Chemodenervation of the Posterior Belly of the Digastric Muscle in Facial Synkinesis

Unveiling Novel Surgical Treatments for Facial Synkinesis: Myectomy of the Posterior Belly of Digastric and Stylohyoid Muscle

Facial synkinesis manifests as involuntary muscle movements alongside volitional facial actions and is typically managed with a combination of neuromuscular retraining, botulinum toxin injections, and in some cases, selective neurectomy. Some patients with synkinesis describe persistent neck tightness or pain at the level of the mandibular angle and horizontally towards the midline, similar to the anatomic course of the posterior belly of digastric (PBD) and stylohyoid muscles. There are limited studies exploring the involvement of the PBD and stylohyoid muscles in facial synkinesis and the use of chemodenervation as treatment. Herein, we present 2 patients with facial synkinesis and ipsilateral neck tightness and pain who underwent novel surgical treatment in the form of the standard selective neurectomy procedure along with a myectomy of the PBD and stylohyoid muscles. Following completion of the standard steps of selective neurectomy, the PBD and stylohyoid muscles were carefully dissected and separated from the surrounding structures. Both muscles were divided using bipolar electrocautery. Both patients reported improvement of neck pain and tightness immediately after the intervention and at the 6.5-month follow-up visit. These preliminary results show promise in aiding a subset of patients with synkinesis-related neck pain and tightness.

Reanimation of the Lower Lip with the Anterior Belly of Digastric Transfer: A Systematic Review

Background: Dynamic reanimation of the lower lip is a challenging issue for patients, with depressor asymmetry commonly addressed with chemodenervation, selective neurectomy, or myectomy. Objective: To determine whether the anterior belly of digastric transfer is an effective method of lower-lip reanimation for patients with either isolated marginal mandibular branch weakness or inadequate depressor function after hemifacial reanimation, as measured by patient satisfaction and objective symmetry evaluation. Method: Systematic review of the literature was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Abstracts and full texts were reviewed. A Risk of Bias assessment was performed. Results: Nine studies with 164 patients were included. Anterior belly of digastric transfer was successfully performed in 162 patients. Most patients (52%) underwent one-staged reanimation innervated by the native nerve to the mylohyoid. A two-staged approach after placement of a cross face nerve graft was performed in 46%. Patient satisfaction was excellent (90.6%), with minimal complications including revision (4/162), infection (4/162), and lipofilling (8/162). Conclusion: In patients seeking a permanent outcome, use of an anterior belly of digastric transfer in either a one-stage or two-stage approach appears to be a safe and effective method to restore symmetry and dynamic function.