Ultrastructural changes in the spiral limbus associated with carboplatin-induced ablation of inner hair cells

Four months after the selective ablation of inner hair cells by carboplatin , the interdental cell epithelium exhibited dilated intercellular spaces an d cytosolic vacuoles not seen in controls. In addition, the wide, often ele ctron-lucent phalanges observed in the interdental cells of the normal chin chilla collapsed into a dense stratum that projected enlarged polypoid prof iles into the limbal zone of the tectorial membrane. Carboplatin treatment also resulted in the restructuring of the tectorial membrane overlying the limbus. Changes in this membrane included a variable accumulation of the ba sal matrix, the rearrangement of intermediate lucent spaces, and the disapp earance of a superimposed filamentous mesh. These three strata are, under n ormal conditions, apparently involved in events underlying tectorial membra ne renewal. The post-carboplatin changes in the interdental cells and tecto rial membrane occurred exclusively in the proposed medial pathway for K+ di ffusion from inner hair cells and presumably resulted from a reduced flow o f ions and fluid secondary to the ablation of these cells.