["Typical" and "atypical" damages of the organ of hearing from the administration of streptomycin].

Two areas of the damage localization in the organs of hearing after streptomycin use were found in the experiments with guinea pigs, i.e. (1) the Corti's organ of the lower part of the basal helix, the zone of perception of the maximum frequency sounds and (2) the tympanic muscles. Administration of streptomycin subcutaneously in a daily dose of 300 mg/kg for 50 days resulted in pronounced atrophic changes in the fibres of m. tensor tympani and some atony of m. stapedius. On the basis of the histological examination of the tympanic muscles after prolonged use of streptomycin and comparison of the periods of the tonus reduction in the skeletal muscles and Preier reflex after a single administration of streptomycin in maximum tolerating doses, it was concluded that streptomycin affected the state of the tympanic muscles as a myorelaxant. The atrophic changes in the tensor as a result of prolonged streptomycin use was due to chronic atony of the muscle. The decrease in the contraction capacity of the tensor must result in loosening of the drum membrane tension, impairement of the muscle activity coordination, decreased ability for elimation of the auditory ossicle fluctuation. Increased audibility limits within middle and low frequencies and noise in the ears during prolonged treatment of patients with streptomycin may be associated with chronic atony of the tympanic muscles and mainly tensor.