Effects of systemic and lateral semicircular canal administration of aminoglycosides on normal and hydropic inner ears.

Streptomycin was injected subcutaneously into guinea pigs (n = 12) with unilateral endolymphatic hydrops. In the unoperated ears, sensory cells were degenerated at the basal ends of all cochleas and to varying extents in the vestibular sense organs. Hydropic ears, in contrast, showed greater ototoxicity in the cochlear and saccular sensory cells, while the drug's effect on the utricular and cristae sensory cells was increased, but less remarkable. In another series of normal animals (n = 16), streptomycin was applied to a fenestra of the lateral semicircular canal. Sensory cells of all three canal cristae and utricular macula were degenerated frequently, but the sensory cells of the cochleas were rarely affected. The vestibular lesions resulting from the canal approach were greater than those produced by systemic injection. Comparison with a former gentamicin-lateral canal series revealed very little difference in action of the two drugs. However, in hydropic ears, gentamicin application to the lateral canal produced increased lesions in all sensory cells, particularly in the organ of Corti. Hydropic ears are vulnerable and a greater caution is needed in administering aminoglycosides by both the systemic and the canal route to patients with Meniere's disease.