Calculating The Vemp Asymmetry Ratio (Vemp Partner); Vemp Scaling - Interacoustics Eclipse Instructions For Use Manual

4.4

Calculating the VEMP asymmetry ratio (VEMP partner)

To calculate and display the asymmetry ratio between two curves, the waveforms to be compared must be
linked together (1 left response and 1 right response). The VEMP asymmetry ratio is not calculated before a
VEMP partner is selected.
1. Double click on the right or left VEMP curve's intensity handle to select it.
2. Next, right click on the opposite ear's VEMP curve intensity handle and select Set as VEMP partner
from the dialog. The asymmetry ratio is now displayed.
3. To remove the link between two waveforms, right click on the non-selected curve's handle and select
Remove as augmented VEMP partner.
The VEMP asymmetry is calculated using the following formula:
Where:
LA is the larger of the left or right curve's amplitude
SA is the smaller of the left or right curve's amplitude
R is the right curve's amplitude
L is the left curve's amplitude.
Note: Setting VEMP partners is only possible when right and left waveforms have been collected with similar
parameters.
4.5

VEMP scaling

The mean rectified (average) EMG for each recording is calculated from the pre-stimulus EMG during
testing. To normalize the raw VEMP amplitudes, to compensate for uneven SCM muscle contractions, the
recording is scaled by a factor, dependent on the EMG size recorded from each pre-stimulus period.
Select EMG scaling by right clicking on the curve. All curves will now be scaled and an indication on the test
screen will indicate scaling is enabled.
D-0120578-C – 2019/11
Eclipse – Instructions for Use - US Page 63