Abstract
Objective: Video oculography is a simple, accurate alternative to the scleral search coil method measuring individual semicircular canal function in Head Impulse Testing (HIT). Here we compare the video HIT with the caloric test for the diagnosis of unilateral or bilateral vestibulotoxicity due to systemic gentamicin therapy.
Method: Using the video HIT (ICS Impulse – GN Otometrics, Taastrup, Denmark) we studied 23/126 patients with gentamicin vestibulotoxicity; 5 unilateral, 18 bilateral. All 126 had caloric testing (30°C, 44°C); 82 also had 0°C testing. The video HIT took about 15 minutes and gave immediate results.
Results: All 126 patients had severe unilateral or bilateral impairment of lateral semicircular canal function on caloric testing. Slow phase velocity was under 5°/s for each 30 or 44°C irrigation and under 7°/s for each 0°C irrigation. The video HIT correctly detected this loss in all 23 patients tested. During the video HIT the gain of the vestibulo-ocular reflex from each lateral semicircular canal varied from 0.3 to 0.9 (N > 0.95). While a gain of 0.9 is near normal, the data in each patient showed covert or overt catch-up saccades, confirming the vestibulo-ocular reflex deficit.
Conclusion: The video HIT is a simple, accurate way of immediately diagnosing unilateral or bilateral gentamicin vestibulotoxicity avoiding the need for caloric testing. It might be applicable for monitoring of patients receiving potentially vestibulotoxic drugs and might in time replace the caloric test for the diagnosis of peripheral vestibulopathies.
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