Sleep apnea patients with epiglottic collapse elevate their larynx more with swallowing; videofluoroscopic swallowing study of 80 patients.

OBJECTIVE: The epiglottis plays an integral role in the swallowing mechanism and is also implicated as an obstruction site in obstructive sleep apnea (OSA). The underlying causes of epiglottic collapse during sleep remain unclear. This study aimed to investigate the cognitive functions using the Loewenstein Occupational Therapy Cognitive Assessment (LOTCA) and the neurophysiological and anatomical factors using videofluoroscopic swallowing studies (VFSS). We compared patients with OSA exhibiting epiglottic collapse to those without, assessing differences in anatomical or neurophysiological characteristics. METHODS: The study included 12 patients with epiglottic collapse (Epi-group) and 68 without (non-Epi group), all undergoing overnight polysomnography (PSG), drug-induced sleep endoscopy (DISE), LOTCA, and VFSS. Oral transit time (OTT), pharyngeal delay time (PDT), and pharyngeal transit time (PTT) were considered as neurophysiological traits, and laryngeal elevation length (LE) as anatomical trait, and were measured across various test diets (10 ml of liquid, soft, or solid). RESULTS: The study comprised 80 individuals, 57 men and 23 women, with no significant age, sex, body mass index or PSG parameters between groups, or DISE findings, with the exception of epiglottic collapse. Swallowing metrics from VFSS were normal, with no differences in OTT, PDT, PTT, or LOTCA scores. Notably, patients with epiglottic collapse showed a greater laryngeal elevation when swallowing soft and solid foods (p = 0.025 and p = 0.048, respectively). CONCLUSIONS: Patients with epiglottic collapse do not exhibit neurophysiological or cognitive impairments when compared to non-Epi group. However, the Epi-group displayed a significantly increased laryngeal elevation length. This suggests that anatomical factors may have a more substantial role in the development of epiglottic collapse than neurophysiological factors.

Surgical results of tympanoplasty after conversion to the endoscopic approach performed by a surgeon experienced in microscopic surgery.

PURPOSE: The aim of this study was to analyze the surgical outcomes of endoscopic tympanoplasty (ET) type I, and to investigate the learning curve of ET type I in a surgeon experienced in microscopic surgery. METHODS: We retrospectively studied patients with tympanic membrane perforations who had undergone ET type I from January 2015 to June 2020. All procedures were performed by a single senior surgeon with considerable microscopic experience. We compared the perforation closure rate in relation to age, previous ear surgery history, graft material, size, and location of perforation. We compared the operation time according to the number of operated patients. RESULTS: A total of 399 patients were enrolled. The success rate of ET type I was 92.7%. Age, prior ear surgery, graft material, size, and location of perforation did not influence the surgical outcomes. The surgical time for the initial ten cases was the longest (78.3 min), and stabilized after the first 100 cases to under 60 min. The surgical success rate was 96.0% in the first 50 cases, and decreased to approximately 92% afterwards. CONCLUSION: The surgical time largely decreased with the number of operated patients. Since the operations were performed by a surgeon experienced in microscopy, the success rate of initial cases was not low, even though the operation time of these initial cases was longer. We believe that endoscope provides a new perspective on ear surgery if it could overcome the difficulties in the early stage.

Intraoperative Handheld Digital X-ray for Assessment of Intracochlear Positioning of Electrode Arrays in Recipients of Cochlear Implants.

Objectives: This study aims to evaluate the practicality of handheld digital X-ray in determining the position of the electrode array following Cochlear implantation (CI). Methods: A retrospective study was conducted involving 11 patients (12 ears) who underwent intraoperative imaging via handheld X-ray (MINE ALNU®, OTOM, Gwangju, South Korea) post-CI between December 2021 and January 2023. Immediate confirmation of the correct electrode array placement in the cochlea was achieved, with subsequent comparisons made to C-arm image and postoperative transorbital view X-ray. Results: Rapid intraoperative imaging was achieved in all instances. The electrode types used included 9 Nucleus slim modiolar electrodes, 1 Nucleus contour electrode, and 2 Medel flex26 electrodes. A malpositioned electrode array was detected in one patient. The handheld digital X-ray also adeptly visualized the electrodes implanted in pediatric patients. Conclusions: The use of intraoperative handheld digital X-ray using MINE ALNU® proves to be a safe, efficient, straightforward, and reliable method for immediate identification of an inserted electrode array. It has potential to replace the traditional C-arm X-ray for verifying electrode positioning in the operating room.

The impact of the Cochlear™ Osia® 2 System on patients with mixed or conductive hearing loss: A comparison with Cochlear™ Baha® Attract System outcomes.

OBJECTIVE: This prospective study assessed the efficacy of the Cochlear™ Osia® 2 System compared to the previous Baha® Attract System in patients with mixed or conductive hearing loss (MHL/CHL). METHODS: In this prospective case-control study, 10 patients (2 men and 8 women) with MHL/CHL were implanted with the Osia® 2 System. Their audiological outcomes were compared with 13 patients (2 men and 11 women) who had previously been implanted with the transcutaneous Baha® Attract system. We compared the complications and compliance of the two groups. Also, in the Osia 2 System group, subjective satisfaction was assessed using the Korean version of the International Outcome Inventory for Hearing Aids (K-IOI-HA) questionnaire and the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire. RESULTS: Complications such as poor magnetization, pain & infection, and abnormal noise were more common in the Baha Attract group, although not statistically significant. Also, the Osia 2 group exhibited better compliance. Subjective satisfaction was assessed using the K-IOI-HA and APHAB questionnaires with the Osia 2 group, revealing significantly improved scores in ease of communication, reverberation, background noise, and higher K-IOI-HA scores post-implantation. Postoperative-aided thresholds with both systems were significantly lower than preoperative-unaided thresholds, with the Osia 2 System demonstrating notably high satisfaction levels. Although both systems showed similar preoperative and postoperative word-recognition scores, the Osia 2 System provided greater audiological gain, especially at 2 kHz and 4 kHz frequencies. Additionally, the functional gain of both systems was comparable across all frequencies. CONCLUSIONS: The Osia 2 System demonstrated high subjective satisfaction and improved audiological outcomes compared to the Baha Attract system in patients with conductive or mixed hearing loss. Its superior audiological gain, particularly at critical frequencies, along with better compliance, suggests it as a favorable option for this patient population.

Factors affecting fat myringoplasty in elderly patients with chronic otitis media: A case control study.

BACKGROUND: We compared and analyzed the surgical results of fat myringoplasty between elderly and young adult patients with chronic otitis media. We also investigated whether underlying diseases and other factors impact the surgical outcome. METHODS: We retrospectively reviewed the data of 141 patients who underwent fat myringoplasty for chronic otitis media for five years. They were compared by age, sex, underlying disease, perforation size, pre- and postoperative pure tone audiometry, postoperative otorrhea, postoperative re-perforation, and cause of re-perforation. RESULT: Postoperative re-perforation was more common in the elderly group, albeit with no significant difference (p = 0.072). The factors affecting re-perforation were insufficient fat graft (44.4%), postoperative infection (33.3%), and nasal blowing (22.2%). Our findings revealed no significant association between preoperative perforation size and re-perforation (p = 0.391). Additionally, we found no significant relationship between hypertension and re-perforation (p > 0.99), nor between age group and postoperative infection (p = 0.488). Diabetes was also not significant (p = 0.640). Following surgery, both groups exhibited a significant improvement in hearing. CONCLUSION: Although age and underlying conditions play significant roles in the healing process, our results suggest that external factors such as infection, nasal blowing, cough, and insufficient grafted fat tissue have a similarly significant impact on surgical outcomes in elderly patients with COM as they do in adults. In conclusion, the decision to perform surgery in elderly patients with COM should be based on a comprehensive assessment of the patient's overall health status, hearing, use of hearing aids, and the indications for surgery.

The Function of Cochlear Implant After Cardioversion in a Patient With Atrial Flutter: A Case Report.

Hearing loss in older people can cause communication impairments, decreased quality of life, social isolation, depression, and dementia. Cochlear implant surgery is an effective treatment for older patients with hearing loss who cannot achieve satisfactory audiologic outcomes with hearing aids. However, older people have an increased risk of heart disease and often take medications that affect heart rhythm. Herein, we report a case of an 80-year-old woman who underwent cardioversion at 50J after cochlear implant surgery. Electrical impedance before and after cardioversion showed only minor changes without abnormality, and the cochlear implant functioned well. We believe that the electronic circuits of the cochlear implant may have been relatively tolerant to the electrical shock from the external defibrillator. Typically, cardioversion should be avoided in cochlear implant recipients because it may damage the implant. If cardioversion cannot be avoided, we strongly recommend starting cardioversion at the lowest energy level (50 J) and removing the sound processor of the implant during the procedure.

Endoscopic Surgery of Congenital Cholesteatoma in the Anterior Epitympanic Recess: A Case Report of a Rare Location.

Congenital cholesteatoma is a whitish mass in the middle ear medial to an intact tympanic membrane. It is often without symptoms and therefore incidentally diagnosed. Pediatric congenital cholesteatoma generally starts as a small pearl-like mass in the middle ear cavity that eventually expands to involve the ossicles, epitympanum, and mastoid. The location, size, histopathological type, and extent of the mass must be evaluated to select the appropriate surgical method. Although microscopic ear surgery has traditionally been performed to remove congenital cholesteatoma, a recently introduced alternative is endoscopic surgery, which allows a minimally invasive approach and has better visualization. Here, we report the first known case of a patient with congenital cholesteatoma in the anterior epitympanic recess and discuss the utility of an endoscopic approach in the removal of a congenital cholesteatoma in the hidden area within the middle ear.

Patients with Epiglottic Collapse Are Less Adherent to Autotitrating Positive Airway Pressure Therapy for Obstructive Sleep Apnea.

Rationale: The anatomic orientation of the epiglottis is such that it points in the opposite direction to inspiratory flow, thereby potentially making positive airway pressure (PAP) treatment challenging in patients with epiglottic collapse. However, no previous studies have analyzed PAP adherence in these patients. Objectives: This study aimed to analyze adherence to autotitrating PAP (APAP) treatment in patients with epiglottic collapse. Methods: We performed an age- and sex-matched case-control study. On the basis of their overnight level-I polysomnogram, patients were prescribed APAP in a tertiary hospital between July 2018 and March 2019. The site of airway collapse was diagnosed with drug-induced sleep endoscopy. Demographic factors, sleep questionnaire, polysomnography, and APAP usage statistics were analyzed. Results: Eighteen patients with epiglottic collapse (epi-group) and 36 without epiglottic collapse (control group) were analyzed. We found that 22.8% of patients in the epi-group terminated APAP within 2 weeks, whereas only 2.8% of patients in the control group terminated APAP within 2 weeks (P = 0.048). The percentage of days with usage over 4 hours was significantly lower in the epi-group (64.6% vs. 75.6%; P = 0.008). In addition, the adherence failure rate was 66.7% in the epi-group and 33.3% in the control group (P = 0.039). Patients with epiglottic collapse were also found to have lower body mass index, which is an unfavorable predictor of APAP adherence. Conclusions: This study suggests that patients with epiglottic collapse have a higher APAP adherence failure rate than patients without epiglottic collapse. Thus, patients with epiglottic collapse should be followed closely during treatment, and alternative therapies should probably be considered for these patients.

Head rotation improves airway obstruction, especially in patients with less severe obstructive sleep apnea without oropharyngeal collapse.

PURPOSE: Head rotation is thought to have an effect on obstructive sleep apnea (OSA) severity. However, keeping the head rotated fully during sleep is difficult to maintain, and the effect of head rotation is not the same in all OSA patients. Thus, this study aimed to identify whether less head rotation has an effect on airway patency and determine the responder characteristics to the head rotation maneuver (HRM). METHODS: We recruited 221 patients who underwent overnight polysomnography and drug-induced sleep endoscopy (DISE) in a tertiary hospital from June 2019 to July 2020. Airway patency and the site of airway collapse were determined in the supine position with the head at 0, 30, and 60 degrees of rotation (HRM0°, HRM30°, and HRM60°, respectively) during DISE. The site of collapse was determined using the VOTE classification system: the velum (palate), oropharyngeal lateral walls, tongue base, and epiglottis. Each structure was labeled as 0, 1, or 2 (patent, partially obstructed, and completely obstructed, respectively). Airway response to the HRM30° and 60° and the clinical characteristics associated with airway opening were analyzed. RESULTS: The study population had a median age of 52 (25-61) years, a body mass index of 26.7(24.6-29.4) kg/m2, and the apnea-hypopnea index (AHI) of 28.2(13.7-71.9) events/h. HRM influenced airway patency positively not only with HRM60° (p<0.001) but also following limited rotation (HRM30°, p<0.001). Patients with tongue base (40.0% with HRM 60°) and epiglottic (52.6% with HRM 60°) collapse responded particularly well to HRM. Multivariate analysis revealed that lower AHI (p<0.001) and an absence of oropharyngeal lateral walls collapse (p = 0.011) were significant predictors of responders to HRM. CONCLUSION: Head rotation improved airway obstruction in OSA patients, even with a small degree of rotation, and should be further explored as a potential form of therapy in appropriately selected patients.

A subglottic foreign body mimicking croup: A case report.

INTRODUCTION: Foreign body (FB) aspiration is one of the causes of respiratory distress in infants is an extremely dangerous and potentially life-threatening event. The diagnosis of FB aspiration is difficult because the signs and symptoms vary according to the degree of airway blockage or location of the FB. PATIENT CONCERNS: An 11-month-old female infant visited a hospital because of a sudden onset cough. She was relatively healthy without fever, rhinorrhea cyanosis, or poor feeding. On physical examination, auscultation revealed inspiratory stridor without wheezing and crackles. DIAGNOSIS: Croup was suspected when considering the history, physical examination, and imaging. However, she did not respond to a 4-day course of treatment for croup. Flexible laryngoscopic examination was performed, and we identified a thin, flat, and sharp FB embedded in the subglottic region. INTERVENTIONS: Emergency surgery was performed to remove the FB. Short-term intravenous corticosteroids and antibiotics were used to prevent laryngeal swelling and aspiration pneumonia. OUTCOMES: One week after the procedure, the laryngeal mucosa had completely healed. CONCLUSION: FB aspiration should be considered in an infant with an impression of croup. In particular, if there is no response to medical or conservative treatment for croup, further evaluation is needed.

Surgical results and factors affecting outcome in patients with fat-graft myringoplasty.

Objectives: We evaluated the closure rate after fat-graft myringoplasty (FGM) of perforations differing in size and location. We explored whether patient's factors and the FGM surgical technique influenced surgical outcomes. Methods: We retrospectively studied patients with tympanic membrane perforations who underwent FGM from March 2015 to March 2019. All procedures were performed by a single senior surgeon at our tertiary hospital. The patients who followed-up for at least 6 months after surgery were enrolled. We recorded hypertension and diabetes status, age, any prior ear surgery, any calcific plaques adjacent to the perforation, and perforation size and location. Results: A total of 150 patients were enrolled. Our success rate of FGM was 90%. Hypertension, diabetes, prior ear surgery history, and eardrum calcific plaques did not affect the surgical outcomes. There was no statistical difference in the surgical success rate according to the size (< 50%) or location of perforation. The closure rate was 97.2% in patients aged 1660 and 87.5% in patients aged > 60, respectively. However, FGM was successful in only two of six children (33.3%) aged ≤ 15 years, thus significantly less than in the other groups. Conclusion: FGM is a fast, safe, and efficient method for repairing tympanic membrane perforation. The surgical outcome is not significantly affected by underlying disease, perforation size or location, or by the condition of the tympanic membrane or older age. However, it may be poor in children with dysfunctional Eustachian tube.

Patients with epiglottic collapse showed less severe obstructive sleep apnea and good response to treatment other than continuous positive airway pressure: a case-control study of 224 patients.

STUDY OBJECTIVES: The purpose of this study was to analyze patients with epiglottic collapse, especially their clinical characteristics related to obstructive sleep apnea and phenotype labeling using drug-induced sleep endoscopy. METHODS: An age-sex matched case-control study was conducted to compare the clinical characteristics of patients with epiglottic collapse (Epi group) and patients without epiglottic collapse (non-Epi group). All patients underwent drug-induced sleep endoscopy January, 2015, to March, 2019, in a tertiary hospital for suspected sleep apnea symptoms. Demographic factors, underlying disease, overnight polysomnography, and their phenotype labeling using drug-induced sleep endoscopy were analyzed. RESULTS: There was no difference in age, sex, the prevalence of hypertension, diabetes, cerebrovascular disease, and coronary artery disease. However, the body mass index was significantly lower in patients in the Epi group (P < .001). Additionally, the apnea-hypopnea index was lower (P = .001), and the lowest oxygen saturation was significantly higher in the Epi group (P = .042). The phenotype labeling on drug-induced sleep endoscopy showed that the prevalence of velum concentric collapse and oropharyngeal lateral wall collapse was lower, and that of tongue-base collapse was higher in the Epi group. Multilevel obstructions were more common in the Epi group. However, the Epi group showed a good response to mandibular advancement or positional therapy. CONCLUSIONS: Although there was no difference in the underlying characteristics and self-reported symptom scores between the groups, the patients with epiglottic collapse showed significantly lower body mass index and obstructive sleep apnea severity. Additionally, patients with epiglottic collapse were expected to respond well to oral devices or positional therapy.

SnO(2) nanotubes fabricated using electrospinning and atomic layer deposition and their gas sensing performance.

A novel method is developed to fabricate a SnO(2) nanotube network by utilizing electrospinning and atomic layer deposition (ALD), and the network sensor is proven to exhibit excellent sensitivity to ethanol owing to its hollow, nanostructured character. The electrospun polyacrylonitrile (PAN) nanofibers of 100-200 nm diameter are used as a template after stabilization at 250 degrees C. An uniform and conformal SnO(2) coating on the nanofiber template is achieved by ALD using dibutyltindiacetate (DBTDA) as the Sn source at 100 degrees C and the wall thickness is precisely controlled by adjusting the number of ALD cycles. The calcination at 700 degrees C transforms the amorphous nanofibers into SnO(2) nanotubes composed of several nanometer-sized crystallites. The SnO(2) nanotube network sensor responds to ethanol, H(2), CO, NH(3) and NO(2) gases, but it exhibited an extremely high gas response to ethanol with a short response time (<5 s). The results demonstrate that the combination of electrospinning and ALD is a very effective and promising technique to fabricate long and uniform metal oxide nanotubes with the precise control of wall thickness, which can be applied to various applications such as gas sensors and lithium ion batteries.

The clinical characteristics of patients with an isolate epiglottic collapse.

OBJECTIVE: We analyzed the clinical characteristics of patients with isolated epiglottic collapse (IEC) who had an epiglottic anteroposterior (AP) collapse as the only cause of snoring during drug-induced sleep endoscopy (DISE). METHODS: A retrospective analysis of 334 consecutive DISE examinations was performed. Patients who had only epiglottic AP collapse were designated as the IEC group. There were four age- and sex-matched controls for each case, and these patients were designated as the control group. Demographic factors, polysomnography findings, cephalometry, and awake nasopharyngoscopic findings were analyzed. RESULTS: A total of 11 IEC cases and 44 controls were included. The IEC group had a significantly lower apnea-hypopnea index, higher minimum oxygen saturation level, lower body mass index, and shorter mandible plane to hyoid distance than the controls. However, there were no differences in epiglottic shape or curvature between the two groups. In addition, no IEC was noted during awake endoscopy. Nine (81.8%) epiglottic collapses were resolved with the mouth open and jaw thrust maneuver, which simulated the use of an oral appliance. Six (54.4%) were resolved with head turning, mimicking the lateral sleep position. CONCLUSION: The clinical characteristics of IEC patients differed from the control group, and IEC could not be identified during awake endoscopy. Therefore, patients with severe snoring but AHI < 5 or mild sleep apnea on polysomnographic findings and DISE, should be considered likely to have IEC. In addition, use of an oral appliance is recommended as an effective treatment for IEC.

An epidermoid cyst of the uvula causing dyspnea in an infant: A case report.

RATIONALE: Congenital epidermoid cysts are benign deformities that rarely affect the uvula. A uvular epidermoid cyst is painless and slow-growing. Most such cysts are asymptomatic and rarely cause oral dysfunction. PATIENT CONCERNS: We present the case of a 10-month-old infant with dyspnea caused by a mass in the uvula. DIAGNOSIS: The patient was diagnosed with a uvular epidermoid cyst via neck soft tissue X-ray and flexible laryngoscopy. INTERVENTIONS: Emergency surgery was performed. OUTCOMES: The patient recovered immediately after the operation and was discharged 1 day later. LESSONS: In an infant with a uvula cyst, early surgical treatment may be needed to prevent symptoms, such as dyspnea, requiring emergency treatment.

Histologic features of sublingual gland herniation through the mylohyoid muscle.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to document histologic features of the herniated sublingual gland (SLG) and investigate the histologic correlation between herniated SLG and plunging ranula. METHODS: One hundred half-heads from 50 adult cadavers (21 females and 29 males) were included in this study. The presence of SLG herniation and the histologic features SLG were analyzed. The histologic features were analyzed according to the part: intraoral, junctional, and herniated parts. Hematoxylin and eosin (H&E), periodic acid Schiff reaction (PAS), and Alcian Blue (pH 2.5) staining were performed. RESULTS: SLG herniation was found in 42 of 100 half-heads. Non-herniated SLG and the intraoral part of the herniated SLG were mainly composed of mucous acini and a few mixed acini. Junctional and herniated parts were mainly composed of serous acini and showed fatty change. PAS and Alcian blue staining showed that both acidic and neutral mucinous acini of junctional and herniated parts were decreased. However, there was no pseudo-epithelium at any site of herniation. CONCLUSIONS: The histologic features of herniated SLG are different according the portions. The herniated part showed fatty degeneration and the remaining acini were mainly serous. We cannot confer any correlation between plunging ranula and the herniated part of SLGs.

Role of preoperative air-bone gap in tinnitus outcome after tympanoplasty for chronic otitis media with tinnitus.

INTRODUCTION: Previous reports indicated that middle ear surgery might partially improve tinnitus after surgery. However, until now, no influencing factor has been determined for tinnitus outcome after middle ear surgery. OBJECTIVE: The purpose of this study was to investigate the association between preoperative air-bone gap and tinnitus outcome after tympanoplasty type I. METHODS: Seventy-five patients with tinnitus who had more than 6 months of symptoms of chronic otitis media on the ipsilateral side that were refractory to medical treatment were included in this study. All patients were evaluated through otoendoscopy, pure tone/speech audiometer, questionnaire survey using the visual analog scale and the tinnitus handicap inventory for tinnitus symptoms before and 6 months after tympanoplasty. The influence of preoperative bone conduction, preoperative air-bone-gap, and postoperative air-bone-gap on tinnitus outcome after the operation was investigated. RESULTS AND CONCLUSION: The patients were divided into two groups based on preoperative bone conduction of less than 25dB (n=50) or more than 25dB (n=25). The postoperative improvement of tinnitus in both groups showed statistical significance. Patients whose preoperative air-bone-gap was less than 15dB showed no improvement in postoperative tinnitus using the visual analog scale (p=0.889) and the tinnitus handicap inventory (p=0.802). However, patients whose preoperative air-bone-gap was more than 15dB showed statistically significant improvement in postoperative tinnitus using the visual analog scale (p<0.01) and the tinnitus handicap inventory (p=0.016). Postoperative change in tinnitus showed significance compared with preoperative tinnitus using visual analog scale (p=0.006). However, the correlation between reduction in the visual analog scale score and air-bone-gap (p=0.202) or between reduction in tinnitus handicap inventory score and air-bone-gap (p=0.290) was not significant. We suggest that the preoperative air-bone-gap can be a predictor of tinnitus outcome after tympanoplasty in chronic otitis media with tinnitus.

Evaluating the ototoxicity of an anti-MRSA peptide KR-12-a2.

INTRODUCTION: Methicillin-resistant staphylococcus aureus is an emerging problem for the treatment of chronic suppurative otitis media, and also for pediatric tympanostomy tube otorrhea. To date, there are no effective topical antibiotic drugs to treat methicillin-resistant staphylococcus aureus otorrhea. OBJECTIVE: In this study, we evaluated the ototoxicity of topical KR-12-a2 solution on the cochlea when it is applied topically in the middle ear of guinea pigs. METHODS: The antimicrobial activity of KR-12-a2 against methicillin-resistant staphylococcus aureus strains was examined by using the inhibition zone test. Topical application of KR-12-a2 solution, gentamicin and phosphate buffered saline were applied in the middle ear of the guinea pigs after inserting ventilation tubes. Ototoxicity was assessed by auditory brainstem evoked response and scanning electron microscope examination. RESULTS: KR-12-a2 produced an inhibition zone against methicillin-resistant staphylococcus aureus from 6.25 µg. Hearing threshold in the KR-12-a2 and PBS groups were similar to that before ventilation tube insertion. However, the gentamicin group showed elevation of the hearing threshold and there were statistically significant differences compared to the phosphate buffered saline or the KR-12-a2 group. In the scanning electron microscope findings, the KR-12-a2 group showed intact outer hair cells. However, the gentamicin group showed total loss of outer hair cells. In our experiment, topically applied KR-12-a2 solution did not cause hearing loss or cochlear damage in guinea pigs. CONCLUSION: In our experiment, topically applied KR-12-a2 solution did not cause hearing loss or cochlear damage in guinea pigs. The KR-12-a2 solution can be used as ototopical drops for treating methicillin-resistant staphylococcus aureus otorrhea; however, further evaluations, such as the definition of optimal concentration and combination, are necessary.