What change is typically observed in BAEPs with brainstem tumors?

In brainstem auditory evoked potentials (BAEPs), the presence of a brainstem tumor is commonly associated with an increased inter-peak latency between waves III and V. This phenomenon occurs because a tumor within the brainstem can disrupt the normal conduction pathways of auditory signals, leading to a delay in the time it takes for these signals to travel along the auditory nerve and brainstem structures.

Waves III and V correspond to specific anatomical structures in the auditory pathway, and an increase in the inter-peak latency between these waves indicates that the signal is being transmitted more slowly, likely due to compression or disruption of the nerves or structures involved. This change serves as a critical marker in the evaluation of brainstem pathology, allowing clinicians to assess the functional impact of the tumor.

In contrast, a decrease in absolute latency for waves or no significant effects are typically not observed in association with brainstem tumors, as the presence of a mass effect would generally disrupt normal conduction rather than enhance it. Additionally, an increase in the inter-peak latency between I and III is less specific to brainstem lesions, further emphasizing the significance of the III-V inter-peak latency as a reliable indicator in this context.