Electromyography-Guided Chemodenervation for Treatment of Nonflaccid Facial Palsy: Analysis of Accuracy

Chemodenervation is a mainstay in the treatment of nonflaccid facial paralysis (NFFP). This study investigates how electromyography (EMG) guidance during chemodenervation may allow for more accurate needle placement.

To compare the accuracy with needle EMG chemodenervation compared with standard non-EMG approaches in patients receiving treatment for NFFP with botulinum toxin (BT) as measured by physician and EMG verification.

The use of needle EMG across three surgeons was recorded to determine if the use of EMG changed the location, angle, or depth of needle insertion into the targeted facial muscle. The determination of accurate needle placement was self-reported by the physician coupled with the physician assessment of muscle EMG activity. Accuracy was determined as the ratio of the number of successful EMG needle insertions (placed within muscle with adequate signal) over the total number of EMG needle insertions.

A total of 137 patients underwent treatment for NFFP, with an average age of 54 (interquartile range [IQR]: 44-65) and weight of 73 kg (IQR: 64-90). Of the 14 facial mimetic muscles, the posterior belly of digastric (accuracy = 19%, standard deviation [SD] 0.4), risorius (accuracy = 46%, SD 0.5), and zygomaticus (accuracy = 47%, SD 0.5) had the lowest accuracy in BT placement (Table 3). Of all the muscles included, only the buccinator (p = 0.015), platysma (p = 0.0093), and zygomaticus (p = 0.024) had statistically significant variation in the accuracy of BT placement between surgeons.

EMG guidance for the treatment of NFFP may improve the precision of needle placement and BT delivery, particularly in the mid and lower facial muscles.