[Effects of transtympanic lidocaine infusion on cochleas]

To investigate into the effects of transtympanic lidocaine infusion on the cochlea, 112 albino guinea pigs were studied by measuring CAP and examining the organ of Corti under optical and electronic microscopes. The changes included prolongation of CAP latency and elevation of threshold microscopeically, the lost OHC-SC of the organ of Corti near the round window. The severity varied with concentrations of lidocaine used. Changes of IHC-SC were slight. Under TEM, the significant changes were that the efferent synaptic spaces were widened and post-synaptic cisternae dilated, the mitochondria in OHC, IHC and their nerve endings became swelled and degenerated. The higher the concentration of lidocaine used, the more obvious the morphological damages were. The damages seemed to develop in 14 days.