Functional Assessment of Hemifacial Spasm Using a Whole-Face Surface Electromyography Electrode Array.

Area of Science:

• Neurology
• Biomedical Engineering
• Clinical Electrophysiology

Background:

• Hemifacial spasm (HFS) is a challenging neuromuscular condition impacting facial movement.
• Current diagnostic methods like electromyography (EMG) have limitations due to invasiveness and resolution.
• Objective assessment tools are needed to quantify HFS severity and understand its pathophysiology.

Purpose of the Study:

• To evaluate facial muscle activity in HFS patients using a whole-face surface EMG (sEMG) technique.
• To explore the utility of sEMG topographic mapping for analyzing midfacial muscle coordination.
• To provide an objective method for quantifying HFS severity and abnormal coactivation patterns.

Main Methods:

• Recruited twenty HFS patients for whole-face sEMG recordings.
• Measured muscle activity (RMS, MDF) in frontalis, orbicularis oculi, orbicularis oris, mentalis, and midfacial muscles.
• Utilized stretchable sEMG electrode arrays for topographic mapping of midfacial muscle activity.

Main Results:

• Significantly higher RMS in the affected frontalis muscle compared to the unaffected side (P <0.001).
• sEMG topographic map showed a significant shift in horizontal center of gravity (CoGx) towards the midline on the affected side during teeth-showing task (P <0.05).
• Lower entropy on the affected side during cheek-showing task indicated altered muscle coordination (P <0.05).

Conclusions:

• sEMG effectively captures compensatory mechanisms in HFS patients.
• Whole-face sEMG and topographic mapping provide objective quantification of HFS severity.
• This technique offers a valuable, non-invasive tool for evaluating abnormal facial muscle coactivation in HFS.