 electrode. The neural response telemetry (NRT) thresholds and impedances for CI532/632 electrodes around the cochlear cupula were lower than those for CI522. No difference was observed in the operative time and the short-term postoperative hearing and clinical performance of the two electrodes. Due to the complexity of the sheath and electrode configuration, insertion of the electrode can be challenging, and tip folding can occur. A broad extension of posterior tympanotomy is required while inserting the CI532/632 electrode. The round-window niche overhang (the ridge of bone around the round window fossa) has to be drilled out following exposure of the round window fossa. If electrode insertion via the round window is difficult, an extended round-window approach should be employed inserted. The NRT threshold and impedance of the Slim Modiolar electrodes were better in the short term. However, Slim Modiolar electrodes showed no significant difference from Slim Straight electrodes in terms of cochlear implant performance after six months. Thus, Slim Modiolar electrodes are options for cases with a normal cochlear study, and long-term evaluations of cochlear implant performance with these electrodes are essential.