Feasibility of Using EMG for Early Detection of the Facial Nerve During Robotic Direct Cochlear Access

Ansó, Juan; Stahl, Maria Christina; Gerber, Nicolas; Williamson, Tom; Gavaghan, Kate; Rösler, Kai Michael; Caversaccio, Marco; Weber, Stefan; Bell, Brett (2014). Feasibility of Using EMG for Early Detection of the Facial Nerve During Robotic Direct Cochlear Access. Otology & neurotology, 35(3), pp. 545-554. Lippincott Williams & Wilkins 10.1097/MAO.0000000000000187

00129492-201403000-00027.pdf - Published Version
Available under License Publisher holds Copyright.

Download (2MB) | Preview


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.

Item Type:

Journal Article (Original Article)


10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Image Guided Therapy
05 Veterinary Medicine > Research Foci > NeuroCenter
04 Faculty of Medicine > Department of Head Organs and Neurology (DKNS) > Clinic of Ear, Nose and Throat Disorders (ENT)
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV)
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > DKV - Clinical Radiology
04 Faculty of Medicine > Pre-clinic Human Medicine > BioMedical Research (DBMR) > DCR Unit Sahli Building > Forschungsgruppe Neurologie
10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Hearing Research Laboratory

UniBE Contributor:

Anso, Juan, Precht, Maria Christina, Gerber, Nicolas, Williamson, Tom, Gerber, Kate, Rösler, Kai Michael, Caversaccio, Marco, Weber, Stefan (B), Bell, Brett


600 Technology > 630 Agriculture
600 Technology > 610 Medicine & health




Lippincott Williams & Wilkins




Martin Kompis

Date Deposited:

05 Mar 2014 16:26

Last Modified:

29 Mar 2023 23:33

Publisher DOI:


PubMed ID:






Actions (login required)

Edit item Edit item
Provide Feedback