Cochlear pathology of long term @entity5154 induced @entity2319 in XXXX .

@entity17 @entity2167 @entity4494 @entity2319 @entity1897 @entity5154 @entity393 @entity468 @entity528 @entity4028
The long term sequelae of hair cell destruction consequent from administration of the @entity2167 @entity4028 antibiotic, @entity5154 , were evaluated in histological and ultrastructural studies of cochlear morphology in @entity468 . @entity393 , as defined by an absence of brainstem evoked responses to click stimulation at 120 dB peak SPL, was induced by intramuscular injections of @entity5154 at 50 mg/kg body weight/day, and cochlear pathology was studied at 6 months and 1, 3 and 4 years following onset of profound @entity2319 . In these long term @entity2167 cases the organ of Corti was collapsed and resorbed over the basal one-quarter to three-quarters of the cochlear spiral, depending on duration of @entity2319 . Significant progressive reduction in the @entity4494 cell population and sequential degenerative alterations in the remaining neurons were observed with increasing time elapsed after induced @entity393 . The sequence of pathological alterations in @entity528 appeared to be: a) swelling, @entity17 and @entity1897 ; b) @entity17 and shrinkage of the cell soma with preservation of the central axon; and c) @entity17 of the central axon and degeneration of the cell perikaryon. In apical cochlear regions, severe degeneration of the @entity4494 preceded the collapse of the tunnel of Corti and regional loss of pillar cells. Residual populations of @entity528 were as low as 1-2% of the normal values in the most severely degenerated cochleae in the series. Light microscopic and ultrastructural studies revealed a selective survival advantage for the unmyelinated type II neurons over the myelinated type I neurons with these long survival periods. The prolonged time course and atrophic nature of these pathological alterations suggests that degeneration of @entity528 progresses continuously following drug-induced insult to the cochlea. Some possible factors contributing to this long term progressive degeneration will be discussed.
