Impedance development after implantation of hybrid-L24 cochlear implant electrodes.

OBJECTIVE: Shorter and thinner electrodes were developed for preserving residual hearing after cochlear implantation by minimising trauma. As trauma is regarded as one of the causes of fibrous tissue formation after implantation, and increase in impedance is considered to be connected to fibrous tissue formation, the aim of the current study was to evaluate impedance development after implantation of Hybrid-L electrodes. DESIGN: Impedance values were retrospectively collected from our clinical database and evaluated for all active contacts and basal, middle and apical contacts separately for up to 10 years. STUDY SAMPLES: All 137 adult patients received a Hybrid-L electrode and had to be implanted for at least 1 year. RESULTS: On average impedances increased to 13 kOhm before first fitting and dropped to 5-7 kOhm under electrical stimulation with lower values measured on apical contacts. Mean values remained stable over years, but variability increased. Values before first fitting were independent of age at implantation whereas lower values were found later in patients of higher age at implantation. CONCLUSION: Despite smaller contacts, impedance values after start of electrical stimulation were comparable to published values of Contour electrodes. This might suggest less tissue growth with the Hybrid-L electrode array.

[Skull and skull base injuries in children and adolescents : Results of a monocentric analysis]. / Schädel- und Schädelbasisverletzungen bei Kindern und Jugendlichen : Ergebnisse einer monozentrischen Auswertung.

BACKGROUND: The present study comprises a retrospective analysis of skull, skull base, and midface fractures in children, to provide clinical orientation for their management. To date, only few data are available on these injuries in this patient group. METHODS: Data from inpatient cases diagnosed with a midface, skull, or skull base fracture in the Children's Hospital Auf der Bult from 2015 to 2020 were evaluated. Age, gender, fracture mechanism, diagnosis, treatment, and possible complications were analyzed. Data of 224 children were grouped into 107 cases with nose fractures, 104 cases with skull fractures, 9 patients with temporal bone fractures, 4 patients with rhinobasal fractures, and 2 cases with fractures of the orbital floor. RESULTS: Among patients with nose fractures, the average age was 10.9 years (64% males), among patients with skull fractures 1.0 year (64% males), and in children with skull base fractures 6.0 years (85% males). Falls were the most frequent genesis (63%), followed by car accidents, collisions (25%), and violence (10%). Patients with skull fractures underwent sonography in 94% of cases; in 87% the fracture was verified. Patients with nose fractures underwent x­ray in 92% of cases, or sonography only in 8%; 95% of patients with nose fractures underwent operative repositioning. Typical fracture signs (i.e., hemotympanum, ophthalmic symptoms) or signs of central nervous system involvement (i.e., nausea, amnesia) occurred in 12 of 13 children with skull base fractures, and CT was performed in all these cases (none of whom developed a cerebrospinal fluid leak). CONCLUSION: The imaging modality should be selected based on the clinically suspected diagnosis and the course. Most fractures can be sufficiently treated without any permanent sequelae, except for nose fractures, which frequently require operative repositioning.

Do Impedance Changes Correlate With a Delayed Hearing Loss After Hybrid L24 Implantation?

OBJECTIVES: Preservation of residual hearing is one of the main goals in present cochlear implantation surgery. Especially for this purpose, smaller and softer electrode carriers were developed that are to be inserted through the round window membrane to minimize trauma. By using these electrodes and insertion technique, residual hearing can be preserved in a large number of patients. Unfortunately, some of these patients with initially preserved residual hearing after cochlear implantation lose it later on. The reason for this is unknown but it is speculated about a correlation with an increase in impedance, since increased impedance values are linked to intracochlear inflammation and tissue reaction. Our hypothesis for this study design was that an increase in impedance predicts changes in residual hearing under clinical conditions. DESIGN: Data of all adult patients (N = 122) receiving a Hybrid-L24 cochlear implant at our center between 2005 and early 2015 were retrospectively evaluated. Impedance values in Common Ground mode as measured during clinical routine and referring audiological test data (audiometric thresholds under headphones) were collected. Changes between consecutive measurements were calculated for impedance values and hearing thresholds for each patient. Correlations between changes in impedances and acoustic hearing thresholds were calculated. Average values were compared as well as patients with largest impedance changes within the observation period were evaluated separately. RESULTS: Group mean values of impedances were between 5 and 7 kΩ and stable over time with higher values on basal electrode contacts compared with apical contacts. Average hearing thresholds at the time of initial fitting were between 40 to 50 dB (250 Hz) and 90 dB (1 kHz) with a loss of about 10 dB compared with preoperative values. Correlation between impedance changes and threshold changes was found, but too inconsistently to imply a true relationship. When evaluating the 20 patients with the largest impedance changes during the observation period (all >1 kΩ from one appointment to the next one), some patients were found where hearing loss is timely connected and highly correlated with an unusual impedance change. But large impedance changes were also observed without affecting hearing thresholds and hearing loss was found without impedance change. CONCLUSIONS: Changes in impedance as measured during clinical routine cannot be taken as an indicator for a late acoustic hearing loss.