This protocol was approved by the local Ethics Committee in accordance with the Helsinki Declaration (Ruhr-University Bochum: Reg.-No.: 21-7373; Medical University Innsbruck Reg.-No.: 1060/2021). Informed consent was obtained from all participants.
1. Preparation for the surgery
<ol>
	<li>Make sure to obtain audiological testing reports, including pure-tone audiometry, objective testing (e.g., brainstem evoked response audiometry, speech testing), and vestibular diagnostics (e.g., video head impulse test or caloric testing). Obtain radiological imaging reports, including high-resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) of the skull base, as preparation and indication for surgery. 
	NOTE: MRI is required to secure the presence of the vestibulocochlear nerve and the patency of the cochlea. In the HRCT, anatomic variances (e.g., of the facial nerve) or malformations may be identified.</li>
	<li>Check the required hardware and software for impedance measurements (i.e., IM software, video recording software, MAESTRO).</li>
	<li>Obtain written informed consent from the patient.</li>
	<li>Perform general anesthesia considering the clinical history and risk factors of the patient as per the decision of the anesthesiologist.</li>
	<li>Position the patient&#39;s head in such a way that the mastoid segment of the facial nerve runs approximately horizontally. Achieve this by reclining the head and slightly positioning it to the opposite side.</li>
	<li>Shave the hair in the retro-auricular region (approximately 3 cm) to avoid the penetration of hair into the situs.</li>
	<li>Install facial nerve monitoring. Insert the monitoring needles into the obicularis oris muscle and the orbicularis oculi muscle. Place the reference electrodes on the thorax or shoulder. Make sure to fix the cables in order not to extract them accidentally during surgery.</li>
	<li>Disinfect the surgical site. Use disinfectant (e.g., Octenisept) according to the clinic&#39;s standard.</li>
	<li>Use sterile foil draping to cover the microscope and the patient. Ensure that the cover is as thin as possible in the area of the planned receiver coil position to avoid connection problems between the transmitting and receiving coil. Do not use hair wraps made of cloth as used in many ORs. Utilize self-sticking foil draping and make sure to avoid multi-layering.</li>
</ol>
2. Surgery
<ol>
	<li>Preparing for the implant
	<ol>
		<li>Mark the position of the processor and the skin incision of approximately 8 cm. Ensure enough space between the auricle and the implant housing.</li>
		<li>Inject local anesthesia (e.g., Ultracain 1% -Suprarenin, Sanofi, Paris, France) in an s-shaped area behind the auricle before skin incision.</li>
		<li>Incise the skin up to the temporal fascia using a scalpel. Dissect the periosteum and display the outer ear canal and Henle&#39;s spine. 
		NOTE: The surgical instruments are variable and not decisive for the presented method. Appropriate surgical instruments can be used to perform the surgical steps.</li>
		<li>Set the wound retractors on the opposite of the planned implant side to avoid later interaction (magnetic attraction/electric interference) with the telemetry coil.</li>
		<li>For cochlear implantation, perform antrotomy, mastoidectomy, and posterior tympanotomy8.</li>
		<li>Expose the dura to the middle cranial fossa as a first landmark using a large cutting burr. 
		NOTE: The size of the burr may vary depending on the surgical site.</li>
		<li>Thin out the posterior canal wall of the outer ear canal with the same burr.</li>
		<li>Expose the short incus process in the antrum and identify the lateral semicircular canal. 
		NOTE: Both antrum and semicircular canal are identified visually during the drilling procedure.</li>
		<li>As a next surgical step, expose the chorda facial angle where the chorda tympani leaves the facial nerve. In this step, use a large diamond burr and drill the bone parallel to the expected facial nerve. 
		NOTE: The size of the diamond burr may vary depending on the surgical site.</li>
		<li>Open the facial recess with a small diamond burr. Leave the facial nerve with thin bony coverage.</li>
		<li>Access the middle ear through posterior tympanotomy.</li>
		<li>Enlarge the posterior tympanotomy caudally until the round window niche is visualized.</li>
		<li>Maximize the posterior tympanotomy for great exposure of the middle ear, optimizing the visualization of the insertion process. Remove the bony overhang of the round window niche using a small diamond burr until the round window membrane may be visualized completely. 
		NOTE: When moving the ossicular chain, a movement of the round window membrane may be seen to clearly identify the round window membrane. Make sure not to touch the membrane with the burr or accidentally open it.</li>
		<li>Before opening the membrane, put some adrenaline (1 mg/mL) in the middle ear and protect it from bone dust with a resorbable sponge (e.g., Spongostan).</li>
	</ol>
	</li>
	<li>Positioning the Implant
	<ol>
		<li>Prepare the implant housing by drilling a bed into the bone in the future position of the receiving coil. Use the implant housing dummy provided by the manufacturer to mark the borders of the implant bed. Avoid slipping of the implant by creating an edge with the rosen burr. Use a diamond burr to smooth the surface. 
		NOTE: The edge of the implant housing prevents the movement of the implant toward the mastoidectomy defect.</li>
		<li>Pack the coil into a sterile sleeve since the coil is placed already at the beginning of the insertion process.</li>
		<li>Position the implant in the drilled implant bed, fix it with sutures, and cover it with the muscle flap.</li>
		<li>Replace the retractors to avoid any magnetic interaction with the stimulating coil.</li>
	</ol>
	</li>
	<li>Implantation and impedance measurement
	<ol>
		<li>Use two computers - one for Maestro and one for IM recordings.</li>
		<li>Start the IM-software.</li>
		<li>Place the telemetry coil above the magnet of the receiving coil. Secure it with a clamp to avoid movements and disconnections.</li>
		<li>Wait for the clinician, engineer, or audiologist to start the software and give feedback about the coupling. Change the position of the receiver coil until a secure connection is achieved.</li>
		<li>Ensure that no bleeding impedes the visualization of the insertion process or enters the perilymph.</li>
		<li>Communicate the visibility of the surgical field on the screens. Make adjustments to the optical focus of the microscope so that the clinician, engineer, or audiologist can follow the insertion process.</li>
		<li>Ensure the facial recess is as dry as possible to avoid early false positive measures.</li>
		<li>Open the round window membrane with a needle.</li>
		<li>Avoid any suction nearby the round window.</li>
		<li>Do not touch the electrode array.</li>
		<li>Communicate the start of insertion to the clinician, engineer, or audiologist so that he/she may adjust the status buttons. Instruct the engineer to mark one status button after the other as the electrode is inserted.</li>
		<li>Insert the first electrode contact into the cochlea. Wait for the feedback of the clinician, engineer, or audiologist and the audio signal to proceed. Apply an audio signal every 10 s to enable a constant and slow insertion speed with an overall insertion time of approximately 2 min.
		<ol>
			<li>For the auditory signal, play a sine wave signal of 500 Hz constant pulsing on and off and repeat it every 10 s using the software Audacity. Do not adjust the timing of the signal and pauses according to the insertion process but keep it constant.</li>
		</ol>
		</li>
		<li>Insert the electrode array slowly to avoid cochlear damage. Advance one electrode contact every 10 s (as guided by the sound signal).</li>
		<li>Inform the clinician, engineer, or audiologist about the progress by clearly communicating the number of contacts inserted so that the clinician, engineer, or audiologist can mark the progress in the software as precisely as possible by pressing the status buttons of the IM tool.</li>
		<li>Instruct the clinician, engineer, or audiologist to mark the number of inserted electrode contacts according to the feedback of the surgeon (Figure 2).</li>
		<li>Continue the measurements until full insertion to observe impedance drops.</li>
		<li>Communicate the surgical steps.</li>
		<li>Store the electrode lead in the mastoid cavity. Make sure to avoid extrusion forces by finding a tension-free position.</li>
	</ol>
	</li>
	<li>End of surgery
	<ol>
		<li>Seal the round window niche with fascia.</li>
		<li>Check the integrity of the implant (impedance telemetry, electrically evoked stapedius reflex thresholds, if applicable, and electrically evoked compound action potentials).</li>
		<li>Close the wound in layers.</li>
		<li>Continue repeated telemetry measurements until the wound is fully closed. Avoid a dislocation of the stimulating coil.</li>
		<li>Check the eardrum and the skin of the outer ear canal for any surgical damage before ending the surgery.</li>
	</ol>
	</li>
</ol>

Real-Time Telemetric Impedance Measurements During Cochlear Implantation

<ol>
	<li>Dalbert, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hearing+preservation+after+cochlear+implantation+may+improve+long-term+word+perception+in+the+electric-only+condition.">Hearing preservation after cochlear implantation may improve long-term word perception in the electric-only condition.</a> Otology &amp; Neurotology. 37 (9), 1314-1319 (2016).</li><li>Thompson, N. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrode+array+type+and+its+impact+on+impedance+fluctuations+and+loss+of+residual+hearing+in+cochlear+implantation.">Electrode array type and its impact on impedance fluctuations and loss of residual hearing in cochlear implantation.</a> Otology &amp; Neurotology. 41 (2), 186-191 (2020).</li><li>Aebischer, P., Meyer, S., Caversaccio, M., Wimmer, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoperative+impedance-based+estimation+of+cochlear+implant+electrode+array+insertion+depth.">Intraoperative impedance-based estimation of cochlear implant electrode array insertion depth.</a> IEEE Transactions on Biomedical Engineering. 68 (2), 545-555 (2021).</li><li>Choi, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrode+impedance+fluctuations+as+a+biomarker+for+inner+ear+pathology+after+cochlear+implantation.">Electrode impedance fluctuations as a biomarker for inner ear pathology after cochlear implantation.</a> Otology &amp; Neurotology. 38 (10), 1433-1439 (2017).</li><li>Shaul, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+impedance+as+a+biomarker+for+inner+ear+pathology+following+lateral+wall+and+peri-modiolar+cochlear+implantation.">Electrical impedance as a biomarker for inner ear pathology following lateral wall and peri-modiolar cochlear implantation.</a> Otology &amp; Neurotology. 40 (5), e518-e526 (2019).</li><li>Bester, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Four-point+impedance+as+a+biomarker+for+bleeding+during+cochlear+implantation.">Four-point impedance as a biomarker for bleeding during cochlear implantation.</a> Scientific Reports. 10 (1), 2777 (2020).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> MED-EL. , (2023).</li><li>Lenarz, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+implant+-+state+of+the+art.">Cochlear implant - state of the art.</a> GMS Current Topics in Otorhinolaryngology, Head and Neck Surgery. 16, Doc04 (2018).</li><li>Gaw&#281;cki, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robot-assisted+electrode+insertion+in+cochlear+implantation+controlled+by+intraoperative+electrocochleography-A+pilot+study.">Robot-assisted electrode insertion in cochlear implantation controlled by intraoperative electrocochleography-A pilot study.</a> Journal of Clinical Medicine. 11 (23), 7045 (2022).</li><li>Jia, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+and+cellular+mechanisms+of+loss+of+residual+hearing+after+cochlear+implantation.">Molecular and cellular mechanisms of loss of residual hearing after cochlear implantation.</a> Annals of Otology, Rhinology, and Laryngology. 122 (1), 33-39 (2013).</li><li>Eshraghi, A. A., Van de Water, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+implantation+trauma+and+noise-induced+hearing+loss:+Apoptosis+and+therapeutic+strategies.">Cochlear implantation trauma and noise-induced hearing loss: Apoptosis and therapeutic strategies.</a> The Anatomical Record. Part A, Discoveries in Molecular, Cellular, and Evolutionary Biology. 288 (4), 473-481 (2006).</li><li>Van De Water, T. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Caspases,+the+enemy+within,+and+their+role+in+oxidative+stress-induced+apoptosis+of+inner+ear+sensory+cells.">Caspases, the enemy within, and their role in oxidative stress-induced apoptosis of inner ear sensory cells.</a> Otology &amp; Neurotology. 25 (4), 627-632 (2004).</li><li>Roland, P. S., Wright, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surgical+aspects+of+cochlear+implantation:+mechanisms+of+insertional+trauma.">Surgical aspects of cochlear implantation: mechanisms of insertional trauma.</a> Advances in Oto-Rhino-Laryngology. 64, 11-30 (2006).</li><li>Tien, H. -. C., Linthicum, F. H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histopathologic+changes+in+the+vestibule+after+cochlear+implantation.">Histopathologic changes in the vestibule after cochlear implantation.</a> Otolaryngology-- Head and Neck Surgery. 127 (4), 260-264 (2002).</li><li>Lenarz, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relationship+between+intraoperative+electrocochleography+and+hearing+preservation.">Relationship between intraoperative electrocochleography and hearing preservation.</a> Otology &amp; Neurotology. 43 (1), e72-e78 (2022).</li><li>Bester, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrocochleography+triggered+intervention+successfully+preserves+residual+hearing+during+cochlear+implantation:+Results+of+a+randomised+clinical+trial.">Electrocochleography triggered intervention successfully preserves residual hearing during cochlear implantation: Results of a randomised clinical trial.</a> Hearing Research. 426, 108353 (2022).</li><li>O'Leary, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoperative+observational+real-time+electrocochleography+as+a+predictor+of+hearing+loss+after+cochlear+implantation:+3+and+12+month+outcomes.">Intraoperative observational real-time electrocochleography as a predictor of hearing loss after cochlear implantation: 3 and 12 month outcomes.</a> Otology &amp; Neurotology. 41 (9), 1222-1229 (2020).</li><li>Dong, Y., Briaire, J. J., Siebrecht, M., Stronks, H. C., Frijns, J. H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+translocation+of+cochlear+implant+electrode+arrays+by+intracochlear+impedance+measurements.">Detection of translocation of cochlear implant electrode arrays by intracochlear impedance measurements.</a> Ear and Hearing. 42 (5), 1397-1404 (2021).</li><li>Giardina, C. K., Krause, E. S., Koka, K., Fitzpatrick, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impedance+measures+during+in+vitro+cochlear+implantation+predict+array+positioning.">Impedance measures during in vitro cochlear implantation predict array positioning.</a> IEEE Transactions on Biomedical Engineering. 65 (2), 327-335 (2018).</li><li>Sijgers, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predicting+cochlear+implant+electrode+placement+using+monopolar,+three-point+and+four-point+impedance+measurements.">Predicting cochlear implant electrode placement using monopolar, three-point and four-point impedance measurements.</a> IEEE Transactions on Biomedical Engineering. 69 (8), 2533-2544 (2022).</li><li>Salkim, E., Zamani, M., Jiang, D., Saeed, S. R., Demosthenous, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insertion+guidance+based+on+impedance+measurements+of+a+cochlear+electrode+array.">Insertion guidance based on impedance measurements of a cochlear electrode array.</a> Frontiers in Computational Neuroscience. 16, 862126 (2022).</li></ol>

The authors have no conflicts of interest to declare.

Repeated impedance measurements are a promising approach to gain real-time feedback from the cochlea during the insertion process. They indicate which electrode contacts are positioned inside the perilymph or not. With the here presented novel method for flexible lateral wall electrodes (MED-EL, Innsbruck, Austria)7, impedances may be measured in real-time during cochlear implantation utilizing the inserting electrode array.&#160;However, for reliable measurements, a standardized procedure is cruc...

Preserving residual hearing is an increasing topic of interest in cochlear implantation (CI) surgery, and the indication has changed towards candidates with functional residual hearing. Thus, measurements that may objectify the position of the electrode array and the resulting potential intracochlear damage during surgery are becoming increasingly important. CI-users with successfully preserved hearing have been shown to have superior hearing performance with the implant after surgery, even when stimulated electrically-only1. Some of them may additionally benefit from acoustic stimulation (electro-acoustic stimulation; EAS). Perioperative hearing loss is assumed to result from traumatic insertion. To improve insights into these intraoperative changes and to establish monitoring algorithms, objective measures, and biomarkers are needed. In this context, impedance telemetry may be of interest2,3. Increased impedances have been shown to be associated with hearing loss or vertigo4,5. Further evidence associates blood inclusions during the insertion of the electrode array6. Nevertheless, further investigation is necessary to explore to what extent impedances may be associated with surgical trauma and postoperative performance. For this purpose, repeated intraoperative impedance measurements are a promising approach. On the other hand, impedances deliver additional information about the electrode&#39;s position. High impedances indicate poor conductivity and thus indicate a contact position outside the cochlea, whereas low impedances (impedance drops) may indicate already inserted contacts. Thus, impedances may be used as an objective feedback mechanism for the status of the electrode array insertion. In this video, we present our setup and first experiences with this novel approach of repeated impedance measurements using flexible lateral wall electrodes from the cochlear implant manufacturer MED-EL (Innsbruck, Austria)7.
A study software designed for research purposes is used to perform repeated impedance measurements. In this study, the software is verified according to the MED-EL internal procedures for research-use-only devices. During surgery, only the most recent impedance telemetry data is shown. Figure 1 shows the electronic measurement setup. The Insertion Monitoring (IM) software has buttons to mark the number of electrode contacts currently inserted (red/green highlighting). After starting, the software measures impedances repeatedly in cycles. The IM software shows a table of the measured impedance results and impedances across time in 12 plots. Furthermore, it shows warnings in case of connection problems. A video recording Software (Open Broadcaster Software [OBS]) is used to record (i) the video of electrode insertion (microscope attached, e.g., via HDMI), (ii) a video of the IM software user interface, including all user interactions and (iii) sound. An audio editor software (Audacity) is used to regularly play a sound during the insertion of the electrode array to facilitate a slow insertion.

<table><tbody><tr><td>Audacity</td><td>Open source</td><td>https://www.audacityteam.org/</td><td>Audio editor software</td></tr><tr><td>Coil cable</td><td>Any appropriate brand</td><td></td><td>Implant interface</td></tr><tr><td>Computer</td><td>Any appropriate brand</td><td></td><td></td></tr><tr><td>Electrode array</td><td>MED-EL</td><td>https://s3.medel.com/pdf/21617.pdf</td><td>Standard, FlexSoft, Flex28</td></tr><tr><td>IM Software</td><td>MED-EL</td><td>https://www.medel.com/</td><td></td></tr><tr><td>Maestro</td><td>MED-EL</td><td>https://www.medel.com/</td><td></td></tr><tr><td>MAX Interface USB</td><td>Any appropriate brand</td><td></td><td>Interface connection</td></tr><tr><td>Octenisept</td><td>SCH&amp;Uuml;LKE &amp;amp; MAYR GmbH</td><td>N/A</td><td></td></tr><tr><td>Open Broadcaster Software</td><td>Open source</td><td>https://obsproject.com/</td><td>Video recording software</td></tr><tr><td>Spongostan</td><td>&amp;nbsp;Ethicon</td><td>N/A</td><td>Resorbable sponge</td></tr><tr><td>Ultracain 1%</td><td>&amp;nbsp;Suprarenin, Sanofi</td><td>N/A</td><td>Local anesthesia</td></tr></tbody></table>

performing repeated intraoperative impedance telemetry measurements during cochlear implantation

Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the electrode's and implant's function. In the postoperative setting, the analysis of impedance changes enables the identification of scarring or inflammation processes around the electrode. Recent studies report associations between impedance telemetry and the site of stimulation. Consequently, repeated impedance measurements during cochlear implant electrode insertion may enable objective feedback on whether the electrode is positioned inside the perilymph or outside the inner ear. With the presented novel method, impedances can be measured in real-time during cochlear implantation. This protocol systematically explains how to perform repeated impedance recordings during CI surgery. These repeated measurements are challenging since they depend on multiple intraoperative methodological factors starting with the draping of the patient. Thus, for successful recordings, a standardized procedure is mandatory. In this article, we comprehensively illustrate the system setup and procedure of performing intraoperative measurements during CI surgery.

For repeated impedance measurements during cochlear implantation, a standardized procedure is mandatory to achieve the highest possible reproducibility. The major aspects that have been considered to play an important role are the video quality as well as the insertion angle. Both may impede the visualization of the electrode contacts entering the round window and thus, the interpretation of the video for future analyses. Further, the placement of the receiver coil is crucial to prevent interruptions during insertion and...

Watch this Scientific Journal Video about Performing Repeated Intraoperative Impedance Telemetry Measurements during Cochlear Implantation at JoVE.com

Author Spotlight: Advancements in Impedance Monitoring for Cochlear Implant Surgery

Here we present a protocol to conduct repeated impedance telemetry measurements during cochlear implantation (CI). They may allow conclusions on the electrode's and implant's function. Repeated impedance measurements enable objective feedback on whether the electrode is positioned inside the perilymph or outside the inner ear.

Performing Repeated Intraoperative Impedance Telemetry Measurements during Cochlear Implantation

Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the ...

performing-repeated-intraoperative-impedance-telemetry-measurements

Research

JoVE Journal

Medicine

1.1K Views.  Ruhr-University Bochum, St. Elisabeth-Hospital Bochum. We werken met impedanties, omdat deze een objectieve feedback geven over of de elektrode-array van het cochleaire implantaat zich buiten of in het slakkenhuis bevindt. Hoge impedanties duiden of suggereren een slechte geleidbaarheid, en dus een elektrodecontact buiten het slakkenhuis. Terwijl lagere impedanties suggereren dat de geleidbaarheid beter is, en dus het elektrodecontact al is ingebracht.En deze informatie kan worden gebruikt om de blootstelling aan straling te verminderen in...

Video: Auteur in de schijnwerpers: Vooruitgang in impedantiebewaking voor cochleaire implantaatchirurgie

Techniques for Processing Eyes Implanted with a Retinal Prosthesis for Localized Histopathological Analysis: Part 2 Epiretinal Implants with Retinal Tacks

Retinal prostheses for the treatment of certain forms of blindness are gaining traction in clinical trials around the world with commercial devices currently entering the market. In order to evaluate the safety of these devices, in preclinical studies, reliable techniques are needed. However, the hard metal components utilised in some retinal implants are not compatible with traditional histological processes, particularly in consideration for the delicate nature of the surrounding tissue. Here we describe techniques for assessing the health of the eye directly adjacent to a retinal implant secured epiretinally with a metal tack.
Retinal prostheses feature electrode arrays in contact with eye tissue. The most commonly used location for implantation is the epiretinal location (posterior chamber of the eye), where the implant is secured to the retina with a metal tack that penetrates all the layers of the eye. Previous methods have not been able to assess the proximal ocular tissue with the tack in situ, due to the inability of traditional histological techniques to cut metal objects. Consequently, it has been difficult to assess localized damage, if present, caused by tack insertion.
Therefore, we developed a technique for visualizing the tissue around a retinal tack and implant. We have modified an established technique, used for processing and visualizing hard bony tissue around a cochlear implant, for the soft delicate tissues of the eye. We orientated and embedded the fixed eye tissue, including the implant and retinal tack, in epoxy resin, to stabilise and protect the structure of the sample. Embedded samples were then ground, polished, stained, and imaged under various magnifications at incremental depths through the sample. This technique allowed the reliable assessment of eye tissue integrity and cytoarchitecture adjacent to the metal tack.

Here we describe histological techniques for visualising ocular tissue directly adjacent to a metal epiretinal tack and retinal prosthesis.

Retinal prostheses for the treatment of certain forms of blindness are gaining traction in clinical trials around the world with commercial devices ...

Intrauterine Telemetry to Measure Mouse Contractile Pressure In Vivo

A complex integration of molecular and electrical signals is needed to transform a quiescent uterus into a contractile organ at the end of pregnancy. Despite the discovery of key regulators of uterine contractility, this process is still not fully understood. Transgenic mice provide an ideal model in which to study parturition. Previously, the only method to study uterine contractility in the mouse was ex vivo isometric tension recordings, which are suboptimal for several reasons. The uterus must be removed from its physiological environment, a limited time course of investigation is possible, and the mice must be sacrificed. The recent development of radiometric telemetry has allowed for longitudinal, real-time measurements of in vivo intrauterine pressure in mice. Here, the implantation of an intrauterine telemeter to measure pressure changes in the mouse uterus from mid-pregnancy until delivery is described. By comparing differences in pressures between wild type and transgenic mice, the physiological impact of a gene of interest can be elucidated. This technique should expedite the development of therapeutics used to treat myometrial disorders during pregnancy, including preterm labor.

Intrauterine Telemetry to Measure Mouse Contractile Pressure In Vivo

This manuscript provides a protocol for implanting telemeters in the mouse for the purpose of measuring intrauterine pressures during pregnancy.

A complex integration of molecular and electrical signals is needed to transform a quiescent uterus into a contractile organ at the end of pregnancy. ...

Long-term Blood Pressure Measurement in Freely Moving Mice Using Telemetry

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. Indeed, research focusing on the discovery of new potential therapeutic targets using genetically altered mice requires a reliable, long-term assessment of the systemic arterial pressure variation. Currently, the gold standard for obtaining long-term measurements of blood pressure in ambulatory mice uses implantable radio-transmitters, which require&#160;artery cannulation. This technique eliminates the need for tethering, restraining, or anesthetizing the animals which introduce stress and artifacts during data sampling. However, arterial blood pressure monitoring in mice via catheterization can be rather challenging due to the small size of the arteries. Here we present a step-by-step guide to illustrate the crucial key passages for a successful subcutaneous implantation of radio-transmitters and carotid artery cannulation in mice. We also include examples of long-term blood pressure activity taken from freely moving mice after a period of post-surgery recovery. Following this procedure will allow reliable direct blood pressure recordings from multiple animals simultaneously.

The goal of this protocol is to assess systemic blood pressure in conscious freely moving mice using implantable radio-telemetry devices.

During the development of new vasoactive agents, arterial blood pressure monitoring is crucial for evaluating the efficacy of the new proposed drugs. ...

Cochlear Implantation in the Guinea Pig

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception outcomes, candidacy criteria have been expanded over the last few decades. This includes patients with substantial residual hearing that benefit from electrical and acoustical stimulation of the same ear, which makes hearing preservation during cochlear implantation an important issue. Electrode impedances and the related issue of energy consumption is another major research field, as progress in this area could pave the way for fully implantable auditory prostheses. To address these issues in a systematic way, adequate animal models are essential. Therefore, the goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address various research questions. Due to its large tympanic bulla, which allows easy surgical access to the inner ear, as well as its hearing range which is relatively similar to the hearing range of humans, the guinea pig is a commonly used species in auditory research. Cochlear implantation in the guinea pig is performed via a retroauricular approach. Through the bullostomy a cochleostomy is drilled and the cochlear implant electrode is inserted into the scala tympani. This electrode can then be used for electrical stimulation, determination of electrode impedances and the measurement of compound action potentials of the auditory nerve. In addition to these applications, cochlear implant electrodes can also be used as drug delivery devices, if a topical delivery of pharmaceutical agents to the cells or fluids of the inner ear is intended.

The goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address a multitude of research questions. Potential applications include the evaluation of pharmaceutical interventions or electrical stimulation for beneficial effects on hearing thresholds or electrode impedances.

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception ...

Performing Intracochlear Electrocochleography During Cochlear Implantation

Electrocochleography (ECochG) measures inner ear potentials generated in response to acoustic stimulation of the ear. These potentials reflect the residual function of the cochlea. In cochlear implant candidates with residual hearing, the implant electrode can directly measure ECochG responses during the implantation process. Various authors have described the ability to monitor the inner ear function by continuous ECochG measurements during the surgery. The measurement of ECochG signals during surgery is not trivial. There are no interpretable signals in up to 20% of cases. For a successful recording, a standardized procedure is recommended to achieve the highest measurement reliability and avoid possible pitfalls. Therefore, seamless collaboration between the CI surgeon and CI technician is key. This video consists of an overview of the system setup and a stepwise procedure of performing intracochlear ECochG measurements during CI surgery. It shows the surgeon's and the CI technician's roles in the process, and how a smooth collaboration between the two is made possible.

Electrocochleography (ECochG) measures inner ear potentials generated in response to acoustic stimulation. In cochlear implant (CI) candidates, such inner ear potentials can be measured directly with the implant electrodes. In this video, we systematically explain how to perform ECochG recordings during CI surgery.

Electrocochleography (ECochG) measures inner ear potentials generated in response to acoustic stimulation of the ear. These potentials reflect the ...

Robotic Cochlear Implantation for Direct Cochlear Access

Robot-assisted systems offer great potential for gentler and more precise cochlear implantation. In this article, we provide a comprehensive overview of the clinical workflow for robotic cochlear implantation using a robotic system specifically developed for a minimally invasive, direct cochlear access. The clinical workflow involves experts from various disciplines and requires training to ensure a smooth and safe procedure. The protocol briefly summarizes the history of robotic cochlear implantation. The clinical sequence is explained in detail, beginning with the assessment of patient eligibility and covering surgical preparation, preoperative planning with the special planning software, drilling of the middle ear access, intraoperative imaging to confirm the trajectory, milling of the inner ear access, insertion of the electrode array, and implant management. The steps that require special attention are discussed. As an example, the postoperative outcome of robotic cochlear implantation in a patient with advanced otosclerosis is presented. Finally, the procedure is discussed in the context of the authors' experience.

Robotic cochlear implantation is a procedure for minimally invasive inner ear access. Compared to conventional surgery, robotic cochlear implantation involves additional steps that need to be carried out in the operating room. In this article we give a description of the procedure and highlight the important aspects of robotic cochlear implantation.

Robot-assisted systems offer great potential for gentler and more precise cochlear implantation. In this article, we provide a comprehensive overview of ...

The Miniature Pig: A Large Animal Model for Cochlear Implant Research

Cochlear implants (CI) are the most effective method to treat people with severe-to-profound sensorineural hearing loss. Although CIs are used worldwide, no standard model exists for investigating the electrophysiology and histopathology in patients or animal models with a CI or for evaluating new models of electrode arrays. A large animal model with cochlea characteristics similar to those of humans may provide a research and evaluation platform for advanced and modified arrays before their use in humans. 
To this end, we established standard CI methods with Bama mini-pigs, whose inner ear anatomy is highly similar to that of humans. Arrays designed for human use were implanted into the mini pig cochlea through a round window membrane, and a surgical approach followed that was similar to that used for human CI recipients. Array insertion was followed by evoked compound action potential (ECAP) measurements to evaluate the function of the auditory nerve. This study describes the preparation of the animal, surgical steps, array insertion, and intraoperative electrophysiological measurements. 
The results indicated that the same CI used for humans could be easily implanted in mini-pigs via a standardized surgical approach and yielded similar electrophysiological outcomes as measured in human CI recipients. Mini-pigs could be a valuable animal model to provide initial evidence of the safety and potential performance of novel electrode arrays and surgical approaches before applying them to human beings.

Miniature pigs (mini-pigs) are an ideal large animal model for research into cochlear implants. Cochlear implantation surgery in mini-pigs can be utilized to provide initial evidence of the safety and potential performance of novel electrode arrays and surgical approaches in a living system similar to human beings.

Cochlear implants (CI) are the most effective method to treat people with severe-to-profound sensorineural hearing loss. Although CIs are used worldwide, ...

A State-of-the-Art Method for Preserving Residual Hearing During Cochlear Implant Surgery

The developments in surgical techniques and cochlear implant (CI) electrode design have expanded the indications for CI treatment. Currently, patients with high-frequency hearing loss may benefit from CIs when low-frequency residual hearing can be preserved, as this enables combined electric-acoustic stimulation (EAS). The possible benefits of EAS include, for example, improved sound quality, music perception, and speech intelligibility in noise.
The risks of inner ear trauma and a deterioration or even complete loss of residual hearing vary according to the surgical technique and the type of electrode array used. Short, lateral-wall electrodes with shallower angular insertion depths have demonstrated higher rates of hearing preservation than longer electrodes. The very slow insertion of the electrode array through the round window of the cochlea contributes to insertion atraumaticity and, thus, may lead to favorable hearing preservation results. However, residual hearing can be lost even after an atraumatic insertion. 
Electrocochleography (ECochG) can be used to monitor inner ear hair cell function during the insertion of the electrode. Several investigators have demonstrated that the ECochG responses during surgery may predict postoperative hearing preservation results. 
In a recent study, we correlated the patients' subjective hearing perception with simultaneously recorded intracochlear ECochG responses during the insertion. This is the first report evaluating the association between intraoperative ECochG responses and hearing perception in a subject undergoing cochlear implantation under local anesthesia without sedation. The combination of intraoperative ECochG responses with the patient's real-time feedback to sound stimuli has excellent sensitivity for the intraoperative monitoring of cochlear function. This paper presents a state-of-the-art method for the preservation of residual hearing during CI surgery. We describe this treatment procedure with the special consideration of performing the surgery under local anesthesia, which makes it feasible for monitoring the patient's hearing during the insertion of the electrode array.

The preservation of cochlear structures and possible residual hearing is one important factor to consider during cochlear implant surgery. Here, we present a state-of-the-art method for preserving residual hearing during cochlear implant surgery under local anesthesia.

The developments in surgical techniques and cochlear implant (CI) electrode design have expanded the indications for CI treatment. Currently, patients ...

Enhancing Electrode Location Assessment in Cochlear Implantation via Computed Tomography Image Fusion

This study aimed to determine whether fusing pre-&#160;and post-operative computed tomography (CT) images could help in assessing electrode placement and center frequency (CF) in cochlear implant (CI) recipients. A secondary objective was to compare automatic fusion with manual methods for measuring cochlear parameters. The study included twenty ears with CIs that underwent both pre-&#160;and post-operative CT scans. Manual measurements of cochlear parameters were initially taken from the post-operative CT images, followed by automatic detection using fused pre-&#160;and post-operative CT images with otological software (OTOPLAN). Angular insertion depth (AID) and CF of each electrode contact were calculated using both methods, and error differences were assessed. The analysis showed significant differences between the two methods for cochlear width (B-value) and cochlear duct length (CDL); however, these differences were not clinically significant. Furthermore, there was no statistically significant difference in cochlear diameter (A-value). The mean differences were 0.04 mm for the A-value, 0.21 mm for the B-value, and 0.73 mm for the CDL. The comparison of AID and CF revealed non-significant differences between manual and automatic fusion methods across all electrode contacts, except for electrode number five. According to this study, fusing pre-&#160;and post-operative CT images can be used to determine electrode positions in CI recipients. Automatic fused images can potentially measure cochlear parameters, AID, and CF with reduced human interference. Therefore, this method may serve as another basis for creating anatomy-based fitting.

This protocol demonstrates a method for fusing pre-operative and post-operative computed tomography images for cochlear implant recipients. The approach may enhance the measurement accuracy of insertion depth and the center frequency of electrode array contacts. Additionally, this method has potential applications in anatomy-based fitting, an emerging area within the cochlear implant field.

This study aimed to determine whether fusing pre-&#160;and post-operative computed tomography (CT) images could help in assessing electrode placement and ...

Neuroscience

Measuring Electrically Evoked Stapedius Reflex for Cochlear Implant Fitting

Electrically Evoked Stapedius Reflex Measurements in Cochlear Implantation and Its Application in the Postoperative Fitting Process

Measuring the electrically evoked stapedius reflex during the fitting of cochlear implants (CIs) provides a reliable estimation of maximum comfort levels, resulting in the programming of the CI with high hearing comfort and good speech understanding. Detection of the stapedius reflex and the required stimulation level on each implant channel is already being performed during surgery, whereby intraoperative stapedius reflexes are observed through the surgical microscope. Intraoperative stapedius reflex detection is both an indicator that the auditory nerve is responding to electrical stimulation up to the brainstem and a test for the ability to perform postoperative stapedius reflex measurements. Postoperative stapedius reflex thresholds can be used to estimate upper stimulation levels in the CI fitting process. In particular, in children or patients unable to provide feedback on loudness perception, this method avoids inadequate stimulation with the CI, which can result in poor hearing performance. In addition, overstimulation can be avoided, which could even lead to refusal to use the device.

The present protocol describes the measurement of the electrically evoked stapedius reflex (eSR) via cochlear implant (CI). Two applications are discussed: intraoperative detection of eSR for verification of the coupling between the cochlear implant and the auditory nerve and postoperative measurement of eSR thresholds (eSRT) for CI fitting.

Measuring the electrically evoked stapedius reflex during the fitting of cochlear implants (CIs) provides a reliable estimation of maximum comfort levels, ...

Performing Repeated Intraoperative Impedance Telemetry Measurements during Cochlear Implantation

Samenvatting

Meer video's verkennen