While microRNAs have emerged as an important component of gene regulatory networks, it remains unclear how microRNAs collaborate with transcription factors in the gene networks that determines neuronal cell fate. Here, we show that in the developing spinal cord, the expression of miR-218 is directly upregulated by the Isl1-Lhx3 complex, which drives motor neuron fate. Inhibition of miR-218 suppresses the generation of motor neurons in both chick neural tube and mouse embryonic stem cells, suggesting that miR-218 plays a crucial role in motor neuron differentiation. Results from unbiased RISC-trap screens, in vivo reporter assays, and overexpression studies indicated that miR-218 directly represses transcripts that promote developmental programs for interneurons. Additionally, we found that miR-218 activity is required for Isl1-Lhx3 to effectively induce motor neurons and suppress interneuron fates. Together, our results reveal an essential role of miR-218 as a downstream effector of the Isl1-Lhx3 complex in establishing motor neuron identity.

ObjectivesTo evaluate the usefulness of silicone blocks as graft material for mastoid cavity obliteration in the prevention of problematic mastoid cavities after canal wall down mastoidectomies.MethodsRetrospective evaluation of 20 patients who underwent mastoid obliteration with silicone blocks between 2002 and 2009 at the Chonnam National University Hospital. The cases consisted of 17 patients with chronic otitis media with cholesteatoma and 3 patients with adhesive otitis media. The postoperative follow-up period was an average 49 months (range, 6 to 90 months). The surgical technique used at our institution composed four major steps: First, the canal wall down mastoidectomy was performed and the middle ear procedure was completed. The silicone blocks were used to fill up the mastoidectomized cavity. Then, a cortical bone pate was used to cover the surface of the silicone blocks. Finally, temporalis fascia and a split musculoperiosteal flap were used to surround the bone pate for reinforcement of the reconstructed canal wall. We examined postoperative success rate and hearing outcomes.ResultsIn 19 cases (95%), the reconstructed canal wall maintained a cylindrical shape and the ear drum healed without perforation. In only 1 case (5%), the reconstructed canal wall was destroyed with ear drum perforation. The mean improvement in air-bone gap was about 12 dB (P<0.05), and the mean improvement in air-conduction was about 16 dB (P<0.05).ConclusionWe suggest that silicone blocks could be valuable resources as graft materials for mastoid obliteration after canal wall down mastoidectomies.

The present study was undertaken to learn the outcome of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) in their only hearing ear. Timing to conduct a cochlear implantation was also determined in those who did not recover the hearing. The study group comprised 25 patients who confronted ISSNHL in their only hearing ear. A total of 192 patients, who had ISSNHL in one ear and had normal contralateral ear, served as the control. Demographically there were no significant differences between the groups. The recovery rate was similar between the groups: 64.0% in the experimental and 62.5% in the control group. The duration until the recovery of ISSNHL in the only hearing ear was 5-90 days (average 17.6 days). In the experimental group, 8 patients did not recover from ISSNHL, and underwent cochlear implantation in 6 with satisfactory results. These results suggest that the same treatment is applicable for patients with ISSNHL regardless of whether their contralateral ear is deaf or normal. For those who do not recover from ISSNHL in their only hearing ear, culminating in bilateral deafness, we may consider further definitive treatment including cochlear implantation as early as 3 months after initiating the treatment of ISSNHL.

ObjectivesWhile a severe to profound sudden sensorineural hearing loss (SSNHL) may cause serious disability in verbal communication, there have been little studies focusing on this high degree SSNHL. The present study was aimed to investigate the characteristics of hearing recovery in a high degree SSNHL (>70 dB).MethodsThree hundred and two SSNHL patients were enrolled. For a long-term follow-up, 46 patients were evaluated. Hearing level was examined by pure tone audiometry on day 1, week 3, month 3, month 6, and year 1 or after. According to the degree of the initial hearing loss, the patients were divided into 4 groups from 70 to ≥100 dB.ResultsAfter 3 weeks, the recovery rate and mean hearing gain was 61%, 23.85 dB in the 70 dB group, whereas 10%, 6.61 dB in the ≥100 dB group. There was a significant correlation between 3-week recovery and final hearing outcome. However, there was almost no recovery after 3 months.ConclusionAn early recovery can be a prognostic factor for the final recovery in severe to profound SSNHL. Since recovery after 3 months is rare, an early hearing intervention like hearing aid or cochlear implantation should be considered in the high degree SSNHL to restore the patient's verbal communication.