Objective: Gentamicin is a useful, sometimes life-saving, antibiotic with two serious adverse effects: nephrotoxicity and ototoxicity – exclusively vestibular not cochlear. Gentamicin vestibulotoxicity (GVT) is almost always missed by the prescriber and patients are referred to neurologists, sometimes years later, with ataxia or oscillopsia or both.
Methods: We reviewed 111 patients with GVT presenting 1974-2010 to determine (1) clinical features (2) if gentamicin therapy was necessary (3) if vestibulotoxity could have been diagnosed during therapy.
Results: Age of patients 18-84 years (mean= 64); 45 presented with ataxia, 5 with oscillopsia, 49 with both. None developed hearing loss or vertigo. All had bilaterally positive clinical head impulse test and a positive Fromberg test (and normal renal function before treatment). Twenty-three developed symptoms during therapy (ignored in 22), 72 afterwards, 16 could not recall. The total dose of gentamicin was 2-318mg/kg (mean 51); daily dose 1.5-5.6mg/kg (mean=3.6); trough serum gentamicin level from 0-12.9; duration of therapy 1-80 days (mean=17); 6 patients had only one dose. Delay to diagnosis 4 days to 15 years; 41 patients were severely disabled by ataxia and experienced falls. Gentamicin was given appropriately in only 50% of patients, according to current and contemporary Australian Antibiotics Guidelines.
Conclusion: GVT produces ataxia – sometimes disabling, especially in elderly, and oscillopsia and not vertigo or hearing loss. There is no relationship between the development of GVT and how much gentamicin is given or in what regime. About half the time gentamicin was administered it was not indicated.