The click ABR is shown.  To facilitate discussion, the normal latencies for a child this age are shown at the bottom of the figure, top row.  The first number is the average latency, and in parentheses is the outer limit of normal. The second row is the data for the I-III, III-V and I-V interpeak latencies.

At the top, this child’s interpeak latencies are shown.  Note the delayed IPLs, and the interaural differences for III and V, for the right ear.  When you see an abnormality, one should always question “Have I made a mistake?”  Is there any possibility of the right wave, especially V, being mismarked?  The normal latency is 6.31, and the left ear’s value is 6.55.  Examining the right ear trace near that time, we see a negative going wave – so there is no other good choice for V.  I believe this is correctly marked.

When the click ABR is abnormal, we should check to see if we might be looking at auditory neuropathy synchrony disorder.  Note the cochlear microphonic, which is highlighted in yellow for the left ear (it is seen on the right trace, too).  It is small, so that’s not typical of ANSD – in ANSD the cochlear microphonic is large and it “rings”.  Only this small wave at about 0.5 ms reverses phase with the stimulus polarity, so the other waves are physiologic, they are not indicating ANSD.