Aminoglycoside Vestibulotoxicity

Many pharmaceuticals have ototoxicity (both cochlear and/or vestibular) as part of their adverse medication profile. The aminoglycoside class of antimicrobials has been especially well studied in this regard. Many questions remain unanswered as to how to best monitor and prevent this complication. A bilateral vestibular loss profoundly affects an individual's quality of life, physical activities, and overall independence. Paradoxically, the effects of gentamicin ototoxicity have provided further insight into the workings of the vestibular system, especially the vestibulo-ocular reflex. The microbiological activity, therapeutic use, toxicities, and genetics predisposing a person to aminoglycoside ototoxicity are presented. The clinical importance of recognizing ataxia, disequilibrium, and oscillopsia as presenting symptoms for vestibulotoxicity rather than hearing loss or vertigo is stressed. Documented risk factors and new observations regarding the spectrum of vestibular dysfunction and differences in vestibulotoxicity from multiple daily dosing vs. single daily dosing schedules are presented for the first time. While most vestibulotoxicity arises from systemic aminoglycoside administration, intratympanic application has been used therapeutically for intractable Ménière's disease. Commercially available ototopical aminoglycoside preparations for the treatment of external/middle ear disease in the presence of a tympanic membrane defect have also been documented to cause unintentional ototoxicity.