Mapping the vestibular evoked myogenic potential (VEMP)

Area of Science:

• Neuroscience
• Biomedical Engineering

Background:

• Vestibular evoked myogenic potentials (VEMPs) are crucial for assessing vestibular and cervical pathways.
• Standardized electrode placement is essential for reliable VEMP recordings from the sternocleidomastoid muscle (SCM).

Purpose of the Study:

• To investigate the impact of different electrode placements and reference electrode locations on SCM VEMP recordings.
• To identify optimal electrode configurations for accurate VEMP analysis.

Main Methods:

• VEMPs were recorded from 5 healthy volunteers using various electrode placements on the SCM, centered around the motor point.
• Two reference electrode positions were tested: sternoclavicular joint and C7 vertebra.
• Electrode grids were used to systematically evaluate recording sites.

Main Results:

• The earliest and largest VEMP responses were consistently obtained with the active electrode positioned over the SCM motor point.
• Different recording sites and reference electrodes produced distinct morphological changes in VEMP waveforms.
• The C7 reference electrode influenced rectified EMG levels and introduced potential artifacts.
• P13 potential latencies increased with distance from the motor point, suggesting a traveling wave, while N23 latencies remained constant, indicating a standing wave.

Conclusions:

• Active electrode placement directly over the SCM motor point is ideal for maximizing VEMP amplitude and minimizing latency.
• The choice of reference electrode, particularly C7, can introduce confounding myogenic activity and affect EMG measurements.
• Understanding electrode placement effects is critical for accurate interpretation of VEMP data in clinical and research settings.