Published papers

In order to clarify the possible mechanism of hearing loss in immune-mediated sensorineural hearing loss, basic research needed includes animal model studies. In the present investigation, we examined hearing thresholds and cochlear histologies of the MRL/lpr mouse which is now well-known as a model for pathology consistent with systemic lupus erythematosis (SLE). Present findings demonstrated that there were no statistically significant differences in auditory brainstem response (ABR) thresholds between 4- to 6-week-old 'young' and 20- to 25-week-old 'old' MRL mice. These differences were not sex-dependent. Under light microscopy, there were no abnormal morphological findings in the cochleas of either young or old MRL mice. With immunohistochemistry, mouse IgG was detected around the capillary walls in the stria vascularis in both young and old MRL mice. Serum IgG level of the MRL mice significantly decreased after predonisolone (PSL) administration. However, expression of mouse IgG in the stria vascularis was not observed in the MRL mice after PSL administration. From these results, we speculate that the hearing of the MRL mouse does not always deteriorate, and the deposition of mouse IgG on the capillary wall in the stria vascularis is not a sufficient factor to induce hearing loss. At this point, we conclude that the MRL mouse should not be considered a useful model for immune-mediated sensorineural hearing loss.

Objective: This study aimed to investigate the factors affecting the quality of postoperative hearing in acoustic neuroma. Study Design: The study was designed as a retrospective case review. Setting: The study was performed at the Department of Otolaryngology, School of Medicine, Keio University, Tokyo, Japan. Patients: The subjects were 94 patients with unilateral acoustic neuroma. Intervention: Hearing preservation surgery was performed in the subjects via the extended cranial fossa approach or the middle cranial fossa approach. Main Outcome Measures: The outcome measures included patient's age and gender, hearing level, speech discrimination score, tumor size, and surgical approach. The relationship between the qualities of preoperative and postoperative hearing and the long-term prognosis of preserved heating also was investigated. Results: In 94 subjects, there were 47 patients whose hearing was preserved (HP group) and 47 patients whose hearing was not preserved (non-HP group). Overall, hearing preservation rate was 50%. There were no significant differences in age, gender, and tumor size between the two groups. The heating preservation rate was significantly higher in patients with an intracanalicular tumor than that with a larger tumor. The better the preoperative quality of hearing was, the higher the postoperative one. Although the preserved hearing deteriorated after surgery in 4 patients, no significant hearing deterioration was observed in the other 43 patients. Conclusions: The results of this study indicated that the diagnosis for acoustic neuroma in the early stage with serviceable hearing is the most important to improve the quality of postoperative hearing.

Acoustic neuroma (AN) patients who had normal hearing accounted for 7% of all our AN cases. It is important to identify AN patients who have normal hearing but are suffering from tinnitus, dizziness, or vertigo, or a combination of these symptoms (without hearing loss), in order to make an early diagnosis. Patients who experience sudden hearing loss and recover completely should also be thoroughly examined in order to rule out AN. In this article, we describe an investigation of the clinical features and results of hearing preservation surgery in AN patients with normal hearing. The overall hearing preservation rate was 57%. The hearing preservation rate did not depend on the auditory brainstem response (ABR) pattern, tumor size, or the origin of the tumor. We think that patients must be properly informed concerning all aspects of the surgery, including the possibility that hearing and/or facial nerve function cannot be preserved.