Name: performing intracochlear electrocochleography during cochlear implantation
Uploaded: 2022-03-08T13:00:00.000+00:00
Duration: 9 min 10 s
Description: Watch this Scientific Journal Video about Performing Intracochlear Electrocochleography During Cochlear Implantation at JoVE.com

The authors would like to thank Marek Polak and his team from MED-EL, Austria, for their support. This study was partly funded by the Department of Otorhinolaryngology, Head and Neck Surgery at the Inselspital Bern, the Clinical trials unit (CTU) research grant, and the MED-EL company. Georgios Mantokoudis was supported by the Swiss National Science Foundation #320030_173081.

This study was performed in compliance with institutional guidelines (Basec ID 2019-01578). The video shows the recording of ECochG measurements with a MED-EL implant. The required hardware, software, system setup, and intraoperative implementation may vary depending on the manufacturer. However, the chronological sequence and measurement steps are independent of the brand. If necessary, additional information will be provided for the Advanced Bionics (AB) and Cochlear systems. The description of the theater is given from the surgeon&#39;s point of view.
1. Before the surgery
<ol>
	<li>Indication
	<ol>
		<li>Perform ECochG measurements in patients where hearing preservation is the goal.</li>
		<li>Our protocol is as follows: Stimulate with a 500 Hz pure tone, 30 dB above the hearing threshold with a minimum level of 100 dB HL and a maximum level of 120 dB HL. Ensure the following: an acoustic stimulus of a duration of 8 ms, the measurement window of 10 ms length for recording the ECochG potentials beginning 1 ms after the acoustic stimulus, and the measurement repetition set to 100 iterations. 
		NOTE: Depending on the preoperative hearing test, other frequencies can also be used (i.e., 250 and 1000 Hz)8,14. Stimuli below 1000 Hz are preferred to avoid crossing the corresponding tonotopic intracochlear frequency region (resulting in a non-traumatic drop of the signal amplitude). More recent software versions allow the synchronous real-time measurement of different frequencies15.</li>
	</ol>
	</li>
	<li>Clean the patient&#39;s ear canal thoroughly. Check the eardrum. 
	NOTE: Obstructing ear wax, liquids or debris might affect the sound transmission during ECochG10. The eardrum must be intact with no sign of infection.</li>
	<li>Evaluate the preoperative administration of steroids. At our institution, we&#160;use methylprednisolone 125 mg, intravenously administered, 6 h before the start of surgery. 
	NOTE: Dexamethasone can also be used as part of the standard clinical practice, either the day before or at the induction of anesthesia16,17.</li>
</ol>
2. Preparation in the theater
<ol>
	<li>Check the required hardware and software for ECochG measurements. See Table 1 for the hardware and software requirements for different manufacturers.</li>
	<li>Have the engineer check the seamless functioning of hard- and software. 
	NOTE: The following room setup is recommended: the engineer positions him/herself opposite the surgeon. In this way, he/she can monitor the measurement process well and give direct feedback to the surgeon (Figure 1).</li>
	<li>Position the patient&#39;s head so that the mastoid segment of the facial nerve runs approximately horizontal. 
	NOTE: The neck is thereby slightly retracted and the upper body in a reverse Trendelenburg position. Furthermore, the neck is slightly tilted away, and the head rotated to the not-operated side to give maximal access to the surgeon.</li>
	<li>Shave the hair in the retro-auricular region (approximately 3 cm).</li>
	<li>Install the facial nerve monitoring.</li>
	<li>Disinfect the surgical site and cover it with sterile drapes. 
	NOTE: It is important that the auditory canal is included in this step. In addition, it is important that the cover must be as thin as possible in the area of the planned receiver coil position (to avoid connection problems between the transmitting and receiving coil). For this reason, choose thin drapes and place the fluid bag as low as possible (Figure 2).</li>
</ol>
3. Getting started
<ol>
	<li>Mark the position of the processor, the implant, and the skin incision.</li>
	<li>Inject the local anesthesia (mepivacaine with 1:200,000 epinephrine).</li>
	<li>Check the ear canal and clean traces of disinfectant solution. Check the eardrum.</li>
	<li>Insert the sterile eartip, connected to a sterile sound tube, deep into the external canal. 
	NOTE: This step is important because displacement of the eartip leads to significant drops in the presented sound pressure10.</li>
	<li>Place a large swab into the concha of the operated ear and tilt the ear forward. Fix the earlobe (including the eartip, soundtube, and swab) with a transparent adhesive foil. 
	NOTE: This technique avoids strong buckling of the eartip and sound tube as well as eartip displacement, which can lead to attenuation of the presented signal. Furthermore, irrigation fluid and blood can no longer enter the external auditory canal.</li>
	<li>Before connecting the sound tube to the non-sterile transducer, have the engineer check the functioning of the acoustic output.</li>
	<li>Connect the sound tube to the non-sterile sound transducer handled by the engineer. Cover the non-sterile part with a sterile blanket. Ensure that the sound transmission parts are tension-free.</li>
</ol>
4. Implant surgery
<ol>
	<li>Incise the skin up to the temporalis fascia. Make an offset incision (5-10 mm anteriorly) of the periosteum in a lazy S fashion18. Dissect the periosteum off the bone and display the bony ear canal and Henle spine for orientation. Check the thickness of the soft tissue above the future receiving coil and thin it out according to the manufacturer&#39;s recommendations as needed. 
	NOTE: The incision should be large enough to show the mastoid plane and accommodate the implant housing in a tight subperiosteal plane under the temporalis muscle.</li>
	<li>Harvest a 5 mm x 5 mm large piece of dermal fat to seal the posterior tympanotomy and 2-3 small pieces (1 mm x 1 mm) of periosteum to seal the entrance point of the electrode into the inner ear later on.</li>
	<li>Place the wound retractors. 
	NOTE: Ensure that the retractor does not compromise the soft tissue of the auditory canal. This can cause the inserted eartip to dislodge, which leads to attenuation of the presented signal.</li>
	<li>Perform the surgical access to the middle and inner ear.
	<ol>
		<li>Drill the mastoid bone with an overhang posteriorly to accommodate the electrode within the mastoid later on. During this step, harvest some bone pat&#233;.</li>
		<li>Display the lateral skull base cranially and drill out the mastoid bone evenly with the deepest point of dissection above the antrum.</li>
		<li>Display the antrum with the lateral semicircular canal.</li>
		<li>Thin out the bony ear canal evenly until the short process of the incus is seen.</li>
		<li>Drill the bone caudal to the lateral semicircular canal toward the mastoid tip, parallel to the expected facial nerve. Display the nerve and, if possible, the chorda tympani.</li>
		<li>Access the middle ear via a posterior tympanotomy. Drill near the buttress between the facial nerve and the chorda until the middle ear space is reached.</li>
		<li>Check the position of visible middle ear structures (e.g., the stapedius tendon). Ensure that the ossicular chain remains intact.</li>
		<li>Enlarge the posterior tympanotomy caudally until the round window niche is visualized.</li>
		<li>Reduce the bony lip of the round window niche until the round window is seen completely.</li>
	</ol>
	</li>
	<li>Drill an anterior step in the area of the planned implant housing position. Check that the step is of sufficient size with the help of an implant bed indicator. Drill a channel for the electrode.</li>
	<li>Rinse the surgical site thoroughly and perform meticulous hemostasis. Finally, place a 1 cm x 1 cm piece of gelatin sponge in the antrum. 
	NOTE: In addition to surgical management, it is important that the anesthesiologist monitors blood pressure throughout the procedure (to minimize bleeding; if possible, the systolic blood pressure should be below 100 mg Hg). The gelatin sponge will stop drops of blood or irrigation fluid from running into the middle ear.</li>
	<li>Change gloves and wait for the engineer to pass the non-sterile stimulating coil to the scrub nurse. Instruct the nurse to pack the coil into a sterile sleeve.</li>
</ol>
5. Insertion and ECochG measurements
NOTE: At this point, the communication between the surgeon and the engineer is crucial.
<ol>
	<li>Rinse the implant and insert it in the previously created subperiosteal pocket. Ensure a stable implant position against the drilled bony step. Depending on the manufacturer, place the separate reference electrode in an anterior, submuscular pocket. Check that ground and reference electrodes of the implant (on top of the implant, right below the coil) are well covered with soft tissue.</li>
	<li>Place the stimulating coil above the magnet of the receiving coil. Rotate the transmitting coil 180&#176; back and forth to align the MR-compatible magnets. Wait for the engineer to measure the wireless connection (coupling check). When the connection is 100%, fix the transmitting coil with an adhesive foil to ensure that the coils do not displace during implantation.</li>
	<li>Inspect the middle ear again. Ensure that the middle ear space is air-filled. Carefully open the round window membrane. Ensure that the opening is sufficiently large and do not accidentally suction the perilymph.</li>
	<li>Insert the first electrode into the round window. If applicable and depending on the manufacturer, condition the electrode. Now, wait for the engineer to perform an impedance check. 
	NOTE: Impedance values are manufacturer-specific.As a rough guide, the impedance should be below 10 k&#937;.</li>
	<li>Insert the electrode slowly while carefully following hearing preservation techniques19. Keep the technician informed of progress (e.g., markers, number of electrodes in the cochlea) during insertion. Also instruct the technician to record and clearly communicate the ECochG potentials, i) if there is a signal (most commonly a CM signal), ii) how the signal evolves, and iii) if there are abrupt signal changes.
	<ol>
		<li>With a MED-EL implant, perform the stepwise procedure described previously7.
		<ol>
			<li>ith the standard software, use condensation polarity with a recording window of 9.6 ms. Set the measurement delay to 1 ms and perform 100 iterations.</li>
			<li>Insert the electrode slowly and halt the insertion process after every second or third electrode (increase the number of recordings towards the end).</li>
			<li>Perform an ECochG measurement while holding the electrode array in place. Instruct the engineer to communicate as soon as the measurement is complete. Repeat ECochG until a full insertion is reached.</li>
		</ol>
		NOTE:&#160;Since our article&#39;s acceptance, MED-EL has released new software (research software version: Maestro with Dataman Acoustic Stimulator v3.0) allowing continuous intraoperative measurements. In our demonstration video, we use this newer version. With the software update, stepwise electrode insertion is no longer necessary to perform intraoperative ECochG recording.</li>
		<li>With AB or Cochlear implants, record ECochG potentials with alternating polarities while the electrode is moved/inserted8,20. Communicate visible landmarks to the engineer (e.g., first implant marker is reached).</li>
	</ol>
	</li>
	<li>In case of an amplitude loss of the ECochG signal, retract the electrode slightly and repeat the measurement21.</li>
	<li>After full insertion, have the engineer continue to record ECochG. Communicate each surgical step (e.g., sealing of the round window niche).</li>
	<li>Drape the electrode within the mastoid cavity. Seal the round window with small pieces of the previously harvested fat. Stabilize the electrode within the posterior tympanotomy with a larger piece of fascia or periosteum. Embed the electrode in the bony channel with some bone pat&#233;.</li>
	<li>Have the engineer check the integrity of the implant (impedance and electrically evoked compound action potentials). Continue with postinsertion ECochG recordings later.</li>
	<li>Close the wound in layers (periosteal layer, subcutaneous layer, skin).</li>
	<li>Remove the sound tube and eartip; check for possible kinking or dislodgment. Finally, check the eardrum.</li>
</ol>

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The authors declare that they have no conflicts of interest to declare.

ECochG measurements are a promising tool to monitor the inner ear function during implantation. These electrophysiological potentials complement the surgeon&#39;s assessment and haptic perception. However, it should be noted that the measurement is not trivial and has many sources of error. To increase the measurement reliability, a standardized procedure is essential. This is key to an accurate interpretation of the signals.
Good communication between the surgeon and the engineer during the entire intervention is particularly important. In addition, the system setup must ensure unimpeded transmission of the acoustic stimulus and good and stable coupling of the transmitting and receiving coil. In a previous paper, we developed a standardized measurement protocol for ECochG recordings during implant surgery10. So far, applying this protocol, we have recorded 12 intraoperative measurements receiving MED-EL implants.
If the impedance is low, start the ECochG measurement. If the impedance is high, i) rinse the implant pocket with saline solution, ii) make sure that the ground electrode is well covered by soft tissue, iii) make sure the tip of the electrode is in good contact with perilymph fluid. If the impedance stays high, repeat an impedance measure with the second or third electrode or insert the electrode slightly deeper into the cochlea.
If ECochG signal drops occur during electrode insertion (usually measured by the CM amplitude), preliminary evidence suggests that the surgical response may affect the inner ear function. A randomized study showed that when the CM amplitude decreased by 30% or more (related to the initial maximum amplitude), a slight withdrawal of the electrode resulted in a significant improvement of postoperative residual hearing21. However, the definition of a detrimental drop is unclear; another publication reported a CM decrease of 61% (or more) at a slope steepness of 0.2 &#181;V/s (or more) to be significant9. A drop in ECochG responses may also be due to other causes, such as the interaction of different signal generators, passing the 500 Hz range within the cochlea, or contact of the basilar membrane with the electrode array 6,24.
It can be concluded that an increasing number of CI candidates have substantial residual hearing. In this cohort, it is essential to preserve the acoustic component during and after CI surgery. ECochG recordings have the potential to provide objective feedback to the surgeon during the implantation process. However, we are just at the beginning of being able to correlate changes of ECochG recordings to the inner ear function and need to improve our knowledge and understanding of successful hearing preservation. ECochG recordings will thereby play an important role, complemented by other inner ear measurements. The goal will be to have an objectified measurement tool that will allow the preservation of residual inner ear function in most implant recipients.

In recent years, the indication for cochlear implants has changed considerably. In the past, the extent of hearing loss in the pure tone audiogram was the primary indication for an implant, whereas today, speech understanding at maximum hearing aid amplification is the decisive factor. This has altered the population of implant candidates. Increasingly, patients who still have natural residual hearing (most commonly in the low-frequency region) receive a CI. Studies have shown that the residual function should be preserved as much as possible during and after surgery. Patients with preserved residual hearing perform better in speech intelligibility tests, have increased spatial awareness, and perceive music more naturally1,2.
In the past, atraumatic implantation primarily depended on the surgeon&#39;s assessment and haptic perception. Intraoperatively measured inner ear potentials (i.e., ECochG) are increasingly gaining interest in monitoring inner ear function3,4,5,6. They can provide the surgeon with additional information about the functioning of the inner ear during and after surgery. ECochG is a generic term for electrophysiological signals generated by the cochlea in response to acoustic stimulation. There are four different signal components, which can be measured depending on their origin; the cochlear microphonic (CM) is the largest and most stable signal component and is therefore used as a key variable in many studies. The origin of this signal component is predominantly in the outer hair cells. Other signal components are the auditory nerve neurophonic (ANN, an early neural response), the compound action potential (CAP, an early neural response), and the summating potential (a hair cell response).
The course of the ECochG signal during the implantation process provides insights into the state of the inner ear; changes in the intraoperative ECochG signal can be correlated with the postoperative residual function of the inner ear3,4,7,8,9. The measurement of ECochG signals is not trivial. No interpretable signal can be derived in up to 20% of cases10,11. On the one hand, there are patient-specific factors (i.e., absence of functioning hair cells) that influence the recordings. On the other hand, numerous technical and operation-specific factors contribute to the success of a measurement. Therefore, residual hearing cannot alone explain the success rate of ECochG. To record data as reliably as possible, a standardized procedure for these measurements is important. This prevents mismeasurements and facilitates the interpretation of intraoperative data.
There is no clear consensus of a required hearing threshold. In our experience, reproducible signals can be obtained in patients with a hearing threshold of up to 100 dB hearing loss (HL). This finding has been confirmed by other authors12. Other research groups perform ECochG measurements with a pure tone average (PTA) between 80 and 85 dB or better3,5,6,8,13,14. This video shows the system setup and a stepwise procedure of performing successful intracochlear ECochG measurements during CI surgery.

<table><tbody><tr><td>&lt;strong&gt;MED-EL&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Arbitrary waveform generator</td><td>Dataman, UK</td><td>Dataman 531 series</td><td></td></tr><tr><td>Foam eartip</td><td>Etymotic, USA</td><td>ER3-14</td><td></td></tr><tr><td>Gelfoam</td><td>Pfizer, USA</td><td></td><td></td></tr><tr><td>Implant software</td><td>MED-EL, Austria</td><td>Maestro 8.03 AS</td><td></td></tr><tr><td>Interface</td><td>MED-EL, Austria</td><td>MAX Programming Interface</td><td></td></tr><tr><td>Max Coil S</td><td>MED-EL, Austria</td><td></td><td></td></tr><tr><td>Python</td><td>Python Software Foundation, USA</td><td>v 03.08.2008</td><td></td></tr><tr><td>Software package Numpy</td><td>Python Software Foundation, USA</td><td>v. 1.19.2</td><td></td></tr><tr><td>Software package Scipy</td><td>Python Software Foundation, USA</td><td>v. 1.6.2</td><td></td></tr><tr><td>Software package Sklearn</td><td>Python Software Foundation, USA</td><td>v. 0.24.2</td><td></td></tr><tr><td>Sterile sleeve</td><td>Pharma-Sept Medical Products, Israel</td><td></td><td>Hand Piece Cover</td></tr><tr><td>Sterile sound tube</td><td>Etymotic, USA</td><td>ER3-21</td><td></td></tr><tr><td>Transducer</td><td>Etymotic, USA</td><td>ER-3C</td><td></td></tr><tr><td>Trigger cable BNC male to 3.5 mm male</td><td>Neurospec, Switzerland</td><td>NS-7345</td><td></td></tr><tr><td>&lt;strong&gt;Cochlear&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Cochlear programming pod Interface</td><td>Cochlear, Australia</td><td></td><td></td></tr><tr><td>Coil</td><td>Cochlear, Australia</td><td>Nucleus 900 series</td><td></td></tr><tr><td>Foam eartip</td><td>Etymotic, USA</td><td>ER3-14</td><td></td></tr><tr><td>Naida Q90 Implant software</td><td>Cochlear, Australia</td><td>v. 1.2</td><td>Cochlear Research Platform</td></tr><tr><td>Nucleus CP900 Audioprocessor</td><td>Cochlear, Australia</td><td></td><td></td></tr><tr><td>Sterile sleeve</td><td>Pharma-Sept Medical Products, Israel</td><td></td><td>Hand Piece Cover</td></tr><tr><td>Sterile sound tube</td><td>Etymotic, USA</td><td>ER3-21</td><td></td></tr><tr><td>Transducer</td><td>Cochlear, Australia</td><td>EAC00 series</td><td>Power speaker unit</td></tr><tr><td>&lt;strong&gt;AB&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>AIM Tablet</td><td>AB, USA</td><td>CI-6126</td><td></td></tr><tr><td>AIM Transducer</td><td>AB, USA</td><td>CI-6129</td><td></td></tr><tr><td>Audioprocessor</td><td>AB, USA</td><td>CI-5280-150</td><td></td></tr><tr><td>Eartip</td><td>AB, USA</td><td>AIM Custom</td><td></td></tr><tr><td>Naida Coil</td><td>AB, USA</td><td>CI-5315</td><td></td></tr><tr><td>Naida Coil cable</td><td>AB, USA</td><td>CI-5415-206</td><td></td></tr><tr><td>ONSuite Implant software</td><td>AB, USA</td><td>SoundWave 3.2</td><td></td></tr><tr><td>Sterile sound tube</td><td>AB, USA</td><td>AIM Custom</td><td></td></tr></tbody></table>

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.

For ECochG measurements during cochlear implantation, a standardized procedure is important to achieve the highest possible reproducibility of signals. Here, a setup is proposed wherein the surgeon and the engineer sit opposite each other to facilitate communication (Figure 1). When setting up the system, it is important that there is an unimpeded stimulus transmission. For example, the ear canal should be completely cleaned and clear; the eartip must sit deep in the ear canal; the eartip and sound tube are not kinked; the sound tube must run visibly on the sterile cover and be accessible during surgery; the retractor does not impact the ear canal, and thorough hemostasis should be done prior to the insertion process to ensure an air-filled middle ear space. In addition, a stable connection between the transmitting and receiving coils is important to prevent interruptions during the insertion process. Therefore, the sterile drapes should be as thin as possible (Figure 2), the skin thickness must be checked at the beginning of the surgery, and the two magnets should be aligned. Furthermore, when starting the ECochG measurement, the implant housing must be covered by soft tissue, and the impedance should be checked before continuing with the insertion.
Using this measurement protocol, we performed measurements with 12 patients (Table 2). These patients had a maximum hearing threshold of 100 dB HL at 500 Hz. When calculating the PTA, the mean of the hearing thresholds was taken at 125 Hz, 250 Hz, and 500 Hz. ECochG recordings were performed using an acoustic stimulus at 500 Hz, condensation polarity, and 30 dB above the individual hearing threshold (minimum 100 dB HL, maximum 120 dB HL). The acoustic stimulus had a duration of 8 ms, with a rise/fall time of 2 ms each22. In total, 100 recordings were taken in each case. For signal processing, the focus was on cochlear microphonic signals using Python. First, we applied bandpass filtering (Butterworth, 4th order, 100 Hz-3 kHz bandpass) in forward-backward mode. Finally, an ECochG response was considered valid if the signal-to-noise ratio (SNR) was greater than one. SNR was calculated using the &#177; averaging method23. The SNR estimate fluctuates due to the small number of epochs. Therefore, the SNR calculation is repeated 1000 times with random subdivisions to obtain a robust estimate. Example measurements are shown in Figure 3: the ECochG signal amplitude increases with its maximum at electrode 9. The mid-peak pattern can be confirmed in the postinsertion measurements (fully inserted electrode). Considering these results, the mid-peak pattern was measured in 8 out of 12 subjects. Others showed an apical-peak (subjects 1, 4, 6) or a start-peak (subject 3)
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63153/63153fig01.jpg" /> 
Figure 1: Operative room setup. Here, a setup is proposed where the surgeon and the engineer sit opposite each other to facilitate communication. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/63153/63153fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63153/63153fig02v2.jpg" /> 
Figure 2: Draping before the surgery. Care must be taken to ensure that there is a stable connection between the transmitting and receiving coils. (A) Thin, sterile drapes and (B) the fluid bag positioned as low as possible shorten the distance between the two coils. In this way, a good connection to the implant can be achieved. (C) The eartip must sit deep in the ear canal. (D) Using a large swab avoids strong buckling of the eartip and sound tube as well as eartip displacement. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/63153/63153fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63153/63153fig03.jpg" /> 
Figure 3: Intraoperative ECochG measurements. ECochG traces during (A) and after (B) electrode insertion are shown. Please note that the numbering of electrodes for A and B starts at opposite ends. (A) measures at the electrode tip and counts the number of electrodes inserted into the cochlea. (B) indicates the measurement electrodes, starting with the tip electrode as number one. Below (C), image taken during the implantation process with six inserted electrodes. Abbreviations: ECochG = electrocochleography; ampl = amplitude; el = electrode. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/63153/63153fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>AB</td>
			<td>Cochlear</td>
			<td>Med-El</td>
		</tr>
		<tr>
			<td>Computer</td>
			<td>Tablet AIM</td>
			<td>Arbitrary</td>
			<td>Arbitrary</td>
		</tr>
		<tr>
			<td>Software</td>
			<td>OMSuite</td>
			<td>Cochlear Research Platform</td>
			<td>Maestro</td>
		</tr>
		<tr>
			<td>Implant interface</td>
			<td>Audio processor, coil cable</td>
			<td>Audio processor, coil cable</td>
			<td>Coil cable</td>
		</tr>
		<tr>
			<td>Interface connection</td>
			<td>Programming cable</td>
			<td>Cochlear Programming Pod, programming cable, USB</td>
			<td>MAXInterface, USB</td>
		</tr>
		<tr>
			<td>Acoustic stimulation</td>
			<td>Transducer AIM</td>
			<td>Transducer Cochlear</td>
			<td>Arbitrary waveform generator, Transducer Etymotic, trigger cable</td>
		</tr>
		<tr>
			<td>Sound tube</td>
			<td>Custom</td>
			<td>Etymotic</td>
			<td>Etymotic</td>
		</tr>
		<tr>
			<td>Eartip</td>
			<td>Custom</td>
			<td>Etymotic</td>
			<td>Etymotic</td>
		</tr>
	</tbody>
</table>
Table 1: Hardware and software required for ECochG recordings by three different manufacturers. Abbreviation: ECochG = electrocochleography.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Subject</td>
			<td>Electrode (inserted ec)</td>
			<td>Cochlear access</td>
			<td>Pre PT at 500 Hz (dB HL)</td>
			<td>Pre PTA (dB HL)</td>
			<td>Post PT at 500 Hz (dB HL)</td>
			<td>Post PTA (dB HL)</td>
			<td>IOS SNR</td>
			<td>IEC</td>
			<td>Final SNR</td>
		</tr>
		<tr>
			<td>0</td>
			<td>Flex 28 (11)</td>
			<td>rw</td>
			<td>100</td>
			<td>80</td>
			<td>115</td>
			<td>101.7</td>
			<td>8.68</td>
			<td>10</td>
			<td>2.32</td>
		</tr>
		<tr>
			<td>1</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>65</td>
			<td>46.7</td>
			<td>85</td>
			<td>68.3</td>
			<td>1.22</td>
			<td>12</td>
			<td>1.22</td>
		</tr>
		<tr>
			<td>2</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>65</td>
			<td>56.7</td>
			<td>110</td>
			<td>98.3</td>
			<td>2.27</td>
			<td>9</td>
			<td>0.77</td>
		</tr>
		<tr>
			<td>3</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>100</td>
			<td>91.7</td>
			<td>110</td>
			<td>106.7</td>
			<td>1.35</td>
			<td>1</td>
			<td>0.95</td>
		</tr>
		<tr>
			<td>4</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>100</td>
			<td>100</td>
			<td>125</td>
			<td>111.7</td>
			<td>1.78</td>
			<td>12</td>
			<td>1.78</td>
		</tr>
		<tr>
			<td>5</td>
			<td>Flex 24 (11)</td>
			<td>c</td>
			<td>70</td>
			<td>58.3</td>
			<td>125</td>
			<td>111.7</td>
			<td>3.42</td>
			<td>9</td>
			<td>0.91</td>
		</tr>
		<tr>
			<td>6</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>80</td>
			<td>45</td>
			<td>110</td>
			<td>91.7</td>
			<td>22.9</td>
			<td>12</td>
			<td>22.9</td>
		</tr>
		<tr>
			<td>7</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>55</td>
			<td>53.3</td>
			<td>125</td>
			<td>111.7</td>
			<td>2.9</td>
			<td>6</td>
			<td>1.43</td>
		</tr>
		<tr>
			<td>8</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>70</td>
			<td>70</td>
			<td>105</td>
			<td>80</td>
			<td>2.87</td>
			<td>6</td>
			<td>1.44</td>
		</tr>
		<tr>
			<td>9</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>55</td>
			<td>40</td>
			<td>105</td>
			<td>68.3</td>
			<td>37.8</td>
			<td>9</td>
			<td>5.3</td>
		</tr>
		<tr>
			<td>10</td>
			<td>Flex 28 (11)</td>
			<td>rw</td>
			<td>65</td>
			<td>58.3</td>
			<td>100</td>
			<td>90</td>
			<td>29.14</td>
			<td>9</td>
			<td>13.5</td>
		</tr>
		<tr>
			<td>11</td>
			<td>Flex 28 (12)</td>
			<td>rw</td>
			<td>80</td>
			<td>78.3</td>
			<td>100</td>
			<td>85</td>
			<td>3.83</td>
			<td>6</td>
			<td>1.89</td>
		</tr>
	</tbody>
</table>
Table 2: ECochG recordings during CI surgery in 12 subjects. ECochG recordings during CI surgery in 12 subjects. IOS SNR displays the maximum SNR of the cochlear microphonic signal reached during insertion. IEC shows at how many inserted electrodes this maximum SNR was reached. The final SNR shows the CM amplitude of the fully inserted electrode at the most apical position. Abbreviations: ECochG = electrocochleography; CI = cochlear implant; rw = round window; C = cochleostomy; IEC = inserted electrode contacts; IOS = intraoperative signal; apical = most apical electrode; pre = preoperative; post = postoperative (4 weeks); PT = pure tone threshold; PTA = pure tone average; SNR = signal-to-noise ratio.

Watch this Scientific Journal Video about Performing Intracochlear Electrocochleography During Cochlear Implantation at JoVE.com

Performing Intracochlear Electrocochleography During Cochlear Implantation

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 ...

performing-intracochlear-electrocochleography-during-cochlear

Universidad San Sebastian

Research

JoVE Journal

Medicine

4.2K Views.  University of Bern. 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.

Video: Performing Intracochlear Electrocochleography During Cochlear Implantation

Performing and Processing FNA of Anterior Fat Pad for Amyloid

Historically, heart, liver, and kidney biopsies were performed to demonstrate amyloid deposits in amyloidosis. Since the clinical presentation of this disease is so variable and non-specific, the associated risks of these biopsies are too great for the diagnostic yield. Other sites that have a lower biopsy risk, such as skin or gingival, are also relatively invasive and expensive. In addition, these biopsies may not always have sufficient amyloid deposits to establish a diagnosis. Fat pad aspiration has demonstrated good clinical correlation with low cost and minimal morbidity. However, there are no standardized protocols for performing this procedure or processing the aspirated specimen, which leads to variable and nonreproducible results. The most frequently utilized modality for detecting amyloid in tissue is an apple-green birefringence on Congo red stained sections using a polarizing microscope. This technique requires cell block preparation of aspirated material. Unfortunately, patients presenting in early stage of amyloidosis have minimal amounts of amyloid which greatly reduces the sensitivity of Congo red stained cell block sections of fat pad aspirates. Therefore, ultrastructural evaluation of fat pad aspirates by electron microscopy should be utilized, given its increased sensitivity for amyloid detection. This article demonstrates a simple and reproducible procedure for performing anterior fat pad aspiration for the detection of amyloid utilizing both Congo red staining of cell block sections and electron microscopy for ultrastructural identification.

Fat pad aspiration is a preferred, minimally invasive, and low cost approach as compared to other methods to detect amyloid for diagnosis of systemic amyloidosis. This video article demonstrates a procedural outline for performing fat pad aspiration with appropriate processing of the specimen for the optimal diagnostic outcome.

Historically, heart, liver, and kidney biopsies were performed to demonstrate amyloid deposits in amyloidosis.  Since the clinical presentation of this ...

FISH for Pre-implantation Genetic Diagnosis 

Pre-implantation genetic diagnosis (PGD) is an established alternative to pre-natal diagnosis, and involves selecting pre-implantation embryos from a cohort generated by assisted reproduction technology (ART). This selection may be required because of familial monogenic disease (e.g. cystic fibrosis), or because one partner carries a chromosome rearrangement (e.g. a two-way reciprocal translocation). PGD is available for couples who have had previous affected children, and/or in the case of chromosome rearrangements, recurrent miscarriages, or infertility. Oocytes aspirated following ovarian stimulation are fertilized by in vitro immersion in semen (IVF) or by intracytoplasmic injection of an individual spermatozoon (ICSI). Pre-implantation cleavage-stage embryos are biopsied, usually by the removal of a single cell on day 3 post-fertilization, and the biopsied cell is tested to establish the genetic status of the embryo. Fluorescence in situ hybridization (FISH) on the fixed nuclei of biopsied cells with target-specific DNA probes is the technique of choice to detect chromosome imbalance associated with chromosome rearrangements, and to select female embryos in families with X-linked disease for which there is no mutation-specific test. FISH has also been used to screen embryos for spontaneous chromosome aneuploidy (also known as PGS or PGD-AS) in order to try and improve the efficiency of assisted reproduction; however, the predictive value of this test using the spreading and FISH technique described here is likely to be unacceptably low in most people's hands and it is not recommended for routine clinical use. We describe the selection of suitable probes for single-cell FISH, spreading techniques for blastomere nuclei, and in situ hybridization and signal scoring, applied to PGD in a clinical setting.

FISH for Pre-implantation Genetic Diagnosis

This article describes the selection of suitable probes for single-cell FISH, spreading techniques for blastomere nuclei, and in situ hybridization and signal scoring, applied to pre-implantation genetic diagnosis (PGD) in a clinical setting.

Pre-implantation genetic diagnosis (PGD) is an established alternative to pre-natal diagnosis, and involves selecting pre-implantation embryos from a ...

The Polyvinyl Alcohol Sponge Model Implantation

Wound healing is a complicated, multistep process involving many cell types, growth factors and compounds1-3. Because of this complexity, wound healing studies are most comprehensive when carried out in vivo. There are many in vivo models available to study acute wound healing, including incisional, excisional, dead space, and burns. Dead space models are artificial, porous implants which are used to study tissue formation and the effects of substances on the wound. Some of the commonly used dead space models include polyvinyl alcohol (PVA) sponges, steel wire mesh cylinders, expanded polytetrafluoroethylene (ePTFE) material, and the Cellstick1,2.
Each dead space model has its own limitations based on its material's composition and implantation methods. The steel wire mesh cylinder model has a lag phase of infiltration after implantation and requires a long amount of time before granulation tissue formation begins1. Later stages of wound healing are best analyzed using the ePTFE model1,4. The Cellstick is a cellulose sponge inside a silicon tube model which is typically used for studying human surgery wounds and wound fluid2. The PVA sponge is limited to acute studies because with time it begins to provoke a foreign body response which causes a giant cell reaction in the animal5. Unlike other materials, PVA sponges are easy to insert and remove, made of inert and non-biodegradable materials and yet are soft enough to be sectioned for histological analysis2,5.
In wound healing the PVA sponge is very useful for analyzing granulation tissue formation, collagen deposition, wound fluid composition, and the effects of substances on the healing process1,2,5. In addition to its use in studying a wide array of attributes of wound healing, the PVA sponge has also been used in many other types of studies. It has been utilized to investigate tumor angiogenesis, drug delivery and stem cell survival and engraftment1,2,6,7. With its great alterability, prior extensive use, and reproducible results, the PVA sponge is an ideal model for many studies1,2.
Here, we will describe the preparation, implantation and retrieval of PVA sponge disks (Figure 1) in a mouse model of wound healing.

A useful tool to analyze the effects of drugs, growth factors, and/or manipulated cells in an animal model of wound repair is described. This technique utilizes the properties of a polyvinyl alcohol (PVA) sponge to deliver and contain the desired treatment and also provide a platform to be excised and analyzed.

Wound healing is a complicated, multistep process involving many cell types, growth factors and compounds1-3. Because of this complexity, wound healing ...

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 ...

Real-Time Telemetric Impedance Measurements During Cochlear Implantation

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.

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.

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

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, ...

Hearing Preservation with Long Electrodes in Electric-Acoustic Stimulation

Enhanced Cochlear Coverage and Hearing Preservation in High-Frequency Hearing Loss via Electric Acoustic Stimulation with Longer Electrode

Electric-acoustic stimulation (EAS) is a promising treatment to improve hearing ability in patients with high-frequency hearing loss (HL). In EAS surgeries, shorter electrodes have been preferred to avoid the presence of an electrode covering the residual hearing region. However, our earlier studies showed that EAS with longer electrodes (28 mm) could preserve acoustic hearing. Additionally, we reported that the hearing preservation (HP) scores were independent of the length of the inserted electrodes, consistent with the systematic review. As most EAS patients gradually lose residual hearing over time due to the natural course of HL, in these cases, providing broader cochlear coverage using longer electrodes was beneficial toward better place-pitch matching. In addition to preparing for the deterioration in&#160;hearing in&#160;the future, EAS with longer electrodes could offer various types of map strategies. Herein, we show the pre-, intra-, and post-procedures for EAS surgery. Appropriate preoperative evaluation, less invasive surgery, flexible lateral-wall electrodes, and steroid administration resulted in good HP following EAS with longer electrodes.

Author Spotlight: Optimizing EAS with Long Electrodes for Enhanced Cochlear Coverage and Hearing Preservation

Electric acoustic stimulation (EAS) with longer electrodes can offer broader cochlear coverage and various types of maps in cases of high-frequency hearing loss. Combining less invasive surgery, flexible lateral-wall electrodes, and steroid administration permits deeper insertion with little or no surgical trauma, resulting in good preservation of hearing.

Performing Intracochlear Electrocochleography During Cochlear Implantation

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Enhanced Cochlear Coverage and Hearing Preservation in High-Frequency Hearing Loss via Electric Acoustic Stimulation with Longer Electrode