A flat cortical trace — absent response or bad recording?
Vignette
During threshold testing at a moderate stimulus level, the averaged trace looks flat. The patient is an adult who has become drowsy, and the recording shows high residual EEG noise with frequent rejected epochs. The tester is about to record the level as 'no response'.
Findings
A flat trace sitting within a wide residual-noise band, recorded while the patient was drowsy.
Diagnostic question
What is the most appropriate next step before calling this an absent response?