Histological effects of intratympanic gentamicin on the vestibular organ of guinea pigs.
BACKGROUND
Transtympanic administration of gentamicin may be suitable to achieve unilateral vestibular ablation, in order to control unilateral Ménière's disease. In low doses, gentamicin appears to affect selectively the vestibular system, with relative sparing of the cochlea. An experimental study on guinea pigs was conducted to determine what single dose of gentamicin would produce a unilateral vestibular organ lesion when applied to the middle ear.


METHODS
Experimental and prospective.


METHODS
Four groups of guinea pigs received different gentamicin doses (1, 5, 10 and 25 mg) administered to the middle ear. The animals' vestibular organs were then assessed by scanning electron microscopy, in order to quantify the level of vestibular damage.


RESULTS
Study of the utricular macula and the ampullar crista of the lateral semicircular canal revealed vestibular neuroepithelial lesions in all infused ears.


CONCLUSIONS
The severity of the vestibular neuroepithelial lesions was dose-dependent. Lower gentamicin doses were observed to damage vestibular structures more than cochlear structures.
Department of Ophthalmology, Otorhinolaryngology and Head and Neck Surgery, University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
R C
RC
Demarco
M
M
Rossato
J A A
JA
de Oliveira
M A
MA
Hyppolito
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004432:Ear, Middle / Q000187:drug effects* / Q000648:ultrastructure; D005260:Female; D005839:Gentamicins / Q000008:administration & dosage / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D008855:Microscopy, Electron, Scanning; D012444:Saccule and Utricle / Q000187:drug effects / Q000648:ultrastructure; D054776:Semicircular Ducts / Q000187:drug effects / Q000648:ultrastructure
D000900:Anti-Bacterial Agents; D005839:Gentamicins