When using constant voltage for facial nerve stimulation and the nerve is bathed in CSF, what occurs after the area is suctioned?

When facial nerve stimulation is conducted using a constant voltage and the nerve is initially bathed in cerebrospinal fluid (CSF), suctioning the area can significantly alter the impedance of the stimulation pathway. This change occurs because CSF has a relatively low resistance compared to the surrounding tissue. When the area is suctioned, the removal of the CSF can increase resistance, affecting how the electrical current flows through the tissue.

In this scenario, to maintain the preset voltage level, the current must adjust accordingly in response to the increased resistance from the lack of CSF. The stimulation system is designed to compensate for these changes in a way that the voltage remains constant, which means that the current flowing through the nerve will vary instead. This adaptability is essential for effective nerve stimulation during intraoperative monitoring, ensuring that the intended stimulation persists even as conditions change due to suctioning or other alterations in the surgical field.