An ex-NICU infant with discordant tests

Vignette

A baby who spent three weeks in neonatal intensive care with hyperbilirubinaemia is referred. Parents report inconsistent responses to sound. The unit had screened with OAE only.

Test findings

Otoacoustic emissions are robustly present in both ears. Tone-burst ABR shows no reproducible neural response; a large potential reversing with stimulus polarity (a cochlear microphonic) is recorded.

Diagnostic question

What does this pattern indicate, and what does it say about the screen?