F171. Testing reliability of modified electrode positioning to record wave V

Abstract

Introduction Auditory Brainstem Responses (ABR) is important modality to preserve the hearing during posterior fossa, skull-base surgeries and microvascular decompressions of the cranial nerves. The hostile environment and electrical interference often obstruct the adequate recording and reliability of waveforms. We aimed to evaluate whether modified location of the recording electrodes would provide additional reliability, especially relevant when the sterile surgical field limits the electrode positioning. Methods Forty ABR from 20 patients were included in the study. ABR were recorded according to the ACNS standards. Recording montages included Ai-Ac, Ai-Cz, Ac-Cz. In addition alternative montages were used and compared to the standard recording. For the unconventional montages, the electrodes placed between the posterior neck and shoulder bilaterally, 2 cm superior to the edge of the scapula (AS). The recording montages included ASi-Cz, and ASc-Cz. Results Wave V was recorded from the alternative channels in 98%. The latency and morphology of the waveforms were in-line with the recordings on conventional channels. The wave V morphology remained stable throughout the critical portions even when it’s reproducibility was in question with the standard channels. In addition the wave III showed very stable responses. Conclusion Alternative montage with recording electrodes positioned away from the surgical field may provide improved far field potentials. The waves III and V from alternative channels showed more resistance to the artifact/interference during surgery, improving the reliability especially during critical portions.