Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7070, USA.
Otol Neurotol. 2011 Jun;32(4):544-52. doi: 10.1097/MAO.0b013e31821343f5.
The goal of the overall project is to develop knowledge about cochlear physiology during cochlear implantation and develop procedures for assessing its status during hearing preservation surgery. As a step toward this goal, for this study, we established an animal model of sloping high frequency sensorineural hearing loss that mimics the hearing condition of candidates for combined electric-acoustic stimulation.
Mongolian gerbils were exposed to band-pass noise using various cutoff frequencies, intensities, exposure times, and survival times. Hearing loss was assessed in far-field recording using preexposure and postexposure auditory brainstem responses (ABRs), and in acute, near-field recordings of the cochlear microphonic and compound action potential from an electrode on the round window. Anatomic loss of hair cells was assessed from dissections.
Postexposure ABRs and near-field recordings from the round window revealed sensorineural hearing loss that varied with the overall noise exposure. Loss of hair cells ranged from relatively sparse to large areas of complete absence depending on the noise exposure. Cases with high intensity (120 dB SPL) and long exposure times (3 h) showed sloping patterns of hearing loss with profound high-frequency loss and mild-to-moderate low-frequency loss. These cases showed complete loss of hair cells in the basal cochlea and preserved hair cells in the apical cochlea. The frequencies comprising the slope in the ABRs and the location of the transition zone between preserved and lost hair cells varied according to the cutoff frequency used.
We were able to reliably induce sensorineural hearing loss and loss of hair cells in the gerbil that is comparable to candidates for hearing preservation surgery. This model can be used to evaluate the effects of electrode introduction in a system with a hearing condition similar to that in cases of hearing preservation operations.
本项目的总体目标是研究人工耳蜗植入过程中的耳蜗生理学，并开发评估听力保护手术期间其状态的程序。为此目的，在这项研究中，我们建立了一种模拟候选人工电-声联合刺激者听力状况的斜高频率感觉神经性听力损失的动物模型。
使用各种截止频率、强度、暴露时间和存活时间，用带通噪声使蒙古沙鼠暴露。使用暴露前后听觉脑干反应（ABR）在远场记录中评估听力损失，并在圆窗上的电极进行急性近场记录以获得耳蜗微音和复合动作电位。从解剖中评估毛细胞的解剖损失。
暴露后 ABR 和来自圆窗的近场记录显示出与整体噪声暴露相关的感觉神经性听力损失。毛细胞的损失范围从相对稀疏到大面积完全缺失，具体取决于噪声暴露。高强度（120dB SPL）和长时间暴露（3 小时）的病例表现出听力损失的斜型模式，表现为高频损失严重，低频损失轻度至中度。这些病例在基底耳蜗中表现出毛细胞完全缺失，而在耳蜗顶部保留毛细胞。ABR 中的斜率频率和保留与丢失毛细胞之间的过渡区的位置随使用的截止频率而变化。
我们能够可靠地诱导沙鼠的感觉神经性听力损失和毛细胞丢失，其与听力保护手术的候选者相当。该模型可用于评估在类似于听力保护手术情况下的听力条件的系统中引入电极的效果。
