Does Addition of Medial Pterygoid Muscle Injection Improve the Outcome of Botulinum Toxin Therapy for Masticatory Myofascial Pain Syndrome?

Does Addition of Medial Pterygoid Muscle Injection Improve the Outcome of Botulinum Toxin Therapy for Masticatory Myofascial Pain Syndrome? A Randomized Controlled Clinical Trial

Masticatory myofascial pain syndrome (MMPS) is a common and debilitating orofacial pain condition characterized by localized or referred pain originating from trigger points in the masticatory muscles. The condition significantly impairs quality of life, affecting mastication, speech, and psychosocial well-being. The masseter and temporalis muscles are the most frequently targeted muscles in conventional botulinum toxin type A (BoNT-A) therapy for MMPS; however, the medial pterygoid muscle, a primary jaw-closing muscle, is often overlooked due to its deep anatomical location and the technical challenges associated with its injection.

Current evidence supports the efficacy of BoNT-A in reducing pain and improving mandibular function in patients with localized MMPS. However, the specific contribution of targeted medial pterygoid injection to overall treatment outcomes remains unclear. This study aims to address this gap by evaluating whether the addition of targeted medial pterygoid injection enhances the clinical efficacy of conventional masseter and temporalis BoNT-A therapy.

Inclusion Criteria:

• Diagnosis of myogenous TMD/myalgia according to DC/TMD.
• Pain modified by jaw movement, function, or parafunction.
• Familiar pain reproduced during standardized masseter/temporalis examination.
• Clinical evidence of medial pterygoid involvement.
• Medial pterygoid provocation reproduces the patient's familiar pain.
• Symptoms present for at least 3 months.
• No major competing odontogenic cause for the patient's pain.

Exclusion Criteria:

• Predominantly arthrogenous TMD.
• Trigeminal neuralgia or other neuropathic facial pain.
• Active systemic inflammatory or infectious disease affecting the masticatory muscles.
• Significant neuromuscular disease.
• Pregnancy or breastfeeding.
• Previous BoNT-A injection into the relevant masticatory muscles during the predefined washout period.
• Known hypersensitivity to the study medication or formulation components.
• Local infection at the injection site.
• Significant bleeding disorder.
• Clinically significant uncontrolled anticoagulation.
• Previous major surgery involving the medial pterygoid region that could alter anatomy.