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Eclipse

What is ABR?
The Auditory Brainstem Response is an Evoked Potential that originates at the auditory nerve (Cranial Nerve VIII). This test is used to assess the auditory system’s function from the cochlea through the brainstem. The response is identified by “peaks” that occur typically between 1 and 15 milliseconds from the stimulus onset. The ABR peaks are measured and marked traditionally as I, II, III, IV, and V. Each peak has an expected latency to be considered “normal”. Delayed or missing peaks are consistent with abnormal auditory function. The amplitudes and latencies (both absolute and inter-peak) are used to diagnose certain auditory pathologies.

Why ABR?
ABR testing is traditionally used to help determine the degree of hearing loss in pediatric or difficult to test populations. It is also used for testing the auditory pathway as related to acoustic neuromas and some nervous system abnormalities.

How to Test?
Patient Preparation is very important. The patient should be relaxed or sleeping in a quiet environment. It is preferable that the patient lie down during the procedure to facilitate a calm and comfortable environment. The electrode sites must be prepared and cleaned in order to obtain acceptably low skin impedance. It is re- commended to have impedance values be 3kΩ or lower. The impedance values between one another should be balanced or similar in value.

Electrode Placement: The electrodes must be placed as indicated below. The must be a few centimetres between the white and black electrode. Alternatively the black electrode can be placed at the cheek.
Check the impedance on the preamplifier and place the transducers. Make sure the patient is relaxed prior to starting the test. You can monitor this by watching the EEG Window on the top right of the recording window.

Setting up the Eclipse
The Eclipse comes with pre-programmed protocols so the system is ready to use immediately. Protocols can be created or modified easily to fit your clinical needs. Consult your Additional Information to learn how to create or modify a protocol. The procedure discussed on the next page is simply a suggested process to be used as a guideline.

Basic ABR Testing Procedure

  1. Choose ABR Threshold e.g. Threshold CE-Chirp LS 
  2. Select ear and intensity
    AutoTest Mode: To begin the Automatic Test Protocol simply click on Start or use the F2 key. This will begin the Auto Sequence set up in the Protocol Setup.

    Hint: To move to the next intensity prior to completion of maximum sweeps choose Next Intensity or F3.
    Manual Mode: To begin the manual mode choose the intensity and select the ear to test on the Record sheet. Next choose Start or hit F2 if needed.

  3. Monitor the EEG during testing to assure a collection with minimal noise.
  4. Monitor the Fmp and Residual Noise to verify that a true response is detected.

    Note: Bayesian Weighting, Fmp, and Residual Noise Calculation are important additional features that are described in dedicated Quick Guides.
  5. Monitor the waveform reproducibility
    The line should be black and relatively flat and consistent. As averaging commences, the waveform will appear on the screen. As averaging continues note the Wave Re-reducibility score.

    When a test is performed, an A and B buffer exist. Each receives half of the responses. An automatic calculation of the correlation (similarity) between the two curves is indicated in this area (above left). The time window over which this correlation calculation occurs is part of the test parameter setup. It is indicated by the bold part of the time scale seen above (right). You may change the width or position of this bold bar by dragging it by its ends or by grabbing it with the mouse and sliding it back and forth along the time scale. Wave reproducibility will be recalculated immediately.

    HINT Waveform Scaling can be increased or decreased by using the arrows on the top left side of the recording window.

    HINT Window sizing may be changed during testing by selecting one of the arrow keys on the bottom, right side of the recording window.

Marking Peaks
Waveforms can be marked during a recording or afterwards from the Recording or Edit sheet. Waveforms can be marked manually or automatically. To mark a waveform automatically, use the Suggest Waveform marker:

This feature will place markers within the latency ranges that may be entered in the Latency template.
To mark a selected waveform manually, choose the appropriate marker or select 1-5 on the keyboard. Now drag the mouse to the correct position on the waveform and click to place the marker (or push Enter). The same function is available if you right click in the graph area with the curve selected.

Hint: If you hold down Crtl key while using the Arrow keys the Waveform Marker will jump from peak to peak!
Hint: You can use the digital filters to “clean up” noisy data even after a completed test or run! You’ll find this feature on the bottom of the Edit sheet.

Latency Data and Latency Intensity graphs
The system has an option to load default latency data during installation. You may also create your own (consult your Additional Information for instruction). While marking waveforms manually, a shaded area will appear indicating such latency data to assist with marking.
Once the waveforms are marked, choose the Latency sheet. The shaded area indicates the range of the latency data.

Reporting
Choose the Report Icon
When complete, choose Save and Exit.

July 2016

What is eABR?
An electrical Auditory Brainstem Response (eABR) is a measurement of the ABR using an electrical stimulus. Instead of a traditional acoustic stimulus the cochlear implant (CI) or auditory brainstem implant (ABI) provides the stimulus that evokes the ABR.

Why eABR?
eABR testing may be performed for the following reasons:

  • To verify adequate placement of the cochlear implant or auditory brainstem implant electrodes during surgery
  • To estimate thresholds and comfortable levels in infants, young children or other patients who cannot be assessed using behavioral techniques
  • To assist in mapping the cochlear implant or auditory brainstem implant device
  • To assess interactions between electrode channels
  • To determine the most appropriate rates of stimulation

How to test?
Patient Preparation
is very important. Optimally, the patient should be lying down, asleep and in a quiet environment. Minimally, the patient should be relaxed with their eyes closed during testing. It is important to note that the eABR is not affected by anesthesia.

Electrode placement: Standard ABR surface electrodes are usually sufficient for acquiring eABR recordings. A 3 electrode montage (shown below) is the preferred method while recording from the contralateral side to minimize the high electrical artifact from the Cochlear stimulation, though it is present at both at the ipsi and contralateral side.
Clean and prepare the electrode sites in order to reduce the impedance. Impedance values at or below 3kΩ will produce cleaner recordings. Arrange electrode cables away from the cochlear implant connections to minimize interference.
The eABR response is recorded from the contralateral mastoid, due to the excessive CI radiation/artefacts. For testing ABI patients during surgery a midline electrode montage is recommended (Cz – Nape, C7 for Ground/Common).

Alternative electrode placement
Setting up the Eclipse
To conduct an eABR the following is required: 

  • CI – patient
  • CI – stimuli system
  • Enable the ‘trigger out’ function in the CI-system
  • eABR recording system (Eclipse-hardware and software) 
  • Trigger cable to connect the CI-stimuli system and eABR recording system

The Eclipse connects to the Cochlear Implant Stimulator which connects to the Cochlear® or Auditory Brainstem Implant.
Trigger cable
Connection to the Eclipse is via a standard 6.3mm stereo Jack. The “Trigger In” signal is on the tip of the jack.
The “Trigger Out” signal is a stereo jack with the signal present on the “middle ring”. Ensure that the trigger cable used is a stereo jack. A mono jack will not work.
Trigger cable for Cochlear®
The following two cables sold by Interacoustics are compatible for use with Cochlear implant devices. The cables are available in either 1.5m (Part #: 8004222) or 5m (Part #: 8004236).
An eABR trigger kit can also be ordered number 8105928. This includes the below two cables and the EPA3 cable collector.
8105924 cable for AB/MedEl/Neurolec/Oticon Medical
8004222 cable for Cochlear Nucleus

Trigger cable connection

  1. Connect the Trigger Cable to the Trigger port on the back of the Eclipse.
  2. Connect the other end of the Trigger Cable to the Cochlear Implant Stimulator.

Protocol settings
The Eclipse comes with a pre-programmed eABR protocol which can be used immediately or modified to suit the test environment/patient. Refer to the manual for instructions about creating a new protocol or modifying the existing protocol.

  1. Ensure the Stimuli per sec. is set to Ext. Trigger.
  2. Ensure that the transducer selected is Headphone (Selection of inserts would incorrectly subtract 0.9ms from the recording). The actual transducer is the Cochlear Implant.
  3. The Level values are used to indicate the electrode numbers from the implant for testing - not the stimulus levels to be delivered. Modify as required.
  4. The Filter settings for input amp. are typically set at 33-5000Hz. For infant eABR, you may like to change the filter settings to 30–1500Hz. Note Filter settings can be changed digitally during or after testing to obtain smoother waveforms.

Recommended test parameters
Settings for eABR acquisition may vary according to the specifications from the Implant manufacturer.

Rejection: If creating your own protocol, be sure to check the Disable rejection (for eABR only) in the Auto protocol tab.
Stimulus: Set as specified by the CI manufacturer instructions on the CI system.
Polarity: Set as specified by the CI manufacturer instruction on the CI system.
Transducers: CI computer.
Intensity: Set as specified by the CI manufacturer instructions on the CI system.
Filters: 50- 5000 Hz. 
30-1500 Hz for an infant eABR.
100-3000 for adult eABR.

Trigger settings
The trigger signal to synchronize the Eclipse EPx5 and the Cochlear Implant Stimulator may work in one of two ways:

  1. A signal is sent from the EPx5 software on the Eclipse to the Cochlear Implant Stimulator.
  2. A signal is sent from the Cochlear Implant Stimulator to the Eclipse hardware (most common setup).

Sending the trigger (synchronization) signal from EPx5
From the EPx5 General Setup you must select the type of trigger signal your Cochlear Implant Stimulator device needs (Source or Sink). The trigger signal is a 5 Volt square wave standard trigger signal which is either positive (Source) or negative (Sink). The duration of the trigger signal can be set to meet the needs of the Cochlear Implant Stimulator device. You may find such specifications by referring to the technical specifications supplied by the manufacturer of the device or simply by trial and error.
The onset of the trigger signal starts at 0ms on the recording scale, however the duration of the trigger signal can be changed to work in accordance with manufacturer specifications.

Cochlear Implant Stimulator sends the trigger signal
From the Auto Protocols tab, the eABR protocol setting for Stimuli per sec. must be set to Ext. Trigger (move the slider to the far right) in order to enable the External Trigger. This allows the EPx5 to record a measurement every time a 5 Volt Source signal (duration >10μs) is sent from the Cochlear Implant Stimulator. The stimulus rate from the Cochlear Implant Stimulator or other external device must not exceed 50 per second in order to allow sufficient recording and processing time.
Ensure that the trigger signal is actually being sent from the Cochlear Implant Stimulator to the EPx5 software. It may need to be manually enabled in the software provided by the manufacturer of the CI or ABI.

Implant manufacture software settings
The follow settings are defined in the Implant manufacturer’s software, eABR testing:

  1. Stimulus type and band number.
  2. Stimulus rate – Max 20/sec, 10/sec preferred to allow sufficient recording and processing time.
  3. Stimulus polarity
  4. Stimulus intensity
  5. Trigger signal – 5 V TTL, with a duration of > 10μs required for the Eclipse to record a measurement.

 eABR test procedure
Patient Safety
The patient undergoing eABR testing is electrically connected to the Eclipse by skin surface electrodes (the same as when a standard ABR test is conducted). To ensure patient safety is maintained during testing, please refer to the Eclipse safety precautions in the ‘Instructions for Use’ guide.

The patient is not electrically connected to the cochlear/auditory brainstem implant system as it transfers the stimuli using wireless RF (radio frequency) communication. Please consult with the implant device operational manual for appropriate stimuli levels.

  1. Ensure there is a connection between the Eclipse and the Cochlear Implant System via the trigger cable.

  2. Ensure that the Cochlear Implant System is connected to the patient’s implant.

  3. Start up both the Eclipse EPx5 software and the software provided by the Implant manufacturer (e.g. Custom Sound by Cochlear®).

  4. Ensure that the patient is connected as described in the electrode montage.

  5. Select the protocol (eABR – Trigger Enabled) from the dropdown menu on the test screen. 

  6. Select the test ear and the electrode number for testing from the Man. Stim window.

  7. Press the Start button or F2. EPx5 will wait for the implant software to send the trigger signal before recording begins. If this is the first time performing an eABR, it may be ideal to do a trial test to ensure the two systems are communicating with each other as expected before connecting a patient.

  8. Follow the instructions provided by the Implant manufacturer to start sending the trigger signal to the Eclipse.

  9. Collect an adequate number of sweeps to see a clearly defined waveform.

Marking the waveform peaks

  • Mark the waveform peaks from the Rec or Edit tab. Only completed waveforms can be marked
  • The waveform must be selected (double click on the waveform handle) prior to placing waveform markers

Waveforms can be marked in three different ways:

  • Click on the marker button (e.g. I, II, III, IV, V) and then click on the curve where you want to place the marker
  • Press the marker number (e.g. 1, 2, 3, 4, 5) on the keyboard. Then use the arrow keys, Ctrl + arrow keys or the mouse to move the cursor to the desired position. Press the enter button or left click with the mouse to place the marker. Using the Ctrl + arrow keys will move the cursor from peak to peak.
  • Right click on the waveform to select and place markers

The corresponding ms and μV values will be displayed in the boxes next to the Waveform Markers. Interlatency values will also be calculated after the relevant markers have been placed.

The eABR response is well documented and is said to be represented by two distinct peaks III occurring at approximately 2ms and V occurring at approximately 4ms.

eABR results
Analysis of eABR waveforms and placement of waveform markers should be conducted by a suitably qualified audiologist or other medical professional trained in cochlear or auditory brainstem implant eABR techniques. The following displays some of the common responses seen when recording an eABR.
The top 4 curves are the recordings from the CI electrode number 11 starting from a high/comfortable loudness level and decreasing until not heard. Note the PAM responses around 8–10ms.The PAM muscle should not be confused with the earlier ABR wave V responses.

The bottom 4 curves are recoding from the CI electrode number 6 starting from a comfortable loudness level and decreasing. The sharp peaks around 9.5ms are the power up from the cochlear implant. Power up may be so small that it is not recorded.

Note: Interference displayed before 2ms is generated by the implant.

A facial nerve response may also be present around 7.5ms to 11msas a reaction to high level stimulation (Cushing et al, 2006). This example shows the wave V of the eABR and power up from the cochlear implant, which is typically around 10ms in latency. This example shows the wave V of the eABR at shorter latencies (around 4ms), a PAM response and power up from the cochlear implant. All recordings were performed on electrode 11. The curve at the bottom of the display was one recorded with no stimulus to the implant.

Intensity selections made in the EPx5 will not match the intensities delivered by the CI stimulating device. Therefore, keep a record of which recording corresponds to which stimulation situation. The Comments field in the upper right hand corner of the Edit tab can be used to write the actual CI current stimulation level and place for each waveform recorded, as one new comment is available for each highlighted waveform.

Other eABR examples

eABR recordings from a Cochlear Freedom adult patient
CI – electrode 11, starting from a high/comfortable level and decreasing current to not heard/Wave V is not visible

eABR recordings from Advanced Bionics young male patient

Quick tips & precautions
The morphology of the eABR may be affected by a number of Cochlear Implant factors such as. 

  • Stimulus polarity
  • Frequency band 
  • Rate and level
  •  Filter Settings
  • RF contamination  Muscle artifact
  • Neural survival

eABR response

  • Wave I and often wave II will not be observed due to the RF contamination, and/or stimuli artifact from the implant
  • Latencies for eABRs are shorter than traditional ABRs because the electrical stimulus directly activates the neural pathway. Therefore it is recommended to avoid the effects of the time delay associated with the acoustic travel time from the earphone to the neural pathways of the inner ear. The wave V latency is approx. 1.5-2ms shorter for eABRs at high stimulus levels.
  • It is rare to see Wave VI and VII
  • No propagation or synaptic delay, no shift of waveform latency with intensity
  • Increased synchrony
  • eABR amplitudes are much bigger than standard ABR amplitudes
  • Be aware of muscle artifact, typically recorded as a large biphasic potential with a latency of 5-10ms. Muscle artifact typically arises from the facial nerve. Muscle artifact – e.g. PAM (post auricular muscle) are typically seen at a latency of 10ms.

 Triggering & system optimization

  •  Consult with the CI manufacturer’s recommendations if special triggering is require
  • The EP25 trigger parameters can be set in the General Setup where you select the type of trigger signal your Cochlear Implant Stimulator device requires
  • In the Auto Protocol Setup you can select External Trigger in the Stimuli per Second box. In this case the CI system is sending the trigger to the Eclipse.
  • The trigger signal to the Eclipse must be based on 5V TLL pulses with duration of minimum 10μs
  • Braid the electrode lead wires to minimize loop area 
  • It is important to obtain similar impedances in each measuring electrode as this improves the preamplifier ability to reduce the CI electrical noise
  • Use the shortest electrode lead wires possible

Electrical stimulus

  •  A cochlear implant does not stimulate all electrodes at the same time. The stimulation is serial so a single electrode is stimulated per time
  • The electrode wire containing the different stimuli bands/electrodes (e.g. 24) is placed inside the cochlea (Scala Tympani) along the basilar membrane
  • When possible do not use longer (wider) pulse widths, since recorded stimulus artifact contaminates a longer segment of the recorded waveform
  • Use alternating polarity
Please refer to the Additional Information manual for a description of how to setup the trigger to the Eclipse.

References
Cushling, S. L., Papsin B, C., Gordon, K.A. (2006) Incidence and characteristics of facial nerve stimulation in children with cochlear implants. 116(19) 1787-91.

July 2017

What is ECochG?
Electrocochleography (ECochG) is a measure of the electrical potentials of the cochlea. Typically, the measurement is characterized by the stimulus onset (baseline), the response of the cochlea to the stimulus (summating potential - SP), and response to the synchronous firing of nerve fibers (action potential - AP). The AP is also known as Wave I. The cochlear microphonic (CM) is also part of the ECochG and has its own protocol. Measuring the CM requires slightly different test parameters than the SP and AP and for this reason it is described in a separate quick guide.

Why Perform an ECochG?
Certain vestibular and auditory conditions may be diagnosed with ECochG. The ECochG is primarily used to

diagnose Meniere’s Disease, particularly Cochlear Hydrops. The SP and AP amplitudes, latencies and their

relationship are used to diagnose these conditions. Perilymph Fistula, sudden hearing loss and other pathologies may result in abnormal ECochG results. Recent studies indicate that Superior Canal Dehiscence (SCD) may also result in elevated SP/AP ratios (Devaiah et al., 2009).

How to Test?
Surface electrodes are not adequate for recording ECochG. It is recommended to use Tiptrodes, TM-trodes or Transtympanic electrodes to measure the electrocochleogram. While transtympanic electrodes will result in the most robust response but are not feasible for most clinics. Gold foil Tiptrodes are sometimes used but TM- trodes will produce larger responses as it is closer to the site of generation. The following is an example of preparation and electrode placement performed with a TM-trode. Note the procedure should only be performed by trained professionals.

Patient Preparation is very important. The patient must lie down and should be relaxed or sleeping in a quiet environment during the procedure. An examination of the ear canal and TM must be performed prior to performing the test.

The electrode sites must be prepared and cleaned in order to obtain acceptable low skin impedance. It is recommended to have impedance values be 5kΩ or lower for Tiptrodes. The impedance values between one another should be balanced or similar in value. For TM-trodes the impedance should be 20kΩ or lower. It may be quite difficult to obtain such low impedance on the ECochG test ear electrode and higher levels may be accepted.

Electrode Placement: The ECochG test leads must be used to acquire the waveform. Below is an example of the electrode placement using the TM-trode with the EPA4 and an example of the EPA3 with a TM-trode.
For both examples the TM-trode and the test ear must be prepared prior to placing the TM-trode on the tympanic membrane. To reduce impedance a solution of saline can be used. Drain the ear prior to inserting the TM-trode. The TM-trode can be placed in a saline solution for a few minutes prior to placing it on the TM and should be dipped in electrode contact gel (e.g. Sonaville) prior to placing it at the TM.

EPA4 TM-trode example
When using EPA4 together with a TM-trode the red TM-trode cable is moved when switching ear.

EPA3 TM-trode example
Only 1-channel is needed to perform an ECochG with the TM-trode and for simplicity EPA3 can be used.

Basic ECochG Testing Procedure
The procedure discussed below is simply a suggested process to be used as a guideline. Consult your Instruction for Use or Eclipse Additional Information to learn how to create or modify a protocol.

Choose the protocol ECochG Click
Manual Mode: To begin the manual mode, choose the intensity and select the ear to test on the Record sheet. Next choose Start (or hit F2).

During testing monitor the EEG to assure a collection with minimal noise. The EEG levels should be low and consistent. As averaging commences, the waveform will appear on the screen.

Hint: Waveform Scaling can be increased or decreased by using the arrows on the top left side of the recording window or on your keyboard.
Hint: Window sizing may be changed during testing by selecting one of the arrow keys on the bottom, right side of the recording window or using the arrows on your keyboard.

Marking Peaks and Areas
Waveforms are marked from the Edit sheet during or after testing either manually or automatically. Amplitude Ratio or Area Ratio Calculation will automatically be computed once the required labels are assigned. The ratio selection is found in the General Setup.


To mark a selected waveform, click the appropriate waveform marker in the Edit sheet (or select 1-6 on the keyboard). Now bring the mouse to the correct position on the waveform and click to place the marker (or hit Enter).

Hint: You can use the digital filters to “clean up” noisy data even after a completed test or run. You’ll find this feature in the bottom of the Edit sheet.

Example of Marked Points for Amplitude Ratio

PBSL=Baseline, SP= Summating Potential, AP=Action Potential, BLst=start of baseline, Blend=end of baseline, AP1=start of AP, AP2=end of AP

Example of Marked Points for Area Ratio

PBSL=Baseline, SP= Summating Potential, AP=Action Potential, BLst=start of baseline, Blend=end of baseline, AP1=start of AP, AP2=end of AP

Amplitude ratio: Amplitude ratio is simply marked with the baseline, the summating potential and the action potential. A ratio between the BSL/SP and BSL/AP is calculated automatically by the system.
Abnormal SP/AP amplitudes are exceeding a ratio of 0.53 as the critical value (Devaiah et al., 2009).

Area Ratio: Area Ratio is marked by first marking the start of the baseline (BLst). The BL end will be marked automatically at the next point in the waveform where the amplitude crosses this baseline. If the waveform does not allow this, you can place the BL end manually. Now mark the SP and the AP1 (the beginning of the AP). Next mark the AP peak. Finally mark the AP2, which is where the AP ends and “changes direction”. A ratio is calculated automatically by the system. Abnormal SP/AP area ratios are exceeding a ratio of 1.94 as the critical value (Devaiah et al., 2009).

Reporting
Choose the Report Icon. When complete, choose Save and Exit. 


References
Devaiah, A.K., Dawson, K.L., Ferraro, J.A., & Ator, G.A. (2009). Utility of area curve ratio electrocochleography inearly meniere disease. Arch Otolaryngol Head Neck Surg, 129, 547-551.

July 2016

What is oVEMP?
The Ocular Vestibular Evoked Myogenic Potential (oVEMP) is an evoked potential measured from the inferior oblique muscle and is used to assess the vestibular system. There is still some debate over the origin of the response (Piker et al., 2011), however, the oVEMP is largely dependent on the integrity of the superior vestibular nerve (Jacobson et al., 2011).

The oVEMP is recorded using surface electrodes at four sites on the face and an Amplitude Asymmetry Ratio is calculated to determine if the above-mentioned parts of the vestibular system are intact and working normally.

The figure shows oVEMP recordings from a normal young adult (Murnane & Aki, 2009).

Why oVEMP?
The oVEMP is a test used in addition to traditional vestibular testing (e.g., VNG) to assist in the assessment of vestibular function. oVEMP recordings provide value information to medical practitioners to assist them in the diagnosis of disorders such as Superior Semicircular Canal Dehiscence (SSCD) (Watters et al., 2006) and Meniere’s disease (Sandhu, 2012).

How to test?
Patient Preparation is very important. The electrode sites must be prepared and cleaned in order to obtain acceptably low skin impedances. It is recommended to have impedance values of 3kΩ or lower. The impedance value between each electrode should be balanced or similar in value.

The subject is either seated or in a reclined position and is instructed to maintain an upward gaze at 35 degrees for the duration of the recording (Kantner & Gürkov, 2014). Placing a static visual target on the wall or ceiling for the patient to look at during testing will ensure consistent activation of the inferior oblique muscle.

Electrode placement (example)

Use of this electrode montage does not require the active (white) electrode to be shifted during testing and is reported to provide the largest oVEMP amplitude (Piker et al., 2011).

The reference electrodes should be placed as close as possible underneath the eye in the orbital midline. Avoid placement close to the medial canthus (inner corner of the eye) as a null-point exists where there is no oVEMP response present (Sandhu, George & Rea, 2013).

The oVEMP response is recorded from the inferior oblique muscle underneath the contralateral eye. Therefore, the right (red) electrode is placed under the left eye while the right ear is stimulated. Correct positioning of the electrode on the inferior oblique muscle is essential in obtaining a response (Sandhu, George & Rea, 2013).

Alternative electrode placement (examples)

Electrode montage for testing the left ear. For testing of the right ear, move the active (white) electrode to the other side (underneath the red electrode).

Typically, the air-conduction stimulus used is a 500Hz tone burst at high intensity level (e.g., 90/95dBnHL). Ensure that the patient is relaxed prior to starting the test. After confirming impedances.

Setting up the Eclipse
The Eclipse comes with pre-programmed protocols so the system is ready to use immediately. Protocols can be created or modified easily to fit your clinical needs. Consult the Eclipse Additional Information manual to learn how to create or modify a protocol. The procedure described below is simply a suggested test process and to be used only as a guideline. 

oVEMP testing procedure
Choose an oVEMP protocol from the dropdown menu 
The oVEMP test should be run in the Manual Mode controlling/selecting stimuli manually. For more collection parameters details, please refer to instruction for use manual.

Manual mode

  1. To begin in manual mode, choose the intensity and select the ear to test on the Record sheet. Instruct the patient to look up and hold their gaze without moving their head.
  2. Next choose Start or press F2.
  3. 100-200 sweeps are typically collected per waveform.

Setting up L & R waveform partners
After collection, choose a left or right ear waveform by double clicking the waveform handle. Next, right click the waveform handle of the opposite ear and select Set as VEMP Partner. The selected waveforms are used in the Asymmetry Ratio Calculation.

EMG scaling
The EMG scaling is not to be used in the oVEMP testing, as there is no contracted muscle as in cVEMP. The reason for gazing up, is not to contract the oblique muscle, but instead to positioning the inferior oblique muscle closer to to the recording electrode.

Marking peaks
The oVEMP response is well documented and is said to be represented by two distinct peaks; N1 occurring at approximately 10 ms and P1 occurring at approximately 15 ms.

Waveforms can be marked from the Record sheet or the Edit sheet. To mark a waveform double click on the waveform handle you would like to mark. Right click and then choose the correct marker. Drag your mouse to the correct area and click. You can also choose 1-4 on the keyboard to bring up the appropriate marker and use Enter to place it.

Example of an oVEMP where N1 and P1 are marked for both ears.

Normative data
A large study investigating the normal characteristics of the oVEMP by Piker and colleagues (2011) defined an upper limit of oVEMP amplitude asymmetry to be 34% (mean + 2 SD).

Example of scaled oVEMP waveforms indicating an abnormal asymmetry ratio between left and right side, along with lowered oVEMP thresholds on the right.

Reporting
Choose the Report Icon 
When complete, choose Save and Exit.


References
Kantner, C., Gürkov, R. (2014). The effects of commonly used upward gaze angles on ocular vestibular evoked myogenic potentials. Otology & Neurotology, 35(2), 289-293.

Jacobson, G. P., McCaslin, D. L., Piker, E. G., Gruenwald, J., Grantham, S. L., & Tegel, L. (2011). Patterns of abnormality in cVEMP, oVEMP and caloric tests may provide topological information about vestibular impairment. J Am Acad Audiol, 22, 601-611.

Murnane, O. D., & Akin, F. W. (2009). Vestibular-evoked myogenic potentials. Seminars in Hearing, 30(4), 267-280. Piker, E.G., Jacobson, G.P., McCaslin, D.L., & Hood, L.J. (2011). Normal characteristics of the ocular vestibular evoked

myogenic potential. J Am Acad Audiol, 22, 222-230.
Sandhu, J. S., George, S. R., & Rea P. A. (2013). The effect of electrode positioning on the ocular vestibular evoked

myogenic potential to air-conducted sound. Clinical Neurophysiology, 124(6), 1232-1236.
Sandhu, J. S., Low, R., Rea, P. A., & Sauders, N. C. (2012). Altered frequency dynamics of cervical and ocular vestibular

evoked myogenic potentials in patients with Meniere’s disease. Otology & Neurotology, 33(3), 344-440.
Watters, K. F., Rosowski, J. J, Sauter, T., & Lee, D. J. (2006). Superior semicircular canal dehiscence presenting as postpartum vertigo. Otology & Neurotology, 27(6), 576-768.

September 2017

What is cVEMP?
The cervical Vestibular Evoked Myogenic Potential (cVEMP) is an evoked potential measured from the sternocleidomastoid (SCM) muscle and is used to assess the vestibular system (the saccule and its afferent pathways). An amplitude asymmetry ratio is then calculated to assess if the vestibular system is working normally. VEMP tracings are easily recorded and provide valuable information to medical practitioners to assist them in the diagnosis of various disorders. Loud tone bursts, at slow rates are used to elicit this response.

Why cVEMP?
The cVEMP is a test used in addition to traditional vestibular testing (e.g., VNG) to assist in the assessment of vestibular function. The cVEMP provides information about the saccule and inferior vestibular nerve, assisting medical practitioners in the diagnosis of disorders such as Superior Semicircular Canal Dehiscence (SSCD) (Milojcic et al., 2013) and Meniere’s disease (Rauch et al., 2004).

How to test?
Patient Preparation
is very important. The electrode sites must be prepared and cleaned in order to obtain acceptably low skin impedances. It is recommended to have impedance values of 3kΩ or lower. The impedance values between each electrode should be balanced or similar in value.

There are different suggested activation techniques for the SCM muscle. The patient can either be sitting and instructed to turn the head only to contract/activate the SCM muscle as shown in the image below.
Alternatively, the patient can be in a reclined position and asked to lift the head and turn the neck to contract the SCM muscle. Use of the patient EMG monitor will ensure consistent activation during testing.

Electrode placement (example):

The reference electrodes should be placed on the upper belly of the SCM muscle on both sides. The vertex electrode is placed on the clavicular joint (or on the high forehead) and the ground/common on the low forehead.

Typically, the air-conduction stimulus used is a 500Hz tone burst at high intensity level (e.g., 90/95dBnHL). Ensure that the patient is relaxed prior to starting the test. After confirming impedances.

Setting up the Eclipse
The Eclipse comes with pre-programmed cVEMP protocols so the system is ready to use immediately. Protocols can be created or modified easily to fit your clinical needs. Consult the Eclipse Additional Information manual to learn how to create or modify a protocol. The procedure described below is simply a suggested test process and to be used only as a guideline.

Patient monitor
An adequate contraction of the SCM muscle is essential for a good cVEMP recording. The patient monitor provides information to the patient during testing to ensure a correct head turn/lift and informs the patient about the test time and contraction of the SCM muscle. The information provided on the patient monitor is a guide to the patient and constitutes to a more accurate test procedure which may shorten the overall test time.


EMG controlled stimulus/recording
when the patient contracts the SCM muscle adequately. This can be monitored by the patient either visually Patient EMG Monitor or audibly Monitor Tone. Please see Additional Information manual for a more detailed explanation of monitoring options.

cVEMP testing procedure
Choose a cVEMP protocol from the dropdown menu 
The cVEMP test should be run in the Manual Mode controlling/selecting stimuli manually.

Manual mode

  1. To begin in manual mode, choose the intensity and select the ear to test on the Record sheet. Instruct the patient to turn their head to the right or left to activate the muscle on the testing side. You should pay particular attention to the ongoing EEG and the target range if needed.
  2. Next choose Start or hit F2.
  3. 100-200 sweeps are typically collected per waveform.

Setting up L & R waveform partners
After collection, choose a left or right ear waveform by double clicking the waveform handle. Next, right click the waveform handle of the opposite ear and select Set as VEMP Partner. The selected waveforms are used in the Asymmetry Ratio Calculation.

EMG scaling
The default protocol is setup to scale the curves automatically. Some prefer to scale after the recordings are completed. After the recording is complete, you can right click on the waveform and choose EMG Scaling. Waveforms will then be scaled according to the average prestimulus EMG values recorded throughout the collection. This will make individual recordings comparable, even though slightly different degrees of muscle tonus may have been applied during the different recordings, which provides a reliable tool in calculation of the amplitude asymmetry (McCaslin et al., 2014).

HINT Display Scaling can be increased or decreased by using the arrows on the top left side of the recording window or by using your keyboard arrows.

Marking peaks
The cVEMP response is well documented and is said to be represented by two distinct peaks; P1 occurring at approximately 13 ms and N1 occurring at approximately 23 ms.

Waveforms can be marked from the Record sheet or the Edit sheet. To mark a waveform double click on the waveform handle you would like to mark. Right click and then choose the correct marker. Drag your mouse to the correct area and click. You can also choose 1-4 on the keyboard to bring up the appropriate marker and use Enter to place it.

Normative data
A number of studies report upper limits of normal for cVEMP recordings between 35 – 45% depending on the use of EMG monitoring and scaling of the response. In a study by McCaslin and colleagues (2013), the upper limit of normal was reported as ~31-37 % when both EMG monitoring and scaling was applied.

Example of a cVEMP where P1 and N1 are marked for both ears. The asymmetry ratio is calculated at 0.06. Curves are scaled.


Example of scaled cVEMP waveforms indicating an abnormal asymmetry ratio (0.80) between left and right side, along with lowered cVEMP thresholds on the right. (Curves in the above example are inverted).

Reporting
Choose the Report Icon .
When complete, choose Save and Exit.


References
McCaslin, D. L., Fowler, A., Jacobson, G. P. (2014). Amplitude normalization reduces cervical vestibular evoked myogenic potential (cVEMP) amplitude asymmetries in normal subjects: proof of concept. J Am Acad Audiol, 25(3), 268-277.

McCaslin, D. L., Jacobson, G. P., Hatton, K., Fowler, A. P., & DeLong, A. P. (2013). The effects of amplitude normalization and EMG targets on cVEMP interaural amplitude asymmetry. Ear Hear, 34(4), 482-490.

Milojcic, R., Guinan, J.J., Rauch, S.D., & Herrmann, B.S. (2013). Vestibular evoked myogenic potentials in patients with superior semicircular canal dehiscence. Otol Neurotol, 34(2), 360-367.

Rauch, S. D., Zhou, G., Kujawa, S. G., Guinan, J. J., Herrmann, B. S. (2004). Vestibular evoked myogenic potentials show altered tuning in patients with Ménière’s disease. Otology & Neurotology, 25(3), 333-338.

Young, Y. H., Wu, C. C., & Wu, C. H. (2002). Augmentation of vestibular evoked myogenic potentials: an indication for distended saccular hydrops. Laryngoscope, 112(3), 509-512.

 

September 2017

The Auditory Brainstem Response (ABR) is an evoked potential that originates at the auditory nerve (Cranial Nerve VIII) and the response is picked up by surface electrodes typically placed at Vertex and Left and Right mastoids. An ABR test is used to assess the auditory system’s function from the cochlea through the brainstem.

The response to auditory broad band or frequency specific stimuli is identified by “peaks” that occur typicallybetween 1 and 15 milliseconds from the stimulus onset. The ABR peaks are measured and marked traditionally as I, II, III, IV, and V. Each peak has an expected latency range to be considered “normal”. Delayed or missingpeaks are consistent with abnormal auditory function. The presence or absence of responses can be used to estimate hearing thresholds. An ABR threshold is an electrophysiological threshold that can be used to predict the behavioral audiogram. The difference between the two may vary quite a lot, but correction of 20dB at 500Hz, 15dB at 1kHz, 10dB at 2kHz and 5dB at 4kHz are typically applied correction factors.

Threshold recording using 2kHz Tone Burst. Note the large PAM response from the right side caused by the loud stimulus of 80dBnHL. The ABR threshold at 20dB nHL at 2kHz found here would be well within the range of normal hearing - applying a typical correction factor would estimate the behavioral audiogram threshold to be 10dBHL at 2kHz.

Improving Threshold testing with Eclipse
Challenges arise when evaluating hearing thresholds. They can include:

CE-Chirp® Stimulus Family
We know that as we get closer to threshold, the waveform latencies increase and the amplitudes decrease. This presents a challenge in “peak picking”. A solution is the implementation and use of the CE-Chirp® LS and NB CE-Chirp® LS. The CE-Chirp® LS Stimulus Family compares to the traditional click while the NB CE-Chirp® LS compares to traditional tone burst. Research indicates that the use of the CE-Chirp LS® and NB CE-Chirp® LS particularly at modest stimulation levels results in waveform amplitudes up to double that of traditional stimuli (Elberling & Don, 2008; Ferm et al., 2013). This is achieved by simply accounting for timing issues within the cochlea. If amplitudes can be increased, the ability of the user to quickly and accurately identify waveform peaks near threshold increases. This clearly reduces test time and increases user confidence. Please see example below.

The larger amplitudes of the CE-Chirp® LS when compared to the traditional Click allows for faster and more reliable testing. Similar benefits can be found when substituting traditional Tone Bursts with the NB CE-Chirps® LS.

Residual Noise Calculation

Noise levels also create a challenge as noise can eliminate the ability to obtain or view the necessary waveform peaks. Lower noise levels increase the ability to identify the waveform peaks and increase the confidence of the presence or absence of a response.

Traditionally, users run a set number of sweeps in an effort to reduce the amount of noise in the recording. However, the number of sweeps may tell us little about the Residual Noise in the tracing. An objective Residual Noise measure should be used instead. Typically, if Residual Noise levels are 40nV or less, the tracing is sufficiently clean to be able to reveal a response if present. Therefore, Interacoustics implemented the Residual Noise calculation. The use of Residual Noise calculation either by monitoring or as a stop criterion greatly improves the certainty. The Residual Noise bar placed on the right side of the Fmp graph indicates the Residual Noise level and will turn green with a checkmark when the criterion for residual noise is reached (e.g. 40nV).

The Fmp value (red curve) has at this point of testing passed the 99% response confidence criteria, and the Residual Noise level (black curve) has not yet reached the 40nV residual noise level suitable for quality recordings around threshold.

Fmp Calculation & Response Confidence
The Fmp is an indication of the Response Confidence of the recorded response. While looking at the waveform being recorded, a confidence level is calculated, and provided as a percentage of statistical certainty of a response being present in the recorded waveform. This statistical analysis assists the clinician in that it can reduce test time since it relies on statistical information and not solely on the experience of the user. The experienced user can encompass the Fmp values when evaluating response presence or absence. Often the Fmp will detect strong responses sooner than confident eyeballing can reach the same conclusion. On the other hand, Fmp may not identify smaller responses close to threshold, in which case eyeballing is to be applied, being the golden standard in response detection at threshold. When the response confidence reaches the set criteria (e.g. 99%) the bar indicating the Response Confidence turns green with a checkmark indicating that the Response Confidence criterion is met.

Bayesian Weighting
In the best testing scenario that one should always try to obtain, the patient will be very quiet or sleeping and the EEG at a constant and low level throughout the data acquisition. This is not always the case and Bayesian Weighting is of great help in such test situations. It is an averaging technique that weighs each sweep individuallygiving more “weight” or importance to quiet sweeps and less “weight” to sweeps with more noise. This is different from traditional averaging since traditional averaging simply accepts or rejects each sweep and not weighing them individually.

The use of Bayesian Weighting will assist the clinician in situations that are not ideal testing conditions, and will not alter the response waveform’s morphology.

A few additional practical hints


The Rearrange Curves and Group Curves functions in the upper tool bar ensure easy manual positioning of waveforms.


The A&B tool in the upper tool bar allows waveform reproducibility to be evaluated without the need to run repeated waveforms.

Important highlights

  • Use eyeballed (or Fmp based) response identification or Noise Level as stop criteria, not a fixed number of sweeps.
  • Use Bayesian Weighting for lowest residual noise.
  • Use CE-Chirp® LS rather than click for larger response amplitudes.
  • Neither Click nor CE-Chirp® LS is sufficient information on which to fit a hearing aid.
  • Use NB CE-Chirps® LS rather than Tone Bursts for larger response amplitudes, when doing the frequency specific testing needed for hearing aid fitting.
  • Consider typically using a relatively fast rate, as the time to get a low noise level rather than wave morphology is of the essence in threshold testing. If in doubt then lower the rate.
  • Spend your time close to threshold rather than trying to obtain overly beautiful responses at loud intensities.
  • Tough filtering (e.g. Low Pass display filtering at 1500Hz) may help eyeballing responses.
  • Consider using the A&B buffers as your reproducibility tool, rather than spending time actually running double sweeps.
  • Remember Fmp is typically not capable of picking out response presence close to threshold, but may be a valuable tool confirming response quickly well above threshold.
  • A typical good threshold practice requires waveforms around threshold to have a residual noise level of 40nV or less, and requires eyeballing of a repeated responses (or similar A&B) at threshold and no visible response just below threshold.

References
Don, M. & Elberling, C. (1996). Use of quantitative measures of auditory brain-stem response peak amplitude and residual background noise in the decision to stop averaging. J. Acoust. Soc. Am., 99(1).

Elberling, C. & Don, M. (1984). Quality Estimation of averaged auditory brainstem responses. Scand Audiol. (13) 187-197.

Elberling, C., & Don, M. (2008). Auditory brainstem responses to a chirp stimulus designed from derived-band latencies in normal-hearing subjects. J. Acoust. Soc. Am. (124) 3022-3037.

Elberling, C. & Wahlgreen (1985). Estimation of auditory brainstem response, ABR, by means of Bayesian interference. Scand. Audiol (14) 89-96.

Ferm, I., Lightfoot, G. & Stevens (2013). J. Comparison of ABR response amplitude, test time, and estimation of hearing threshold using frequency specific chirp and tone pip stimuli in newborns. International Journal of Audiology, (52) 419-423.

July 2016
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