A method is described for determining an optimal placement location for an auditory brainstem implant (ABI) electrode array. A cochlear implant (CI) electrode array is inserted into a patient cochlea, and the ABI electrode array is initially placed at an initial placement location on a patient brainstem. The optimal placement location for the ABI electrode array is then determined by, for multiple electrode contacts on the ABI electrode array: i. selecting a specific electrode contact, ii. delivering a stimulation signal to the selected electrode contact, iii. sensing an efferent nerve signal from the stimulation signal using the electrode contacts of the CI electrode array, and iv. determining a maximum response location in the patient cochlea where a largest efferent nerve signal is sensed. The ABI electrode array is then repositioned to the optimal placement location.