Effects of fine structure and extended low frequencies in pediatric cochlear implant recipients

In recent years, new speech coding strategies have been developed with the aim of improving the transmission of temporal fine structure to cochlear implant recipients. This study reports on the implementation of one such strategy (fine structure processing, FSP) in children.

This was a prospective study investigating the upgrade to a new speech processor. The upgrade used a repeated measures design with an alternating order of conditions (A-B-A-B design). Twelve pre- and perilingually deaf children with MED-EL C40+ cochlear implants were enrolled in the study. Patients were upgraded from their Tempo+ speech processor, which used continuous interleaved sampling (CIS) in combination with a frequency spectrum of 200-8500 Hz, to an Opus speech processor, which used FSP with an extended frequency spectrum of 70-8500 Hz. The primary means of testing was an HSM (Hochmair, Schulz and Moser) sentence test at 65 and 80 dB in quiet. In addition, the "Mainzer Kindersprachtest" (Mainz audiometric speech test for children) was applied at 65 and 70 dB.

When the new FSP speech processor was used together with the extended low frequency range, HSM sentence tests at 65 and 80 dB resulted in scores indicating statistically significant improvements of 7.1 and 9.9 percentage points, respectively. Scores in the "Mainzer Kindersprachtest" at 65 and 70 dB indicated statistically significant improvements of 9.3 and 6.1 percentage points, respectively.

The present study clearly shows that children benefit from the fine structure speech coding strategy in combination with an extended frequency spectrum in the low frequencies, as is offered by the Opus speech processors. This should be taken into consideration when fitting pre- and perilingually deaf children implanted almost a decade previously.