Electrically Evoked Stapedius Reflex Threshold (eSRT)

This video will take you through the procedure of how to obtain an electrically evoked stapedius reflex threshold (eSRT) and its clinical applications.

You can read the full transcript below.

Introduction

This video will take you through the procedure of how to obtain an electrically evoked stapedius reflex threshold, also abbreviated as eSRT. The video will cover the clinical application of eSRT, the basics of the eSRT test procedure, and the use of the eSRT test screen and setup. 

Clinical applications

The eSRT test can be used by all clinicians fitting cochlear implants in the process of setting the upper levels. The test has its benefit being an objective measure, which limits the need of the patient's subjective feedback. This is a benefit in the pediatric population and for adults unable to tell us subjectively how the sound is perceived.

In addition, the test is beneficial in the follow-up adjustments. On occasions, the subjective adjustment of the upper levels can lead to over stimulation. In these cases, the objective eSRT measure has its benefit as the patient's feedback is not needed.

Test procedure

The eSRT test makes use of the direct link between the uncomfortable level perception of the patient and the objective stapedial reflex threshold. Therefore, the test builds upon the principle of the reflex measurement with the ability to measure the reflex ipsilateral and contralateral to the area of the sound being presented.

The Titan is used to monitor when a reflex is present while the cochlear implant software is used as the stimulus source, providing the electrical stimulus one electrode at a time during the fitting.

A good probe fit is essential in recording the eSRT and therefore, it is recommended to perform the test using a clinical probe. A probe tone is presented through the probe in order to detect when a reflex is present.

The probe tone used can be set to 226 Hz, 678 Hz, 800 Hz, and 1000 Hz. Wolfe et al. (2017) suggest cochlear implant surgery can lead to an increase in the middle ear stiffness. Their study showed that 678 Hz and 1000 Hz probe tones provide a significant improvement in the eSRT detection relative to using a 226 Hz probe tone.

While the reflex can be obtained both ipsilaterally and contralaterally, it is recommended to measure the eSRT contralateral to the implant. As with traditional reflex measures, it is recommended to check the middle ear functionality prior to reflex measurement. Therefore, it is recommended to include tympanometry as part of the protocol.

Test screen and setup

The eSRT test screen is made such that it can be easily monitored as to when a reflex is present. In order to be able to monitor this over time, the time window is running continuously.

When a reflex is seen to be present, it can be tagged by clicking at the peak. From the table at the right, one can edit the name of the peak or go back in time to look at another reflex. Jump back to the current point in time by pressing the small square.

The measure is stopped by pressing the stop button and at any time can be restarted.  In case the curve drifts away from zero, press the stop button and start it again. Thereby, the system compensates from the drifting that sometimes happens within the first five to ten seconds of the measure.

From the Titan eSRT setup, it is possible to set the threshold indication to be obtained at ambient or peak middle ear pressure. The probe tone can be set for the four different probe tone frequencies described previously.

Smoothing can be applied to remove noise from the trace. From the display settings, the reflex can be set to a positive or negative deflection. And the threshold indication line, providing the visual target of when a reflex is present, can be changed.

References

For additional information about the eSRT, please refer to some of the following articles:

Andrade, K. C., Leal, M.deC., Muniz, L. F., Menezes, P.deL., Albuquerque, K. M., & Carnaúba, A. T. (2014). The importance of electrically evoked stapedial reflex in cochlear implant. Brazilian journal of otorhinolaryngology, 80(1), 68–77.

Baysal, E., Karatas, E., Deniz, M., Baglam, T., Durucu, C., Karatas, Z. A., Mumbuc, S., & Kanlikama, M. (2012). Intra- and postoperative electrically evoked stapedius reflex thresholds in children with cochlear implants. International journal of pediatric otorhinolaryngology, 76(5), 649–652.

Cinar, B. C., Atas, A., Sennaroglu, G., & Sennaroglu, L. (2011). Evaluation of objective test techniques in cochlear implant users with inner ear malformations. Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 32(7), 1065–1074.

Kosaner, J. (2010). Generating Speech Processor Programmes for Children Using ESRT Measurements. Cochlear Implants International, 11(sup2), 20–24.

Vaerenberg, B., Smits, C., De Ceulaer, G., Zir, E., Harman, S., Jaspers, N., Tam, Y., Dillon, M., Wesarg, T., Martin-Bonniot, D., Gärtner, L., Cozma, S., Kosaner, J., Prentiss, S., Sasidharan, P., Briaire, J. J., Bradley, J., Debruyne, J., Hollow, R., Patadia, R., … Govaerts, P. J. (2014). Cochlear implant programming: a global survey on the state of the art. TheScientificWorldJournal, 2014, 501738.

Walkowiak, A., Lorens, A., Kostek, B., Skarzynski, H., & Polak, M. (2010). ESRT, ART, and MCL correlations in experienced paediatric cochlear implant users. Cochlear implants international, 11 Suppl 1, 482–484.

Wolfe, J., Gilbert, M., Schafer, E., Litvak, L. M., Spahr, A. J., Saoji, A., & Finley, C. (2017). Optimizations for the Electrically-Evoked Stapedial Reflex Threshold Measurement in Cochlear Implant Recipients. Ear and hearing, 38(2), 255–261.