Direct Drive Simulation-Preoperative Sound Simulation of "Vibroplasty-Hearing" in Patients With Mixed Hearing Loss.

OBJECTIVE: Validation of the preoperative sound simulation test for vibroplasty-hearing so-called "Direct Drive Simulation" (DDS) in case of mixed hearing loss. STUDY DESIGN: Retrospective data analysis. SETTING: Tertiary referral center with a large hearing implant program. MAIN OUTCOME MEASURE: Comparison of sound impression during preoperative Direct Drive Simulation, and postoperative testing with the activated active middle ear implant (AMEI) under free-field condition and in daily routine. PATIENTS: Fifty-four data sets from 18 patients with mixed hearing loss with a mean age of 60.78 ±â€Š3.18 were included. RESULTS: Comparing the sound impression during DDS preoperatively versus free-field testing with the implanted AMEI, no significant differences were found. DDS offers a slightly better sound quality than the AMEI in daily routine, fitting well to the ideal listening situation in DDS versus some background noise in daily routine. CONCLUSION: The DDS offers the possibility of a realistic preoperative sound simulation of the "vibroplasty-hearing" in cases of mixed hearing loss. This probably facilitates patient's decision towards a vibroplasty. The audiologist as well as the surgeon get additional information regarding the indication especially when audiologic inclusion criteria are critical. Thus, the DDS is a useful extension of preoperative diagnostics before vibroplasty.

BDNF in Lower Brain Parts Modifies Auditory Fiber Activity to Gain Fidelity but Increases the Risk for Generation of Central Noise After Injury.

For all sensory organs, the establishment of spatial and temporal cortical resolution is assumed to be initiated by the first sensory experience and a BDNF-dependent increase in intracortical inhibition. To address the potential of cortical BDNF for sound processing, we used mice with a conditional deletion of BDNF in which Cre expression was under the control of the Pax2 or TrkC promoter. BDNF deletion profiles between these mice differ in the organ of Corti (BDNF (Pax2) -KO) versus the auditory cortex and hippocampus (BDNF (TrkC) -KO). We demonstrate that BDNF (Pax2) -KO but not BDNF (TrkC) -KO mice exhibit reduced sound-evoked suprathreshold ABR waves at the level of the auditory nerve (wave I) and inferior colliculus (IC) (wave IV), indicating that BDNF in lower brain regions but not in the auditory cortex improves sound sensitivity during hearing onset. Extracellular recording of IC neurons of BDNF (Pax2) mutant mice revealed that the reduced sensitivity of auditory fibers in these mice went hand in hand with elevated thresholds, reduced dynamic range, prolonged latency, and increased inhibitory strength in IC neurons. Reduced parvalbumin-positive contacts were found in the ascending auditory circuit, including the auditory cortex and hippocampus of BDNF (Pax2) -KO, but not of BDNF (TrkC) -KO mice. Also, BDNF (Pax2) -WT but not BDNF (Pax2) -KO mice did lose basal inhibitory strength in IC neurons after acoustic trauma. These findings suggest that BDNF in the lower parts of the auditory system drives auditory fidelity along the entire ascending pathway up to the cortex by increasing inhibitory strength in behaviorally relevant frequency regions. Fidelity and inhibitory strength can be lost following auditory nerve injury leading to diminished sensory outcome and increased central noise.