Rapid Increase in Neural Conduction Time in the Adult Human Auditory Brainstem Following Sudden Unilateral Deafness

Individuals with sudden unilateral deafness offer a unique opportunity to study plasticity of the binaural auditory system in adult humans. Stimulation of the intact ear results in increased activity in the auditory cortex. However, there are no reports of changes at sub-cortical levels in humans. Therefore, the aim of the present study was to investigate changes in sub-cortical activity immediately before and after the onset of surgically induced unilateral deafness in adult humans. Click-evoked auditory brainstem responses (ABRs) to stimulation of the healthy ear were recorded from ten adults during the course of translabyrinthine surgery for the removal of a unilateral acoustic neuroma. This surgical technique always results in abrupt deafferentation of the affected ear. The results revealed a rapid (within minutes) reduction in latency of wave V (mean pre = 6.55 ms; mean post = 6.15 ms; p < 0.001). A latency reduction was also observed for wave III (mean pre = 4.40 ms; mean post = 4.13 ms; p < 0.001). These reductions in response latency are consistent with functional changes including disinhibition or/and more rapid intra-cellular signalling affecting binaurally sensitive neurons in the central auditory system. The results are highly relevant for improved understanding of putative physiological mechanisms underlying perceptual disorders such as tinnitus and hyperacusis.     

外伤性截瘫合并耳聋11例临床分析

初步分析了11例外伤性截瘫合并耳聋患者,指出外伤性截瘫多有慢性肾功能不全、肾性贫血等并发症。这些并发症对耳聋的发生有一定的影响,但长时间或反复使用耳毒性药物是一个不可忽视的重要因素。作者对此提出了预防耳聋的一些具体措施,可供临床参考或借鉴。     

豚鼠爆震性聋耳蜗结构与功能的动态变化

目的 探讨爆震性聋与耳蜗损伤之间的关系。方法 通过畸变产物耳声发射及扫描电镜进行研究。结果 豚鼠爆震后即刻出现听阈的提高，与爆震前相比，DPOAEs幅值于1kHz处开始出现非常显著的减低（P〈0．05），在8kHz处两者的差值更大（P〈0．05），DPOAEs幅值随频率升高而逐渐下降，以高频段更为严重。爆震后20天DPOAEs幅值在0．5、0．7、1kHz处基本恢复至爆震前水平，在1．5—8kHz处较爆震后即刻明显提高，但仍低于爆震前水平（各频率均P〈0.05）。爆震后40天DPOAEs幅值与爆震后20天无明显改变（各频率均P〉0．05）。扫描电镜下见豚鼠爆震后即刻出现IHC纤毛排列紊乱，第一排OHC形态基本正常，第二排OHC部分纤毛扭曲或倒伏，尚可看到鸟翼状结构，第三排OHC倒伏、分散，部分折断；20天组IHC纤毛排列仍然紊乱，第一排OHC纤毛基本正常，第二、第三排OHC纤毛排列极度扭曲，以第三排更为严重，少数OHC溶解变性，空位由支持细胞取代；40天组与20天组无明显差别。结论 爆震性聋出现耳蜗HC结构改变及功能减退，提示耳蜗损伤与爆震性聋紧密相关。     

Pure word deafness and pure anarthria in a patient with frontotemporal dementia

A 66-year-old right-handed man developed pure anarthria following pure word deafness. In addition to language disorders, his behavior gradually changed and finally included violence against his wife. Brain magnetic resonance imagings revealed atrophy of the left perisylvian area, which included the inferior half of the precentral gyrus and the upper portion of the superior temporal gyrus, consistent with frontotemporal dementia (FTD). It has been documented as either a disorder of expressive language or as an impaired understanding of word meaning. Unlike with pure anarthria, pure word deafness is not included in the clinical diagnostic current criteria for FTD. However, a large variety of language symptoms can appear in FTD according to the distribution of pathological changes in the frontotemporal cortices. This case suggests that pure word deafness could be a prodomal symptom of FTD.     

Chameleon voices: Interpreting for deaf parents

As interpreters for their deaf parents, hearing children are a cultural link between two often separate worlds: the Deaf and the Hearing. Data from a 4 year study of adult hearing children throughout the United States indicate significant differences between hearing daughters and hearing sons. Not only were daughters more likely than sons (regardless of birth order or age differences) to interpret for their parents, but daughters were also far more likely to be bilingual: fluent in both spoken English and American Sign Language. A similar gender bias has been observed among the general hearing public: women are far more likely to attend sign language classes and to work as interpreters for the deaf. This paper explores the social mechanisms and cultural values which determine the gender of the way we communicate with one another. Informants' narratives suggest that sign language and the practice of interpreting often touched upon a larger pattern of socialization and status differences between women and men. The discussion then turns to consider how these differences affect the cultural identity of hearing sons versus hearing daughters.     

Neuroradiology and clinical aspects of Usher syndrome

We describe the neurological evaluation and MRI analysis of 30 patients, belonging to 16 families with Usher syndrome (US) type I and type II (US1 and US2). In addition to the classic visual and audiological abnormalities seen in these patients, we observed abnormal gait in 88.9% of US1 and in 66.7% of US2 patients and abnormal coordination in 33.4% of US1, and in 58.3% of US2. Borderline mental retardation, depression or bipolar affective disorder were observed in 16.7% of US1 and 33.3% of US2 patients. MRI analysis showed cerebellar abnormalities in 50% of US 1 and 75% of US2 patients, but no clear correlation was observed between structural abnormalities and clinical findings. A pattern for the MRI classification of US patients is suggested.     

Mutations in the gene encoding KIAA1199 protein,an inner-ear protein expressed in Deiters’ cells and the fibrocytes,as the cause of nonsyndromic hearing loss

We report three possibly disease-causing point mutations in one of the inner-ear-specific genes, KIAA1199. We identified an R187C mutation in one family, an R187H mutation in two unrelated families, and an H783Y mutation in one sporadic case of nonsyndromic hearing loss. In situ hybridization indicated that the murine homolog of KIAA1199 mRNA is expressed specifically in Deiters cells in the organ of Corti at postnatal day zero (Pn) P0 before the onset of hearing, but expression in those cells disappears by day P7. The signal of KIAA1199 was also observed in fibrocytes of the spiral ligament and the spiral limbus through to P21, when the murine cochlea matures. Thus, the gene product may be involved in uptake of potassium ions or trophic factors with a particular role in auditory development. Although the R187C and R187H mutations did not appear to affect subcellular localization of the gene product in vitro, the H783Y mutation did present an unusual cytoplasmic distribution pattern that could underlie the molecular mechanism of hearing impairment. Our data bring attention to a novel candidate for hearing loss and indicate that screening of mutations in inner-ear-specific genes is likely to be an efficient approach to finding genetic elements responsible for deafness.Nucleotide sequence data reported herein are available in the DDBJ/EMBL/GenBank databases; for details, see the electronic eatabase section of this article.     

Pyrosequencing for detection of mutations in the connexin 26 (GJB2) and mitochondrial 12S RNA (MTRNR1) genes associated with hereditary hearing loss

Hereditary hearing loss (HHL) is one of the most common congenital disorders and is highly heterogeneous. Mutations in the connexin 26 (CX26) gene (GJB2) account for about 20% of all cases of childhood deafness, and approach 50% in documented recessive cases of non-syndromic hearing loss. In addition, a single mitochondrial DNA mutation, mt1555A>G, in the 12S rRNA gene (MTRNR1), is associated with familial cases of progressive deafness. Effective screening of populations for HHL necessitates rapid assessment of several of these potential mutation sites. Pyrosequencing links a DNA synthesis protocol for determining sequence to an enzyme cascade that generates light whenever pyrophosphate is released during primer strand elongation. We assessed the ability of Pyrosequencing to detect common mutations causing HHL. Detection of the most common CX26 mutations in individuals of Caucasian (35delG), Ashkenazi (167delT), and Asian (235delC, V37I) descent was confirmed by Pyrosequencing. A total of 41 different mutations in the CX26 gene and the mitochondrial mt1555A>G mutation were confirmed. Genotyping of up to six different adjacent mutations was achieved, including simultaneous detection of 35delG and 167delT. Accurate and reproducible results were achieved taking advantage of assay flexibility and experimental conditions easily optimized for a high degree of standardization and cost-effectiveness. The standardized sample preparation steps, including target amplification by PCR and preparation of single-stranded template combined with automated sequence reaction and automated genotype scoring, positions this approach as a potentially high throughput platform for SNP/mutation genotyping in a clinical laboratory setting. .