Targeted chemodenervation of the posterior belly of the digastric muscle for the management of jaw discomfort in facial synkinesis

Summary Background Botulinum toxin (BT-A) chemodenervation has been proved to significantly improve the physical and psychological well-being of patients suffering from facial synkinesis. Despite this, a cohort of patients has persistent tightness and discomfort around the angle of the jaw, which may be caused by synkinesis within the posterior belly of digastric (PBD) muscle. This study was designed to evaluate the benefits of ultrasound-guided BT-A injections into the PBD. Methods Thirty-three patients with recalcitrant tightness and discomfort around the angle of the jaw, despite maximal facial therapy and platysmal chemodenervation were selected for inclusion. Patients underwent ultrasound-guided BT-A injection into the ipsilateral PBD muscle (skin puncture site 1 cm inferior and posterior to the angle of mandible). Outcomes consisted of the Facial Disability Index (FDI), Synkinesis Assessment Questionnaire (SAQ), and a visual analogue scale (VAS) designed to assess tightness and pain around the PBD when moving the jaw, swallowing, and masticating. Questionnaires were completed two weeks before and postinjection. Statistical analysis was performed using a paired t-test. Results Nineteen patients completed the post-treatment outcome questionnaire. A statistically significant improvement was noted in the physical and social function aspects of the FDI and all aspects of the patient-reported VAS scores apart from tightness and pain on jaw retrusion and swallowing. There was no significant difference in the SAQ. Conclusion This study has demonstrated the patient-perceived benefit of ultrasound-targeted BT-A chemodenervation of PBD. This represents a low-risk treatment option that can be easily added to the repertoire of treatments offered to patients with post paralysis facial synkinesis.