A Neuromonitoring Approach to Facial Nerve Preservation During Image-guided Robotic Cochlear Implantation.

Ansó, Juan; Dür, Cilgia; Gavaghan, Kate; Rohrbach, Helene; Gerber, Nicolas; Williamson, Tom; Calvo, Enric M; Wyss, Thomas; Precht, Maria Christina; Ferrario, Damien; Dettmer, Matthias; Rösler, Kai Michael; Caversaccio, Marco; Bell, Brett; Weber, Stefan (2016). A Neuromonitoring Approach to Facial Nerve Preservation During Image-guided Robotic Cochlear Implantation. Otology & neurotology, 37(1), pp. 89-98. Lippincott Williams & Wilkins 10.1097/MAO.0000000000000914

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HYPOTHESIS A multielectrode probe in combination with an optimized stimulation protocol could provide sufficient sensitivity and specificity to act as an effective safety mechanism for preservation of the facial nerve in case of an unsafe drill distance during image-guided cochlear implantation. BACKGROUND A minimally invasive cochlear implantation is enabled by image-guided and robotic-assisted drilling of an access tunnel to the middle ear cavity. The approach requires the drill to pass at distances below 1 mm from the facial nerve and thus safety mechanisms for protecting this critical structure are required. Neuromonitoring is currently used to determine facial nerve proximity in mastoidectomy but lacks sensitivity and specificity necessaries to effectively distinguish the close distance ranges experienced in the minimally invasive approach, possibly because of current shunting of uninsulated stimulating drilling tools in the drill tunnel and because of nonoptimized stimulation parameters. To this end, we propose an advanced neuromonitoring approach using varying levels of stimulation parameters together with an integrated bipolar and monopolar stimulating probe. MATERIALS AND METHODS An in vivo study (sheep model) was conducted in which measurements at specifically planned and navigated lateral distances from the facial nerve were performed to determine if specific sets of stimulation parameters in combination with the proposed neuromonitoring system could reliably detect an imminent collision with the facial nerve. For the accurate positioning of the neuromonitoring probe, a dedicated robotic system for image-guided cochlear implantation was used and drilling accuracy was corrected on postoperative microcomputed tomographic images. RESULTS From 29 trajectories analyzed in five different subjects, a correlation between stimulus threshold and drill-to-facial nerve distance was found in trajectories colliding with the facial nerve (distance <0.1 mm). The shortest pulse duration that provided the highest linear correlation between stimulation intensity and drill-to-facial nerve distance was 250 μs. Only at low stimulus intensity values (≤0.3 mA) and with the bipolar configurations of the probe did the neuromonitoring system enable sufficient lateral specificity (>95%) at distances to the facial nerve below 0.5 mm. However, reduction in stimulus threshold to 0.3 mA or lower resulted in a decrease of facial nerve distance detection range below 0.1 mm (>95% sensitivity). Subsequent histopathology follow-up of three representative cases where the neuromonitoring system could reliably detect a collision with the facial nerve (distance <0.1 mm) revealed either mild or inexistent damage to the nerve fascicles. CONCLUSION Our findings suggest that although no general correlation between facial nerve distance and stimulation threshold existed, possibly because of variances in patient-specific anatomy, correlations at very close distances to the facial nerve and high levels of specificity would enable a binary response warning system to be developed using the proposed probe at low stimulation currents.

Item Type:

Journal Article (Original Article)

Division/Institute:

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)
04 Faculty of Medicine > Pre-clinic Human Medicine > Institute for Surgical Technology & Biomechanics ISTB
04 Faculty of Medicine > Service Sector > Institute of Pathology > Clinical Pathology
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV)
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > DKV - Clinical Radiology
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > Small Animal Clinic
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 - Image Guided Therapy > ARTORG Center - Artificial Hearing Research
10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Image Guided Therapy
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > DKV - Anaesthesiology

UniBE Contributor:

Anso, Juan; Dür, Cilgia; Gerber, Kate; Rohrbach, Helene; Gerber, Nicolas; Williamson, Tom; Wyss, Thomas; Precht, Maria Christina; Dettmer, Matthias; Rösler, Kai Michael; Caversaccio, Marco; Bell, Brett and Weber, Stefan

Subjects:

600 Technology > 630 Agriculture
600 Technology > 610 Medicine & health
500 Science > 570 Life sciences; biology

ISSN:

1531-7129

Publisher:

Lippincott Williams & Wilkins

Language:

English

Submitter:

Doris Haefelin

Date Deposited:

27 Jan 2016 12:45

Last Modified:

13 Jun 2018 11:01

Publisher DOI:

10.1097/MAO.0000000000000914

PubMed ID:

26649610

BORIS DOI:

10.7892/boris.74673

URI:

https://boris.unibe.ch/id/eprint/74673

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