Case 01 of 8 · Trainee · Ototoxicity → BVP

Unsteadiness on the ward

A 38-year-old with cystic fibrosis on day 9 of intravenous tobramycin.

CASE VIGNETTE

A 38-year-old man with cystic fibrosis is admitted with a pulmonary exacerbation due to multidrug-resistant Pseudomonas aeruginosa. He is started on intravenous tobramycin and ceftazidime, with trough levels monitored every other day and renal function unchanged from baseline.

On day 9 he reports that the ward television looks blurry when he turns his head, that he feels unsteady walking to the bathroom, and that he is sleeping poorly because the room appears to 'wobble' when he changes position. There is no rotational vertigo, no spontaneous hearing change, no tinnitus.

On bedside examination, head-impulse testing shows visible catch-up saccades on both rightward and leftward thrusts — absent on the pre-treatment exam two weeks earlier. Bedside DVA loses three lines in both directions, compared with a baseline of zero. Romberg is positive with eyes closed; tandem stance is impossible. Audiometry at the bedside (informal tuning fork) is unchanged.

The audiometric paradox of aminoglycoside vestibulotoxicity: hearing is preserved despite established bilateral vestibular loss. Around 90% of cases of gentamicin vestibulotoxicity have no measurable hearing change. This is why audiometric-only monitoring programmes miss the diagnosis and why DVA-based surveillance matters.

DVA SIGNATUREModerate

Ototoxicity — bilateral, symmetric

DVA loss: Symmetric loss of three lines (~0.3 logMAR) in both directions
Laterality: Symmetric — drug exposure is systemic, both ears equally affected
Asymmetry: Near zero — no directional asymmetry
Corroborating tests: Bedside HIT abnormal bilaterally · audiogram normal · pre-treatment baseline confirms iatrogenic origin

Key signature: The temporal pattern matters as much as the absolute findings — emerging deficit during week 2 of treatment with normal pre-treatment baseline points squarely at vestibulotoxicity.

Test-battery findings

DVA loss	≈0.3 logMAR bilaterally (3-line loss each direction)
Pre-treatment baseline DVA	0 logMAR (documented day 0)
Bedside head-impulse test	Catch-up saccades both directions
Spontaneous nystagmus	Absent
Romberg	Positive with eyes closed
Audiogram	Normal (15-25 dB across frequencies)
Subjective visual vertical	Normal

Question

What is the most appropriate next clinical step?

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Ototoxicity — bilateral, symmetric

Test-battery findings

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Further reading

References