Acute Histopathologic Inner Ear Changes in Deafness Due to Neomycin: A Case Report

Abstract

A case presentation of a patient receiving 8 of neomycin intramuscularly in preparation for surgery is presented. Acute renal failure and total deafness followed this injection and the temporal bones were removed on the seventeenth day postinjection. Histological findings showed inner and outer hair cell degeneration and a normal spiral ganglion count. There were some changes in the stria vascularis which were noted in the basal turn.The ototoxicity of neomycin is well known, but new case reports continue with oral ~s e , l -~ irrigations of the pleural cavitv,5 mediastinume and infected wounds.' Renal failure and deafness with intramusculars and mediastinal irrigationss have been reported within the last year.Ototoxicity of neomycin, though well known, has not been explained. Renal lesions seen in cases of ototoxicity with ncomycin suqest a common mthological process fnr the kidney and the inner ear. Stunp.9 in a study of guinea pigs, states "all antibiotics belongine to the group of aminodycosides including streptomycin and dihydrostreptomycin, as well as kanamvcin and neomycin are concentrated and retained in the inner ear fluids. Their concentration both in the inner ear and the kidney, exceeds that of all other organs, even of the blood level manv timw over. The higher the toxicity of the substances, the more intense is their accumiilation in the inner ear fluid. Evidently, there exists a relation between the concentration and the ototovicitv of the different aminoglycoside antibiotics." "In comparison, -_--other antibiotics like penicillin attain only the lowcst level of the inner ear, w h i l e tetracvcline and polymyxin (Colistin@) will not penetrate in the inner ear at all, thus lacking the ototoxic effect." Nord ct al.1° reported a study of cquimolar concentrations in mice and reported the relative toxicity of four aminoglycosides. The relative toxicity in decreasina order was neomycin, gentamycin. kanamycin and dihydrostreptomycin.

Aminoglycoside Ototoxicity: A Human Temporal Bone Study

“… 30 In other reports of ototoxicity from streptomycin 15 and gentamicin, 10,12,29 ganglion cell reduction was present throughout the cochlea. Additional studies have reported normal ganglion cell populations in ototoxicity associated with neomycin, 10,21,22 streptomycin, 18 kanamycin, 15,18 and gentamicin. 9,10,32 …”

“… 9,10,15,18,26,28 Only a few studies have included actual counts of the number of surviving ganglion cells and compared them with normal populations of ganglion cells in patients without ototoxicity. 12,19,20,22,27 …”

“…Among these are examples of toxicity from ethacrynic acid, 13 cisplatin, 14 -16 and aminoglycoside antibiotics. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] However, aminoglycoside ototoxicity provides the majority of examples of human temporal bone, including patients treated with streptomycin, 15,[17][18][19][20] neomycin, 10,15,18,21,22 kanamycin, 18,20,[23][24][25][26][27][28] amikacin, 9,10 and gentamicin. 9,10,12,15,29 -32 In addition, there are many other descriptions of patients who were given combinations of ototoxic medications, and descriptions of tobramycin effects are among these.…”

“…9,10,15,18,26,28 Only a few studies have included actual counts of the number of surviving ganglion cells and compared them with normal populations of ganglion cells in patients without ototoxicity. 12,19,20,22,27 Therefore, we present two additional cases of ototoxicity in patients who were given aminoglycoside therapy. In contrast to many earlier cases of ototoxicity that have been reported, the administration of the ototoxic medications, drug serum levels, and renal function were all well documented during life.…”