What is the primary reason platinum is used in epidural electrodes?

Platinum is predominantly used in epidural electrodes due to its characteristic that it is bio-compatible and does not release harmful ions into the tissue when current is applied. Other metals may undergo oxidation or reaction which can create toxic ions that could negatively impact the surrounding neural tissue or lead to adverse effects during neurophysiological monitoring. The biocompatibility of platinum ensures that it can safely exist within the body, minimizing the risk of inflammatory reactions or toxic effects, making it a preferred choice for epidural electrodes where direct contact with nerve tissue occurs.

While the other factors such as cost, conductivity, and corrosion resistance are relevant in selecting materials for various applications, they do not match the critical importance of biocompatibility and the non-toxic nature of platinum when comparing it with other metals in the context of neurophysiologic monitoring.