Lenarz Minoo, Lim Hubert H, Patrick James F, Anderson David J, Lenarz Thomas
Otorhinolaryngology Department, Medical University of Hannover, Hannover, Lower Saxony 30625, Germany.
J Assoc Res Otolaryngol. 2006 Dec;7(4):383-98. doi: 10.1007/s10162-006-0056-5. Epub 2006 Oct 31.
The auditory midbrain implant (AMI) is a new treatment for hearing restoration in patients with neural deafness or surgically inaccessible cochleae who cannot benefit from cochlear implants (CI). This includes neurofibromatosis type II (NF2) patients who, due to development and/or removal of vestibular schwannomas, usually experience complete damage of their auditory nerves. Although the auditory brainstem implant (ABI) provides sound awareness and aids lip-reading capabilities for these NF2 patients, it generally only achieves hearing performance levels comparable with a single-channel CI. In collaboration with Cochlear Ltd. (Lane Cove, Australia), we developed a human prototype AMI, which is designed for electrical stimulation along the well-defined tonotopic gradient of the inferior colliculus central nucleus (ICC). Considering that better speech perception and hearing performance has been correlated with a greater number of discriminable frequency channels of information available, the ability of the AMI to effectively activate discrete frequency regions within the ICC may enable better hearing performance than achieved by the ABI. Therefore, the goal of this study was to investigate if our AMI array could achieve low-threshold, frequency-specific activation within the ICC, and whether the levels for ICC activation via AMI stimulation were within safe limits for human application. We electrically stimulated different frequency regions within the ICC via the AMI array and recorded the corresponding neural activity in the primary auditory cortex (A1) using a multisite silicon probe in ketamine-anesthetized guinea pigs. Based on our results, AMI stimulation achieves lower thresholds and more localized, frequency-specific activation than CI stimulation. Furthermore, AMI stimulation achieves cortical activation with current levels that are within safe limits for central nervous system stimulation. This study confirms that our AMI design is sufficient for ensuring safe and effective activation of the ICC, and warrants further studies to translate the AMI into clinical application.
听觉中脑植入物（AMI）是一种针对神经性耳聋患者或耳蜗手术无法触及且无法从人工耳蜗（CI）中获益的患者恢复听力的新疗法。这包括患有II型神经纤维瘤病（NF2）的患者，由于前庭神经鞘瘤的发展和/或切除，他们通常会经历听觉神经的完全损伤。尽管听觉脑干植入物（ABI）为这些NF2患者提供了声音感知并有助于唇读能力，但它通常只能达到与单通道CI相当的听力性能水平。我们与科利耳有限公司（澳大利亚莱恩科夫）合作，开发了一种人类原型AMI，其设计用于沿着下丘中央核（ICC）明确的音频拓扑梯度进行电刺激。考虑到更好的语音感知和听力性能与更多可分辨的频率信息通道相关，AMI有效激活ICC内离散频率区域的能力可能会带来比ABI更好的听力性能。因此，本研究的目的是调查我们的AMI阵列是否能在ICC内实现低阈值、频率特异性激活，以及通过AMI刺激激活ICC的水平是否在人体应用的安全范围内。我们通过AMI阵列电刺激ICC内的不同频率区域，并使用多部位硅探针在氯胺酮麻醉的豚鼠中记录初级听觉皮层（A1）中的相应神经活动。根据我们的结果，AMI刺激比CI刺激实现了更低的阈值和更局部化、频率特异性的激活。此外，AMI刺激在中枢神经系统刺激的安全电流水平内实现了皮层激活。这项研究证实，我们的AMI设计足以确保安全有效地激活ICC，并值得进一步研究将AMI转化为临床应用。
