When using a C5 spine to Fpz montage with lower extremity stimulation, the expected response is generated at which location?

In the context of monitoring neurophysiological responses during surgeries, using a C5 spine to Fpz montage for lower extremity stimulation typically generates responses that are recorded from the caudal medial lemniscus. This area is responsible for processing sensory information, including proprioception and fine touch from the lower extremities.

The expected response manifests as a far-field response rather than a near-field potential. This is because the signals originating from lower extremity stimuli traverse a significant distance through the central nervous system before they can be recorded at the scalp level (Fpz). This illustrates the propagation of the sensory evoked potentials and highlights the concept of far-field potentials in the context of intraoperative monitoring.

In contrast, responses that would be considered near-field potentials occur much closer to the recording site or are generated from the sensory pathways directly beneath the electrode. However, with the C5-Fpz montage, the distance from the site of stimulation in the lower extremities to the recording electrode results in a far-field response, emphasizing that the activity is being collected at a location significantly removed from the site of generation.

Understanding this concept is crucial in the practice of intraoperative monitoring, as it helps technicians and clinicians interpret the data collected during procedures and determines how to