Olfactory Evoked Potential Monitoring: Technical Note and Challenges Faced.

Background and aim: Despite the sustained progress in the realm of intraoperative neurophysiologic monitoring of the nervous system, little progress has been achieved in monitoring the olfactory pathway. Loss of olfactory function due to retraction-induced physical damage during operations has ill-appreciated negative consequences for the patients and is often underreported. Improvements in this area of neuromonitoring require a revisit of the technical challenges. We aim to describe the method to construct flexible, bipolar silver ball electrodes to stimulate the olfactory mucosa during cranial neurosurgery and suggest ways to overcome the challenges in eliciting olfactory evoked potentials.

Materials and methods: We analyze the potential difficulties in routinely eliciting olfactory evoked potential in neurosurgical operations and summarize ways to overcome them. We also describe the construction of a simple electrical stimulator electrode for the olfactory mucosa, its application, and potential recording sites in an effort to detect the potential during cranial neurosurgery.

Results: We created flexible, insulated bipolar silver electrodes and placed them atraumatically on the olfactory mucosa under endoscopic guidance, bilaterally, in 22 patients. We obtained an optimal position in less than 10 minutes in most cases. We also summarize the challenges faced and potential paths to overcome them.

Conclusions: Though electrical stimulation of the olfactory mucosa using custom-made silver electrodes is possible and takes little time to place them as part of an intraoperative neurophysiologic monitoring setup, detecting the minute potential remains elusive.