Testing utricular function by means of on-axis rotation.

CONCLUSIONS

Subjective visual vertical (SVV) estimation during on-axis rotation provides an efficient screening test of utricle function. The survey demonstrates that isolated disorders of peripheral utricular function can occur while SCC function appears normal.

OBJECTIVE

The present study aimed to investigate estimation of SVV during constant velocity yaw rotation (with the head held on-axis--to enhance any asymmetry between right and left utricular responses), as a useful screening test.

METHODS

In all, 230 patients were recruited from the dizziness clinic. For each patient, the SVV was estimated (a) while held stationary, and (b) during constant angular velocity (240 degrees/s), with the head centred on-axis. Bithermal caloric testing was also performed in 201 of the patients.

RESULTS

Of those patients with normal SVV results during stationary testing, 18.3% were pathological during rotation testing. In those cases with pathological SVV during stationary testing, a significantly greater deviation from the norm was observed during rotation (p<0.001). Of those patients with normal caloric responses, 44.4% showed pathological SVV estimates; this increased to 54.3% for cases with unilateral weakness, and 56.5% for unilateral loss. No clear correlation was found between reports of tilt illusion and pathological SVV, respectively, between rotatory vertigo and pathological caloric responses.