Temporal bones from five patients with hearing loss as a result of aminoglycoside treatment were examined by the method of microdissection and surface preparations, followed by celloidin embedding and serial sectioning of the modiolus. Three patients had received the newer antibiotics, gentamicin, tobramycin, and amikacin; the other two neomycin. In the cochleas from two patients of the first group there was only a small loss of hair cells, restricted to the lower end of the basal turn. The third, who had been treated with several antibiotics over a longer period of time, showed more extensive but strikingly asymmetrical patterns of degeneration in the two ears. This patient, as well as the fourth, who had received neomycin during peritoneal lavage, had numerous patchy areas of complete disappearance of Corti's organ in the basal turn, with incipient degeneration of the distal ends of the nerve fibers in adjacent portions of the osseous spiral lamina. The fifth patient, who had become deaf after prolonged treatment with neomycin by mouth, showed a complete loss of cochlear hair cells. Nerve fibers were present only in the middle and upper turns, where supporting cells remained. Midmodiolar sections showed a proportionately much greater loss of the distal than of the proximal processes of the cells of the spiral ganglion. These findings underscore once again the special hazard for the inner ear that is associated with the clinical use of neomycin, regardless of the route of administration.
