Functional Significance of Medial Olivocochlear System Morphology in the Mouse Cochlea

OBJECTIVES: Baso-apical gradients exist in various cochlear structures including medial olivocochlear (MOC) efferent system. This study investigated the cochlear regional differentials in the function and morphology of the MOC system, and addressed the functional implications of regional MOC efferent terminals (ETs) in the mouse cochlea. METHODS: In CBA/J mice, MOC reflex (MOCR) was assessed based on the distortion product otoacoustic emission in the absence and presence of contralateral acoustic stimulation. High, middle, and low frequencies were grouped according to a mouse place-frequency map. Cochlear whole mounts were immunostained for ETs with anti-α-synuclein and examined using confocal laser scanning microscopy. The diameters of ETs and the number of ETs per outer hair cell were measured from the z-stack images of the basal, middle and apical regions, respectively. RESULTS: The middle cochlear region expressed large, clustered MOC ETs with strong MOCR, the base expressed small, less clustered ETs with strong MOCR, and the apex expressed large, but less clustered ETs with weak MOCR. CONCLUSION: The mouse cochlea demonstrated regional differentials in the function and morphology of the MOC system. Strong MOCR along with superior MOC morphology in the middle region may contribute to ‘signal detection in noise,’ the primary efferent function, in the best hearing frequencies. Strong MOCR in spite of inferior MOC morphology in the base may reflect the importance of ‘protection from noise trauma’ in the high frequencies.

Cochlear Implantation after Subtotal Petrosectomy in Patients with Chronic Otitis Media / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: This study investigated the surgical and rehabilitative results of cochlear implantation combined with subtotal petrosectomy in patients with chronic otitis media. SUBJECTS AND METHOD: We retrospectively reviewed the medical records of nine adult patients (7 men and 2 woman; mean age 58.9 years), who were operated between 2004 and 2014. Out of the nine, seven patients received simultaneous cochlear implantation and subtotal petrosectomy and two patients were operated by stage depending on the condition of the middle ear. All cases underwent closure of the external auditory canal and Eustachian tube, and the obliteration of mastoid cavity using abdominal fat. Surgical outcomes and performance of the patients after cochlear implantation were analyzed. RESULTS: Middle ear inflammation was completely managed with this surgical technique. No patients showed postoperative symptoms related to otitis media after the surgery. Cochlear implant was successfully replaced and active electrodes were fully inserted in all of the cases. There were no immediate complications including abscess, infection, meningitis, cerebrospinal fluid leakage and ear canal problem. One patient was observed with delayed extrusion of the ball electrode, which was replaced with cartilage reinforcement under local anesthesia. Patient performance, measured in terms of speech evaluation and quality of life during the medical interview, were successful and satisfactory. CONCLUSION: Cochlear implantation with subtotal petrosectomy seems to be very safe and effective for patients deafened by chronic otitis media. Long term follow-ups for possible extrusion of the electrode or other complications are still necessary.

The Effect of Intratympanic Steroid Injection for Sudden Sensorineural Hearing Loss / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Intratympanic injection is used for treatment of various inner ear diseases. We studied the effect of intratympanic steroid injection for sudden sensorineural hearing loss (SSNHL). MATERIALS AND METHOD: We carried out a retrospective review of 40 patients with SSNHL with oral steroid therapy and 32 patients with SSNHL with intratympanic steroid injection. Intratympanic steroid injection was performed with tuberculin syringe with a 25-gauge spinal needle under local anesthesia. Hearing was assessed immediately before therapy and at 3 weeks after therapy. RESULTS: Hearing improvement was documented in 25 of 40 patients (62.5%) in the oral steroid therapy group and 21 of 32 patients (65.6%) in the intratympanic steroid therapy group. CONCLUSION: Intratympanic steroid injection was a safe and effective treatment method for SSNHL. This method may be another treatment modality for patients with SSNHL ; moreover, it is a prior treatment method for patients with systemic disease such as diabetes mellitus or hypertension.