Electrically evoked compound action potentials (eCAP) and electrically evoked stapedius reflex threshold (eSRT) techniques were compared to establish how well the two techniques correlated and which yielded quicker results in a group of paediatric cochlear implant (CI) users. This team using MED-EL devices, compared the eCAP measurements recorded on x1 apical, x1 medial and x1 basal electrode on each of the 52 patients identified as having eSRTs on the same range of electrodes. A total of 156 electrical contacts with eSRTs were compared with 152 eCAP measures. Patients were unilaterally implanted and were under the age of 18 (range 1 – 17.5 years). The team found that there was a weak to medium correlation between the thresholds obtained from the two techniques. eCAP thresholds tended to be lower and took 4.2 times longer to record. This confirms MED-EL’s programming philosophy that eSRTs are excellent predictors of behavioural fitting values, providing better maps than those based on eCAPs. It is not possible to directly transfer these results to the programming of devices from different CI manufacturers without further studies. Other implant companies have different software for measuring the two techniques which could be quicker/slower or more/less accurate than the MED-EL software. In addition, the transfer of these results to other clinics should be made cautiously as the following factors: bilateral implantation; the prevalence of otitis media with effusion and the implant population itself all influence the efficacy of these recording techniques, particularly when measuring eSRTs.
eSRTs versus eCAP: Which is better?
Reviewed by Kerri Millward and Morag Lockley
Comparing eSRT and eCAP measurements in pediatric MED-EL cochlear implant users.
CONTRIBUTOR
Kerri Millward
Manchester Paediatric Cochlear Implant Programme, Manchester, UK.
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