Rotational responses in patients with bilateral caloric reduction.

Caloric irrigation and earth vertical axis rotation, both horizontal semicircular canal stimuli, occasionally provide conflicting information about the presence of bilateral vestibular loss. The caloric and rotational responses of an unselected group of 1274 dizzy patients were compared to identify discrepancies between the two tests. Results indicated a poor correlation between the magnitude of response to caloric and rotational stimuli; about half of patients with reduced caloric responses (total eye speed less than or equal to 10 degrees per second) had rotational response magnitudes (at 0.05 Hz and above) that were within normal limits. Our findings confirm that bilateral caloric reduction is not sufficient evidence for diagnosing bilateral vestibular loss and indicate that, in some case, caloric responses may be absent despite apparent normal vestibular sensitivity as assessed by rotational testing.