What is ESRT
Nov 01, 2007 @ 11:18 AM
I thought I'd add to what I wrote earlier by
explaining what ESRT is, and why it is important.
Here is what an audiology site says about it:
Electrically Evoked Stapedius Reflex Threshold (ESRT):
A stapedius reflex involves contraction of a tiny muscle in the middle ear in response to loud sounds. In the normal hearing ear, the reflex is elicited bilaterally in response to acoustic stimulation in either ear. The reflex can be measured in either the ipsilateral or contralateral ear using a standard tympanometer. In cochlear implant patients, a stapedius reflex can be measured in the contralateral (non-implanted) ear in response to electrical stimulation through the implant. An Electrically Evoked Stapedius Reflex Threshold (ESRT) is defined as the lowest level of electrical stimulation that elicits a measurable response. Measurement of the ESRT requires passive cooperation, meaning that the patient should remain relatively still and quiet during each recording. Excessive swallowing, talking, or head movements could disrupt the measurement. To record an ESRT, the patient must exhibit a healthy middle ear status. Fluid in the middle ear or dysfunction of the eardrum or middle ear ossicles can prevent measurement of the ESRT. In some cases, a patient with normal middle ear function may not exhibit a measurable reflex response.
The ESRT is measured using a standard tympanometer, cochlear implant software, and the patient’s cochlear implant equipment. A soft recording probe is placed in the ear contralateral to the cochlear implant. Tympanometry is performed to confirm normal middle ear status. A good seal of the recording probe and peak compliance of the middle ear should also be confirmed prior to recording an ESRT. The tympanometer is set for measurement of reflex decay, providing a longer recording window. Electrical stimulation is presented through the cochlear implant via interactive software. Stimulation is gradually increased until a sufficient deflection is observed in the reflex decay window, and a standard bracketing procedure is used to determine the stapedius reflex threshold.
ESRT measurements are performed using the same software platform and electrical stimulus utilized for fitting the cochlear implant.10 Thus, stimulus parameters, including pulse duration and repetition rate, can be identical to those used to obtain behavioral judgments for psychophysical levels.1 This allows a direct comparison between ESRT and behavioral measurements, making the ESRT data potentially more predictive for purposes of fitting the cochlear implant. Studies have been conducted to determine the correlation between ESRTs and behavioral measures of THR and MCL values. A positive correlation between two values is represented by a correlation coefficient value between 0.0 and 1.0. A coefficient value of 0.0 would represent a random relationship, and a perfect correlation would be represented by a coefficient of 1.0.
Measurement of the ESRT can be performed both intraoperatively and postoperatively. Studies have shown that postoperative ESRT results are more closely correlated to behaviorally measured MCL values. The overall correlation between postoperative ESRT and MCL is extremely high, indicating that ESRTs are highly predictive of MCL values. Stephan and Welzl-Müller reported a correlation coefficient of 0.92.1 Similarly, Hodges et al. found a correlation of 0.91.10 In most cases, the behavioral MCL is recorded at levels exceeding the ESRT.1 A number of investigators have confirmed that the ESRT can be measured with no discomfort to the patient.1, 5, 10, Stephan and Welzl-Müller concluded that measurement of ESRTs during the fitting process can help avoid overstimulation via the cochlear implant, which is of particular importance when fitting children.1
The ESRT pattern across electrodes is similar to the pattern observed in behaviorally measured MCL values. Thus, individuals with flat MCL responses also demonstrate flat ESRT responses. Likewise, an irregularly shaped MCL response will be replicated by the ESRT response. ESRT data for the MED-EL COMBI 40 and COMBI 40+ cochlear implant systems reveal no significant variance in the ESRT/MCL based on location of the electrode stimulated. This finding is significant in relation to the loudness balancing between MCL values across electrodes.1
Collection of ESRT data on all stimulating electrodes can be completed in less than one hour in most cases.10 Based on findings that patterns for ESRT and behavioral MCL responses are similar across the array,1 it may not be necessary to record ESRT data for every stimulating electrode. For young children, recordings can be performed on a sampling of basal, medial, and apical electrodes. In this way, ESRT measurements could likely be completed on a total of 3-5 electrodes in approximately 15 minutes. For all other electrodes that utilize the same pulse duration, the ESRT-derived MCL value can be interpolated based on the electrodes measured. The use of cartoon videos or the child’s natural sleep schedule has been found successful for measuring ESRTs with less cooperative and very young children.10 Hodges et al. concluded that the ESRT is ''an accurate and rapid method of estimating maximum comfortable loudness levels, which may be useful in the initial programming of young implant recipients.''10
Researchers have compared speech perception results between maps with ESRT-based MCL values and maps based on behavioral measurements of MCL. Spivak et al. showed that 5 of 7 subjects performed either better with the ESRT map or equally well with both maps. This study also found that 4 of 7 subjects preferred the sound quality of the ESRT map when compared with conventionally determined maps.5 Other researchers have reported similar findings.1, 10
Hodges et al. found that the majority of adult subjects with the Nucleus multichannel cochlear implant system prefer a map set using ESRTs over a map set behaviorally, ''generally describing the sound as sharper and clearer.''10 Spivak et al. concluded that ESRTs ''may be an adequate substitute for comfort levels when programming the implant for patients who are unable to make reliable psychophysical judgments.''5 Finally, because the ESRT has been shown to be a more stable measurement over time than behavioral MCL values, it has been speculated that the ESRT may be ''a more reliable and consistent measure on which to base the map.''
from:
http://www.speechpathology.com/articles/article_detail.asp?article_id=44
Electrically Evoked Stapedius Reflex Threshold (ESRT):
A stapedius reflex involves contraction of a tiny muscle in the middle ear in response to loud sounds. In the normal hearing ear, the reflex is elicited bilaterally in response to acoustic stimulation in either ear. The reflex can be measured in either the ipsilateral or contralateral ear using a standard tympanometer. In cochlear implant patients, a stapedius reflex can be measured in the contralateral (non-implanted) ear in response to electrical stimulation through the implant. An Electrically Evoked Stapedius Reflex Threshold (ESRT) is defined as the lowest level of electrical stimulation that elicits a measurable response. Measurement of the ESRT requires passive cooperation, meaning that the patient should remain relatively still and quiet during each recording. Excessive swallowing, talking, or head movements could disrupt the measurement. To record an ESRT, the patient must exhibit a healthy middle ear status. Fluid in the middle ear or dysfunction of the eardrum or middle ear ossicles can prevent measurement of the ESRT. In some cases, a patient with normal middle ear function may not exhibit a measurable reflex response.
The ESRT is measured using a standard tympanometer, cochlear implant software, and the patient’s cochlear implant equipment. A soft recording probe is placed in the ear contralateral to the cochlear implant. Tympanometry is performed to confirm normal middle ear status. A good seal of the recording probe and peak compliance of the middle ear should also be confirmed prior to recording an ESRT. The tympanometer is set for measurement of reflex decay, providing a longer recording window. Electrical stimulation is presented through the cochlear implant via interactive software. Stimulation is gradually increased until a sufficient deflection is observed in the reflex decay window, and a standard bracketing procedure is used to determine the stapedius reflex threshold.
ESRT measurements are performed using the same software platform and electrical stimulus utilized for fitting the cochlear implant.10 Thus, stimulus parameters, including pulse duration and repetition rate, can be identical to those used to obtain behavioral judgments for psychophysical levels.1 This allows a direct comparison between ESRT and behavioral measurements, making the ESRT data potentially more predictive for purposes of fitting the cochlear implant. Studies have been conducted to determine the correlation between ESRTs and behavioral measures of THR and MCL values. A positive correlation between two values is represented by a correlation coefficient value between 0.0 and 1.0. A coefficient value of 0.0 would represent a random relationship, and a perfect correlation would be represented by a coefficient of 1.0.
Measurement of the ESRT can be performed both intraoperatively and postoperatively. Studies have shown that postoperative ESRT results are more closely correlated to behaviorally measured MCL values. The overall correlation between postoperative ESRT and MCL is extremely high, indicating that ESRTs are highly predictive of MCL values. Stephan and Welzl-Müller reported a correlation coefficient of 0.92.1 Similarly, Hodges et al. found a correlation of 0.91.10 In most cases, the behavioral MCL is recorded at levels exceeding the ESRT.1 A number of investigators have confirmed that the ESRT can be measured with no discomfort to the patient.1, 5, 10, Stephan and Welzl-Müller concluded that measurement of ESRTs during the fitting process can help avoid overstimulation via the cochlear implant, which is of particular importance when fitting children.1
The ESRT pattern across electrodes is similar to the pattern observed in behaviorally measured MCL values. Thus, individuals with flat MCL responses also demonstrate flat ESRT responses. Likewise, an irregularly shaped MCL response will be replicated by the ESRT response. ESRT data for the MED-EL COMBI 40 and COMBI 40+ cochlear implant systems reveal no significant variance in the ESRT/MCL based on location of the electrode stimulated. This finding is significant in relation to the loudness balancing between MCL values across electrodes.1
Collection of ESRT data on all stimulating electrodes can be completed in less than one hour in most cases.10 Based on findings that patterns for ESRT and behavioral MCL responses are similar across the array,1 it may not be necessary to record ESRT data for every stimulating electrode. For young children, recordings can be performed on a sampling of basal, medial, and apical electrodes. In this way, ESRT measurements could likely be completed on a total of 3-5 electrodes in approximately 15 minutes. For all other electrodes that utilize the same pulse duration, the ESRT-derived MCL value can be interpolated based on the electrodes measured. The use of cartoon videos or the child’s natural sleep schedule has been found successful for measuring ESRTs with less cooperative and very young children.10 Hodges et al. concluded that the ESRT is ''an accurate and rapid method of estimating maximum comfortable loudness levels, which may be useful in the initial programming of young implant recipients.''10
Researchers have compared speech perception results between maps with ESRT-based MCL values and maps based on behavioral measurements of MCL. Spivak et al. showed that 5 of 7 subjects performed either better with the ESRT map or equally well with both maps. This study also found that 4 of 7 subjects preferred the sound quality of the ESRT map when compared with conventionally determined maps.5 Other researchers have reported similar findings.1, 10
Hodges et al. found that the majority of adult subjects with the Nucleus multichannel cochlear implant system prefer a map set using ESRTs over a map set behaviorally, ''generally describing the sound as sharper and clearer.''10 Spivak et al. concluded that ESRTs ''may be an adequate substitute for comfort levels when programming the implant for patients who are unable to make reliable psychophysical judgments.''5 Finally, because the ESRT has been shown to be a more stable measurement over time than behavioral MCL values, it has been speculated that the ESRT may be ''a more reliable and consistent measure on which to base the map.''
from:
http://www.speechpathology.com/articles/article_detail.asp?article_id=44