Lee Sinyoung, Motegi Masaomi, Koike Takuji
Department of Mechanical Engineering, Faculty of Engineering, Graduate Faculty of Interdisciplinary Research, University of Yamanashi, Yamanashi, Japan.
Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
Front Neurol. 2024 Aug 8;15:1417711. doi: 10.3389/fneur.2024.1417711. eCollection 2024.
Active middle ear implants (AMEI) amplify mechanical vibrations in the middle ear and transmit them to the cochlea. The AMEI includes a floating mass transducer (FMT) that can be placed using two different surgical approaches: "oval window (OW) vibroplasty" and "round window (RW) vibroplasty." The OW and RW are windows located on the cochlea. Normally, sound stimulus is transmitted from the middle ear to cochlea via the OW. RW vibroplasty has been suggested as an alternative method due to the difficulty of applying OW vibroplasty in patients with ossicle dysfunction. Several reports compare the advantages of each approach through pre and postoperative hearing tests. However, quantitatively assessing the treatment effect is challenging due to individual differences in pathologies. This study investigates the vibration transmission efficiency of each surgical approach using a finite-element model of the human cochlea. Vibration of the basilar membrane (BM) of the cochlea is simulated by applying the stimulus through the OW or RW. Pathological conditions, such as impaired stapes mobility, are simulated by increasing the stiffness of the stapedial annular ligament. RW closure due to chronic middle ear diseases is a common clinical occurrence and is simulated by increasing the stiffness of the RW membrane in the model. The results show that the vibration amplitude of the BM is larger when the stimulus is applied to the RW compared to the OW, except for cases of RW membrane ossification. The difference in these amplitudes is particularly significant when stapedial mobility is limited. These results suggest that RW vibroplasty would be advantageous, especially in cases of accompanying stapedial mobility impairment. Additionally, it is suggested that transitioning to OW vibroplasty could still ensure a sufficient level of vibratory transmission efficiency when placing the FMT on the RW membrane is difficult due to anatomical problems in the tympanic cavity or confirmed severe pathological conditions around the RW.
有源中耳植入物（AMEI）可放大中耳的机械振动并将其传递至耳蜗。AMEI包括一个浮动质量传感器（FMT），可通过两种不同的手术方法进行放置：“卵圆窗（OW）振动成形术”和“圆窗（RW）振动成形术”。卵圆窗和圆窗是位于耳蜗上的窗口。通常，声音刺激通过卵圆窗从中耳传递至耳蜗。由于在听小骨功能障碍患者中应用卵圆窗振动成形术存在困难，圆窗振动成形术已被提议作为一种替代方法。一些报告通过术前和术后听力测试比较了每种方法的优势。然而，由于病理情况存在个体差异，定量评估治疗效果具有挑战性。本研究使用人耳蜗的有限元模型研究了每种手术方法的振动传递效率。通过卵圆窗或圆窗施加刺激来模拟耳蜗基底膜（BM）的振动。通过增加镫骨环形韧带的刚度来模拟诸如镫骨活动度受损等病理状况。由于慢性中耳疾病导致的圆窗封闭是一种常见的临床情况，在模型中通过增加圆窗膜的刚度来模拟。结果表明，与卵圆窗相比，当刺激施加于圆窗时，基底膜的振动幅度更大，但圆窗膜骨化的情况除外。当镫骨活动度受限，这些幅度差异尤为显著。这些结果表明，圆窗振动成形术可能具有优势，特别是在伴有镫骨活动度受损的情况下。此外，还表明当由于鼓室腔解剖问题或圆窗周围确诊为严重病理状况而难以将FMT放置在圆窗膜上时，转换为卵圆窗振动成形术仍可确保足够水平的振动传递效率。
