Preservation of auditory brainstem response thresholds after cochleostomy and titanium microactuator implantation in the lateral wall of cat scala tympani.

HYPOTHESIS: The safety of implanting a titanium microactuator into the lateral wall of cat scala tympani was assessed by comparing preoperative and postoperative auditory brainstem response (ABR) thresholds for 1 to 3 months. BACKGROUND: The safety of directly stimulating cochlear perilymph with an implantable hearing system requires maintaining preoperative hearing levels. This cat study is an essential step in the development of the next generation of fully implantable hearing devices for humans. METHODS: Following GLP surgical standards, a 1-mm cochleostomy was drilled into the lateral wall of the scala tympani, and a nonfunctioning titanium anchor/microactuator assembly was inserted in 8 cats. The scala media was damaged in the 1 cat. ABR thresholds with click and 4- and 8-kHz stimuli were measured preoperatively and compared with postoperative thresholds at 1, 2, and 3 months. Nonimplanted ear thresholds were also measured to establish statistical significance for threshold shifts (>28.4 dB). Two audiologists independently interpreted thresholds. RESULTS: Postoperatively, 7 cats implanted in the scala tympani demonstrated no significant ABR threshold shift for click stimulus; one shifted ABR thresholds to 4- and 8-kHz stimuli. The eighth cat, with surgical damage to the scala media, maintained stable click threshold but had a significant shift to 4- and 8-kHz stimuli. CONCLUSION: This cat study provides no evidence of worsening hearing thresholds after fenestration of the scala tympani and insertion of a titanium anchor/microactuator, provided there is no surgical trauma to the scala media and the implanted device is securely anchored in the cochleostomy. These 2 issues have been resolved in the development of a fully implantable hearing system for humans. The long-term hearing stability (combined with histologic studies) reaffirm that the microactuator is well tolerated by the cat cochlea.

Implantation and monitoring of a novel telemetry unit in the Syrian golden hamster model.

Radiotelemetry allows for real-time remote monitoring of biological parameters in freely moving laboratory animals. The HD-X11 transmitter is a novel telemetry device that enables simultaneous collection of body temperature, activity, blood pressure, electrocardiogram (ECG), and other biopotentials in small animal models. Previously, researchers could only collect either blood pressure or ECG parameters; prioritizing the signal of most interest or increasing the number of animals on study to capture both signals at one time. This new device eliminates the need for separate animal groups for assorted measurements and allows for a more complete cardiovascular assessment. Evaluation of the transmitter from both surgical and data collection perspectives indicates that the HD-X11 transmitter can be a useful tool to researchers in a wide range of scientific and medical fields.