Cochlear implant (CI) users who live in rural regions experience several limitations in receiving adequate care, including high travel costs and time away from work or school. The current telemedical technology is expected to resolve these disparities in providing access to medical care. The number of rural CI centers in Hokkaido is very limited; therefore, there is an urgent need to improve CI center access in rural settings. We consider CI fitting well-suited to telemedicine, especially in Hokkaido. Telefitting technology may be a potential viable alternative to local MAPping, and an overwhelming majority of participants responded with positive feedback. Although the Nucleus Fitting Software (NFS) could not operate each electrode serially and create precise MAPping, and could only save one MAP, the Custom Sound Pro released on September 2020 overcame these weaknesses, and based on our experience, we believe that telefitting technology is a potential viable alternative to local MAPping. In addition, telefitting saves travel time and cost for CI users. Thus, telefitting of CI would appear to be superior to conventional methods, especially during natural disasters or in the present the spread of pathogens such as, including the current pandemic caused by SARS-CoV-2.

　　There are concepts of the ability to maintain function without clinically developing dementia even if there are pathological changes in the brain. These concepts are called such as cognitive reserve, brain reserve, and brain maintenance. In the cognitive reserve hypothesis, that assumes resistance to brain degeneration, the indicators used as surrogate measures for reserve include brain morphological parameters such as the brain volume, head circumference, and brain weight, which are relatively easy to measure, and also the level of education (years of education and/or quality of education), occupational complexity, IQ and literacy, mental activity, social activity, physical activity, etc. There are various research reports that indicate that hearing loss is disadvantageous in terms of the brain volume atrophy rate, academic achievement rate, continuation of employment, and social interaction. If hearing loss and issues involving hearing loss interfere with the strengthening of the reserve capacity that may delay the onset of dementia, we believe that care of hearing loss will be more important than ever.

　　We investigated the neuroplasticity of auditory neurons (ANs) in adult mice with conductive hearing loss (CHL). Eight-week-old male C57BL/6 mice were bilaterally earplugged for 4 weeks (CHL (+) group) and allowed to survive for a further 4 weeks after removal of the earplugs (CHL (+/－) group). The control mice (CHL (－) group) did not undergo the earplugging process. The ABR threshold was significantly elevated across all tested frequencies in the earplugged mice. After removal of the earplugs, the threshold shifts recovered fully. The ABR amplitude of peak 1 significantly decreased and the latency significantly increased for all tested frequencies in the CHL (+) mice as compared to the CHL (－) mice. These changes were only partially restored in the CHL (+/－) mice. Auditory deprivation had no significant impact on the survival of the hair cells and ANs. However, the synapses and myelin were significantly damaged, and the neuronal sizes of the ANs were significantly decreased in the CHL (+) mice. These changes also recovered only partially in the CHL (+/－) mice as compared to the CHL (+) mice. These results suggest that auditory activities are required to maintain peripheral auditory synapses and myelination.

　　Loss of outer hair cells (OHCs) has been considered to cause hearing loss at frequencies corresponding to the characteristic frequencies (CFs) in the area of loss. However, the relationship between cellular damage and the hearing level has not been clarified. In this study, the relationship was investigated by simulating hearing tests, i.e., audiometry and DPOAE, using the finite-element model of the human cochlea, considering the activity of the OHCs. The activities of the OHCs were formulated based on the measurement of isolated OHCs from a guinea pig and DPOAE measurements in subjects with normal hearing. The activities are partially restricted in partial functional loss models to enable clarification of the relationship between hearing level and the non-active area on the basilar membrane. A pure tone or a complex tone was applied to the stapes head of each partial functional loss model to simulate audiometry and DPOAE. The effect of partial non-active area on the hearing level was evaluated by changes in the amplitude of the vibration of the basilar membrane and the level of distortion component at the footplate of the stapes. The results suggest that the hearing level at specific frequencies is influenced by the OHCs, located not only at the CF points, but also in specific higher-frequency areas.

　　We developed the Extended-wired Hearing Instrument for Mono-hearing Ear (EHIME) for people with unilateral deafness, and measured the usefulness of EHIME by real ear measurement (REM), speech intelligibility testing, and a questionnaire survey. As a result, in the REM, the frequency characteristic determination method that yields a gain that compensates for the head shadow effect was preferred. In the speech intelligibility test, we observed that the effect was more pronounced higher than the dis-adverse effect of wearing EHIME. We think that there is a relationship between the gain of the CROS aid and advantage/disadvantage in terms of the speech intelligibility, and evaluation by REM and speech intelligibility testing seems to be useful for frequency characteristic setting. According to the questionnaire survey, the listeners’ sense of noise and speech intelligibility improved, but their sense of localization and distance deteriorated. However, some of them found localization based on the difference between a live speech and speech via EHIME and additional study is needed. At the end of the trial use period of EHIME, we noted that the subjects reported improvement in comfort and quality of life rather than the troublesomeness of using EHIME.

　　We analyzed the relationship between the prevalence of tympanic membrane (TM) perforation after intratympanic steroid administration for sudden deafness and the results of Eustachian tube (ET) function tests. Subjects were 75 affected ears of patients with sudden deafness. Five ET function tests, namely, sonotubometry, Valsalva maneuver, deep breath through nose method, sniffing method, and Toynbee's maneuver were conducted using an ET function test apparatus. Based on the results of each of the ET function tests, the ETs were classified as normal, stenotic, patulous, and indeterminate types. Nineteen ears were classified as showing a stenotic type ET in multiple tests, and three of these ears (15.8%) had TM perforation. Of the remaining 56 ears, only one ear (1.8%) had TM perforation. The prevalence of the TM perforation was statistically significantly different between the two groups (p=0.0478). Two ears showed an input sound pressure level of 123dB in sonotubometry, which is the maximum level that can be determined with an ET function test apparatus, and both ears showed TM perforation. These results suggest that ET function test results might provide important information for doctors and patients to select or not select intratympanic steroid administration for the treatment of sudden deafness.

　　We retrospectively analyzed the medical records of 23 children with inner ear malformations (IEMs) who had undergone cochlear implantation (CI) at the University of Tokyo hospital. Cases with a narrow internal auditory canal or cochlear nerve aplasia were not included. We classified the IEMs according to Sennaroglu’s criteria. There were 7 cases of incomplete partition (IP)-I, 7 cases of IP-II, 1 case of IP-III, 1 case of cochlear hypoplasia (CH)-III, 4 cases of CH-IV, and 3 cases of common cavity (CC). At around the time of elementary school entry, the IP-II cases generally developed good auditory skills and vocabulary comprehension ability. In the IP-I and CC cases, the results varied significantly among cases. In the CH-IV cases, vocabulary comprehension ability remained poor, even when good auditory skills were achieved. The integration rate into regular schools was not inferior to that reported previously for children with no IEMs. Presence of IEMs is not a contraindication for CI, but it needs to be borne in mind that the performance may vary among cases.