What does the Fpz-C5s channel record when performing a posterior tibial nerve SSEP?

The Fpz-C5s channel is specifically designed to capture potentials generated in response to stimulation of the posterior tibial nerve. When looking at this channel in the context of somatosensory evoked potentials (SSEPs), it is important to understand its placement and recording capability.

In this case, the Fpz electrode is positioned at the forehead (Fpz) and the C5s is located over the cervical spine region. This configuration allows for the detection of far-field potentials that originate from deeper structures within the central nervous system as a response to sensory stimulation. The term "far-field" refers to voltage signals that travel a longer distance to reach the recording electrode, indicating that the potentials being captured are from subcortical areas rather than directly from the cortical surfaces.

As the nerve stimulation elicits sensory pathways that conduct from the periphery through the spinal cord and into the brain, the signals recorded via the Fpz-C5s channel typically reflect these subcortical activities, making it suitable for identifying far-field potentials. This is crucial in intraoperative monitoring to assess the integrity of the sensory pathway during procedures that may place these pathways at risk.

In this specific context, the correct identification of the Fpz-C5s channel