Down for the count: The critical endpoint in ototoxicity remains the cytocochleogram.

There are three major assays that must be conducted in standard investigational new drug (IND) -enabling ototoxicity study designs: 1) functional acoustic threshold measurements (Auditory Brainstem Respsonse, ABR); 2) otohistopathology and 3) cytocochleograms. We provide evidence to demonstrate the unreliability of auditory threshold shifts (ABRs) to predict cochlear cell death and build a case for conducting full cochlea processing and cell count measurements from the complete cochlea from apex to base.