Attias Joseph, Hod Roy, Raveh Eyal, Mizrachi Aviram, Avraham Karen B, Lenz Danielle R, Nageris Ben I
Department of Communication Sciences and Disorders, University of Haifa, Haifa, Israel; Institute for Audiology and Clinical Neurophysiology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
Department of Otorhinolaryngology-Head and Neck Surgery, Rabin Medical Center, Beilinson Campus, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Am J Otolaryngol. 2016 Mar-Apr;37(2):162-8. doi: 10.1016/j.amjoto.2015.12.004. Epub 2015 Dec 9.
The mechanism and the type of hearing loss induced by cochlear implants are mostly unknown. Therefore, this study evaluated the impact and type of hearing loss induced by each stage of cochlear implantation surgery in an animal model.
Original basic research animal study.
The study was conducted in a tertiary, university-affiliated medical center in accordance with the guidelines of the Institutional Animal Care and Use Committee.
Cochlear implant electrode array was inserted via the round window membrane in 17 ears of 9 adult-size fat sand rats. In 7 ears of 5 additional animals round window incision only was performed, followed by patching with a small piece of periosteum (control). Hearing thresholds to air (AC) and bone conduction (BC), clicks, 1 kHz and 6 kHz tone bursts were measured by auditory brainstem evoked potential, before, during each stage of surgery and one week post-operatively. In addition, inner ear histology was performed.
The degree of hearing loss increased significantly from baseline throughout the stages of cochlear implantation surgery and up to one week after (p<0.0001). In both operated groups, the greatest deterioration was noted after round window incision. Overall, threshold shift to air-conduction clicks, reached 61 dB SPL and the bone conduction threshold deteriorated by 19 dB SPL only. Similar losses were found for 1-kHz and 6-kHz frequencies. The hearing loss was not associated with significant changes in inner ear histology.
Hearing loss following cochlear implantation in normal hearing animals is progressive and of mixed type, but mainly conductive. Changes in the inner-ear mechanism are most likely responsible for the conductive hearing loss.
人工耳蜗植入所致听力损失的机制和类型大多未知。因此，本研究在动物模型中评估了人工耳蜗植入手术各阶段所致听力损失的影响和类型。
原创性基础研究动物实验。
本研究在一所大学附属的三级医疗中心按照机构动物护理和使用委员会的指南进行。
将人工耳蜗电极阵列经圆窗膜插入9只成年肥胖沙土鼠的17只耳中。在另外5只动物的7只耳中仅进行圆窗切开，然后用一小片骨膜修补（对照组）。在手术各阶段之前、期间及术后1周，通过听觉脑干诱发电位测量气导（AC）和骨导（BC）的听阈、短声、1kHz和6kHz短纯音。此外，进行内耳组织学检查。
在人工耳蜗植入手术各阶段直至术后1周，听力损失程度较基线均显著增加（p<0.0001）。在两个手术组中，圆窗切开后听力损失最为严重。总体而言，气导短声的阈值偏移达到61dB SPL，而骨导阈值仅恶化了19dB SPL。在1kHz和6kHz频率也发现了类似的听力损失。听力损失与内耳组织学的显著变化无关。
正常听力动物人工耳蜗植入后的听力损失是进行性的，且为混合型，但主要是传导性的。内耳机制的改变很可能是传导性听力损失的原因。
