Development of a Micro-coil Based Cochlear Implant

我们一直在评估来自微小的可植入线圈（称为微线圈）的磁刺激， 下一代人工耳蜗（CI）现有的CI可以实现语音识别，但它们的有效性 当背景噪音水平很高时，大多数用户无法欣赏音乐。虽然一些 的因素被认为有助于这些限制，一般认为，复杂的听觉信号， 例如在存在背景噪声或音乐的情况下由语音引起的那些，需要更多的独立性， 光谱通道比由现有的基于电极的CI创建的光谱通道要多。增加频道数量， 然而，由于植入物周围的高导电溶液（外淋巴）使植入物扩张， 激活从每个电极扩散，使得来自相邻电极的场重叠， 不再独立。由于刺激的目标（螺旋神经节） 神经元）位于耳蜗的骨腔之一内， 激活，这导致电流扩散增加。微弹簧圈可能是电极的一种有吸引力的替代品 因为控制感应场扩散的物理学（麦克斯韦方程）表明， 激活的限制。此外，生物组织对磁场的高渗透性允许 刺激容易地穿过骨壁，而不需要增加刺激水平（并且 导致激活的扩散）。与此一致，植入耳蜗的微线圈刺激， 两种小鼠（Lee等，2022）和豚鼠（目前的建议）的结果在狭窄的通道激活， 下丘，即，更好地近似正常生理信号，并且小于来自 个电极创建窄光谱通道的能力表明有更多的独立通道 使用微线圈是可能的，因此存在改善听力康复的潜力。我们的目标是 进一步评价微弹簧圈用于CI的潜力。目标集中在（1）电生理学 评价植入的微弹簧圈，（2）评价微弹簧圈上相邻通道之间的相互作用， 多线圈阵列，（3）基于线圈的植入物的长期测试，以及（4）开发计算机模型以帮助 理解激活的机制。所有的生理测试都将在豚鼠身上进行，一个很好的- 建立动物模型，用于评价CI性能;我们的团队具有使用该动物的经验 新的初步结果验证了我们的设备和方法的整体可行性。我们的多学科 团队在微弹簧圈设计和开发、磁刺激、计算机建模 人工耳蜗和听觉生理学。几乎所有的团队都位于马萨诸塞州。总医院或下一个 门在Mass。眼睛和耳朵;这里展示的结果是团队之间2年多合作的结果 成员

We have been evaluating magnetic stimulation from tiny, implantable coils (referred to as microcoils) for use in a next-generation cochlear implant (CI). Existing CIs enable speech discrimination, but their effectiveness decreases when background noise levels are high, and most users cannot appreciate music. While a number of factors are thought to contribute to these limitations, it is generally agreed that complex auditory signals, such as those arising from speech in the presence of background noise, or music, require more independent spectral channels than are created by existing, electrode-based CIs. Increasing the number of channels has proven challenging however, as the highly conductive solution surrounding implants (perilymph) expands the spread of activation from each electrode so that fields from neighboring electrodes overlap and channels are no longer independent. The spread of fields is worsened because the targets of stimulation (spiral ganglion neurons) are within one of the bony cavities of the cochlea and thus higher stimulus levels are required for activation which lead to increased current spread. Microcoils may be an attractive alternative to electrodes because the physics governing the spread of induced fields (Maxwell’s equations) suggests narrower confinement of activation. Further, the high permeability of biological tissues to magnetic fields allows stimulation to pass readily through the bony wall, without the need for increased stimulation levels (and the resulting spread of activation). Consistent with this, stimulation from micro-coils implanted in the cochleae of both mice (Lee et al., 2022) and guinea pig (present proposal) results in narrow channels of activation in the inferior colliculus, i.e., better approximating the normal physiological signal, and smaller than those from electrodes. The ability to create narrow spectral channels suggests a larger number of independent channels are possible with microcoils and thus the potential exists for improved rehabilitation of hearing. Our goal here is to further evaluate the potential of microcoils for use in CIs. The Aims focus on (1) electrophysiological evaluation of implanted microcoils, (2) evaluation of the interactions between neighboring channels on the multi-coil array, (3) chronic testing of coil-based implants, and (4) development of a computer model to help understand the mechanism(s) of activation. All physiological testing will take place in guinea pigs, a well- established animal model for evaluation of CI performance; our team has previous experience with this animal and new preliminary results validate the overall viability of our device and the approach. Our multi-disciplinary team has strong expertise in microcoil design and development, magnetic stimulation, computer modeling, cochlear implants and auditory physiology. Almost all of the team is located at Mass. General Hospital or next door at Mass. Eye and Ear; the results presented here are the result of a 2+ year collaboration between team members.