Gentamicin tympanoclysis: effects on the labyrinthine sensory cells.
OBJECTIVE
The objective of the study was to determine whether a selective vestibular hair cell toxicity with sparing of the cochlear hair cells could be achieved by infusing different concentrations of gentamicin into the middle ears of adult cats.


METHODS
Prospective experimental animal study treating only the left ear of each cat, the right ear serving as individual control.


METHODS
Gentamicin solution at concentrations of either 30 or 3 mg/mL was infused daily into the left middle ear of adult cats until overt ataxia occurred. After 1 month or 6 months, each cat was killed and its temporal bones prepared for optical microscopy.


RESULTS
Animals treated with 30 mg/mL gentamicin until ataxic required a median of five daily doses. These animals had clear-cut cochlear basal turn hair cell losses accompanying toxic lesions in the utricle and cristae. In contrast, animals treated with 3 mg/mL gentamicin until ataxic required an average of 19 daily doses. These animals had lesions restricted to the utricle and cristae with sparing of the cochlea hair cells. Animals that failed to develop ataxia manifested neither lesions of the cochlear nor vestibular hair cells.


CONCLUSIONS
Gentamicin tympanoclysis in the cat animal model, using a dilute solution and continued once daily until clinical ataxia occurs, is capable of producing selective vestibular hair cell toxicity while sparing cochlea hair cells.
Pender
Daniel J
DJ
Department of Otolaryngology, Columbia Presbyterian Medical Center, New York, NY, USA.
D008267:Acoustic Maculae / Q000187:drug effects / Q000473:pathology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000633:toxicity*; D001259:Ataxia / Q000139:chemically induced; D002415:Cats; D004432:Ear, Middle / Q000187:drug effects / Q000473:pathology; D005839:Gentamicins / Q000008:administration & dosage / Q000633:toxicity*; D006198:Hair Cells, Auditory / Q000187:drug effects* / Q000473:pathology; D018069:Hair Cells, Vestibular / Q000187:drug effects / Q000473:pathology; D008575:Meniere Disease / Q000188:drug therapy; D009925:Organ of Corti / Q000187:drug effects / Q000473:pathology; D010033:Otitis Media / Q000473:pathology; D012444:Saccule and Utricle / Q000187:drug effects / Q000473:pathology; D013701:Temporal Bone / Q000187:drug effects / Q000473:pathology; D014432:Tympanic Membrane
D000900:Anti-Bacterial Agents; D005839:Gentamicins