Related Experiment Video
Updated: Jul 5, 2026
Using Facial Electromyography to Assess Facial Muscle Reactions to Experienced and Observed Affective Touch in Humans
Published on: March 15, 2019
Optimal placement of recording electrodes for quantifying facial nerve compound muscle action potential
LanJun Guo1, Paul Jasiukaitis, Lawrence H Pitts
1Neurophysiological Monitoring Service, University of California, San Francisco, California 94143-0112, USA. lanjun.guo@ucsfmedctr.org
Objective:
To analyze optimal placement of recording-needle electrodes surrounding the eye and lip for facial nerve monitoring by identifying the maximum compound muscle action potential (CMAP) recorded by electrode pairs of different spatial configurations.
Study Design:
Prospective clinical trial.
Setting:
Ambulatory surgery at a tertiary care center.
Patients:
Thirty adults undergoing chronic ear surgery such as tympanoplasty, mastoidectomy, ossicular chain reconstruction, stapedectomy, and cochlear implantation.
Intervention:
Facial nerve monitoring.
Main Outcome Measure:
Suprathreshold (threshold + 0.2 V) CMAP responses are recorded from referential paired needle electrodes placed into orbicularis oculi (1.5-cm spacing; n = 15) and orbicularis oris (1.0-cm spacing; n = 15) muscles. Optimal recording electrode placement is inferred by identifying the maximum evoked CMAP amplitude.
Results:
For the eye, placement of electrodes by the orbital rim and into the upper eyelid is significantly better (Friedman test; p < 0.01) than the other 2 configurations. For the lip, placement of electrodes into the oral commissure and either the upper or lower lip is satisfactory because there is no statistically significant difference among the configurations (Friedman test; p > 0.2).
Conclusion:
Recording electrode placement configurations that capture the largest CMAP responses are recommended as standard operating procedure for intraoperative facial nerve monitoring.
