Ansó Juan, Stahl Christina, Gerber Nicolas, Williamson Tom, Gavaghan Kate, Rösler Kai Michael, Caversaccio Marco-Domenico, Weber Stefan, Bell Brett
*ARTORG Center for Biomedical Engineering, †VetSuisse Faculty, ‡Department of Neurology, ENMG-Station and §Department of ENT Head and Neck Surgery, Inselspital, University of Bern, Bern, Switzerland.
Otol Neurotol. 2014 Mar;35(3):545-54. doi: 10.1097/MAO.0000000000000187.
Facial nerve monitoring can be used synchronous with a high-precision robotic tool as a functional warning to prevent of a collision of the drill bit with the facial nerve during direct cochlear access (DCA).
Minimally invasive direct cochlear access (DCA) aims to eliminate the need for a mastoidectomy by drilling a small tunnel through the facial recess to the cochlea with the aid of stereotactic tool guidance. Because the procedure is performed in a blind manner, structures such as the facial nerve are at risk. Neuromonitoring is a commonly used tool to help surgeons identify the facial nerve (FN) during routine surgical procedures in the mastoid. Recently, neuromonitoring technology was integrated into a commercially available drill system enabling real-time monitoring of the FN. The objective of this study was to determine if this drilling system could be used to warn of an impending collision with the FN during robot-assisted DCA.
The sheep was chosen as a suitable model for this study because of its similarity to the human ear anatomy. The same surgical workflow applicable to human patients was performed in the animal model. Bone screws, serving as reference fiducials, were placed in the skull near the ear canal. The sheep head was imaged using a computed tomographic scanner and segmentation of FN, mastoid, and other relevant structures as well as planning of drilling trajectories was carried out using a dedicated software tool. During the actual procedure, a surgical drill system was connected to a nerve monitor and guided by a custom built robot system. As the planned trajectories were drilled, stimulation and EMG response signals were recorded. A postoperative analysis was achieved after each surgery to determine the actual drilled positions.
Using the calibrated pose synchronized with the EMG signals, the precise relationship between distance to FN and EMG with 3 different stimulation intensities could be determined for 11 different tunnels drilled in 3 different subjects.
From the results, it was determined that the current implementation of the neuromonitoring system lacks sensitivity and repeatability necessary to be used as a warning device in robotic DCA. We hypothesize that this is primarily because of the stimulation pattern achieved using a noninsulated drill as a stimulating probe. Further work is necessary to determine whether specific changes to the design can improve the sensitivity and specificity.
面神经监测可与高精度机器人工具同步使用，作为一种功能警示，以防止在直接耳蜗入路（DCA）过程中钻头与面神经发生碰撞。
微创直接耳蜗入路（DCA）旨在通过在立体定向工具引导下，经面神经隐窝钻一小隧道至耳蜗，从而无需进行乳突切除术。由于该手术是在盲视下进行，面神经等结构存在风险。神经监测是在乳突常规手术过程中帮助外科医生识别面神经（FN）的常用工具。最近，神经监测技术被集成到一种商用钻孔系统中，能够实时监测FN。本研究的目的是确定该钻孔系统是否可用于在机器人辅助DCA过程中警示即将与FN发生碰撞。
由于绵羊耳部解剖结构与人类相似，故选择绵羊作为本研究的合适模型。在动物模型中执行适用于人类患者的相同手术流程。将作为参考基准的骨螺钉置于耳道附近的颅骨中。使用计算机断层扫描仪对绵羊头部进行成像，并使用专用软件工具对FN、乳突和其他相关结构进行分割以及规划钻孔轨迹。在实际手术过程中，将手术钻孔系统连接到神经监测器，并由定制的机器人系统引导。在按计划轨迹钻孔时，记录刺激和肌电图反应信号。每次手术后进行术后分析以确定实际钻孔位置。
利用与肌电图信号同步校准的位姿，对于在3个不同受试者中钻出的11条不同隧道，可确定在3种不同刺激强度下到FN的距离与肌电图之间的精确关系。
从结果来看，确定神经监测系统的当前实施方案缺乏在机器人DCA中用作警示装置所需的灵敏度和可重复性。我们推测这主要是因为使用非绝缘钻头作为刺激探针所实现的刺激模式。需要进一步开展工作来确定设计上的特定改变是否能提高灵敏度和特异性。
