Faq - Vemp - Interacoustics Eclipse Additional Information

Eclipse Additional Information
10.3 FAQ – VEMP
Q: I cannot record a VEMP because I get rejection all the time?
A: Patient EMG is too strong for the default input gain – use a lower input gain setting.
Q: Why is my Waveform displayed upside down, with P pointing downwards?
A: This depends on the electrode montage used. The electrode cables may be switched or inserted to
the wrong socket. Another option is to invert the VEMP display which can be done in the General
Setup.
Q: What is the benefit of the LA-SA/L+R?
A: This is a calculation of the differences between right and left side recordings - The higher the number
– the greater the difference. Note patient cooperation/muscle fatigue will have a major impact on this
calculation. Applying scaling may reduce such impact.
Q: I get repeatable VEMP waveforms, but P is not exactly at 13ms, and N is not exactly at 23ms
A: As seen during ABR recordings – results are individual. Timing and amplitude will differ from patient to
patient and also can be affected by pathology.
The timing difference can also be caused by incorrect setup. Wrong headphone (normally insert ear-
phones are used). If changes have been made to the default test protocol (type of stimuli, level, win-
dow, filtering etc.) - timing differences may also cause this.
Note also that using a longer stimuli compared to e.g. a click will also create a later response.
Q: Can I record both sides simultaneously?
A: Yes, use simultaneous stimulating which can be set manually or within the System Setup | Auto Pro-
tocols. But only one side ("ipsi") can hold cursors for measurement.
Q: How can I check reproducibility?
A: The reproducibility is the similarity between some recordings. Create more recordings with the same
parameters – and drag the newly created curve manually down to overlay the existing curve. The re-
producibility is an objective evaluation of the curves in the region 13-23 ms where the VEMP takes
places.
The reproducibility is used to demonstrate that VEMP can be made several times with similar results in
the region 13-23ms.
If patient cooperation is poor or patient muscles are fatigued the reproducibility will be very poor – and
VEMP can be difficult to find. The reproducibility is very patient dependent.
Q: What kind of 500Hz Tone Burst is used in the default VEMP protocol?
A: It is a 5 cycle 2-2-2 stimulus at 500Hz. This adheres well to the typical Tone Burst stimuli mentioned in
the VEMP literature. Like all click and brief tone burst stimuli used in the Eclipse it is calibrated to ISO
389-6 when a dB nHL scale is used.
Q: Does there exist published cVEMP norm for children tested on the Eclipse?
A: Yes, Pereira et al, 2015 established norm values in 30 children, 15 females and 15 male (8 to 13 years
old, mean 10.2 ±1.7) without neurotological complaints.
P1 peak average latency of 17.26 (± 1.78) ms and a mean amplitude of 49.34 (± 23.07) µV, and the
N2 peak showed an average latency of 24.78 (± 2.18) ms and mean amplitude of 66.23 (± 36.18) µV.
P1-N2 mean amplitude was 115.6 (±55.7) µV. There were no statistically significant differences when
comparing by gender or by laterality.
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