Selective zygomaticus muscle activation by ball electrodes in synkinetically reinnervated patients after facial paralysis.
Dirk Arnold, Jovanna Thielker, Carsten M Klingner and 2 others
PMID 37908489WHAT IT FOUND
Stimulating the cheekbone muscle near the mouth corner selectively lifted it without closing the eye in nine of ten patients with facial synkinesis.
This proves selective activation is possible but does not show that stimulation improves facial movement or quality of life.
Key findings
01Selective activation of the zygomaticus muscle, which lifts the mouth corner, was achieved without triggering unintended eye closure in nine out of ten patients.
02The effective stimulation zone was consistently located within approximately 4.5 cm horizontally and 3 cm vertically from the corner of the mouth.
03No adverse events were reported during the stimulation sessions, indicating the procedure was safe for this small group.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study included only ten patients, making it a proof-of-principle investigation rather than a trial of efficacy. No statistical analyses were performed due to the small sample size. The assessment of muscle activity and synkinesis severity relied on subjective visual evaluation by examiners, supported by needle EMG. The study did not evaluate the long-term effects of stimulation or whether selective activation leads to improved voluntary facial movement. Discomfort thresholds varied greatly between patients, meaning the optimal amplitude is highly individual and not universally applicable.
Declared interests
The authors declared no conflicts of interest. The study was approved by the Ethics Committee of Jena University Hospital and registered in the German Clinical Trials Register.
The easy way to misread this
Do not interpret this as evidence that electrical stimulation improves facial function or synkinesis in patients. This was a single-session mapping study that showed selective activation is physically possible, but it did not test whether this activation translates to better voluntary movement, reduced synkinesis, or improved quality of life.