A comparison of brainstem auditory evoked responses evoked by rarefaction and condensation stimulation in control subjects and in patients with Wernicke-Korsakoff syndrome and multiple sclerosis.

Brainstem auditory evoked responses (BAER) evoked by rarefaction and condensation stimulation were compared in patients with Wernicke-Korsakoff syndrome (WKS) and multiple sclerosis (MS) and click polarity-related differences in topodiagnosis were found in 24% of the WKS and 40% of the MS patients. These results suggest the need to record BAER routinely with both stimulus polarities separately if practicable. BAER from rarefaction and condensation stimulation were recorded from control subjects of both sexes to provide control data for the patient study and also to investigate the interaction between sex and click polarity. BAER latency and amplitude differences between males and females were found to be independent of click polarity. However, the study did show an interaction between female sex and click polarity-related BAER latency differences although differences in amplitude and waveform morphology were essentially independent of sex. This further emphasises the importance of taking into account the variables of sex and stimulus polarity in establishing BAER control values.