Maico MB 11 Classic Operation Manual page 55

Operation Manual MB 11 Classic
Figure 33
Typical ABR-Response with the Time Step Stimulus Signal
The white bars show the frame within which wave V for each of the evoking
clicks is expected. Click intensities are located above the corresponding
column (white bar).
The step stimulus curves permit a direct reading of the ABR hearing
threshold. The white bars with the anticipated latency of the relevant wave
V are very useful. The center of these white bars is set for the timing of the
normal latency intensity function and is shifted according to the age of the
patient (as entered in the patient data).
Therefore: The latencies of the wave V's for an individual must always be in
the same temporal relationship to the bars. It is not possible for wave V at
50 dB for example to be at the end of the 50 dB bar but for 40 dB at the
beginning of the 40 dB bar.
From the highest intensity onwards, waves must be traceable without a gap
through to the threshold. The amplitude of the highest intensity can turn out
to be slightly smaller but must still be recognisable. It is not possible for the
60 dB and 50 dB waves and also the 30 dB wave for example to be clearly
recognizable but no response identifiable at 40 dB. In this case, the wave at
30 dB is determined to be artifact and not a reliable evoked potential. If
necessary, repeat the measurement to clarify the situation. A good indication
for genuine ABR-potentials is a peak one column width before the wave V.
This is the wave III, but it is not always well formed.
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