Variations in microanatomy of the human cochlea.
Bottom Line: At the lateral region, the height decreased significantly at the beginning of the second turn.We found a correlation between the length of the RC and that of the ST.These differences could have considerable implications for approaches to the design of CI arrays, especially in terms of their ability to preserve residual hearing during insertion of the electrode array.
Affiliation: Cluster of Excellence Hearing4all, Institute of AudioNeuroTechnology and Department of Experimental Otology, Ear, Nose, and Throat Clinics, Hannover Medical University, Hannover, 30625, Germany.Show MeSH
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Mentions: For this study, 16 fresh-frozen human temporal bones without any evidence of malformation were analyzed. Ten left and six right temporal bones were used. The fresh-frozen bones were slowly thawed at room temperature, and were subsequently cut around the cochlea in blocks of approximately 3.5 × 3.5 cm, containing the outer, middle, and inner ear. This procedure has been shown to preserve the cochlea well, including its micromechanical properties (Ravicz et al., 2000; Rosowski et al., 1990). To gain access to the inner ear, a standard mastoidectomy and posterior tympanotomy were performed. This approach allowed direct access to the inner ear. The cochlear fluid (perilymph) and the fine structures in the cochlea have a similar X-ray attenuation coefficient, which reduces the resulting image contrast. To visualize the fine structures in the cochlea, the round window (RW) membrane was opened and a small opening at the oval window was drilled. By using a suction tube and the two openings (round and oval windows), the cochlear fluid was gently removed at the RW. This intervention allowed a substantial increase in the image contrast between the soft tissue (basilar membrane, spiral ligament, endosteum) and the scalae. Subsequently, the cochlea was wrapped with formaldehyde-immersed cotton tissue for fixation. The subsequent μCTs were used to assess the quality of the storage and preparation technique. In all cochleae used, no damage of the microanatomy was observed attributable to preparation and fixation. Figure 1 shows the difference between image quality in fluid-filled (Fig. 1A) and air-filled (Fig. 1B) scalae.
Affiliation: Cluster of Excellence Hearing4all, Institute of AudioNeuroTechnology and Department of Experimental Otology, Ear, Nose, and Throat Clinics, Hannover Medical University, Hannover, 30625, Germany.