Binaural hearing aid intervention for a patient with nonserviceable hearing loss after surgery for vestibular schwannoma: A case report.

A vestibular schwannoma is a benign tumor; however, the schwannoma itself and interventions can cause sensorineural hearing loss. Most vestibular schwannomas are unilateral tumors that affect hearing only on one side. Attention has focused on improving the quality of life for patients with unilateral hearing loss and therapeutic interventions to address this issue have been emphasized. Herein, we encountered a patient who was a candidate for hearing preservation surgery based on preoperative findings and had nonserviceable hearing after the surgery, according to the Gardner-Robertson classification. Postoperatively, the patient had decreased listening comprehension and ability to localize sound sources. He was fitted with bilateral hearing aids, and his ability to localize sound sources improved. Although the patient had postoperative nonserviceable hearing on the affected side and age-related hearing loss on the unaffected side, hearing aids in both ears were useful for his daily life. Therefore, the patient was able to maintain a binaural hearing effect and the ability to localize the sound source improved. This report emphasizes the importance of hearing preservation with vestibular schwannomas, and the demand for hearing loss rehabilitation as a postoperative complication can increase, even if hearing loss is nonserviceable.

Development of cochlear spiral ligament fibrocytes of the common marmoset, a nonhuman model animal.

Spiral ligament fibrocytes generate potassium gradients, which hair cells require to convert mechanical sound waves into electrical palsy. Together with the stria vascularis, they regulate endolymph electrolyte homeostasis. Developing spiral ligament fibrocytes and generating endocochlear potential with an appropriate endolymph ion composition are essential for hearing. Understanding spiral ligament fibrocyte development is useful for studying age-related and genetic hearing loss, as well as for regenerative therapy and cochlear immunology. Despite interspecies differences, most studies of cochlear development have been conducted in rodent models due to the difficulty of using human fetal samples. This study investigated the cochlear development of spiral ligament fibrocytes in a small New World monkey species, the common marmoset (Callithrix jacchus). We examined the developmental expression of specific genes in spiral ligament fibrocytes, including those essential for the generation of endolymphatic potential. Our results showed that this animal model of spiral ligament fibrocyte development is similar to that of humans and is a suitable alternative for the analysis of human cochlear development. The time course established in this study will be useful for studying the primate-specific developmental biology of the inner ear, which may lead to novel treatment strategies for human hearing loss.

Development of the stria vascularis in the common marmoset, a primate model.

Stria vascularis is a structure that generates potassium gradients in the cochlea, which is vital for hair cells to convert mechanical sound waves into electrical pulses. The precise development of the stria vascularis and subsequent generation of endocochlear potential are thus essential for hearing. Understanding the development of the stria vascularis is valuable for studying hearing loss caused by aging or genetics and designing regenerative therapy. Although inter-species differences have been reported between rodents and humans, most of our current knowledge regarding cochlear development has been obtained from rodent models because of the difficulty in using human fetal samples in this field of research. Therefore, we investigated the development of the cochlear stria vascularis in the common marmoset (Callithrix jacchus), a small monkey species native to the New World. Our study confirms that stria vascularis development in the common marmoset is similar to that in humans and is suitable for furthering our understanding of human cochlear development. The time course established in this report will aid in studying the primate-specific developmental biology of the inner ear, which could eventually lead to new treatment strategies for hearing loss in humans.

Trapezius muscle branch of the spinal accessory nerve without penetrating the sternocleidomastoid muscle as a pitfall in neck dissection: prevalence in a Japanese institution and a protocol for the prevention of iatrogenic injury.

BACKGROUND: The spinal accessory nerve (SAN) has several anatomical variations, which may be a pitfall in neck dissection (ND). These include the trapezius muscle branch (TB), which stems from the common trunk before entering the sternocleidomastoid muscle (SCM). AIMS/OBJECTIVES: To investigate the prevalence of this variation and suggest a protocol for preventing unexpected injury of the TB in ND. MATERIALS AND METHODS: We conducted a retrospective cohort study for 93 patients who had undergone neck dissection (117 sides) without resection of the SCM nor SAN. We recorded the division of the TB after and before penetration of the SCM by the common trunk (penetrating type TB [PTB]) and non-penetrating type TB [NPTB], respectively). RESULTS: Among NDs, PTB and NPTB were observed in 61 (52%) and 56 (48%) sides, respectively. In the subgroup of 24 cases with bilateral ND, PTB/PTB, NPTB/NPTB, and NPTB/PTB were observed in eight (33%), nine (38%), and seven (29%) cases, respectively. The prevalence of PTB/NPTB did not differ according to age, sex, or laterality. CONCLUSIONS AND SIGNIFICANCE: NPTB is a common anatomical variation. The presence or absence of a branch from the common trunk must be initially checked to avoid unexpected damage to the TB.

Early hearing improvement predicts the prognosis of idiopathic sudden sensorineural hearing loss.

PURPOSE: To determine pre- and post-treatment factors that are useful for predicting the prognosis of hearing improvement in idiopathic sudden sensorineural hearing loss (ISSHL). METHODS: This retrospective study included 332 patients with ISSHL. Patients received intravenous steroid treatment (prednisolone sodium succinate; 120 mg/day followed by dose tapering). Complete recovery of hearing levels was defined as a final pure-tone audiometry of ≤ 20 dB HL or the same level as the contralateral ear. Patients' age; sex; side of hearing loss; initial hearing level; days from onset to treatment; presence of vertigo, diabetes, and hypertension; and hearing improvement on days 3-4 and 6-7 after treatment initiation were analyzed as potential prognostic factors. RESULTS: Overall, 109 patients (32%) had complete recovery. Results of the multivariate logistic regression model identified age (odds ratio [OR] = 0.974), initial hearing level (OR = 0.949), vertigo (OR = 0.409), and hearing improvement on days 6-7 after treatment initiation (OR = 1.11) as significant independent predictors of complete recovery. Age ≥ 60 years, initial hearing level ≥ 72.5 dB HL, and vertigo contributed to poor prognosis. Patients without these three factors and a hearing improvement of ≥ 10 dB HL on days 6-7 post-treatment had a complete recovery rate of 80%. Only 1.5% of the patients with 2-3 of these factors and a hearing improvement of < 10 dB HL on days 6-7 after treatment initiation achieved complete recovery. CONCLUSION: Age, initial hearing level, vertigo, and hearing improvement on days 6-7 after treatment initiation were independent predictors of hearing recovery in ISSHL.

Bile acid binding resin prevents fat accumulation through intestinal microbiota in high-fat diet-induced obesity in mice.

BACKGROUND: Bile acid binding resin (BAR) absorbs intestinal bile acids, and improves obesity and metabolic disorders, but the precise mechanism remains to be clarified. Recent findings reveal that obesity is associated with skewed intestinal microbiota. Thus, we investigated the effect of BAR on intestinal microbiota and the role of microbiota in the prevention of obesity in high-fat diet-induced obesity in mice. PROCEDURES: Male Balb/c mice were fed a low-fat diet (LFD), high-fat diet (HFD), or HFD with BAR (HFD+BAR), and then metabolic parameters, caecal microbiota, and metabolites were investigated. The same interventions were conducted in germ-free and antibiotic-treated mice. MAIN FINDINGS: The frequency of Clostridium leptum subgroup was higher in both HFD-fed and HFD+BAR-fed mice than in LFD-fed mice. The frequency of Bacteroides-Prevotella group was lower in HFD-fed mice than in LFD-fed mice, but the frequency was higher in HFD+BAR-fed mice than in HFD-fed mice. Caecal propionate was lower in HFD-fed mice than in LFD-fed mice, and higher in HFD+BAR-fed mice than in HFD-fed mice. HFD+BAR-fed mice showed lower adiposity than HFD-fed mice, and the reduction was not observed in germ-free or antibiotic-treated mice. Colonized germ-free mice showed a reduction in adiposity by BAR administration. Energy expenditure was lower in HFD-fed mice and higher in HFD+BAR-fed mice, but the increments induced by administration of BAR were not observed in antibiotic-treated mice. CONCLUSIONS: Modulation of intestinal microbiota by BAR could be a novel therapeutic approach for obesity.