Micco Alan Gerard, Richter Claus-Peter
Northwestern University Feinberg School of Medicine, Department of Otolaryngology-Head and Neck Surgery, The Hugh Knowles Center, Chicago, Illinois , USA.
Curr Opin Otolaryngol Head Neck Surg. 2006 Oct;14(5):352-5. doi: 10.1097/01.moo.0000244195.04926.a0.
In individuals with severe to profound hearing loss, cochlear implants bypass normal inner ear function by applying electrical current directly into the cochlea, thereby stimulating cochlear nerve fibers. Stimulating discrete populations of spiral ganglion cells in cochlear implant users' ears is similar to the encoding of small acoustic frequency bands in a normal-hearing person's ear. Thus, spiral ganglion cells stimulated by an electrode convey the information contained by a small acoustic frequency band. Problems that refer to the current spread and subsequent nonselective stimulation of spiral ganglion cells in the cochlea are reviewed.
Cochlear anatomy and tissue properties determine the current path in the cochlea. Current spreads largely via scala tympani and across turns. While most of the current leaves the cochlea via the modiolus, the facial canal and the round window constitute additional natural escape paths for the current from the cochlea. Moreover, degenerative processes change tissue resistivities and thus may affect current spread in the cochlea.
Electrode design and coding strategies may result in more spatial stimulation of spiral ganglion cells, resulting in a better performance of the electrode-tissue interface.
对于重度至极重度听力损失患者，人工耳蜗通过直接向耳蜗施加电流来绕过正常的内耳功能，从而刺激耳蜗神经纤维。刺激人工耳蜗使用者耳内离散的螺旋神经节细胞群体类似于正常听力者耳内对小的声频段进行编码。因此，由电极刺激的螺旋神经节细胞传递小的声频段所包含的信息。本文综述了与耳蜗中电流扩散以及随后对螺旋神经节细胞的非选择性刺激相关的问题。
耳蜗的解剖结构和组织特性决定了耳蜗中的电流路径。电流主要通过鼓阶并跨蜗圈扩散。虽然大部分电流通过蜗轴离开耳蜗，但面神经管和圆窗构成了电流从耳蜗流出的额外自然逃逸路径。此外，退行性过程会改变组织电阻率，从而可能影响耳蜗中的电流扩散。
电极设计和编码策略可能会导致对螺旋神经节细胞进行更多的空间刺激，从而使电极 - 组织界面表现更佳。
