Radiologic measurement of cochlea and hearing preservation rate using slim straight electrode (CI422) and round window approach.

Hearing preservation surgery constitutes a considerable branch of cochlear implantation surgery and is being steadily developed and perfected. The aim of the study was to verify if insertion of a cochlear implant electrode according to individually calculated linear insertion depth improves hearing preservation. We evaluated the relations between the size of a cochlea, insertion depth angle, linear insertion depth and hearing preservation rate (HP) according to Hearing Preservation Classification in a retrospective case review of 54 patients implanted with a slim straight electrode Nucleus CI422 in 2008-2011. Group HP was 0.75 at activation, 0.67 at 12 months (for 53 patients) and 0.60 at 24 months. In 53 cases, the mean insertion depth angle was 375° (SD 17°); mean calculated cochlear duct length 35.87 mm (SD 1.95); mean calculated linear insertion depth 23.14 mm (SD 1.68). There was no significantly relevant relation between HP values and angular insertion depth or insertion depth. Preoperative measurements of cochlea and specific parameters such as linear insertion depth have no effect on hearing preservation. Poor hearing preservation in some deep insertion cases cannot be explained entirely by the electrode position.

Preservation of cochlear structures and hearing when using the Nucleus Slim Straight (CI422) electrode in children.

OBJECTIVE: In cochlear implantation, there are two crucial factors promoting hearing preservation: an atraumatic surgical approach and selection of an electrode that does not damage cochlear structures. This study aimed to evaluate hearing preservation in children implanted with the Nucleus Slim Straight (CI422) electrode. METHODS: Nineteen children aged 6-18 years, with partial deafness, were implanted using the 6-step Skarzynski procedure. Electrode insertion depth was 20-25 mm. Hearing status was assessed with pure tone audiometry before surgery, and at 1, 5, 9, 12 and 24 months after surgery. Electrode placement was confirmed with computed tomography. RESULTS: Mean hearing preservation in the study group at activation of the cochlear implant was 73 per cent (standard deviation = 37 per cent). After 24 months, it was 67 per cent (standard deviation = 45 per cent). On a categorical scale, hearing preservation was possible in 100 per cent of cases. CONCLUSION: Hearing preservation in children implanted with the Nucleus CI422 slim, straight electrode is possible even with 25 mm insertion depth, although the recommended insertion depth is 20 mm. A round window approach using a soft, straight electrode is most conducive to hearing preservation.

A comparison of audiometric and objective methods in hearing screening of school children. A preliminary study.

OBJECTIVE: In newborn hearing screening, one exclusively applies objective hearing testing methods--based on evoked potentials and/or on otoacoustic emissions. However, when testing school children, one can consider both audiometric and electrophysiological methods. The choice of methods is determined by the aims of the program. If one wants to detect conductive hearing losses, impedance audiometry seems to be the method of choice. METHODS: The aim of this study was to compare test performance measures from audiometric and objective methods (OAEs and impedance audiometry), in the hearing screening of school children. Screening protocols were applied on a group of 190 children of about 12 years of age (6th grade of primary school). RESULTS: For a single application of a screening procedure, the best performance was observed in the automated four-tone audiometry, followed by the tympanometry and the TEOAE-based procedures. Screening performance was enhanced using a combination of automated and impedance audiometry. A four-tone audiometry test combined with tympanometry gives a sensitivity of 65%, and the PPV of 46%, which are reasonable values, acceptable for practical use. The use of a TEOAE protocol degrades the overall performance of screening. CONCLUSIONS: Screening of school children is feasible with a combination of automated audiometry and tympanometry with time requirements equal to 3 min per subject.