Neuromonitoring During Robotic Cochlear Implantation: Initial Clinical Experience

Entirely robotic cochlear implant surgery

INTRODUCTION

Robot-assisted cochlear implant surgery (RACIS) as defined by the HEARO®-procedure performs minimal invasive cochlear implant (CI) surgery by directly drilling a keyhole trajectory towards the inner ear. Hitherto, an entirely robotic automation including electrode insertion has not been described yet. The feasability of using a newly developed, dedicated motorised device for automated electrode insertion in the first clinical case of entirely robotic cochlear implant surgery was investigated.

AIM

The aim is to report the first experience of entirely robotic cochlear implantation surgery.

INTERVENTION

RACIS with a straight flexible lateral wall electrode.

PRIMARY OUTCOME MEASUREMENTS

Electrode cochlear insertion depth.

SECONDARY OUTCOME MEASUREMENTS

The audiological outcome in terms of mean hearing thresholds.

CONCLUSION

Here, we report on a cochlear implant robot that performs the most complex surgical steps to place a cochlear implant array successfully in the inner ear and render similar audiological results as in conventional surgery. Robots can execute tasks beyond human dexterity and will probably pave the way to standardize residual hearing preservation and broadening the indication for electric-acoustic stimulation in the same ear with hybrid implants.

True keyhole cochlear implant surgery

INTRODUCTION

Minimal invasive Robotic Assisted Cochlear Implant Surgery (RACIS) is a keyhole surgery by definition. It is therefore not possible to visualize the electrode array during insertion in the scala tympani. Hitherto, surgeons visualised the round window via the external auditory canal by folding over the tympanic membrane. However, the opening of a tympanomeatal flap is not minimal invasive and is especially in conventional cochlear implantation surgery not even necessary. Here we prove that image guided and robot assisted surgery can also allow correct electrode array insertion without opening the tympanomeatal flap.

AIM

The aim is to report the first experience of robotic cochlear implantation surgery fully based on image guided surgery and without the opening of a tympanomeatal flap for electrode array insertion.

INTERVENTION

RACIS with a straight flexible lateral wall electrode.

PRIMARY OUTCOME MEASUREMENTS

Electrode cochlear insertion depth with RACIS and autonomous inner ear access with full electrode insertion of a flexible lateral wall electrode array.

SECONDARY OUTCOME MEASUREMENTS

The audiological outcome in terms of mean hearing thresholds.

CONCLUSION

After a series of 33 cases and after fine-tuning the insertion angles and yet another new version of planning software to depict the round window approach, a new clinical routine for inserting electrodes fully based on image guided surgery without opening a tympanomeatal flap was developed in robotic-assisted cochlear implant surgery.

Using EMG signals to assess proximity of instruments to nerve roots during robot-assisted spinal surgery

BACKGROUND

Detecting neural threats using electromyography (EMG) has gained recognition in the field of spinal surgery. To provide an efficient approach to detect neural threats during the operation of the spinal surgery robot, an automated method based the internal connection between EMG signal and neural proximity (NP) was explored by experiments.

METHODS

A NP classifier was designed to distinguish the pattern of the threats. Then, it was evaluated in rabbit models in vivo. The experiments were conducted using 20 rabbits. In each rabbit, two puncture paths were created using a surgical robot. For each path, EMG signals were recorded at series of path-points with different neural proximities, and were constructed as datasets after data cleaning and processing. The proposed NP classifier was trained and tested on the datasets.

RESULTS

Classification accuracy of Path 1 and Path 2 were 99.1% and 94.0%, respectively.

CONCLUSION

This feasibility study proved that EMG can be used to detect the proximity of surgical instruments to nerve roots during robot-assisted spinal surgery. As the methods of detecting neural threats for surgical robots are still scarce, we believe this work will improve the clinical performance of spinal surgery robots and help the doctors to perform surgery safely.

Robotics, automation, active electrode arrays, and new devices for cochlear implantation: A contemporary review

In the last two decades, cochlear implant surgery has evolved into a minimally invasive, hearing preservation surgical technique. The devices used during surgery have benefited from technological advances that have allowed modification and possible improvement of the surgical technique. Robotics has recently gained popularity in otology as an effective tool to overcome the surgeon's limitations such as tremor, drift and accurate force control feedback in laboratory testing. Cochlear implantation benefits from robotic assistance in several steps during the surgical procedure: (i) during the approach to the middle ear by automated mastoidectomy and posterior tympanotomy or through a tunnel from the postauricular skin to the middle ear (i.e. direct cochlear access); (ii) a minimally invasive cochleostomy by a robot-assisted drilling tool; (iii) alignment of the correct insertion axis on the basal cochlear turn; (iv) insertion of the electrode array with a motorized insertion tool. In recent years, the development of bone-attached parallel robots and image-guided surgical robotic systems has allowed the first successful cochlear implantation procedures in patients via a single hole drilled tunnel. Several other robotic systems, new materials, sensing technologies applied to the electrodes, and smart devices have been developed, tested in experimental models and finally some have been used in patients with the aim of reducing trauma in cochleostomy, and permitting slow and more accurate insertion of the electrodes. Despite the promising results in laboratory tests in terms of minimal invasiveness, reduced trauma and better hearing preservation, so far, no clinical benefits on residual hearing preservation or better speech performance have been demonstrated. Before these devices can become the standard approach for cochlear implantation, several points still need to be addressed, primarily cost and duration of the procedure. One can hope that improvement in the cost/benefit ratio will expand the technology to every cochlear implantation procedure. Laboratory research and clinical studies on patients should continue with the aim of making intracochlear implant insertion an atraumatic and reversible gesture for total preservation of the inner ear structure and physiology.

Robotic Cochlear Implant Surgery: Imaging-Based Evaluation of Feasibility in Clinical Routine

Background: Robotic surgery has been proposed in various surgical fields to reduce recovery time, scarring, and to improve patients' outcomes. Such innovations are ever-growing and have now reached the field of cochlear implantation. To implement robotic ear surgery in routine, it is of interest if preoperative planning of a safe trajectory to the middle ear is possible with clinically available image data.

Methods: We evaluated the feasibility of robotic cochlear implant surgery in 50 patients (100 ears) scheduled for routine cochlear implant procedures based on clinically available imaging. The primary objective was to assess if available high-resolution computed tomography or cone beam tomography imaging is sufficient for planning a trajectory by an otological software. Secondary objectives were to assess the feasibility of cochlear implant surgery with a drill bit diameter of 1.8 mm, which is the currently used as a standard drill bit. Furthermore, it was evaluated if feasibility of robotic surgery could be increased when using smaller drill bit sizes. Cochlear and trajectory parameters of successfully planned ears were collected. Measurements were carried out by two observers and the interrater reliability was assessed using Cohen's Kappa.

Results: Under the prerequisite of the available image data being sufficient for the planning of the procedure, up to two thirds of ears were eligible for robotic cochlear implant surgery with the standard drill bit size of 1.8 mm. The main reason for inability to plan the keyhole access was insufficient image resolution causing anatomical landmarks not being accurately identified. Although currently not applicable in robotic cochlear implantation, narrower drill bit sizes ranging from 1.0 to 1.7 mm in diameter could increase feasibility up to 100%. The interrater agreement between the two observers was good for this data set.

Discussion: For robotic cochlear implant surgery, imaging with sufficient resolution is essential for preoperative assessment. A slice thickness of <0.3 mm is necessary for trajectory planning. This can be achieved by using digital volume tomography while radiation exposure can be kept to a minimum. Furthermore, surgeons who use the software tool, should be trained on a regular basis in order to achieve planning consistency.

Facial Nerve Intraoperative Monitoring in Otologic Surgeries under Sedation and Local Anesthesia - A Case Series and Literature Review

Introduction  Local anesthesia with sedation has been employed for an increasingly number of otolaryngology procedures, and might be associated with lower surgical morbidity and costs. Facial nerve monitoring is often advisable in otology to minimize the risks of injuries to this cranial nerve, but the principles, techniques and parameters involved have only been studied for procedures under general anesthesia. Objective  To report the preliminary outcomes of intraoperative facial nerve monitoring during otologic procedures under sedation and local anesthesia. Methods  A total of five procedures and their respective intraoperative electrophysiological main findings were described. Facial neuromonitoring was performed using the same device by an electrophysiologist. The monitor sensitivity was set at 100 mV, and a stimulating probe was used whenever needed. Results  Progressively decreasing low-amplitude baseline values were usually obtained as the level of anesthesia increased, with isolated oscillations possibly related to some degree of voluntary muscular activity. These oscillations could be easily distinguished from those of the surgical manipulation or electrical stimulation of the nerve, which tended to be of much greater amplitude and shorter latency, occurring during specific surgical steps. Conclusion  With a surgical team with proper procedural knowledge and broad expertise regarding the technique, intraoperative facial nerve monitoring under local anesthesia with sedation seemed both feasible and reliable. Thus, the need for intraoperative neuromonitoring should not be an obstacle for otologic procedures under less aggressive anesthetic management.

A microsurgical robot research platform for robot-assisted microsurgery research and training

Purpose

Ocular surgery, ear, nose and throat surgery and neurosurgery are typical types of microsurgery. A versatile training platform can assist microsurgical skills development and accelerate the uptake of robot-assisted microsurgery (RAMS). However, the currently available platforms are mainly designed for macro-scale minimally invasive surgery. There is a need to develop a dedicated microsurgical robot research platform for both research and clinical training.

Methods

A microsurgical robot research platform (MRRP) is introduced in this paper. The hardware system includes a slave robot with bimanual manipulators, two master controllers and a vision system. It is flexible to support multiple microsurgical tools. The software architecture is developed based on the robot operating system, which is extensible at high-level control. The selection of master–slave mapping strategy was explored, while comparisons were made between different interfaces.

Results

Experimental verification was conducted based on two microsurgical tasks for training evaluation, i.e. trajectory following and targeting. User study results indicated that the proposed hybrid interface is more effective than the traditional approach in terms of frequency of clutching, task completion time and ease of control.

Conclusion

Results indicated that the MRRP can be utilized for microsurgical skills training, since motion kinematic data and vision data can provide objective means of verification and scoring. The proposed system can further be used for verifying high-level control algorithms and task automation for RAMS research.

Prospective Validation of Facial Nerve Monitoring to Prevent Nerve Damage During Robotic Drilling

Facial nerve damage has a detrimental effect on a patient's life, therefore safety mechanisms to ensure its preservation are essential during lateral skull base surgery. During robotic cochlear implantation a trajectory passing the facial nerve at <0.5 mm is needed. Recently a stimulation probe and nerve monitoring approach were developed and introduced clinically, however for patient safety no trajectory was drilled closer than 0.4 mm. Here we assess the performance of the nerve monitoring system at closer distances. In a sheep model eight trajectories were drilled to test the setup followed by 12 trajectories during which the ENT surgeon relied solely on the nerve monitoring system and aborted the robotic drilling process if intraoperative nerve monitoring alerted of a distance <0.1 mm. Microcomputed tomography images and histopathology showed prospective use of the technology prevented facial nerve damage. Facial nerve monitoring integrated in a robotic system supports the surgeon's ability to proactively avoid damage to the facial nerve during robotic drilling in the mastoid.

Robotic middle ear access for cochlear implantation: First in man

To demonstrate the feasibility of robotic middle ear access in a clinical setting, nine adult patients with severe-to-profound hearing loss indicated for cochlear implantation were included in this clinical trial. A keyhole access tunnel to the tympanic cavity and targeting the round window was planned based on preoperatively acquired computed tomography image data and robotically drilled to the level of the facial recess. Intraoperative imaging was performed to confirm sufficient distance of the drilling trajectory to relevant anatomy. Robotic drilling continued toward the round window. The cochlear access was manually created by the surgeon. Electrode arrays were inserted through the keyhole tunnel under microscopic supervision via a tympanomeatal flap. All patients were successfully implanted with a cochlear implant. In 9 of 9 patients the robotic drilling was planned and performed to the level of the facial recess. In 3 patients, the procedure was reverted to a conventional approach for safety reasons. No change in facial nerve function compared to baseline measurements was observed. Robotic keyhole access for cochlear implantation is feasible. Further improvements to workflow complexity, duration of surgery, and usability including safety assessments are required to enable wider adoption of the procedure.

Electrical Impedance to Assess Facial Nerve Proximity During Robotic Cochlear Implantation

Reported studies pertaining to needle guidance suggest that tissue impedance available from neuromonitoring systems can be used to discriminate nerve tissue proximity. In this pilot study, the existence of a relationship between intraoperative electrical impedance and tissue density, estimated from computer tomography (CT) images, is evaluated in the mastoid bone of in vivo sheep. In five subjects, nine trajectories were drilled using an image-guided surgical robot. Per trajectory, five measurement points near the facial nerve were accessed and electrical impedance was measured (≤1 KHz) using a multipolar electrode probe. Micro-CT was used postoperatively to measure the distances from the drilled trajectories to the facial nerve. Tissue density was determined from coregistered preoperative CT images and, following sensitivity field modeling of the measuring tip, tissue resistivity was calculated. The relationship between impedance and density was determined for 29 trajectories passing or intersecting the facial nerve. A monotonic decrease in impedance magnitude was observed in all trajectories with a drill axis intersecting the facial nerve. Mean tissue densities intersecting with the facial nerve (971-1161 HU) were different (p <0.01) from those along safe trajectories passing the nerve (1194-1449 HU). However, mean resistivity values of trajectories intersecting the facial nerve (14-24 Ωm) were similar to those of safe passing trajectories (17-23 Ωm). The determined relationship between tissue density and electrical impedance during neuromonitoring of the facial nerve suggests that impedance spectroscopy may be used to increase the accuracy of tissue discrimination, and ultimately improve nerve safety distance assessment in the future.