gms | German Medical Science

Patients with hearing loss bordering on deafness or complete deafness can be fitted with a cochlear implant (CI) to regain an auditory perception. Listening with a CI is perceived by most patients as unpleasant and disturbing, especially at the beginning. The hearing performance of CI patients is highly variable, even after a period of familiarization, and is often inadequate in real-life listening situations with background noise. One potential reason for the poor hearing quality is that the distribution of frequency bands is the same for all patients, regardless of where the individual electrodes are positioned within the cochlea. The electrical frequency bands at a given intra cochlear position may differ up to two octaves from the physiological frequency assignment. This study investigates whether a customized mapping of frequency bands, known as anatomy-based fitting (ABF), could improve sound quality and speech perception compared to the conventional “one size fits all” standard mapping approach. Hereby, the exact electrode position is determined using high-resolution digital volume tomography and subsequent 3D-reconstruction.

A randomized cross-over design was employed, with participants randomly assigned to two groups. One group received the manufacturer’s standard map (STD), while the other underwent ABF. After three months, participants switched to the alternative mapping for another three months. Subsequently, all participants had both mappings for three months, enabling them to determine their preferred setting.

Speech perception tests in quiet (Freiburg Monosyllables, FMS) were conducted at various intervals to assess the benefits of each mapping method. Subjective hearing quality was also evaluated using the SSQ questionnaire. Participants were implanted with Synchrony 2 implant devices, using either Rondo3 or Sonnet2 audio processors.

Among the 47 subjects so far recruited, 13 patients were marked as dropouts due to various reasons. Preliminary results at the 3-month interval showed that median FMS for STD group and ABF group was 58% (N=21) and 51% (N=16), respectively. The average SSQ total score for the STD group was 4–7 and 5.7 for the ABF group, indicating better hearing quality in the ABF group. However, at the 6-month interval, the median FMS was equal in both groups (60%). SSQ scores were 5.9 and 4.4 for STD and ABF group, indicating the difficulty of the adaptation to modified frequency settings.

Preliminary results showed no clear advantage of ABF in speech perception scores at the different test intervals. However, a trend towards better quality scores in the ABF group was observed. Results of the 9-month endpoint of the study will be presented at the meeting.