COCHLEAR IMPLANT-RELATED OSTEONEOGENESIS IN AN ANIMAL-MODEL - FLUORESCENT LABELING

Cochlear osteoneogenesis may result from a variety of pathologic condi tions, including cochlear implantation. The etiology of cochlear osteo neogenesis following implantation, however, is not known. Cochlear imp lant-related osteoneogenesis has been demonstrated in laboratory anima ls, but the specific cause, extent, or time-course of this process has not been determined. In this preliminary study, fluorescent bone labe ls were used to assess osteoneogenesis in six chinchillas in three exp erimental categories: surgical trauma to the cochlea, chronic nonstimu lated cochlear implantation, and intrascalar neomycin infusion. Comput er image analysis was used to measure the area of labeled bone on repr esentative mid-modiolar histologic sections. The amount of bone deposi tion was greatest in ears treated with intracochlear neomycin (mean = 2.3835 mm2, SD = 3.7308). Surgical trauma alone (mean = 0.9549 mm2, SD = 1.384) and chronic implantation without stimulation did not produce substantial bone growth when compared to contralateral control ears ( mean = 0.0574 mm2, SD = 0.0731). Fluorochrome labeling was also used t o differentiate types of bone deposition. The morphology and timing of new bone growth appeared to be related to the type of cochlear injury . These results confirm that intracochlear neomycin may contribute to osteoneogenesis in animal studies of cochlear implantation. This study supports the use of fluorescent bone labeling in the evaluation of co chlear osteoneogenesis.